Hospital Infection Control

Hand surfaces/equipment; disinfection/sterilization

What specific organisms pose a risk via contaminated surfaces?

There is increasing evidence that contaminated surfaces in hospital rooms contributes to patient-to-patient transmission of important healthcare-associated pathogens. The key pathogens for which environmental contamination has been shown to play an important role are methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), multidrug-resistant Acinetobacter,Clostridium difficile, and norovirus.

Even though endoscopes represent a valuable diagnostic and therapeutic tool, and the incidence of infection associated with their use is reportedly low (1 in 1.8 million procedures), more nosocomial infections have been linked to contaminated endoscopes than to any other medical device. Such devices, which should minimally be high-level disinfected between patients (see below), represent a major challenge for disinfection/sterilization because of long-narrow lumens, sharp angles, springs and valves, occluded dead ends, and rough or pitted surfaces. Improperly disinfected bronchoscopes have most commonly been associated with transmission of Mycobacterium tuberculosis, Legionella pneumophila, non-tuberculous mycobacteria, and Pseudomonas aeruginosa. Improperly disinfected gastrointestinal endoscopes have most commonly been associated with transmission of Pseudomonas aeruginosa and Salmonella spp.

What is the impact of not preventing these infections?

Several of the pathogens associated with transmission due to contaminated environmental surfaces (i.e., MRSA, VRE, MDR-Acinetobacter, C. difficile) may lead to colonization of patients with a subsequent risk of infection if host defenses are breached (i.e., for MRSA, VRE, MDR-Acinetobacter) or if antibiotics are administered (i.e., for C. difficile). Infection with all these environment-mediated pathogens is potentially serious and even life threatening.

The pathogens associated with inadequately processed endoscopes have been associated with pseudo-outbreaks (i.e., patient not infected but laboratory cultures falsely positive) and true outbreaks. However, pseudo-outbreaks may result in serious consequences for patients who may receive prolonged courses of drug therapy with the attendant risks (e.g., anti-tuberculous therapy). True infection may result in serious infection and even death.

How can transmission to patients be minimized with disinfection and sterilization of hand surfaces and equipment?

More than 50 years ago, Earle H. Spaulding devised a rational approach to disinfection and sterilization of patient-care items or equipment. This classification scheme is so clear and logical it has been retained, refined, and successfully used by infection preventionists when planning methods for disinfection or sterilization. Spaulding described 3 categories depending on the degree of risk of infection in the use of item.

First, critical items are so called because of the high risk of infection if such an item is contaminated with any microorganism including bacterial spores. Thus, it is critical that objects that enter sterile tissue or the vascular system be sterile because any microbial contamination could result in disease transmission. Examples of such items include surgical instruments, implants, and cardiac catheters. The items in this category should be purchased as sterile or sterilized by steam sterilization, if possible. If heat sensitive, the object may be treated with ethylene oxide, hydrogen peroxide gas plasma, ozone, vaporized hydrogen peroxide, or liquid chemical sterilants if other methods are unsuitable.

Second, semicritical items come into contact with mucous membranes or nonintact skin. Gastrointestinal endoscopes, bronchoscopes, endocavitary probes, and prostate biopsy probes are included in this category. Semicritical items minimally require high-level disinfection using FDA cleared high-level disinfectants or chemical sterilants.

Finally, noncritical items have contact with intact skin but not mucous membranes. Intact skin acts as a barrier to most pathogens and therefore the sterility coming into contact with intact skin is "not critical". Examples of such items include bed rails, bedside tables, patient furniture, blood pressure cuffs, and crutches. Low-level disinfectants (e.g., quaternary ammonium compounds, alcohols, chlorine, and improved hydrogen peroxide) may be used to disinfect non-critical items. The exposure time for disinfectants used on noncritical items is at least 1 minute.

Table I shows the methods of disinfection and sterilization of surfaces and items.

Table I.

Methods for disinfection and sterilization of patient-care items and environmental surfaces
Process Level of Microbial inactivation Method Examples (with processing times [exposure times for HLD and CS are temperature dependent]) Healthcare application (examples)
Sterilization Destroys all microorganisms, including bacterial spores High temperatureLow temperatureLiquid immersion Steam (~ 40 min), dry heat (1-6 hr depending on temperature)Ethylene oxide gas (~ 15 hr), hydrogen peroxide gas plasma (~ 40 min), ozone, vaporized hydrogen peroxide (~ 55 min)Chemical sterilantsb: >2% glut (~ 10 hr);1.12% glut and 1.93% phenol (12 hr at 25C); 7.35% HP and 0.23% PA (3 hr); 7.5% HP (6hr); 1.0% HP and 0.08% PA (8 hr); ≥0.2% PA (~ 50 min [12 min CS time] at 50-56°C); 8.3% HP and 7.0% PA (5 hr at 25C); 3.4% glut and 26% isopropanol (10h) Heat-tolerant critical (surgical instruments) and semicritical patient-care itemsHeat-sensitive critical and semicritical patient-care itemsHeat-sensitive critical and semicritical patient-care items that can be immersed
High-level disinfection (HLD) Destroys all micro-organisms except high numbers of bacterial spores Heat-automatedLiquid immersion Pasteurization (~ 50 min at 65-77C)Chemical sterilants/HLDs*:>2% glut (20-45 min at 20-25C); 0.55% OPA (12 min); 1.12% glut and 1.93% phenol (20min at 25C); 7.35% HP and 0.23% PA (15 min); 7.5% HP (30 min); 1.0% HP and 0.08% PA (25 min); 650-675 ppm chlorine (10 min at 25C); 8.3% HP and 7.0% PA (5 min at 25C); 2.0% improved HP (8min) Heat-sensitive semicritical items (respiratory therapy equipment)Heat-sensitive semicritical items (GI endoscopes, bronchoscopes)
Intermediate-level disinfection Destroys vegetative bacteria, mycobacteria, most viruses, most fungi but not bacterial spores Liquid contact EPA-registered hospital disinfectant with label claim regarding tuberculocidal activity (e.g., chlorine-based products, improved HP, phenolics-exposure times at least 1 min) Noncritical patient care item (blood pressure cuff) or surface with visible blood
Low-level disinfection Destroys vegetative bacteria, some fungi and viruses but not mycobacteria or spores Liquid contact EPA-registered hospital disinfectant with no tuberculocidal claim (e.g., chlorine-based products, phenolics, improved HP, quaternary ammonium compounds-exposure times at least 1 min) or 70-90% alcohol Noncritical patient care item (blood pressure cuff) or surface (bedside table) with no visible blood

What data support current recommendations regarding contaminated surfaces?

There is increasing evidence that the selected pathogens associated with contaminated hospital surfaces play an important role in patient-to-patient transmission. Common characteristics of these pathogens include persistence in the environment, frequent contamination of surfaces in rooms of patients colonized/infected with these pathogens, and frequent colonization of the hands of healthcare personnel. Person-to-person transmission has been demonstrated by molecular techniques. For all these pathogens except norovirus, admission to a hospital room previously occupied by a colonized or infected patient has been shown to be a risk factor for disease acquisition. Importantly for some pathogens, improved cleaning/disinfection has been shown to lower the incidence of infection in hospitals.

More outbreaks have been associated with inappropriately cleaned/disinfected endoscopes than any other medical device. However, implementation of current disinfection guidelines has been demonstrated to eliminate the risk of cross-infection.

Sterilization of critical items, especially steam sterilization, has been demonstrated to be highly effective in preventing cross-infection.

How can the cleaning of equipment and surfaces be monitored? At what frequency?

Cleaning of environmental surfaces can by monitored in a number of ways. First, the education of environmental service workers should be monitored to ensure they are appropriately trained. Second, environmental services should use a checklist to ensure that all environmental surfaces are cleaned. Third, after cleaning the environmental surfaces should be visually clean. Finally, a number of more specific measures of cleaning can be used to include fluorescent dyes and ATP measurements.

Whenever medical devices are sterilized, the sterilization process should be monitored by physical (e.g., time, temperature, gas concentration), chemical (e.g., usually are heat- or chemical-sensitive inks that change color when one or more sterilization parameters are present), and biological methods (e.g., directly monitor the lethality of the process by using the most resistant microorganisms [i.e., Bacillus spores] to the sterilization process).

When high-level disinfection is used, there are several procedures to ensure high-level disinfection. First, personnel assigned to reprocess endoscopes should receive device-specific reprocessing instructions and competency testing performed and documented (e.g., at the start of use, annually). Second, healthcare facilities should ensure that users can readily identify whether and when an endoscope has been reprocessed. Third, ensure that the hospitals policies and practices are consistent with guidelines from the CDC and professional organizations (e.g., ASGE, SHEA). Fourth, routinely test the liquid sterilant/high-level disinfectant to ensure minimal effective concentration of the active ingredient. Check the solution each day of use (or more frequently) using the appropriate chemical indicator and document the results of this testing. Discard the solution if the chemical indicator shows the concentration is less than the minimum effective concentration.

All persons performing disinfection or sterilization of medical devices should receive appropriate education at initiation of employment and at least annually.

What are the controversies related to hospital management of disinfection/sterilization of hand surfaces/equipment?

There are several controversies in this area. First, the need and the method for routine monitoring of the effectiveness of cleaning the hospital environment are unclear. Further, the best method (e.g., fluorescent dye, ATP monitoring) has not been determined. Second, the use of a "no touch" method for terminal room disinfection such as ultraviolet light or hydrogen peroxide systems (e.g., hydrogen peroxide vapor, hydrogen peroxide dry mist) to reduce the incidence of healthcare-associated infections has not been completely validated. Third, the use of routine environmental microbiological testing of endoscopes for quality assurance has not been established. Fourth, what are the best methods for disinfecting prion-contaminated instruments.

What data support each side of the above controversies?

A number of studies have demonstrated that newer methods to assess surface contamination are more sensitive than visual inspection. Studies have demonstrated that when combined with other interventions (e.g., repeated performance feedback to environmental services personnel) such methods lead to improved cleaning practices and reduced microbial contamination. However, no study has assessed the cost-benefit of such methods or allows determination of the ideal sampling strategy or monitoring tool.

Several studies have demonstrated that "no touch" methods can eliminate bacterial contamination of environmental surfaces, including those contaminated with C. difficile. However, only a single study using a before-and-after study design has demonstrated reduced healthcare infections that were limited to C. difficile. Additional studies assessing the effectiveness of no-touch room decontamination systems are needed to further assess the benefits of these technologies. Cost-effectiveness studies would be useful in aiding selection among the different room decontamination echnologies. Whether the benefits exceed the costs has not been determined.

As part of a quality assurance program, some healthcare facilities have conducted random bacterial surveillance cultures of processed endoscopes to ensure high-level disinfection or sterilization. Reprocessed endoscopes should be free of microbial pathogens except for small numbers of relatively avirulent microbes that represent exogenous environmental contamination (e.g., coagulase-negative Staphylococcus, Bacillus species, diphtheroids). However, there are no national recommendations for sampling as a microbiologic standard has not been set and the value of routine endoscope cultures has not been shown by correlating viable counts on an endoscope to infection after an endoscopic procedure.

Current prion guidelines are not based on reprocessing procedures used in a clinical setting and the results of inactivation studies of prions have been varied according to prion strain, prion concentration, prion detection, tissue of composition of the brain material tested, animal tested, exposure container, cycle parameters of the sterilizer, concentration of the disinfectant at the beginning and end of the experiment, etc. Thus, the current guidelines are based on the best available data with its limitations.

What guidelines are currently in place?

  1. Rutala WA, Weber DJ, Hospital Infection Control Practices Advisory Committee (HICPAC). 2008. www.cdc.gov

  2. Petersen BT, Chennat J, Cohen J et al. Multisociety guideline on reprocessing flexible gastrointestinal endoscopes. 2011. Gastroint Endoscopy. 2011;73: 1-10.

  3. Rutala WA, Weber DJ. Guideline for disinfection and sterilization on prion-contaminated medical instruments. Infect Control Hosp Epidemiol 2010; 31:107-117

  4. Sehulster L, Chinn RYW, HICPAC. Guidelines for environmental infection control in health-care facilities. www.cdc.gov

  5. MacCannell T, Umscheid CA, Agarwal RJ et al. Guideline for the prevention and control of norovirus gastroenteritis outbreaks in healthcare settings. 2011. www.cdc.gov

  6. Dubberke ER, Gerding DN, Classen D et al. 2008. Strategies to prevent Clostridium difficile infections in acute care hospitals. infect Control Hosp Epidemiol 2008;29:S81-S92.

References

Weber, DJ, Rutala, WA, Miller, MB, Huslage, K, Sickbert-Bennett, E. "Role of hospital surfaces in the transmission of emerging health care-associated pathogens: Norovirus, Clostridium difficile, and Acinetobacter species". Am J Infect Control. vol. 38. 2010. pp. S25-33.

Otter, JA, Yezli, S, French, GL. "The role played by contaminated surfaces in the transmission of nosocomial pathogens". Infect Control Hosp Epidemiol. vol. 32. 2011. pp. 687-99.

Rutala, WA, Weber, DJ. "Guideline for disinfection and sterilization in healthcare facilities". 2008.

Rutala, WA, Weber, DJ. "Sterilization, high-level disinfection, and environmental cleaning". Inf Dis Clin N Am. vol. 25. 2011. pp. 45-76.

Orenstein, R, Aronhalt, KC, McManus, JE, Fedraw, LA. "A targeted strategy to wipe out Clostridium difficile". Infect Control Hosp Epidemiol. vol. 32. 2011. pp. 1137-39.

Boyce, JM, Havill, Otter, JA. "Impact of hydrogen peroxide vapor room decontamination on Clostridium difficile environmental contamination and transmission in a healthcare setting". Infect Control Hosp Epidemiol. vol. 29. 2008. pp. 723-9.

Petersen, BT, Chennat, J, Cohen, J. "Multisociety guideline on reprocessing flexible gastrointestinal endoscopes: 2011". Gastroint Endoscopy. vol. 73. 2011. pp. 1-10.

Carling, PC, Parry, MM, Rupp, ME. "Improving cleaning of the environment surrounding patients in 36 acute care hospitals". Infect Control Hosp Epidemiol. vol. 29. 2008. pp. 1035-41.

Boyce, JM, Havill, NL, Havill, HL. "Comparison of fluorescent marker systems with 2 quantitative methods of assessing terminal cleaning practices". Infect Control Hosp Epidemiol. vol. 32. 2011. pp. 1187-93.

Rutala, WA, Weber, DJ. "Are room decontamination units needed to prevent transmission of environmental pathogens". Infect Control Hosp Epidemiol. vol. 32. 2011. pp. 743-7.

Rutala, WA, Weber, DJ. "Guideline for disinfection and sterilization of prion-contaminated medical instruments". Infect Control Hosp Epidemiol. vol. 31. 2010. pp. 107-17.

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