Sterilization Hospitals Disinfection Not Enough
Hospitalisation of sick people increases the risk of transmission of nosocomial infections from one person to another (Goering et al., 2008). These healthcare associated infections (HAI) are endemic worldwide, and in the United Kingdom, one in ten patients is affected. The costs of treating HAIs, although difficult to measure with certainty, may cost the NHS as much as £1,000 million each year.
In a prevalence survey undertaken by Health Protection Scotland during October 2005 and October 2006, the cost was estimated to be £183 million per year in Scotland alone (NHS Scotland National HAI Prevalence Survey, 2007). It is not possible to prevent all hospital acquired infections, since the very old, young, those undergoing invasive procedures and those with suppressed immune systems are particularly susceptible. The Public Health Laboratory Service's view is if existing knowledge and infection control practices are improved, then about 30% of hospital acquired infections could be avoided (Bourn, 2001).
Prevention of HAIs depends partly on the availability of clean, sterile equipment, instruments and dressings, isolation facilities and safe disposal of infected material (Goering et al., 2008).In order to limit the transmission of organisms related to reusable equipment, it is imperative that proper cleaning, sterilization and disinfection of patient care equipment is carried out (Canada Communicable Disease Report, 1998). Sterilization eliminates all microbial life and disinfection will reduce the numbers of micro-organisms to a safe level but does not destroy bacterial spores and some viruses (Rutala and Weber, 2008; LDI Infection Control Policies, 2010).
Based on the ability of these processes of decontamination, the question arises: should hospitals use sterilisation, or is disinfection enough?In the 1970s, E. H. Spaulding devised a rational approach to disinfection and sterilization of patient-care items and equipment, based on the potential risk of infection involved in their use. He categorized items as critical, semicritical, and noncritical. Critical items pose a high risk for infection if they are contaminated with microorganisms and must be sterile. This category includes surgical instruments, catheters, implants, and probes used in sterile body cavities and tissues and as well dental instruments that penetrate soft tissue or bone. (Rutala and Weber, 2008; Drummond and Skidmore, 1991).
These items should be purchased as sterile or be sterilized with steam and in the case of dental instruments, discarded if possible. Semicritical items include respiratory and anaesthesia equipment, endoscopes, cystoscopes and dental instruments that do not penetrate tissue. These medical devices should be free from all microorganisms, however, small numbers of bacterial spores are permissible, so high-level disinfection using chemical disinfectants is sufficient (Rutala and Weber, 2008.) Sterilization of semicritical dental instruments is recommended after each use, if the instruments are heat-tolerant (Kohn et al., 2003).
Intact skin serves as a barrier to most microorgansisms, so the sterility of items coming in contact with intact skin is not much critical and so these items are categorised as 'noncritical items'. These items include bedpans, blood pressure cuffs, etc., and need only be cleansed with soap and water (Canada Communicable Disease Report, 1998; Rutala and Weber, 2008; Fuselier and Mason, 1997).The choice of a disinfection and sterilization method to be used with healthcare equipment will often depend upon the simplicity of the method, compatibility with equipment and cost (Kendrick et al., 2003). Disinfection methods include thermal washer-disinfectors, low temperature steam and chemical disinfectants.
Although chemical disinfection offers a relatively convenient and rapid decontamination without high financial outlay on equipment, it can be toxic, flammable, corrosive or have other material incompatibilities (Medical Devices Agency, 2002). Furthermore, the chemicals themselves can sometimes pose risks to hospital staff as well as patients. In 2002, a brand of gluteraldehyde by Johnson and Johnson, had to be taken off the market because of these fears (BBC News, 2002).
Chlorine and hydrogen peroxide can be corrosive to metals, and glutarladehye and formaldehyde can be toxic to the skin (BC Centre for Disease Control, 2003). The corrosive nature of chlorine makes it unsuitable for semicritical devices such as endoscopes (Rutala and Weber, 2001). Since these methods will only disinfect and not sterilize, it is impractical for use for surgically invasive devices which are required to be free of all microbial contamination (Medical Devices Agency, 2002).Sterilisation includes steam, dry heat, gas plasma and ethylene oxide and low temperature steam and formaldehyde.
All these methods will eliminate microbial life, however each is limited in use, eg., steam cannot be used on devices comprising thermo-labile plastics which will not withstand exposure to temperatures of 121- 138°C and dry heat cannot be used to sterilise intravenous fluids, glycerol/water mixtures, rubber and plastics (Medical Devices Agency, 2002), and this is one of the problems associated with implementing Spaulding's scheme. Complicated medical equipment, classified as critical, e.g., laparoscopes and endoscopes cannot be steam sterilized because they are heat-sensitive (Rutala and Weber, 1999). Biofilms can form in the outer sleeve of laparoscopes, especially when soaked in fluids for prolonged periods.
Opportunistic pathogens are able to survive in these biofilms, unless the outer sleeves are dismantled and brushed thoroughly on the inside. Often, inadequate cleaning of the disinfectant trays to remove the biofilm can be a contributing factor (Vijayaraghavan et al., 2006). It has also been observed that different types of bacteria may develop resistance to disinfectants through mutations or acquisition of plasmids (McDonnell and Russell, 1999).A solution is to treat heat sensitive equipment with ethylene oxide (EtO), hydrogen peroxide gas plasma, or with liquid chemical sterilants (Canada Communicable Disease Report, 1998; Rutala and Weber, 2008). Several germicides, glutaraldehyde, phenol/phenate, stabilized hydrogen peroxide, peracetic acid, etc., are categorised as liquid chemical sterilants. Sterilants can be dependable, high-level disinfectants, provided that equipment is cleaned prior to treatment to eliminate organic and inorganic material.
Also, if the proper guidelines for concentration, contact time, etc. are followed, all microorganisms except bacterial spores should be eliminated from the equipment, and the device should not represent an infection risk (Rutala and Weber, 2008). It is however, impossible to maintain sterility after processing and during storage as devices cannot be wrapped during processing (Rutala and Weber, 2004).Vijayaraghavan et al. (2006), have shown that glutaraldehyde is ineffective as a chemical sterilant for laparoscopes, as an outbreak of atypical mycobacterial infections (AMI) occurred in 35 patients following decontamination and reuse of laparoscopes. Prior to this outbreak, researchers stated that usually <10 organisms are introduced into the abdominal cavity during laparoscopy and the equipment is simple to clean and disinfect, therefore sterility was not necessary for all laparoscopic equipment (Rutala and Weber, 2008).
However, complete disassembly, cleaning, and high-level disinfection of laparoscope parts has led to reported infections in patients (Chan-Myers and Antonoplos, 1997).Research has also shown case reports of bacterial infections after endoscopy, related to unacceptable cleaning and disinfection (Bronowicki, et al., 1997), and failure to sterilize accessory equipment (Lo Passo, et al., 2001). It has also been suggested that biofilm formation in endoscopes may be the cause for the failure of the disinfection/sterilization process (Pajkos et al., 2004). The question then arises, whether a semicritical item such as an endoscope, when used in conjunction with a critical instrument that contacts sterile body tissue, should still only be high-level disinfected, or will this now require sterilisation? (Rutala and Weber, 2008).
Ideally, surgical equipment entering sterile tissue should be sterilized between patients rather than disinfected (Rutala and Weber, 1999).Spaulding's scheme presents further ambiguity in the difficulty associated with inactivating infectious agents like transmissible spongiform encephalopathies (TSEs), e.g., prions, such as Creutzfeldt-Jakob disease [CJD] (Rutala and Weber, 2008). Prions display unusual resistance to conventional chemical and physical decontamination methods (Lemmer et al., 2008), and they have a high affinity and tenacity to bind to steel surfaces, (Flechsig, et al, 2001), therefore CJD contaminated surgical instruments require specific decontamination procedures (Rutala and Weber, 2010). Critical or semi-critical equipment that has had contact with high-risk tissue by being used on a high-risk patient (with suspected or known CJD) must be decontaminated in a proper manner to ensure the elimination of prions.
Medical devices that have had contact with low-risk or no-risk tissue can be treated by means of conventional methods. Research has shown that most disinfectants are inadequate for the elimination of prion infectivity, and the corrosive nature of disinfectants like chlorine make it unsuitable for semicritical devices such as endoscopes (Rutala and Weber, 2001).Recorded case histories have shown that CJD has developed in patients after surgery, although prion contaminated electrodes had been disinfected with 70% alcohol and formaldehyde vapour.
Since standard sterilisation techniques fail to eradicate prions from instruments (Ramasamy, et al., 2003; O' Flynn et al., 2007), nearly 50% of sterilisation units fail to meet ISO 2000 standards, and the use of bleach and NaOH to reduce instrument decontamination are corrosive to instruments, (O' Flynn et al., 2007), it is recommended that prion-contaminated medical devices that are impractical to clean should be discarded (Rutala and Weber, 2001). Experimental studies to determine effective inactivation by germicides and sterilisation procedures for prions have been conducted, but it is often difficult to reproduce hospital setting conditions in the experiment. (Ramasamy, et al., 2003).Transmission by non critical items that comes into direct skin contact with many patients is difficult to dismiss.
Research has shown that blood pressure cuffs are a potential vehicle for transmission of nosocomial infection in selected patient populations and that disinfecting with 70% alcohol, and/or mild bleach solution alone will not eliminate all microbial life (De Gialluly et al., 2006). A more stringent decontamination method using ethylene oxide as a gas sterilizing agent for blood cuffs and other medical equipment, although effective, introduces a new complication for this old chemical agent.
The blood pressure cuff sterilized with ethylene oxide can cause burns or allergic reactions even if the cuff has been adequately aerated (Karacalar and Karacalar, 2000).Factors such as the lack of evidence in the literature of transmission of infectious diseases by the use of certain equipment, unreported cases of infection from contaminated instruments, risk of transmission by various infectious agents, and the fact that different hospitals may have different policies depending on the experience of those that draw up their decontamination guidelines, have to be taken into consideration. Even if all these are addressed, the problem of finding the ideal disinfection agent that should inactivate all infectious agents, including bacterial spores, tubercle bacilli, viruses and prions, act quickly, be cost-effective, be non-toxic to its handlers, and should not damage the surgical equipment, remains (Lim and Gupta, 2006).
It is therefore difficult to choose a method of disinfection or sterilisation even after considering the categories of risk to patients (Rutala and Weber, 1999).Through the various literature cited, and reported cases of HAIs occurring through inefficient decontamination processes, it can be seen that disinfection alone is not an effective solution for the modern hospital environment. It is not strong enough on medical items previously considered non-critical eg., blood pressure cuffs, and is also not suitable for critical, heat labile items. Also, the risks associated with CJD, complicated medical equipment and biofilms warrant stricter decontamination methods, and while not feasible in all situations, sterilisation or a combination of disinfection followed by sterilisation seems to be the better solution to reduce hospital acquired infections.
Article name: Sterilization Hospitals Disinfection Not Enough essay, research paper, dissertation