1 Infection control in the health care setting Michaela Dingová
1. 1 Infectious process and its control in health care c are facilities
People receiving health care, whether in a hospital or outpatient clinic, are at risk of becoming infected. About 5-10 % of patients admitted to hospitals in the United States develop these particular infections that are normally related to a procedure or treatment used to diagnose or treat the patient’s illness or injury. These hospital-acquired infections, also called nosocomial infections, are usually ones that first appear two days (48 – 72 hours) after the patient is admitted to a hospital or other health care setting. Approximately 25% of these infections can be prevented by healthcare professionals taking proper precautions when caring for patients. Nosocomial infection has the same components as infection in general; the main difference is that nosocomial infections are associated with the delivery of health care services in a health care facility. For these reasons it is necessary to comprehend some basics related to the infection process. Definitions of key terms Microorganisms are the causative agents of infection. They include bacteria,
viruses, fungi and parasites. For infection prevention purposes, bacteria can be further divided into three categories: vegetative (e.g. staphylococcus), mycobacteria (e.g. tuberculosis) and endospores (e.g. tetanus). Of all the common infectious agents, endospores are difficult to kill due to their protective coating. Resident microorganisms (normal resident flora) are not harmless either beneficial, because they perform an essential function in the body. Some microorganisms produce substances which are lethal to related strains of bacteria or repress the growth of other microorganisms. (Table 1.1) Colonization means that pathogenic (illness or disease causing) organisms are present in a person (i.e. they can be detected by cultures or other tests) but do not cause symptoms or clinical findings (i.e. cellular changes or damage). Infection means that the colonizing organisms are causing an illness or disease (cellular response) in the person. Coming in contact with and acquiring new organisms, while increasing the risk of infection, usually does not lead to infection because the body’s natural defence mechanisms, including the immune system, are able to tolerate and/or destroy them. Thus, when organisms are transmitted from one person to another, colonization
rather than infection generally is the result. Colonized persons, however, can be a major source of transfer of pathogens to other persons (crosscontamination), especially if the organisms persist in the person (chronic carrier), such as with HBV, HCV and HIV. Table 1.1 Example of common resident microorganisms Body area Microorganisms Staphylococcus epidermidis, Skin
Nasal passages Oropharynx Mouth Intestine
Urethral orifice Urethra (lower) Vagina
Propionibacterioum acnes, Staphlylococcus aureus, Corynebacterium xerosis, Pityrosporum oxale (yeast) Staphylococcus aureus Staphylococcus epidermidis Streptococcus pneumoniae Lactobacillus, Bacteroides, Actinomyces Bacteroides, Fusobacterium, Eubacterium, Lactobacillus, Streptococcus, Enterobacteriacae, Shigella, Escherichia coli Staphylococcus epidermidis Proteus Lactobacillus, Bacteroides, Clostridium, Candida albicans
Infectious circle
There must be an infection agent – something that can cause illness (virus, bacteria, fungus etc.). The agent must have a place it can live; this is called a host or reservoir. Many microorganisms that cause disease in humans (pathogenic organisms) multiply in humans (cells) and are transmitted from person to person. Some are transmitted through contaminated food or water (typhoid), faecal matter (hepatitis A and other enteric viruses) or from the bites of infected animals (rabies from dog, fox) and insects (malaria from mosquitoes). The agent must have the right environment outside the host to survive. After the microorganism leaves its host, it must have a suitable environment in which to survive until it infects another person. For example, the bacteria that cause tuberculosis can survive in the sputum for weeks, but will be killed by sunlight within a few hours. There must be a person who can catch the disease. People are exposed to disease-causing agents every day but do not always get sick. As for a person to catch an infectious disease (e.g. mumps, measles or chicken pox) she/she must be susceptible to that disease – a
susceptible host.
The main reason most people do not catch the disease is that they have been previously exposed to it (e.g. vaccinated for it or previously had the disease) and their body’s immune system now is able to destroy the agents when they enter the body. An agent must have a way to move from its host to infect the next susceptible host (Figure 1.1) Infectious (communicable) diseases are spread mainly in these ways – methods of transmission: - airborne: through the air (chicken pox or mumps); - blood or body fluids: if blood or body fluids contaminated with HBV or HIV comes in contact with another person, such as through a syringe, he/she may become infected; - contact: either direct (touching an open wound or draining pustule) or indirect (touching an object contaminated with blood or other bodily fluids); - faecal-oral: swallowing food contaminated by human or animal faeces (e.g. putting your fingers in your mouth after handling contaminated objects without first washing your hands); - foodborne: eating or drinking contaminated food or liquid that contains bacteria or viruses (hepatitis A from eating raw oysters); - animal or insect-borne: contact with infected animals or insects through bites, scratches, secretions or waste. Infection prevention deals primarily with preventing the spread of infectious diseases through the air, blood or body fluids and contact, including faecaloral and foodborne means of transmission. .
Purpose
The main purpose is to prevent and minimize the onset and outbreak of infection via preventive actions. Infection prevention largely depends on placing barriers between a susceptible host (person lacking effective natural or acquired protection) and the microorganisms. Protective barriers are physical, mechanical or chemical processes that help prevent the spread of infectious microorganisms from: - person to person (patient, health care professionals, visitors); and/or - equipment, instruments and environmental surfaces to people.
Figure 1.1 The disease transmission circle
Adapted from HIV/AIDS reference library for nurses, vol.3. 1993 Regional Office for the Western Pacific (WPRO) & WHO, ISBN 9-29061-112-x, p. 7. Collaborative level
- interdependent All health care professionals and other staff are responsible for conducting an infection prevention regimen. Even the students, using the medical environment for educational purposes, are responsible for maintaining infection precautions with the aim not to contribute to the onset and spread of infections. Expected patient outcomes
- the risk of onset and spread of infection will be minimized following infection prevention precautions,
- factors associated to the infection will be controlled in a current/up to date status of knowledge, - patient is not exposed to infectious dangerous, - patient will not develop signs or symptoms symptoms of infection whilst staying in health care settings. 1.2 Hospital acquired infection
Patient care is provided in health care settings which range from highly equipped clinics and technologically advanced university hospitals to frontline units with only basic facilities. Hospital-acquired infections represent an increasing significant problem despite progress in public health and hospital care, infections continue to develop in hospitalized patients and may also affect hospital staff. A nosocomial infection – also called “hospital acquired infection” is: “An infection acquired in hospital by a patient who was admitted for a reason other than that infection. An infection occurs in a patient in a hospital or other health care facility in whom the infection was not present or incubating at the time of admission. This includes infections acquired in the hospital but appearing after discharge, and also occupational infections among staff of the facility.”
Definition
Nosocomial infections, also called “hospital-acquired infections”, are infections acquired during hospital care which are not present or incubating at admission. Infections occurring more than 48 hours after admission are usually considered nosocomial. Definitions to identify nosocomial infections have been developed for specific infection sites (e.g. urinary, pulmonary). These characteristic features – site, time and health care facility relation are referred by the Centre for Diseases Control and Prevention (CDC) in the US, and are adopted worldwide. These are used for surveillance of nosocomial infections. They are based on clinical and biological criteria and include approximately 50 potential infection sites. Changes in health care delivery have resulted in shorter hospital stays and increased outpatient care. It has been suggested that the term nosocomial infections should encompass infections occurring in patients receiving treatment in any health care facility. Infections acquired by staff or visitors to the hospital or other health care facility may be also considered to be nosocomial infections.
Frequency of infection
Nosocomial infections, as was already mentioned, occur worldwide, affect both developed and resource-poor countries. Infections acquired in health care settings are among the major causes of death and increased morbidity among hospitalized patients. They are a significant burden both for the patient and for public health. For illustrative reasons, WHO stated in 2002 that over 1.4 million people worldwide suffer from infectious complications acquired in hospital. The highest frequencies of nosocomial infections were reported from hospitals in the Eastern Mediterranean and South-East Asia Regions (11.8 and 10.0% respectively), with a prevalence of 7.7 and 9.0% respectively in the European and Western Pacific Regions. The most frequent nosocomial infections are infections of surgical wounds, urinary tract infections and lower respiratory tract infections. The highest prevalence of nosocomial infections occurs in intensive care units and in acute surgical and orthopaedic wards. Infection rates are higher among patients with increased susceptibility because of old age, underlying disease or treatment, especially chemotherapy and immunosupression. Impact of nosocomial infections
Hospital-acquired infections add to the functional disability and emotional stress of the patient and they may, in some cases, lead to disabling conditions that reduce the quality of life. Nosocomial infections are also one of the leading causes of death. The economic costs are considerable especially due to increased length of stay of infected patients, use of drugs, the need for isolation and the use of additional laboratory and other diagnostic studies. The advancing age of patients admitted to health care settings, the greater prevalence of chronic diseases among admitted patients and the increased use of diagnostic and therapeutic procedures which affect the host defences will provide continuing pressure on nosocomial infections in the future. Factors influencing the development of nosocomial infections
Many factors promote infection among hospitalized patients: decreased immunity among patients; increasing variety of medical procedures and invasive techniques creating potential routes of infection; and the transmission of drug-resistant bacteria among crowded hospital populations, where poor infection control practices may facilitate transmission. Some of them are discussed in detail as follows:
The microbial agent,
to which the patient is exposed during hospitalization. Contact between the patient and a microorganism does not by itself necessarily result in the development of clinical disease – other factors influence the nature and frequency of nosocomial infections. The likelihood of exposure leading to infection depends partly on the characteristics of the microorganisms, including resistance to antimicrobial agents, intrinsic virulence and amount (inoculum) of infective material. Many different bacteria, viruses, fungi and parasites may cause nosocomial infections. Infections may be caused by a microorganism acquired from another person in the hospital (cross-infection) or may be caused by the patient’s own/resident flora (endogenous infection). Some organisms may be acquired from an inanimate object or substances recently contaminated from another human source (environmental infection). Before introduction of basic hygienic practices and antibiotics into medical practice, most hospital infections were due to pathogens of external origin (foodborne and airborne diseases, gas gangrene, tetanus, etc.) or were caused by microorganisms not present in normal flora of the patients (e.g. diphtheria, tuberculosis). Progress in the antibiotic treatment of bacterial infections has considerably reduced mortality from many infectious diseases. Most infections acquired in hospital today are caused by microorganisms which are common in general population, in whom they cause no or only milder disease than among hospital patients (Staphylococcus aureus, oagulase-negative staphylococci, enterococci, Enterobacteriaceae). Patient susceptibility (important factors on patient side) influencing the acquisition of infection includes age, immune status, underlying disease and diagnostic and therapeutic interventions. The extremes of life phases, like infancy and old age, are associated with decreased resistance to infection. Patients with chronic diseases such as malignant tumours, leukaemia, diabetes mellitus, renal failure or the acquired immunodeficiency syndrome (AIDS) have an increased susceptibility to infections with opportunistic pathogens. The latter are infections with organism(s) that are normally part of normal bacterial flora in the human, but may become pathogenic when the body’s immunological defences are compromised. The patients, who are more susceptible to infections – not only nosocomial, but infections in general, are called immunocompromized. Immunosuppressive drugs or irradiation may lower resistance to infection. Injuries to skin or mucous membranes bypass natural defence mechanisms. Malnutrition is also a risk. Many modern diagnostic and therapeutic procedures, such as biopsies,
endoscopic examinations, catheterization, intubation/ventilation and suction and surgical procedures in general increase the risk of infection. Contaminated objects or substances may be introduced directly into i nto tissues or normally sterile sites such as the urinary tract and the lower respiratory tract. of health care settings are represented by the environment where both infected persons and persons at increased risk of infection congregate. Patients with infections or carriers of pathogenic microorganisms admitted to hospital are potential sources of infection for patients and staff. Patients who become infected in the hospital become a further source of infection. Crowded conditions within the hospital, frequent transfers of patients from one unit to another and the concentration of patients highly susceptible to infection in one area (e.g. newborn infants, burn patients and intensive care) all contribute to the development of nosocomial infections. Microbial flora may contaminate objects, devices and materials which subsequently contact susceptible body sites of patients. Many patients receive antimicrobial drugs (antibiotics, chemotherapeutical drugs, antiviral drugs, antifungal/antimycotic drugs). Through the selection and exchange of genetic resistance elements, antibiotics promote the emergence of bacterial resistance; microorganisms in the normal human flora sensitive to the given drug are suppressed, while resistant strains persist and may become endemic in the hospital. The widespread use of antimicrobials for therapy or prophylaxis (including topical) is the major determinant of resistance. Antimicrobial agents are, in some cases, becoming less effective because of resistance. As an antimicrobial agent becomes widely used, bacteria resistant to this drug eventually emerge and may spread in the health care setting. Many strains of pneumococci, staphylococci, enterococci and tuberculosis are currently resistant to most or all antimicrobials which were once effective. Multiresistant Klebsiella, Pseudomonas aeruginosa and MRSA (Methicilin-resistant staphylococcus) are prevalent in many hospitals. This problem is particularly critical in developing countries where more expensive second-line antibiotics may not be available or affordable. A high frequency of nosocomial infections is the evidence of poor quality of health service delivery. Many factors contribute to the frequency of nosocomial infections and many of them are hardly manageable such as: immunocompromised status, need for invasive examinations and treatments, patient care practices and the hospital environment - all may facilitate the transmission of microorganisms among Environmental factors
patients. The selective pressure of intense antibiotic use promotes antibiotic resistance. While progress in the prevention of nosocomial infections has been made, changes in medical practice continually present new opportunities for the development of infection. i nfection. Nosocomial infection sites
An example of the distribution of sites of nosocomial infections is shown in Figure 1.2 Figure 1.2 Distribution of sites of nosocomial infections
Adapted from Prevention of hospital-acquired infections, A practical guide. 2002. 2nd ed., WHO, Department of Communicable Disease, Surveillance and Response, p. 5. Urinary infections
They These are the most common nosocomial infections; 80% of infections are associated with the use of an indwelling bladder catheter. Urinary infections are associated with less morbidity than other nosocomial infections, but can occasionally lead to bacteraemia and death. Infections are usually defined by microbiological criteria: positive quantitative urine culture (≥105 microorganisms/ml, with a maximum of 2 isolated microbial species). The bacteria responsible arise from the gut flora, either normal Escherichia coli) or are acquired in hospital (multiresistant Klebsiella).
Surgical site infections
Surgical site infections are also frequent: the incidence varies from 0.5 to 15%. It depends on the type of operation and underlying patient status. These infections represent a significant problem limiting the potential benefit of surgical intervention. The impact on hospital costs and postoperative length of stay is considerable. The definition is mainly clinical: purulent discharge around the wound or the insertion site of the drain, or spreading cellulitis from the wound. Infections of the surgical wound (whether above or below the aponeurosis) and deep infections of organs or organ spaces are identified separately. The infection is usually acquired during the operation itself; either exogenously (e.g. from the air, medical equipment, surgeons and other staff), endogenously from the flora on the skin or in the operative site, or, rarely, from blood used in surgery. The infecting microorganisms are variable, depending on the type and location of surgery and antibiotics received by the patient. The main risk factor is the extent of contamination during the procedure (clean, clean contaminated, contaminated, dirty), which is to a large part dependent on the length of the operation and the patient’s general condition. Other factors include the quality of surgical technique, the presence of foreign bodies including drains, the virulence of the microorganisms, concomitant infection at other sites, the use of preoperative shaving and the experience and professionalism of the t he surgical team. Nosocomial pneumonia
Nosocomial pneumonia occurs in several different patient groups. The risk is highest for patients on ventilators in intensive care units. The rate of ventilator-associated pneumonia is 3% per day. There is a high fatality rate associated with this kind of pneumonia, although the risk attributable is difficult to determine because patient comorbidity is also so high. Microorganisms colonize the stomach, upper airway and bronchi and cause infection in the lungs (pneumonia). They are often endogenous (digestive system or nose and throat of a patient) but may be exogenous, the most often from contaminated respiratory equipment. The definition of pneumonia may be based on clinical and radiological criteria which are readily available but non-specific (recent and progressive radiological opacities of the pulmonary parenchyma, purulent sputum and recent onset of fever). Diagnosis is more specific when quantitative microbiological samples are obtained using specialized protected bronchoscopy methods. Known risk factors for infection include the type and duration of ventilation, the quality of
respiratory care, the severity of the patient’s condition and previous use of antibiotics. Apart from ventilator-associated pneumonia, patients with seizures or a decreased level of consciousness are at risk from nosocomial infection, even if not intubated. Viral bronchiolitis (respiratory syncytial virus, RSV) is common in children’s units and influenza and secondary bacterial pneumonia (hypostatic, due to inappropriate ventilation of basal parts of lungs) may occur in institutions for the elderly. With highly immunocompromised patients, Legionella spp. and Aspergillus pneumonia may occur. Nosocomial bacteraemia
These infections represent a small proportion of nosocomial infections (approximately 5%) but case fatality rates are high – more than 50% for some microorganisms. The incidence is increasing; particularly for certain organisms such as multiresistant coagulase-negative Staphylococcus and Candida spp. Infection may occur at the skin entry site of the intravascular device or in the subcutaneous path of the catheter (tunnel infection). Organisms colonizing the catheter within the vessel may produce bacteraemia without visible external infection. The resident or transient cutaneous flora is the source of infection. The main risk factors are the length of catheterization, level of asepsis at insertion and continuing catheter care. Other nosocomial infections
The four most frequent and significant nosocomial infections were mentioned, but there are many other potential sites of infection. For example, skin and soft tissue infections like open sores (ulcers, burns and bedsores) encourage bacterial colonization and may lead to systemic infection. Also the common nosocomial infection is gastroenteritis in children ( rotavirus is a chief pathogen). Clostridium difficile is the major cause of nosocomial gastroenteritis in adults in developed countries. Other potential sites of infections are e.g. sinuses (sinusitis), eyes and conjunctiva, endometritis and other infections of the reproductive organs following childbirth. 1.3 Prevention of hospital acquired infection
Prevention of nosocomial infections requires a systematic approach (integrated, monitored programme) which includes the following foll owing key components:
- limiting transmission of organisms between patients in direct patient care through adequate hand washing and glove use and appropriate aseptic practice, isolation strategies, sterilization and disinfection practices and -
laundry, controlling environmental risks for infection, protecting patients with appropriate use of prophylactic of prophylactic antimicrobials, nutrition and vaccinations, limiting the risk of endogenous infections by minimizing invasive
procedures and promoting optimal antimicrobial use, - surveillance of infections, identifying and controlling outbreaks, - prevention of infection in staff members, - enhancing staff patient care practices and continuing staff education. Infection control is the responsibility of all health care professionals – physicians, nurses, therapists, pharmacists as well as managers and others like medical or nursing students, who use hospital setting for educational reasons. Definition of key terms The terms asepsis (aseptic technique), antisepsis, decontamination, cleaning, disinfection and sterilization are often confusing. For the purposes
of understanding the following topic, these definitions are going to be used: Decontamination is the process that makes inanimate objects safer to be handled by staff before cleaning (i.e. inactivates HBV, HCV and HIV and reduces, but does not eliminate, the number of other contaminating microorganisms). Ideally, soiled surgical instruments, gloves and other items should always be handled by staff wearing gloves or using forceps. Because this is not always possible, it is safer first to soak these soiled items for a short time in a disinfectant solution (e.g. for 10 minutes in 0.5% chlorine solution) especially if they will be cleaned by hand. Metal objects should then be rinsed to prevent corrosion before cleaning. Other objects that should be decontaminated, by wiping with the 0.5% chlorine solution, include large surfaces (e.g. pelvic examination or operating tables) and equipment that comes into contact with patients’ blood or body fluids, secretions or excretions. Cleaning is the process that physically removes all visible dust, soil, blood or other body fluids from inanimate objects as well as removes sufficient numbers of microorganisms to reduce risks for those who touch the skin or handle the object. It consists of thoroughly washing with soap or detergent
and water, rinsing with clean water and drying. Cleaning is an essential prerequisite of any disinfection or sterilisation. Disinfection is the process used to reduce the numbers of micro-organisms by boiling, steaming or the use of chemical disinfectants, but which may not destroy bacterial spores or some viruses. Disinfection is considered to reduce the numbers of micro-organisms to a level that is safe for the purpose for which the piece of equipment is intended. High-level disinfection (HLD) is the process that eliminates all microorganisms except some bacterial endospores from inanimate objects. Antiseptics are chemical preparations used on skin or tissue. Sterilization is the process that eliminates all microorganisms (bacteria, viruses, fungi and parasites) including bacterial endospores from inanimate objects by high-pressure steam (autoclave), dry heat (oven), chemical sterilants or radiation. Risk stratification
Acquisition of nosocomial infection is determined by both patient factors, such as degree of immunocompromise and interventions performed which increase the risk. The level of patient care may differ for patient groups at different infectious risk. A risk assessment is helpful to categorize patients and plan infection control interventions. The risk for different patient groups is stratified in Table 1.2. Table 1.3 provides a hierarchy of patient care practice for different levels of patient risk. Table 1.2 Categorisation of infectious risk by patients and interventions features Risk of infection Type of patients Type of procedure not immunocompromised, non-invasive 1. Minimal 2. Medium
no significant underlying disease infected patients, or patients with some risks factors (age, neoplasm)
no exposure to biological fluids* exposure to biological fluids, invasive nonsurgical procedure (e.g. peripheral venous catheter, introduction of urinary catheter) surgery, high-risk invasive procedures (e.g. central venous catheter, endotracheal intubation)
severely immunocompromised patients (<500 WBC/ml), multiple trauma, severe burns, organ transplant * biological fluids include blood, urine, cerebrospinal fluid (CSF), fluid from body cavities 3. High
Table 1.3 Aseptic measures appropriate for diff erent levels of risk of infection Risk of Asepsis Antiseptics Hands Clothes Devices* infection clean none simple clean clean or 1. handwashing professional disinfected at Minimal
uniform
protection against blood and biological fluids as appropriate surgical specific surgical surgical 3. High asepsis major handwashing clothes: products or surgical dress, hand masks, caps, disinfection sterile by rubbing gloves *all devices entering body cavities must be sterile 2. Medium
asepsis/ standard medical antiseptic asepsis products
or hand disinfection hygienic handwashing or hand disinfection by rubbing
intermediate or low level disinfected at high lever or sterile
sterile (whenever possible) or disinfected at high level
1.3.1 Reducing person-to-person transmission
The importance of hands in the transmission of hospital infections has been well demonstrated so can be minimized with appropriate hand hygiene and decontamination. Staff compliance with hand washing is frequently suboptimal. This is due to a variety of reasons, for example: lack of appropriate equipment, high staff to patient ratios, allergies to washing products, insufficient knowledge about risks, too long duration recommended for washing and the time required. All staff must maintain good personal hygiene. Nails must be clean and kept short. False nails should not be worn. Hair must be worn short or pinned up. Beard and moustaches must be kept trimmed short and clean. Staff can normally wear a personal uniform or street clothes covered by a white coat, (but it is not usual in our conditions). In special areas such as burn or intensive care units, uniform trousers and a long-sleeved gown are required for men and women. In other units, women may wear a short sleeved dress. The working outfit must be made of a material easy to wash and decontaminate. If possible, a clean outfit should be worn each day. An outfit must be changed after exposure to blood or if it becomes wet through excessive sweating or other fluid exposure. In aseptic units and in operating rooms, staff must wear dedicated shoes, which must be easy to clean. In
aseptic units, operating rooms, or performing selected invasive procedures, staff must wear caps or hoods which completely cover the hair. Masks are an effective barrier against microorganisms. Masks are used in various situations; mask requirements differ for different purposes. Staff wear masks to work in the operating room, to care for immunocompromised patients, to puncture body cavities for patient protection. A surgical mask is sufficient. Staff must wear masks when caring for patients with airborne infections, or when performing bronchoscopies or similar examination for their own protection. A high-efficiency mask is recommended. Patients with infections which may be transmitted by the airborne route must use surgical masks when outside their isolation room. Gloves are used for many reasons such as: - patient protection: staff wear sterile gloves for surgery, care for immunocompromised patients, invasive procedures which enter body cavities, - disposable gloves should be worn for all patient contact where hands are likely to be contaminated, or for any mucous membrane contact, - staff protection: staff wear disposable gloves to care for patients with communicable disease transmitted by contact, to perform bronchoscopies or similar examinations. Hands must be washed and/or disinfected when gloves are removed or changed. Disposable gloves should not be reused. The materials most frequently used for gloves are latex or polyvinyl-chloride. Quality, i.e. absence of porosity or holes and duration of use, varies considerably from one glove type to another. 1.3.2 Preventing transmission from the environment, instruments and tools
To minimize the transmission of microorganisms from equipment and the environment, adequate methods for cleaning, disinfecting disi nfecting and sterilizing must be in place. Written policies and procedures which are updated on a regular basis must be developed for each type of health care setting. Routine cleaning of the hospital environment is necessary to ensure a hospital environment which is visibly clean and free from dust and soil. Almost 90% of microorganisms are present within “visible dirt” and the purpose of routine cleaning is to eliminate this dirt. Neither soap nor detergents have antimicrobial activity and the cleaning process depends essentially on mechanical action. There must be organisational policies or
recommendations specifying the frequency of cleaning and cleaning agents used for walls, floors, windows, beds, curtains, screens, fixtures, furniture, baths and toilets and all reused medical devices. Methods must be appropriate for the likelihood of contamination and necessary level of asepsis. Decontamination is the first step in processing soiled (contaminated) surgical instruments, gloves and other items, especially if they will be cleaned by hand (e.g. briefly soaking contaminated items in 0.5% chlorine solution or other locally available disinfectants, making them safer for handling during cleaning). Larger surfaces, such as examination and operating tables, laboratory bench tops and other equipment that may have come in contact with blood or other body fluids also should be decontaminated. Wiping with a suitable disinfectant (e.g. 0.5% chlorine solution or 1–2% phenol) is a practical, inexpensive way to decontaminate them. After instruments and other items have been decontaminated, they need to be cleaned and finally either sterilised or high-level disinfected (Figure 1.3) Figure 1.3 Instrument processing
1.4 Disinfection
Disinfection removes microorganisms without complete sterilization to prevent transmission of organisms between patients. Disinfection procedures must: - meet criteria for the killing of organisms, - have a detergent effect, - act independently on the number of bacteria present, the degree of hardness of the water or the presence of soap and proteins (that inhibit some disinfectants), - be acceptable in the hospital environment (easy to use; non-volatile; not harmful to equipment, staff or patients; free from unpleasant smells; effective within a relatively short time). Different products or processes achieve different levels of disinfection. These are classified as high-, intermediate- or low-level disinfection. Table 1.4 provides characteristics of the three levels. In using a disinfectant, the manufacturer’s recommendations must always be followed. High-level disinfection (critical) will destroy all microorganisms, with the exception of heavy contamination by bacterial spores. Intermediate disinfection (semi-critical) inactivates Mycobacterium tuberculosis, vegetative bacteria, most viruses and most fungi, but does not necessarily kill bacterial spores. Low-level disinfection (non-critical) can kill most bacteria, some viruses and some fungi, but cannot be relied on for killing more resistant bacteria such as M. tuberculosis or bacterial spores. These levels of disinfection are attained by using the appropriate chemical product in the manner appropriate for the desired level of disinfection. Table 1.4 Categorisation of infection risk to the patient from contact with an item Level of Spectrum of Active Factors affecting disinfection activity of ingredients the efficacy of a required disinfectant potentially disinfectant capable of satisfying these spectra of activity sporicidal peracetic acid - concentration High
mycobactericidal virucidal fungicidal bactericidal
chlorine dioxide formaldehyde glutaraldehyde sodium hypochloride
- exposure time - temperature - presence of organic matter - pH
Intermediate
Low
tuberculocidal virucidal vungicidal bactericidal bactericidal
stabilized hydrogen peroxide succinaldehyde phenol derivates ethyl and isopropyl alcohols quaternary ammonium amphiprotic, amino acids
- presence of calcium or magnesium ions (e.g. hardness of the water used for dilution) - formulation of the disinfectant
1.4.1 Methods of disinfection and type of disinfectants
The two main methods of disinfection are the use of an automatic washer disinfector or the use of chemical disinfectants. Automatic washer-disinfectors
Washer-disinfectors combine mechanical cleaning and heat disinfection and are used to process items for reuse (e.g. safety spectacles) or to tender items clean and safe prior to sterilisation. Items that are compatible with washerdisinfectors should be processed in this way in preference to the use of chemical disinfectants. Items may be disinfected using a washer-disinfector in the Hospital Sterilisation and Disinfection Units. Chemical disinfection
Chemical disinfectants can be used for: - blood and body fluid spillage, - hard surface/equipment decontamination, - disinfection of equipment that is damaged by heat (e.g. flexible endoscopes), - hand and skin disinfection (prior to invasive procedures), - environmental disinfection (e.g. during and after outbreaks of infection). Chemical disinfectants can fail if not selected and used properly. Phenolics,
the mechanism of these agents is referred as the cause of cytoplasmic membrane disruption and coagulation of proteins of vegetative cells. Examples: phenol (carbolic acid), hexachlorophene, O-phenylphenol. destroy the cell membrane of a microorganism and thus cause the lysis and death of a cell. The strong oxidizers are chlorine and oxides. In clinical use there is a hydroxide peroxide, per-acetic acid, chlorine
Oxidizing agents
dioxide. Mechanisms of effect - vegetative cells are killed by coagulation and oxidation of cellular proteins. Chlorine examples: Chlorine gas, Clorox and other hypochlorite bleaches (NaClO). Oxidizing examples: Ozone, hydrogen peroxide, benzoyl peroxide, potassium permanganate. (Quats) act as low-level disinfectants. They are effective against bacteria but do not kill Pseudomonas aeruginosa and bacterial spores. They include benzalkonium chloride (BAC), cetypyridium chloride (Cetrim, CPC). They are used for skin disinfection. Effect is caused by cytoplasmic membrane disruption of vegetative cells. Examples: Zephiran and other quaternary ammonium compounds. Quaternary ammonium compounds
Alcohols (ethanol, isopropanol) are usually used as antiseptics. Alcohols like
ethanol (60-90%), 1-propanol (60-70%) and 2-propanol/isopropanol (7080%) are used to disinfect skin before injections. Vegetative cells are killed by coagulation of proteins as well as dehydration and lipid solvation by effect of alcohols. Examples: Ethyl alcohol and isopropyl alcohol are used in concentrations of 70% to 90%. The alcohols exhibit reduced efficacy as disinfectants when used at concentrations above 90%. At concentrations below 45%, the alcohols are ineffective as disinfectants. Alkylating agents
Formaldehyde provides for disinfection when used as a solution (formalin) or sterilization when used as a gas. This T his agent produces protein coagulation. Glutaraldehyde provides for either sterilization or disinfection depending upon the concentration. This agent produces protein coagulation. Example: Cidex, Ethylene oxide gas. is used for skin and wound disinfection. It is usually a water-based solution that contains povidone-iodine (Betadine). It is far better tolerated than previous alcohol-based solutions. The great advantage of iodine antiseptics is the wider scope of antimicrobial activity, killing even endospores. The mechanism of killing vegetative cells is provided by protein coagulation. Examples: Tincture of iodine, Betadine, Isodine. Iodine
Other agents Heavy metal compounds
The agents provide for disinfection when used in high concentrations and stasis when used in low concentrations. When used in high concentrations, the agents kill vegetative cells by enzyme denaturation. When used in low concentrations, the agents produce enzyme inhibition. Examples: Mercurochrome, merthiolate, silver nitrate, mercury bichloride. Organic and mineral acids The agents provide for disinfection. The agents produce protein coagulation.
Examples: Calcium propionate, acetic acid, esters of benzoic acid. 1.5 Sterilization
Sterilization is the destruction of all microorganisms. Operationally this is defined as a decrease in the microbial load by 106 microorganisms. Sterilization can be achieved by either physical or chemical means. Sterilization is required for medical devices penetrating sterile body sites, as well as all parenteral fluids and medications. For reprocessed equipment, sterilization must be preceded by cleaning to remove visible soil. The object must be wrapped for sterilization. Only a wrapped sterilized object should be described as sterile. Packaging materials include: - paper packages/covers which prevent contamination if intact, maintain sterility for a long period, can act as a sterile field and can also be used to wrap dirty devices after the t he procedure (e.g. Lukasterick®) - selected plastics, paper-folic only polyethylene and polypropylene are suitable for sterilization with ethylene oxide. - non-woven disposable textile containers can be used only if they contain material intended for a single treatment procedure for a single patient; they must be provided with a filter and a valve, which must be monitored regularly, - metal perforated containers (called “bowls”) – used for sterilising swabs, sterile textiles used in operating rooms. The items are considered to be sterile for 24 hours if the bowl has been opened. If the container is not open, items are referred to as being sterile for 48 hours after the sterilisation process. These containers are not used anymore in Slovakia due to sucking in nonsterile air.
- glass container with lids (called “cassette”) – used for storage of metal instruments after their sterilisation. These are sterile for 24 hours if the cassette has been opened. If the cassette is not open, items are referred to as being sterile for 48 hours after the sterilisation process. Written policies based on state medical laws are developed and updated on a regular basis for each type of health care setting as institutional guidelines e.g. as for handling with different types of sterile tool covers. Table 1.5 shows directed expiration time of different covers in the Slovak republic. Table 1.5 Expiration time of different kinds of wrapping and methods of sterilisation Wrapping/cover Methods of Expiration time* Note material sterilisation Bowls, cassettes
steam sterilisation/ autoclaving
Paper (Lukasterick®)
48 hours
protected (if not protected expiration time is 24 hours only)
3 months 6 months
sealed** wrapping
Paper-folic sealed wrapping Cassettes Paper-folic
heat sterilisation radiation
Foil
Paper (Lukasterick®) Paper-folic Foil 0,5 mm
48 hours 6 months 6 months
Formaldehyd sterilisation Ethylenoxid sterilisation
sealed wrapping
3 months
only in a case of re-sterilisation, the manufacturer date of expiry is valid in a first place sealed wrapping
6 months
sealed wrapping
6 months
sealed wrapping
*time
in which tools after some kind of sterilisation and wrapping are referred to as being sterile ** sealed wrapping protects wrapped sterile material and so extends expiration time
Packaging material - paper and plastic and paper-folic and non-reusable textiles must be used only once.
Packaging systems for sterile items have to meet local legislation and/or regulations, but must nevertheless: - provide adequate seal integrity and be tamperproof, - provide an adequate barrier to particulate matter, - withstand physical conditions of the sterilization sterilizat ion process, - provide an adequate barrier to fluids, - permit adequate air removal, - allow penetration and removal of sterilant (water steam, chemical steam) - protect package content from physical damage, - resist tears and punctures, - be free of holes, - be free of toxic ingredients, - have a positive cost/benefit ratio, - be used according to the manufacturers’ written instructions, - be dated. Proper storage conditions are essential to maintain the integrity of sterilized items. The end-user must check the integrity of the package before use. The sterilization of endoscopes, mini-invasive instruments and robotic instrumentation is necessary, but may present a particular challenge because of the configuration of these instruments - high disinfection/chemical sterilisation is acceptable. There are strong regulations related to the quality control parameters of sterilization. The quality control process must record information on the sterilization processing cycle including load number, load content, temperature and time exposure record in chart and regular (at least daily) physical/chemical testing. The chemical indicator changes colour to indicate that the item passed through the sterilisation process. However, chemical indicators do not necessarily indicate that an item is sterile. Regular (at least weekly) biological testing is provided by using biological indicators. They should be used regularly to monitor the sterilisation process (e.g. steam processing used Bacillus stearothermophilus as a biological indicator). Regular maintenance must be performed and documented. The following records must be maintained for all sterilisations: - date of service, - model and serial number, - location, - descriptions of replaced parts, - biological testing records,
- name and signature of controller. 1.5.1 Methods of sterilization Autoclaving
Heat is the most commonly used source for sterilisation. Heat autoclaves may use dry heat (see below) or steam heat. Steam heat autoclaves consist of a sterilization chamber surrounded by a steam chamber. Now autoclaves commonly use steam heated to 121 °C or 134 °C under a pressure of 2 or 3 atmospheres. To achieve sterility, a holding time of at least 20 minutes at 121°C (2 atm) or 10 minutes at 134°C (3 atm) is required. Steam sterilisation is used for material which endures temperatures up to 140 °C (iron, glass, rubber articles, porcelain, and textile). All materials are sterilized in containers or paper covers. For effective sterilisation, steam needs to penetrate the autoclave load uniformly, so an autoclave must not be overcrowded, and the lids of containers must be left ajar. Sterilization time is markedly shortened by the high-vacuum or high-pressure autoclaves now widely used. To ensure the autoclaving process is able to cause sterilisation, most autoclaves have meters and charts that record or display relevant information such as temperature and pressure as a function of time. For indication of sterilisation, staff place an indicator tape inside the autoclave prior to autoclaving. The tape will change colour when appropriate conditions have been met. Some types of paper cover have built-in indicators on them (e.g. Lukasterick®). Autoclaving is used for sterilizing instruments, dressings and linen. All surgical instruments and supplies are sterilized before being wrapped into protective sleeves. Sterility can only be assured if items are placed or maintained in a sterile environment after coming out of an autoclave. Bags are the most common methods of storing sterile items. However, bags must not be stored when wet – an autoclave drying circle must be used. Wet bags are permeable by micro-organisms.
Dry heat
Dry heat sterilisation is used for moisture sensitive products or instruments that could be corroded by humidity or for those that steam cannot penetrate. They sterilize these items within 2 hours at 160 oC, or one hour at 160 oC with forced air circulation (or 20 minutes at 180 oC) since bacteria and spores are more resistant to heat in dry states that in wet states and therefore higher temperatures and longer sterilization time are necessary. Dry heat sterilisers are particularly useful in cases where heating is the preferred method of pathogen destruction, but moisture can damage the inserted instruments, either through immediate contact or rust generation. This method is also not appropriate for some kinds of material like gauze swabs because they lose their absorption function. In spite of this, the spectrum of material suitable for this kind of sterilisation is wide (metal surgical tools, glass, porcelain) In Slovakia, unlike the trends in Europe, dry heat sterilisation is the most popular and many clinical wards are supplied with dry heat sterilisers. Gas sterilization
Gas autoclaves use a vapour solution to sterilize contents. The unsaturated chemical vapour method is a low-humidity process and because of the low moisture content, instruments do not corrode and drying time is not required. Common sterilizing agents include formaldehyde gas and ethylene oxide. They consume less heat and take less time to complete the cycle, which allows for greater instrument turnover. Sterilization of metal instruments in gas autoclaves is undoubtedly the most protective mode of sterilization, because corrosion and formation of spots is minimal. - Chemical sterilisation depends upon pressure (1,36 atm), heat (132°C) and a specific solution of various alcohols, acetone, ketone, formaldehyde (0.23%) and distilled water. The sterilization time is 20 minutes exclusive of pressure rise time. - Ethylene oxide gas sterilisers are fully automatic devices that sterilise, either resistant to heat or not, any kind of plastic, rubber, sensitive, metal, mechanic or electromechanical medical and surgical materials (including gloves, catheters, tubes, endoscopic instruments etc.) and laboratory equipment by applying the anti-bacteriologic agent, 100% ethylene oxide (EO), at a low temperature of 54°C. Sterilisation is achieved using heat generated by the sterilisers, but it takes time (from 6 hrs to as long as 7 days). EO sterilises through an alkalization reaction that prevents an organism from reproducing. Products are conditioned and then treated with 100% ethylene oxide gas. After sterilisation, products are transferred
to an aeration cell, where they remain until the gas disperses and the product is safe to handle. EO is very effective as a germicide, fungicide and antivirus. It is not corrosive, can penetrate porous substances and can be easily neutralized with water. However, it is flammable and explosive in the presence of air. Radiation sterilisation Gamma radiation
Gamma rays, emitted from cobalt-60, are similar in many ways to microwaves and X-rays. Gamma rays delivered during sterilisation break chemical bonds by interacting with the electrons of atomic constituents. And although they are highly effective in killing microorganisms, they leave no residues or have sufficient energy to impart radioactivity. The gamma process is repeatable and easy to use. It does not require high pressures or vacuum. Gamma rays are ideally suited for sterilization of disposable items, however, reliable sterilisation of solutions, instruments, catheters, gloves and even sealed plastic material can also be achieved. Packages remain intact with gamma processing. Electron-beam (e-beam) radiation
E-beam radiation, a form of ionizing energy, is good for high-volume, lowvalue products such as syringes or low-volume, high-value products such as cardiothoracic devices. These products are irradiated by concentrated, highlycharged streams of electrons generated by the acceleration and conversion of electricity. This is similar to gamma processing in that it alters various chemical and molecular bonds on contact, including the reproductive cells of micro-organisms. The e-beam accelerators range in energies from 3 MeV to 12 MeV (million electron volts). Generally, e-beam irradiation performs best on low-density, uniformly packaged products. Shorter exposure time often leads to less oxidation on materials. With gamma and e-beam radiation, products are ready to be released immediately after processing through a procedure known as dosimetric release. X-rays are less penetrating than gamma rays and require longer exposure times, but need less shielding. Ultra violet light irradiation (UV), from a germicidal lamp is useful only for sterilisation of surfaces and some transparent objects. The most effective is radiation with a length of 260 nm.
Test your knowledge
1. When do symptoms of nosocomial infection first appear after admission? 2. What does colonization mean? 3. Which is the most common hospital acquired infection? Why? Extras for further study
How to control operation room infections? Mechanisms, devices, air, tools, etc. Methicillin-Resistant Staphyloccocus Aureus (MRSA) – cause, symptoms, spread, prevention. References
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