Chapter 24 Principles of infection control
Chief sources and reservoirs of infection
Disruption of transmission routes
HBV, HCV and HIV: implications for podiatrists
Infection control: strategies and methods
Infection control: terminology and concepts
The prevention of all treatment-associated infection, both in patients and in staff, is an integral part of the professional responsibilities of podiatrists. An increased awareness of viral hepatitis and acquired immunodeficiency syndrome (AIDS) has heightened the concern of healthcare personnel over risks of infection. While concern over infections caused by hepatitis B and C viruses (HBV and HCV) and the human immunodeficiency virus (HIV) has focused attention on danger in clinical practice, this must be viewed in the context of infection control in general.
The basic principles and terminology of infection and its control are considered here, but because initial training, professional experience and working circumstances vary greatly, it is impossible to dictate a single infection-control regimen suitable for all practitioners. However, equipped with a sound knowledge of the principles involved, individuals can select and implement measures most appropriate to their own practice.
The fields of infection and infection control have evolved specialised terminology but, unfortunately, there are not universally agreed definitions of all terms, and some variation in usage is demonstrated in the published literature. However, there is agreement on the essential concepts, and these are the basis of the following summary of terminology and associated information.
Pathogenicity is the ability of a microorganism to invade a host and cause disease; hence, organisms that do so are termed ‘pathogens’. However, it is important to realise that the original concept of there being pathogens and non-pathogens must be modified in the light of modern knowledge. While only true (virulent) pathogens may cause infection in a completely healthy host, there are many others that can cause infection if the body is weakened in some way. These opportunistic pathogens demonstrate that infection is but one outcome of a complex relationship between the body and microorganisms, infection occurring when the balance of circumstances favours a potential pathogen. Given appropriate circumstances, virtually all microorganisms are potential pathogens.
Infection is the multiplication of microorganisms in or on body tissues, with an accompanying response by the body’s immune system. Products of this immune response (e.g. antibodies against the organism) can be used to detect and diagnose infection or to monitor the progress of an infection. Note that this differs from contamination, which merely implies the presence of microorganisms, which may or may not become established.
Importantly, not all infections result in clinical infection (i.e. visible disease symptoms). Lower level infections occur in which microorganisms become established and there is an immune response but no clinical symptoms become apparent (i.e. subclinical infection is present). Even infections that eventually become overt will not show clinical symptoms in the early stages.
The number of cells or particles of a microorganism that is required to establish infection is termed the infective dose. Pathogens differ in their infective dose, some requiring smaller numbers for successful invasion than others. More importantly, for any infectious agent, the greater the number contacting the body, the more probable it is that infection will become established. It follows that practical measures taken to reduce the number of microorganisms reaching the patient’s tissue will reduce the likelihood of infection.
It is not possible to achieve the complete absence of microorganisms in the proximity of a patient. However, for minor non-invasive procedures, appropriate cleaning or disinfection will reduce the probability of microorganisms reaching the body in sufficient numbers to cause infection. When the body is more susceptible to invasion, such as when there has been surgery or other tissue damage, more stringent efforts must be made, by the use of sterile instruments and aseptic techniques, to minimise the numbers of microorganisms entering tissue.
This differs from infection in that in colonisation an organism becomes established in or on the body but neither symptoms nor a significant immune response occur. However, colonisation may progress to infection should circumstances subsequently favour the microorganism.
Carriers are people who are colonised by or subclinically infected with a pathogen while showing no clear symptoms, but who are nevertheless infectious. The carrier state may be preceded by clinical infection, but not necessarily. Carrier states may be temporary or long term, even permanent. Relevant pathogens include Staphylococcus aureus, HBV, HCV and HIV.
A source is a site where potential pathogens can grow and multiply. A similar but more variable term is ‘reservoir of infection’, which has been used for sites where survival rather than growth occurs, as an alternative to the term ‘source’, or to describe a particular category of source. It will be used here for sites where survival or accumulation rather than growth is to be expected.
Many movable objects can become contaminated and transfer microorganisms to a susceptible person or body site. Some are naturally mobile because of their lightness (e.g. minute skin scales or respiratory droplets), while others are deliberately moved (e.g. instruments). Such objects are vehicles of infection that are capable of transmitting an infective dose but not usually of supporting microbial growth. Viruses, in particular, cannot multiply outside host cells, but transmission can occur via contaminated instruments (e.g. wart viruses, HBV, HCV and HIV).
The preceding points have important implications for infection control. While it is relatively straightforward to identify high-risk vehicles (e.g. instruments) and to render them safe by appropriate techniques, individual sources of infection are less easily identified. In particular, staff or patients colonised by a pathogen or in a symptomless stage of infection are sources, but they will not exhibit convenient symptoms warning of a possible infection risk. Continual awareness of the potential threat from sources, even unidentified ones, is required, and safe working practices that minimise the risk of infection from such sources must be implemented.
The term cross-infection is used in the clinical context specifically to describe the spread of infections to patients from staff or other patients. It often involves staff–patient contact or transfer of organisms via clinical equipment. Cross-infection is a significant risk to patients, and many control procedures are aimed at its prevention.
These are sites by which microorganisms gain access to the body. Most pathogens have one usual portal, although some are more versatile. Once established, organisms may remain near the entry site, causing localised infection, or spread internally to involve other areas of the body. The respiratory, gastrointestinal and genitourinary tracts are common portals of entry, but microorganisms rarely penetrate intact healthy skin.
Entry through the skin is usually via damaged areas, including minute abrasions, sites damaged by pressure, venous ulcers and areas weakened by excessive exposure to moisture. Deliberate penetration occurs in surgery, but damage may also result from other procedures such as nail reduction or treatment of keratoses and verrucae. As the skin is an important part of the body’s defence, every effort should be made to avoid unnecessary damage and accidental penetration during procedures. Furthermore, any article penetrating skin or contacting damaged tissue is a potential vehicle of infection and must be free of microorganisms, which it could transport across the integument barrier.
These are sites from which pathogens exit the body and from where they are spread to other people, or other sites on the same body. Portals of entry and exit are often one and the same, for example infected wounds exuding pus, but pathogens causing systemic infections may exit from different sites. Hepatitis viruses and HIV may exit from any site where bleeding is caused by deliberate or accidental penetration of skin. Pathogens infecting superficial tissues (e.g. dermatophyte fungi, wart viruses, Streptococcus pyogenes) will be shed in skin particles or lesion exudates, while other pathogens whose primary target is not skin may, particularly in advanced cases, cause skin lesions containing the infectious agent (e.g. tuberculosis).
The spread of infectious material from exit sites must be minimised by, for example, the use of adequate dressings on infected lesions, safe disposal of contaminated dressings and decontamination of instruments.
Every human body is colonised by a large number of commensal microorganisms – the normal indigenous microflora of the body. Many species, mainly but not exclusively bacterial, occur among the flora, and different body sites support mixed populations of organisms suited to the particular conditions. The skin, mouth, upper respiratory tract and the large intestine are important sites of body flora.
The skin not only has resident flora permanently present (e.g. Staphylococcus epidermidis) but it is also frequently contaminated with flora from other body sites. These do not usually become established permanently on the skin but are so often present that they may be considered as transient normal flora. Above the waist, organisms from the respiratory tract often occur (e.g. Staph. aureus), while below the waist intestinal species may be present (e.g. Pseudomonas spp.). At any time additional transient contaminants acquired from the environment and other people may occur on the skin.
In health, the normal body flora is harmless or even beneficial, presenting competition to the establishment of incoming pathogens. However, it includes species that, while usually harmless in their normal sites, can be serious pathogens in wounds or damaged skin (e.g. Staph. aureus and Strep. pyogenes). In circumstances when local conditions allow excessive growth of a commensal species (e.g. erythrasma), when contamination of wounds occurs or when the body is weakened by systemic disease (e.g. venous ulcers in diabetics), many other commensal species act as opportunistic pathogens of skin tissue.
The chief sources of infection may be categorised as:
Infections of wounds and damaged skin are most commonly caused by organisms from the patient’s own body, which gain access to vulnerable areas on the foot. Examples include:
In addition to sites of body flora, any existing infected area (e.g. boils, ulcers) is a dangerous potential source from which pathogens can be transferred to damaged tissue. The importance of endogenous sources in potential wound infections means that local flora must be reduced before invasive procedures, and transmission of organisms from other body sites must be prevented.
In clinical situations, important and obvious sources of cross-infection are staff or patients with clinical infections of the skin or other accessible sites such as the respiratory tract. However, it is worth reiterating that human sources of pathogens, including Staphylococcus aureus bacteria, hepatitis viruses or HIV, and fungi such as Candida albicans, are often in symptomless states.
Commoner sources of cross-infection are sites of flora on staff or other patients which, while harmlessly colonising those people, can cause infection if transferred to vulnerable foot tissue, for example approximately 30% of patients and staff will be nasal and/or skin carriers of Staphylococcus aureus.
Animals can be colonised or infected by microorganisms that can cause human infections. Patients attending for treatment may have been infected from domestic animals, for example by zoophilic dermatophytes such as Microsporum canis. Infestation of premises by mice, cockroaches or pharaoh ants (a minute, inconspicuous species sometimes encountered in warm clinical environments) may occur. Such vermin and pests can harbour pathogens, including species acquired from clinical and human waste.
Survival or growth of microorganisms outside the body is determined by their requirements and the environmental conditions. Many microorganisms associated with the human body are unlikely to grow in the environment as they have specific requirements that will be absent (e.g. complex nutrients or living host cells). All organisms need moisture for growth, and therefore even less-demanding species are prevented from multiplying by the dryness of most clinical areas. However, wet sites in clinical areas are potential sources or reservoirs, allowing the growth of some organisms and aiding the survival of others. Any body of standing water supports growth of bacteria, particularly Gram-negative bacilli which need minimal nutrients. Wet sites such as soap receptacles, leaks or spillages from pipes or equipment, and residual water in stored utensils are potential risks. Even aqueous solutions of chemicals, including disinfectants, especially if overdiluted or aged, will allow survival and even growth of microorganisms.
Dry sites are reservoirs of viable microorganisms surviving in dirt and dust. In general, Gram-negative bacteria survive poorly in dry conditions, whereas Gram-positive bacteria and fungi survive rather better. The resistance of bacterial spores to desiccation and even disinfection is well established. Protection by materials of bodily origin (e.g. dried blood, exudate and skin particles) aids survival of all types of organisms. Reduction in numbers due to cleaning procedures is counterbalanced by day-to-day contamination from staff and patients, clinical waste (e.g. skin and nail debris), and dirt or dust from clothing and footwear. Therefore, continual effort is required to restrict contamination to acceptable levels.
For infection to occur, microorganisms from an exogenous or endogenous source must be transmitted by some means to a new host or host site. Details of transmission routes vary widely in individual instances but may be generally categorised as follows.
This involves direct physical contact with, or close proximity to, a human source or reservoir. It includes close-range transmission of pathogens in droplets or skin particles shed from the body that fall immediately onto surfaces of persons within 1–2 m (i.e. they do not become truly airborne). Those most likely to transmit exogenous infection to patients are staff who are themselves infected or colonised or whose hands and clothing have become contaminated from other patients. Staff involvement in direct-contact transmission, especially via the hands, is of major importance in clinically acquired infections.
This category can also include endogenous infection involving transmission from own-body sites, for example wound infections caused by organisms from the skin or other sites spread via the hands or clothing. Some pathogens more usually spread by direct sexual contact (e.g. hepatitis viruses and HIV) may also be transmitted by clinical contact if blood contaminates the skin or mucous membranes. Measures to prevent direct transmission in clinical situations include hand/skin cleaning and disinfection, protective clothing and ‘no-touch’ techniques.
These usually involve intermediate vehicles of infection that transfer microorganisms from an animate (including human) or inanimate source or reservoir to a vulnerable host site. The source or reservoir is not directly involved or in close proximity, and could in fact be very distant.
Any contaminated article coming into close proximity to or contact with vulnerable tissue is capable of transmitting infection. Background items, for example furniture, are relatively low risk, while articles in direct patient contact are high risk. Potential vehicles include scalpels, burrs, handpieces and other instruments, swabs, dressings and drapes, antiseptics, syringes and injected solutions. Reusable instruments and multi-use containers of pharmaceuticals are more likely to become contaminated than are single-use items. Surfaces, including trolley tops, may contaminate items placed on them. Adjustable lamps used during procedures may transfer contaminants to and from hands. Surfaces allowed direct contact with a patient’s skin (e.g. foot rests if not protected by a sheet) can transfer organisms between patients.
True airborne transmission, commonly associated with respiratory infections, should have little significance in podiatric procedures. Apart from the previously noted close-range contamination near the body, airborne contamination appears to be significant only when tissue is exposed for prolonged periods, such as during extensive surgery (Ayliffe & Lowbury 1982, Ayliffe et al 1999, Meers 1983).
However, clinic dust is a reservoir of infection and may contain remnants of skin, nail, blood, pus and lesion exudates. Various activities may render the dust airborne, and thus able to settle afterwards on exposed surfaces. Dry sweeping of skin and nail debris, vigorous movement of curtain screens, overcrowding and unnecessary human activity all increase airborne contamination. While this risk is difficult to quantify, these activities are undesirable near clinical procedures or unprotected sterile items.
Vermin and insects may shed contaminants when feeding or defecating. They may also act simply as vehicles, transferring contamination on their body surfaces from dirty areas such as drains and disposed wastes. Either way, contamination of the clinical environment, surfaces and unprotected materials may occur.
Faecal–oral transmission is of major importance in food and waterborne infections. While this has no direct relevance to podiatry, note that the hands and skin are often contaminated with faecal organisms, including potential wound pathogens, after toilet use, and dispersion of such contamination is more likely if diarrhoea is present.
In view of current concern over these blood-borne infections, a brief overview is given below, drawing on the concepts established above. These are complex infections and only a general summary is possible here.
HBV and HCV are two important types of the several viruses that can cause hepatitis, which is characterised by inflammation and necrosis of liver tissue. Although the more recently characterised of the two, the incidence of HCV is now known to be many times that of HBV and about ten times that of HIV (Dinsdale 2004). Viral hepatitis infection may result in a range of consequences, for example:
As with all viruses, the components of HBV and HCV are antigenic, and these antigens together with the antibodies formed against them are used to monitor infection, to indicate the carrier state or its level of infectiousness, and to track the effectiveness of treatment. For example, the presence of the HBV surface antigen (HbsAg) indicates that the person is infected with HBV and is infectious. The antigen disappears on recovery, but its persistence longer than 6 months after infection indicates a chronic carrier state. Subsequently, the presence of HBeAg (from the HBV core) in the blood of carriers indicates that the person is highly infectious.
The latest drug therapies can reduce liver inflammation and infectiousness in HBV (in approximately 50% of cases) and are more successful in HCV, approximately 40% of cases being ‘cured’ as measured by virus elimination from the blood. Nevertheless, the proportion of unsuccessful treatments and the fact that many cases go untreated means that most people currently infected with HBV and HCV live with the threat of associated long-term consequences.
HIV (human immunodeficiency virus) causes AIDS (acquired immunodeficiency syndrome), which is the final stage of this virus’s progressive attack on the human immune system. From the first described cases of AIDS in the 1980s, HIV infection has advanced to a global epidemic. There are currently tens of millions of people at various stages of HIV infection, from initial seroconversion to fully developed AIDS. Thus the likelihood of podiatrists unknowingly encountering infected people among their patients has increased greatly.
The main cellular target of HIV infection is a type of T-lymphocyte known as a CD4 (T4,-helper) cell. These cells play a vital part in controlling the body’s response to infection. Any reduction in the number or function of CD4 cells leads to impaired humoral and cell-mediated immunity, with a consequent vulnerability to infection.
Initial infection by HIV causes little or no discernible illness, although the infected person is infectious. Within several weeks seroconversion (i.e. the production of anti-HIV antibodies) occurs. The person is now ‘HIV-positive’. However, while these antibodies are useful in detection tests for HIV infection, within the individual they are ineffective in eradicating the virus, and the person remains permanently seropositive and infectious. The progress of the infection and the effectiveness of treatments can now be monitored by direct tests for viral load in the individual and CD4 cell counts.
Individuals who are HIV-positive present differing states of health, reflecting progressive stages (of very variable duration) of the infection:
The exact proportion of HIV infections that results in symptoms is unknown, but from experience to date it is likely that all HIV-infected individuals develop some degree of illness eventually, up to and including AIDS. Developments in antiretroviral drug regimens have resulted in significant extension of relative well-being and life expectancy in many recipients, although these aggressive and expensive therapies are not available or appropriate for all. While an advance, these therapies are not a cure, and a vaccine remains unavailable despite extensive research.
HBV, HCV and HIV are blood-borne but are also present in other body fluids, including semen and vaginal secretions – hence their association with entry of blood through mucous membranes or damaged skin, sexual transmission and mother-to-baby transfer. These infections have an increased incidence in certain high-risk-activity groups such as drug injectors sharing equipment, homosexual/bisexual men, and heterosexuals with multiple sexual partners. However, in the podiatry context it is much more relevant that these infections are not confined to such high-risk-activity groups and have become much more widespread in the general population. Workers in situations where blood spillage or transfer is likely (e.g. healthcare, prison personnel, police, other emergency services) are at increased risk. Patients who received blood transfusions or blood products before detection or preventive measures were available may also have become infected. Even children, seemingly unlikely risks among podiatry patients, may have been infected by maternal transmission. The crucial point is that a podiatrist will not know whether or not a patient belongs to a high-risk-activity group, and the incidence of these infections is now much more widespread among other people not in these categories.
HBV, HCV and HIV infections are all on the increase, and all have potentially serious consequences. Despite advances in treatments there are no real cures, and thus prevention of infection is the only effective strategy (Department of Health 1998).
Therefore, practitioners must treat all invasive procedures, contacts with blood/tissue fluids, and blood/tissue fluid contamination of instruments as dangerous, however unlikely it seems that the patient constitutes a risk. In effect, procedures must prevent transmission from any patient in case they are a source, while also protecting each patient from becoming a victim of clinically transmitted infection. All sharps used in procedures must be sterile, with particular care being taken with the decontamination of reusable instruments if employed. Any differences in infectiousness or hardiness between these viruses are irrelevant in most circumstances, as effective prevention must take into account the possible presence of all of them.
No vaccine is currently available against HCV or HIV infection, and although an effective HBV vaccine is now available only a minority of the general population will be protected by this in the foreseeable future. As professionals with direct patient contact, podiatrists are at risk and should seek HBV vaccination. In no way does staff vaccination reduce the necessity for other control measures, which are essential to protect patients from these and other infections.
Following a large outbreak in the UK of bovine spongiform encephalopathy (BSE) in cattle, human cases of a new variant of Creutzfeldt–Jakob disease (CJD) appeared, and it is now accepted that food-borne transmission from cattle to humans occurred. The number of cases of this invariably fatal disease that will eventually develop in infected but as yet symptomless people is unknown. Although originally food-borne the danger now is that transmission via blood or tissue can occur, hence the relevance of CJD in clinical contexts. The agent is a prion protein (not a living organism as such) that is highly resistant, and it is essential that tissue traces are removed from reusable instruments by scrupulous cleaning prior to heat sterilisation to avoid its possible survival of the process. The arrival of this new threat is another reason to move towards the ideal of single-use sharps for invasive procedures wherever feasible.
The term ‘infection control’ reflects the realistic objective of reducing infection to the practicable minimum, rather than claiming the ideal of total prevention. Infection has always been of major concern to professionals involved in the surgery and treatment of wounds. Much is now known about prevention of infection generally and wound infections in particular. If the established principles and practices of infection control are implemented, infection following podiatric procedures should be uncommon, especially as many procedures are relatively minor in terms of tissue invasion. Infection control in clinics must encompass measures to prevent patient infections from both endogenous and exogenous sources, and also to protect staff from becoming infected by patients. As time progresses, higher standards are expected of professionals, particularly as awareness has increased of threats from blood-borne pathogens and antibiotic multiresistant bacteria such as MRSA (methicillin-resistant Staph. aureus).
Knowledge of infection control in clinical situations stems largely from efforts to prevent infections in hospitals, and comprehensive texts on these aspects have been produced (Ayliffe et al 1990, 1999, 2000, Bennett & Brachman 1986). In addition, the Society of Chiropodists and Podiatrists in the UK has indicated to its members recommended procedures for particular aspects of routine practice (Anon. 1987, Burrow 2004). A very important resource now available to practitioners is the information available on internet websites. Advantages of these include worldwide access, frequent updating and the availability of search facilities for the user. The following section summarises the underlying principles of infection control in the context of podiatry, and indicates how they provide a rational basis for safe procedures.
This is a process that renders an item free from all living microorganisms, that is it becomes sterile (British Standards Institution 1986a). There are no degrees of sterilisation; all microorganisms, including bacterial spores, must be killed or removed. Any process that does not achieve this is a disinfection and not a sterilisation process. Sterilants are chemical agents capable of sterilising, but few can achieve this in routine podiatric circumstances.
Disinfection is a process by which microorganisms are reduced to a level harmless to health. In contrast to sterilisation, there are degrees of disinfection, the level of microbial reduction considered necessary being dependent on the item to be disinfected and the infection risk it presents in that situation. Bacterial spores are often little affected. Disinfection, unlike sterilisation, can be applied to living tissue, for example skin, as well as to inanimate articles.
Disinfection methods, particularly chemical disinfectants, often demonstrate a particular spectrum of antimicrobial activity, varying in effectiveness against different types of microorganisms. The terms ‘bactericidal’ and ‘fungicidal’ indicate a capability of killing bacteria and fungi, respectively. Similarly, ‘sporicidal’ and ‘virucidal’ indicate an ability to kill spores and to inactivate viruses, respectively. These properties are determined under laboratory test conditions, and such terms should not be taken to mean that disinfection so described or labelled will kill all of the specified type of microorganism under conditions of ordinary use. A term such as ‘germicidal’, while implying antimicrobial activity, is too vague and should not be used.
Antisepsis is the destruction or inhibition of microorganisms on living tissues, having the effect of limiting or preventing the harmful results of infection (British Standards Institution 1986a). Antiseptics are chemical agents used to achieve antisepsis; they are usually unsuitable for general use on inanimate articles, for reasons of either lower antimicrobial action or cost-effectiveness. Some antiseptics inhibit rather than kill microorganisms, this capability being described by terms such as ‘bacteriostatic’ or ‘fungistatic’.
The term ‘asepsis’ means an absence of contamination or, perhaps more realistically, absence of infection (sepsis) resulting from contamination. This should be the objective underlying all clinical procedures. Aseptic techniques are safe methods of working on patients by which contamination is minimised and thus infection prevented – in this context, largely by the prevention of cross-infection and the protection from contamination of damaged foot tissue. As appropriate, both sterilisation and disinfection are employed to achieve asepsis.
As microorganisms may be transmitted by so many routes, a similarly wide range of measures must be employed in infection control. All individual control measures stem from three basic strategies of infection control that are long-established but still relevant in the 21st century (Ayliffe et al 2000, Lowbury et al 1981):
In any particular circumstances, which will vary for individual practitioners, these strategies provide a framework for a sensible choice of suitable control measures. Strategies 1 and 2 above are especially relevant to practical podiatry and are discussed in the following sections.
Important sources of infection are patients with existing clinical infections, for example septic lesions, fungal infections and verrucae. Successful treatment not only benefits that patient but also eliminates him or her as a source of cross-infection. During a course of treatment, dressings minimise the exit of pathogens from such sources. Endogenous infected sites must be covered by dressings before invasive techniques or exposing nearby tissue.
Less commonly, podiatrists providing hospital ward services may encounter source isolation. Some patients with serious infections are isolated by a variety of measures to prevent cross-infection from them to others. Essentially, both the patient and his immediate environment are considered to be contaminated, and measures are enforced to prevent transfer of pathogens from these by either personnel or equipment. Appropriate protective clothing must be donned and, after patient care, must be discarded within the isolation area. Instruments may require special arrangements for decontamination before re-use, and thorough hand cleansing after patient contact is most important. Practitioners treating such patients should familiarise themselves with, and adhere to, the isolation procedures in force at that time.
Podiatrists with clinical infections are clearly a risk to patients. Particularly relevant are infections on the hands or other exposed areas of skin, for example furuncles, infected cuts or paronychia. Covering small lesions with waterproof plasters and wearing gloves reduces the risk to patients, but such measures may not suffice to eliminate the risk, especially in procedures where glove puncture is possible. Where there is any doubt, direct contact with patients should be avoided until the infection has resolved. Infections of other parts of the body also constitute a significant risk, for example streptococcal sore throat. Skin affected by chronic skin conditions such as eczema or psoriasis may become colonised with Staph. aureus and lead to profuse shedding of the organism. Practitioners who become carriers of HBV, HCV or HIV are unlikely to transmit these to patients but, as personal circumstances vary greatly, practitioners should seek medical advice if in any doubt of the advisability of contact with patients, particularly with regard to invasive procedures. Other possible sources among staff include symptomless carriers of wound pathogens such as Staph. aureus and Strep. pyogenes. Routine screening of staff for such carriage is not generally justified, but it may be necessary in certain circumstances, for example to investigate an outbreak of wound infections.
Accumulations of dirt or dust anywhere in the clinical environment are reservoirs of infection and should be eliminated by cleaning, with additional disinfection if necessary. Clinical waste must not be allowed to contaminate the area and should be disposed of hygienically. Collection of patient debris at source is a sensible measure, for example by using a disposal bag underneath the foot or similar measures. Wet sites resulting from faulty equipment or plumbing can be eliminated by repair or replacement. Other wet sites need a common-sense approach to changing working procedures or choice of materials. Examples include disinfecting and drying cleaning utensils before storage, and replacing bars of soap lying in a wet dish by cleaner draining storage or, better still, by a suitable detergent/disinfectant dispenser.
Prevention of animal pest infestations is aided by maintenance of building structure (to inhibit access) and high standards of general cleanliness throughout the premises to deny them food, water and breeding sites. Should infestation occur, eradication can be difficult and professional pest-control operatives should be contacted. If the source of a patient’s infection is found to be a family pet (for example M. canis), then successful treatment of the person may require veterinary treatment of the animal to prevent reinfection.
Essentially, this is achieved by effective decontamination of inanimate vehicles and by procedures designed to exclude contamination at the point of patient contact, the latter including hand/skin disinfection and other aspects of aseptic technique.
Decontamination of inanimate articles is based on cleaning, disinfection and sterilisation. These techniques represent increasing degrees of decontamination and are employed according to the infection hazard posed by particular articles or circumstances. As a general rule, the closer an article approaches susceptible tissue or vulnerable items such as sterile instruments, the more thorough the decontamination required. Cleaning is usually adequate for most general items, such as furniture, utensils and laundry. Disinfection is necessary when a specific infection risk is known to exist, for example articles in the vicinity of treatment procedures, blood spillages, and for articles that are unsuited to sterilisation but require more thorough decontamination than cleaning. Sterilisation is necessary for all items penetrating the body or contacting exposed tissues.
The clinical environment should present a high standard of general cleanliness. Inadequately cleaned clinics will not only contain unnecessary reservoirs of microorganisms but will also reduce patients’ confidence and staff morale. Cleaning should not be dismissed as a background chore that has little to do with the professional staff, but should be part of an integrated programme of clinical decontamination. In this context, it implies thorough cleaning at sufficiently frequent intervals using effective agents and appropriate, well-maintained equipment. Such cleaning is a surprisingly efficient method of decontamination and is all that is usually necessary for routine surfaces and equipment, such as floors, furniture, sinks, toilet facilities and similar items. Disinfection of these is unnecessary, firstly because such items normally present an insignificant infection risk, and secondly because recontamination is inevitable and reaches a similar equilibrium level whether or not disinfectants are used. However, disinfection is justified for such items on specific occasions of known increased risk, for example blood spillage.
In addition to preventing excessive accumulations of contaminated dirt, cleaning should not itself increase any risk of infection. Both the methods and materials employed must themselves be hygienic. There are two main dangers here: the distribution of dust-borne contamination and the growth of bacteria on wet cleaning utensils. Dry dusting or sweeping, including the sweeping up of debris after patient treatment, is not acceptable in clinical areas, and suitable vacuum cleaners (British Standards Institution 1986b) or dust-attracting mops should be used instead. Vacuum cleaners should incorporate efficient filters and/or bags, regularly checked and replaced as necessary, which retain debris and microorganisms efficiently and do not spread contamination via exhausted air. Dust-attracting mops must themselves be cleaned as soon as they are visibly dirty or at least every 1–2 days.
Wet cleaning should be done with clean water and a detergent, changed frequently to maintain effectiveness. Cloths, preferably disposable, for damp-dusting surfaces and string mops for cleaning floors are more suitable than sponge utensils, which are less easy to decontaminate after use. Utensils for wet cleaning are known to support the growth of bacteria, particularly Gram-negative organisms, if they are not effectively decontaminated after use. Ideally, items such as reusable cloths, mop heads, buckets and wet parts of cleaning machines should be cleaned after use, heat-disinfected if possible, and then stored dry. Unless their premises are serviced by a centralised hospital cleaning service, practitioners may consider this an unattainable standard, but serious efforts should be made to avoid heavy contamination of wet utensils, which in turn would contaminate the very items they are supposed to clean. Utensils should at least be cleaned in fresh hot water and detergent, and then rinsed and dried. Storage of all ancillary equipment, including cleaning materials, should, of course, be separate from the area used for patient treatment. Routine cleaning activities, even if done well, carry a risk of dust disturbance or splashing and should be completed as long as possible (ideally at least an hour) before treatment of patients, to allow airborne contamination to finish settling.
Floors, toilet facilities and furniture should be washed or damp-dusted daily, as appropriate. Sinks also require thorough cleaning daily, and additional cleaning if soiled during use, with either detergent or mild abrasive cleaning products. Sites that could harbour stagnant water, for example soap ledges, must be dried. Walls in good repair are of little significance in infection and, unless soiled, require infrequent cleaning; every few months should suffice. In contrast, adjustable lamps positioned immediately above the patient and that are handled frequently should be cleaned daily, and disinfection between patients could be recommended.
Some exceptions to daily cleaning of floors and furniture may be necessary. If there are floor areas on which patients walk barefoot there is the risk of cross-infection; careful organisation of patient movements or use of disposable coverings for floors or feet could eradicate this. As some foot conditions will render patients vulnerable to infections, while other patients may have existing infections, it is difficult to justify contact with a floor that is not at least cleaned between patients. Similarly, furniture or surfaces in the immediate vicinity of treatment procedures justify extra cleaning, and even disinfection, between patients, especially before invasive procedures.
Reusable instruments should be cleaned scrupulously after use before further decontamination and reuse. After a rinse in cold water, they may be cleaned manually using a brush and mild detergent. Rubber gloves should be worn, as thick as is consistent with dexterity, and every care taken to avoid accidental injury while cleaning, rinsing and drying sharps, because of the risk of HBV, HCV and HIV infection. Used instrument brushes should be cleaned and disinfected, preferably sterilised, and not simply left by the sink. Instruments and other utensils should not be cleaned in the same sink used for clinical handwashing, but if this is completely unavoidable the sink should be cleaned and disinfected after use for instruments. Alternatively, ultrasonic cleaning in detergent solution can be employed for instruments, in which case the manufacturer’s instructions on method and suitable agents should be followed. Note that ultrasonic baths are a cleaning aid only and do not kill microorganisms – they may even disperse aerosols of microorganisms if lids are not tightly fitted. Furthermore, they should not be allowed to retain water or stagnant cleaning solution, which could support the accumulation of bacteria. For further details of cleaning methods and agents, the reader is referred to texts on clinical hygiene (Babb 1993, Maurer 1985).
Many agents have been employed for disinfection in clinical situations, including steam, hot water, chemical vapours, chemical solutions and ultraviolet radiation. The agents most relevant to podiatric clinics generally are hot water and chemical disinfectants. Hot water has the advantage of being effective against all types of microorganisms except bacterial spores; it needs little expertise, leaves no residues and is inexpensive. However, it is unsuitable for very heat-labile items, cannot be used on living tissue, and is not practicable for larger items. Chemical disinfectants can be used on surfaces and furniture, and some are suitable for skin disinfection; unfortunately, as a group, they have many disadvantages – including possible toxicity, corrosiveness, variable antimicrobial effectiveness, inactivation by many materials, undesirable odours or residues, limited in-use life, and a general requirement for skilled use to be effective.
Despite the widespread use of chemical disinfectants in the past, it is now accepted that they should be used only when there is a clear need for disinfection additional to thorough cleaning, and when no practical alternative is available. If possible, hot water should be used instead, particularly as items too sensitive for heat sterilisation often withstand the lower temperatures used for disinfection.
In summary, heat disinfection is the preferred method for inanimate items of suitable size for immersion, whereas chemicals are employed for larger items and surfaces, for skin disinfection, and when heat is not practicable.
Articles should be cleaned first, then fully immersed in hot water, ensuring parts are not protected by trapped air. Temperatures of at least 65°C are necessary; higher temperatures decrease the time required for effective disinfection. For routine use, the values in Table 24.1 are applicable.
Table 24.1 Disinfection by hot water
| Temperature (°C) | Minimum time |
|---|---|
| 65 | 10 minutes |
| 71 | 3 minutes |
| 80 | 1 minutes |
| 90 | 1 second |
Such treatments are recommended to kill vegetative bacteria on items such as heat-labile instruments (British Standards Institution 1993). Thermostatically controlled washer/disinfectors with timed cycles, and washing machines incorporating a disinfecting hot water rinse are available. Heat-resistant instruments should be immersed in boiling water for at least five minutes (Ayliffe et al 1999, British Medical Association 1989). ‘Instrument boilers’ need careful use as they usually lack time-controlled cycles and can also pose problems of operator safety. It must be emphasised that disinfection, even at high temperatures, is not sterilisation and it should not be used when sterility is required.
Despite their disadvantages, chemical disinfectants are required for certain tasks and are effective when used correctly. However, users should be aware of various factors that influence the efficiency of disinfectants.
The concentration of disinfectant solutions is important in determining efficiency, and the recommendations of manufacturers or suppliers must be followed. For this reason, in-use solutions should never be ‘topped up’ by the addition of more water, with or without additional disinfectant. Once prepared, in-use solutions deteriorate, resulting eventually in a lower actual concentration and thus becoming ineffective. If possible, make up fresh solutions daily; this need not be wasteful if appropriate quantities are prepared. Otherwise, it is essential to note shelf-life information and to prepare fresh solutions when required, marking the date prepared and a use-by date as appropriate. Remember that disinfectant solutions can act as sources or reservoirs of pathogens.
All disinfectants can be inactivated to some extent by various natural or synthetic materials, such as hard water, detergents, soaps, tissue or other body material, cork, cellulose (e.g. cotton wool) and plastics. This is potentially serious, as many articles used to contain or apply the disinfectants, and items for disinfection themselves, may reduce the effectiveness of the process. If required, the manufacturer’s advice should be sought on these aspects.
Dirt, especially dried organic material, may inhibit disinfectants by inactivation and by presenting a physical barrier to penetration of the solution. The level of initial microbial contamination also influences the number of microorganisms surviving after a given treatment. It is important, therefore, that articles should be cleaned if possible to remove dirt and reduce contamination before disinfection.
Disinfection is not instantaneous, and adequate contact time must be allowed. This varies from seconds to prolonged soaking, depending on the agent and the item involved.
An important and very variable factor in chemical disinfection is the user, and many studies have shown that human ignorance or error is responsible for ineffective clinical disinfection. The number of different chemical agents should be kept to a minimum, and clear instructions must be available on the preparation, circumstances for use, method of use and acceptable in-use life.
Many types of chemicals have been used in disinfection, but relatively few are suitable for clinical use. Others, while effective, have been superseded by more modern agents. The properties of the chief types in current use are summarised here.
These are widely effective against bacteria and fungi but have a poorer action against viruses. Organic matter has little inactivating effect, and therefore they are suitable for use in dirty conditions or on soiled items, but not when there is contamination by blood. In-use concentration is usually 1% or 2% v/v for clean or dirty conditions, respectively.
Combination with a suitable detergent (anionic or non-ionic) aids penetration of dirt, but phenolic compounds are inactivated by cationic detergents. Clear, soluble phenolics (e.g. Stericol, Clearsol and similar products) are preferred to cruder coal tar derivatives, and are used for environmental disinfection in hospitals (e.g. contaminated areas and floors, operating rooms). ‘Pine’-type products, although chemically related, are often poor disinfectants and are too easily inactivated to be generally accepted for clinical use.
These are very effective against most microorganisms, including viruses. They are usually the agent of choice when there is risk of viral infection, including blood spillages. However, they are more easily inactivated by organic matter than are phenolic compounds, and therefore items must be cleaned first, or sufficiently high concentrations must be used to compensate for the loss. It is important to ensure adequate activity of the in-use solution, usually expressed in terms of percentage or p.p.m. (parts per million) of available chlorine. Solutions for routine clinical use should contain 1000 p.p.m. (0.1%) and strong solutions (e.g. for blood spillage) should contain 10 000 p.p.m. (1%) available chlorine. Products may be purchased as liquid concentrates, powders or tablets, which are diluted or dissolved in water. Typical chlorine-releasing agents employed as ingredients include hypochlorites and dichloroisocyanurates (NaDCC). Product information must enable accurate calculation of the available chlorine concentration.
Sample calculation. Thickened liquid concentrates (e.g. Domestos) typically contain 10% (100 000 p.p.m.) available chlorine. If diluted in water, a 1% v/v solution (1 volume disinfectant to 99 volumes water) would contain 100 000/100 = 1000 p.p.m. (0.1 %) available chlorine. A cautionary note on liquid concentrates: concentration varies between brands, and degeneration can occur in storage (Coates 1988).
Dichloroisocyanurate tablets are available; these have the advantages of long storage stability and simplicity of preparing in-use dilutions of various strengths as required (Coates 1985).
Alcoholic solutions of iodine are effective disinfectants but cause tissue irritation and staining. Improved alternatives are available. Iodophors, which are organic complexes containing iodine (e.g. povidone-iodine), are less irritant and less likely to stain. Iodophors have a wide spectrum of activity against bacteria, fungi, viruses and, unusually, bacterial spores on prolonged contact. Iodophor preparations are used for skin and hand disinfection, and wound antisepsis.
Ethyl and isopropyl alcohols have a wide and rapid antibacterial action, but a poorer action against some viruses. They are most effective in aqueous solution, typical concentrations being ethanol at 70% and isopropanol at 60–70%, although higher concentrations are sometimes used. They may be used for rapid disinfection of clean skin, hands and hard surfaces, and for combination with other antimicrobial agents. Ready-to-use disposable wipes containing isopropanol are available.
The most widely used of these is chlorhexidine (Hibitane), which is effective against Gram-positive and Gram-negative bacteria but poorly effective against viruses. Combination with alcohol increases its effectiveness and accelerates disinfection. It is inactivated by many materials, including soaps and anionic detergents, and cannot be recommended for general environmental use. However, it is widely used for skin and hand disinfection, as it shows very little toxicity and has both immediate and residual action. It is available as both aqueous and alcoholic preparations (e.g. Hibiscrub, Hibisol).
This is effective against Gram-positive and Gram-negative bacteria. It has little reported toxicity, and is available as both aqueous and alcoholic preparations (e.g. Aquasept, Manusept). Several products of this type have been reported to be effective in hand disinfection, but generally chlorhexidine or povidone-iodine preparations are better.
These form a group of chemicals that have both surfactant and disinfectant properties, to varying degrees. Although active against Gram-positive bacteria, they are poorly effective against other microorganisms, and are too easily inactivated for clinical use. However, cetrimide is one which, in combination with chlorhexidine, provides effective wound-cleansing agents (e.g. Savlon-type products).
This has been used widely for cold ‘sterilisation’ in podiatry, although probably only disinfection was achieved in normal practice. It is a widely effective disinfectant, with good antiviral action, and is sporicidal in certain conditions. Thorough disinfection requires 20–30 minutes of immersion (sterilisation requires 3–10 hours). As it is an irritant, disinfected items should be rinsed in sterile water. Glutaraldehyde (e.g. Cidex) still has restricted specialised use in hospitals, but its routine use in podiatry cannot be recommended (Health and Safety Executive 1998). Alternative disinfection, or sterilisation by heat, should be used for items previously treated with glutaraldehyde.
Items suitable for heat disinfection include cleaning utensils (especially if used in operating rooms or on contaminated areas), routine laundry, instrument brushes, reagent bottles before refilling, containers for antiseptics, general-purpose bowls and containers for non-sterile cotton balls, etc. Sterilisation may be preferable for some of these (e.g. instrument brushes). In the absence of sophisticated disinfection facilities, cloths and mops may be cleaned and then placed in a container to which boiling water is added, and kept immersed for at least 10 minutes before drying and storing dry. Alternatively, after cleaning they can be immersed in a 1% phenolic or chlorine-based disinfectant for 30 minutes, and then rinsed and stored dry. Note that some materials, such as plastics, may inactivate disinfectants, and that utensils should be stored dry, not in disinfectant. Clinical laundry can be cleaned in an ordinary automatic machine using a prewash followed by a wash at the highest temperature setting, unless known contamination by HBV or HCV is present.
Floors and surfaces contaminated with tissue other than blood should be cleaned and then disinfected with a 1% phenolic or 0.1% chlorine-releasing agent. Ideally, blood spillages should be disinfected before cleaning to counter any risk of hepatitis viruses and HIV; disposable gloves should be worn and the spillage covered with paper towels or other absorbent, disposable material. A chlorine-releasing agent (10 000 p.p.m. available chlorine) is then poured on and left for at least 10 minutes. The area is then cleaned, again using disposable materials. All items (gloves, towels, etc.) are then disposed of as contaminated waste. Alternatively, purpose-made packs of granular NaDCC or other antiviral agents are available for wet-spillage treatment, in which case the manufacturer’s instructions should be followed. Hands should always be washed after dealing with spillages.
Small areas of clean impervious surfaces, such as trolley tops, foot rests, adjustable lamps and other hand-contact surfaces in the chair’s vicinity, can be disinfected with agents that are unsuitable or uneconomic for wider environmental use. Although 1% phenolics could be used, alcohols or alcoholic chlorhexidine, as wipes or sprays, are faster acting and drying and likely to be more convenient for use between patients (e.g. Alcowipes and Azospray type products). Cartridges of local anaesthetic should be wiped with alcohol before use. Handpieces are potential vehicles of infection between patients via the operator’s hands, and ideally should be sterilised. If disinfection is used, manufacturers may advise on appropriate methods; alternatively, clean thoroughly and then disinfect with alcoholic chlorhexidine.
The hands of staff and the skin of patients both require adequate decontamination, the degree necessary being dictated by the circumstances. Whatever method is used, effectiveness depends largely on the care and thoroughness of the operator. Handwashing facilities vary, but taps operated without hand contact (e.g. foot operated) are best, and if ordinary taps are fitted they should be turned off using a paper towel.
The main purpose of routine handwashing is to remove transients acquired from previous contacts, particularly patients. Although loosely adhering transients can be removed by washing with ordinary soaps, detergent/disinfectant preparations containing chlorhexidine, povidone-iodine or Triclosan are more effective, and on repeated use they progressively reduce the more accessible flora. Intervening washes with ordinary products eliminate this residual benefit, and, therefore, as daily case loads may include treatments that require hand disinfection, it is sensible to use disinfectant preparations for all clinic handwashing. However, choice of agent is less important than thoroughness of application (Ayliffe et al 1990, 1999). If hands are visibly clean, rapid and highly effective disinfection between patients or during procedures can be achieved with alcoholic disinfectant preparations. Handwashing with non-disinfectant products is not adequate for surgery, invasive techniques, treatment of damaged tissue or dressing changes.
Further reduction of skin contamination is required for some procedures (e.g. nail surgery). The aim is to reduce flora as much as possible on the hands and the forearms, from where organisms may also be shed. Initially, the hands and forearms are subjected to prolonged double washing with detergent/disinfectant preparations (as above), attention also being paid to cleaning the nails and nail folds. If brushing is employed to remove loose skin squames, it should be done only at the start of a clinical session. Use of an alcoholic disinfectant preparation after washing will increase the degree of this initial disinfection. For subsequent cases, these alcoholic preparations alone, well rubbed in, are very effective, although washing is necessary if hands are soiled. Note that hand disinfection is not an alternative, but an addition, to wearing gloves for aseptic procedures.
Hand cream may be employed to offset the drying effects of disinfectant products, but it should be one that is compatible, as commercial products often inhibit disinfection; pharmacists can advise on suitable products.
Recently there has been debate and discussion regarding the use of clinical dress that has sleeves reaching the wrist (Department of Health 2008). It is considered that the dress material is a possible vehicle for transporting flora. At this stage no national guidelines have been formulated, but some NHS Trusts in the UK are implementing the wearing of clinical clothing such as ‘scrub suits’ for all clinical procedures. This facilitates handwashing extending to the elbows.
If possible, intact skin should be cleaned before disinfection. As immediate and effective disinfection is required, alcoholic skin disinfectants are the agents of choice. Chlorhexidine is less likely to cause any reaction, although povidone-iodine has wider antimicrobial action; normally either is suitable. Friction is an important factor in skin disinfection; rubbing the site thoroughly with the agent (subject to patient comfort) is more effective than merely wiping or spraying. Combined detergents/disinfectants (e.g. Savlon) may be used for damaged skin that requires cleaning. Injections (e.g. local anaesthetic) present little danger of infection but skin is often prepared by swabbing with alcohol.
Of the many methods of sterilisation available, only steam at increased pressure and dry heat are likely to be used directly by the podiatrist.
This is generally recommended for use on clinical materials whenever possible (British Pharmacopoeia 1998). Steam hot enough to sterilise necessitates pressure vessels, termed ‘sterilisers’ or ‘autoclaves’. Saturated steam sterilises the articles it contacts, the time required depending on the temperature. Minimum treatments required are:
Additional time must be allowed for heating to sterilisation temperature and for cooling after sterilisation. Saturated steam can be obtained only in the absence of air. In sophisticated equipment, air is evacuated, enabling penetration of steam even into wrapped porous materials (e.g. dressings), and evacuation after sterilisation facilitates the drying of such items. Basic units affordable by many practitioners rely on simple displacement of air by steam generated within the steriliser. Removal of air, steam penetration and subsequent drying are, therefore, not as efficient in these models. However, these small sterilisers are suitable for rapid sterilisation of instruments, either unwrapped or in steam-permeable containers. When removed, instruments must be covered immediately to prevent contamination. A sterile cloth may be used, or a lid sterilised separately in the same cycle could be clipped onto the instrument tray.
Where practicable, central sterile supplies units or similar local services should be used as a first-choice option, as these facilities should be able to guarantee sterility of products and incorporate a total quality management system. However, where such a service is not available or is not practicable, the minimum standard for clinical practice in podiatry is that instruments must be sterilised using steam pressure sterilisers. Advice on the purchase and operation of bench-top steam sterilisers is available (Medical Devices Agency 1996). In the UK, The Pressure Systems and Transportable Gas Containers Regulations 1989 set out the legal requirements for the monitoring and validation of sterilisers and must be followed. To help practitioners to comply with these regulations Health Technical Memorandum 2010 (Department of Health 1994) provides guidelines governing the maintenance, monitoring and validation of steam sterilisers. Following these guidelines will enable practitioners to demonstrate clear evidence of maintenance, monitoring and validation of their sterilisation process and procedures. The daily checks recommended by Health Technical Memorandum 2010 for sterilisers include undertaking an operational cycle at the beginning of the working day. The cycle may contain a load, provided such a load is consistently used for each daily cheek. There are also recommended weekly, quarterly and annual checks to ensure the efficacy, efficiency and maintenance of sterilisers.
To ensure the effective functioning of bench-top sterilisers there are a number of additional measures that practitioners must ensure are carried out. All instruments must be decontaminated prior to sterilisation using ultrasonic cleaning or some other suitable method. The reservoir of the steriliser must be emptied and cleaned regularly, refilling it with sterile water. The internal surfaces of the chamber of the steriliser should be cleaned using sterile water for irrigation and a lint-free cloth. The sterilising chamber should be emptied and a visual inspection of the water made to determine its colour and the presence of any debris and contaminants. Complying with these requirements will demonstrate that the instruments used have undergone a satisfactory sterilisation process. This is reinforced by the introduction of a system of audit of these processes, with documentation to show that all instruments have undergone a sterilisation cycle.
In the UK there are further legal requirements for practitioners to conform to a range of legislative requirements that come under the umbrella of the Health and Safety at Work etc. Act (1974), The Management of Health and Safety at Work Regulations (1992), The Pressure Systems and Transportable Gas Containers Regulations (1989) and The Provision and Use of Work Equipment Regulations (1992). It is a requirement of The Pressure Systems and Transportable Gas Containers Regulations (1989) that practitioners using bench-top autoclaves have third-party insurance cover and that the equipment is inspected regularly. Additional health and safety information relating to the use of bench top pressure autoclaves is given in Chapter 29.
An electrical, fan-assisted, hot-air oven may be used. Microorganisms are more resistant to dry heat than to steam, and therefore higher temperatures are required for sterilisation within a practicable time (e.g. a minimum of 30 minutes at 180°C) (British Pharmacopoeia 1998). All items must reach sterilisation temperature before the holding time commences. As heating time varies with the load, it is often underestimated, especially for items that are wrapped or in containers; for example, individually wrapped small instruments require about 15 minutes of initial heat penetration time. Dry heat has the advantage that instruments can be packaged and it is suitable for non-stainless steel, but the longer cycle time is a disadvantage.
Sterilisers must be of a suitable design (British Medical Association 1989) and must be regularly serviced and tested. On a more frequent basis, chemical indicators that change colour when exposed to specific temperatures for sufficient time (available from medical equipment suppliers) are useful to detect failure to achieve sterilising conditions, although they are not an absolute guarantee of sterility. Such indicators are available for steam and dry heat, and their use is recommended, particularly for hot-air sterilisers, where it is very difficult to predict the time required for packaged items.
Items that should be sterilised include scalpels, files, burrs, forceps, probes, nail clippers, tissue nippers, drill handpieces (if suitable), scissors, cryosurgical probes and instrument brushes. For materials that are obtained presterilised (e.g. dressing packs) it is important to check the integrity of packaging and the sterility indicator if present, discarding any items that are suspect.
These units reach very high temperatures (235–250°C) and very short process times are suggested by manufacturers, but note that, as only part of an instrument is treated, use must be immediate and sterilising conditions cannot be checked directly. Overall, their use cannot be recommended in a modern fully effective sterilisation programme and Medical Devices Agency (1998) advises that these units cannot give the quality assurance of sterility now required for podiatric practice.
Any serious attempt at aseptic technique precludes contact of the practitioner’s bare hands with damaged skin or exposed tissue (i.e. ‘no-touch’ techniques should be used). Routine wearing of sterile single-use gloves for such procedures should be adopted, with satisfactory tactile sensitivity achieved by the choice of an appropriate glove size and material. Apart from patient protection, there is the risk of contamination of podiatrists’ skin by HBV, HCV or HIV, and gloves should always be worn, after a suitable and sufficient risk assessment, for giving injections, changing dressings, cleaning wounds and for any invasive procedure. Cuts or abrasions on the hands should be covered by waterproof plasters, even when gloves are worn. Hands require washing after gloved procedures, as not all gloves are structurally perfect.
The wearing of masks is unnecessary for minor procedures, including routine dressing changes. Situations requiring masks include nail drilling (for the podiatrist’s protection) and nail surgery (where effective masks to filter/deflect organisms from the podiatrist’s mouth away from the operation site are necessary). Masks must be discarded after each use and not worn around the neck to be donned at intervals. Note that drilling of mycotic nails is unwise; not all debris is removed by the drill vacuum and significant amounts escape to contaminate the clinical environment and the practitioner.
The usual clinical coat is satisfactory for many procedures but needs protection when significant debris is expected, particularly from an infected patient, to prevent cross-infection occurring via the coat. A gown, plastic apron or adequately sized impermeable paper sheet or drape would serve the purpose. Purpose-made gowns or suits of appropriate material should be used for surgical procedures, and hair should be completely covered with a surgical cap. If surgical footwear is worn, avoid contamination of previously disinfected hands.
Initial disinfection of the patient’s skin should be followed by the use of sterile instruments whenever skin is penetrated, accidental breach is likely, or previously wounded tissue is being treated. Other materials used on or near such vulnerable areas (e.g. dressings) must also be sterile. Single-use sachets of antiseptics, etc., are preferred, but if communal ones are used individual quantities should be dispensed without contaminating the remainder. For example, small quantities can be poured from bottles into sterile pots, taking care not to touch the pot with the outside of the bottle, or solutions can be transferred using bulb pipettes, which should be disposable or cleaned and disinfected before reuse.
A sterile field is an area in which contamination is kept to an absolute minimum, although it is unlikely to be fully sterile in the microbiological sense. Such a field may be established by starting with a sterile surface and thereafter taking every care to avoid contamination of that area. The surface must not be touched by bare hands, and any necessary items are transferred aseptically onto it. The initial surface may be formed by a sterile drape/towel, or the unfolded inner (sterile) wrapping of a dressing pack, placed on a disinfected trolley top. If pack wrapping is used it must be unfolded by the corners, taking care not to reach over the contents as they are uncovered because contaminants are shed from skin and clothing. Additional items may be slid gently from their sterile wrapping onto the sterile field, or transferred using sterile forceps. Outer wrappings are always contaminated and should not be opened near the sterile field.
Sterile instruments should be arranged conveniently within reach in the field. After use (i.e. when they are contaminated) they should be placed elsewhere for disposal, or on a separate secondary field (e.g. clearly to one side) for possible reuse, but not back among sterile items. (Note that reuse on a patient may be contraindicated, for example if an infected or dirty lesion is being treated an instrument used earlier may reintroduce contamination into cleaned tissue.) It may prove convenient to use a sterile, empty steriliser tray as a secondary field, which can be used later to transport used instruments. Contaminated disposable items such as swabs should be disposed of immediately and should not re-enter the sterile field. Overall, there should be a one-way movement from sterility to patient to disposal or secondary field.
Hand disinfection is necessary before commencing dressing removal, after removal of the old dressing and after completion of the treatment, and at any time during the procedure when hands become contaminated. The old dressing is removed using disposable gloves (or forceps), which are immediately carefully disposed of with the dressing. After hand disinfection, sterile gloves are worn for the remainder of the treatment.
Microbiologically clean wounds should need no further cleaning, but practice varies. Sterile saline may be used, or antiseptic preparations for contaminated areas as considered necessary. After treatment, all used and unused materials from dressing packs should be disposed of, as they are no longer sterile.
Clinical waste should be placed carefully in bags and sealed before removal to prevent contamination of the area. Bags should be colour-coded to distinguish ordinary from contaminated waste (e.g. used dressings). There is no universal code, although yellow is used in the UK to denote contaminated waste for incineration, and practitioners should check local policy. Bags should not be overfilled and must be removed from the clinical area frequently, at least daily. They should be stored safely and protected from damage, until removed by disposal personnel.
Reusable instruments should be bagged or containerised for return to a central sterile supplies unit, or cleaned before return, or cleaned and resterilised in-house, depending on individual arrangements. Disposal of sharps requires great care to protect the practitioner and others from the risk of HBV, HCV and HIV infection; they must be discarded into a rigid container meeting approved specifications such as those given in BS7320:1990 (British Standards Institution 1990), and sent for incineration.
The design of operating facilities has evolved essentially for the needs of hospital surgery. Such facilities, with positive-pressure, high-efficiency filtered ventilation systems and various ancillary support areas, may sometimes be available to hospital practitioners, and indeed access to these may be necessary for the treatment of high-risk patients. However, the infection rates associated with minor surgery and ambulatory care services are low, and such complex facilities will not always be necessary.
In general surgery, airborne contamination appears to have little responsibility for postoperative sepsis (Ayliffe & Lowbury 1982, Ayliffe et al 1999), and during minor operations of short duration true airborne contamination is unlikely. The greatest risk will be from staff and the standards of their aseptic techniques but, nevertheless, adequate ventilation is important to reduce contamination dispersed from personnel while minimising entry of airborne contamination from outside. If extraction alone is used, there is a risk that extracted air will be replaced by contaminated air from surrounding areas (i.e. an inflow of ‘dirty’ air to the operation area). A compromise would be extraction to the outside in combination with sufficient filtered air inlets at selected sites to replace the extracted air. Practitioners intending to expand significantly into surgery should seek expert advice on their particular facilities to ensure that adequate safe ventilation is provided.
Operating rooms should be clearly separated from the general clinic and access restricted to essential personnel. They must be large enough to allow unimpeded movement without contact contamination from other people, furniture and surfaces. Only essential equipment and surgical supplies should be stored in the room, and their use should be restricted to surgery and associated procedures, such as immediate instrument sterilisation. Initial interview and preparation of the patient should take place elsewhere, and adequate facilities for scrubbing up and dressing of surgical staff must be provided.
Thorough cleaning of general surfaces should be carried out daily and the floor cleaned after each session; routine disinfection of floors should not be necessary. Known occurrences of contamination, especially by tissue or blood, do require disinfection. Overcrowding and vigorous movements should be avoided in operating rooms, as they increase airborne contamination. Clinical waste must be removed carefully to avoid contamination of the room or associated clean facilities.
Podiatrists could make more use of the expertise of microbiology laboratories. Laboratory investigation of samples from skin, nails or infected wounds can confirm infection and/or identify the pathogen, thus aiding the choice of the most effective patient management. In fungal infections, where symptoms are often insufficiently specific, definitive diagnosis can only be achieved by microscopy and culture techniques.
If possible, samples should be taken before commencing antimicrobial treatment, as this may inhibit the isolation of pathogens. The receiving laboratory will advise on containers, and packaging for samples. Usually, swabs from wounds are collected into capped containers, while skin scrapings and nail clippings are collected in paper sachets that maintain dry conditions and prevent overgrowth by saprophytes. As much material as possible should be collected to increase the probability of isolating the pathogen. Specimens must be taken carefully, avoiding contamination of self, the clinical surroundings and the outside of the container. As much clinical information as possible should be provided to aid investigation.
Any practice, large or small, should have a written control policy. This should include instructions on the sterilisation of various items, the use and concentrations of disinfectants or antiseptics, waste disposal, the treatment of spillages, etc. For the individual practitioner this will serve as a useful aide memoire, while in larger units all staff should be able to consult it for information on agreed procedures. Health service and hospital podiatrists should ensure compliance with the local health authority or hospital policy on infection control. In units with several staff, there should be a designated person with responsibility for implementing and monitoring the control measures.
Cleaning staff must be given clear instructions on methods required and adequate facilities, and they should be given time to discharge their duties effectively.
Elaborate infection surveillance systems are not necessary, in view of the low risk associated with well-run ambulatory care facilities. However, full note should be taken of any infections that apparently result from podiatric treatment, and the overall incidence of these should be reviewed periodically. An unduly high incidence should alert staff to review control measures, and seek expert advice if necessary.
Infection-control personnel are employed by health authorities and hospitals, and these local sources are the best initial point of contact for any practitioner. Much published information is also available, including material from public health laboratories and government departments, and it is continually being augmented.
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