Total elimination of pathogens using HPV
Mark Hodgson, head of healthcare sales for BioQuell Inc., looks at the role of hydrogen peroxide vapour systems in infection control
In the continual challenge faced by infection preventionists to drive down healthcare-acquired infection (HAI) rates, the impact of the environment as a reservoir of pathogens is becoming increasingly clear.1-3 It has been demonstrated that not only do pathogens shed by prior occupants of a room remain viable for prolonged periods,4-6 but that these present a significantly increased risk of infection to subsequent room occupants.7,8
While routine cleaning can reduce the microbiological burden in a patient room it does not always eliminate the presence of bacteria and hence risk of infection.9,10 Even where very stringent cleaning regimens are in place, it is a constant challenge to maintain high-quality cleaning in a room.10,11 As increasingly resistant organisms are shed by patients into the environment, the need to prevent infection becomes ever more pressing. How clean do you need to get to reduce infection rates?
The hydrogen peroxide vapor (HPV) system relies on micro-condensation to effect total elimination of pathogens, including endospore forming bacteria such as Clostridium difficile, from the inanimate environment.12,13) It has been established that the closest proxy for "total elimination" is a full six-log reduction of spore-forming bacteria, usually in the form of biological indicators.
The basic question is, "How clean do you need to get to reduce infection rates?" At present, there is simply not enough data to answer this question and, due to the difficulties with designing infection control studies, we may never know the answer. What we do know is that at present all of the clinical data published on reducing infection rates though area sterilisation is based on a total elimination of pathogens, validated by a six-log kill; other lower-level kill methods have not yet been shown to reduce infection rates.12-15
This is surprising, as the detectable bioburden in the hospital environment is rarely more than 100 to 1000 cfu/cm3; however, the complications of room topology, and the presence of dust, grime or biofilm significantly increase the resistance of bacteria to decontamination methods. Decontamination cycles designed to produce less than total elimination are frequently found to leave a contaminated environment.
HPV can be used proactively to prevent infection or reactively to stop outbreaks. HPV is used in hospitals worldwide, primarily for the terminal disinfection of rooms used to care for patients with MDROs to reduce the risk of acquisition for subsequent room occupants.13 The most efficient way to achieve this is to have HPV decontamination equipment on the hospital site integrated into the hospital's procedures. This can be achieved either as a service or through equipment purchase.
Another key application of HPV in hospitals is for decontamination during outbreaks.15 Decontamination of areas used to care for patients who have acquired an outbreak strain can help to prevent the outbreak reoccurring from an environmental source. Other applications in hospitals include decontamination for mobile medical equipment, fixed installations in high-risk areas, and preventative decontamination of lower risk areas.
HPV is infinitely scalable from a single room to an entire unit, or even an entire hospital. When the process of HPV was first introduced to US hospitals, the equipment required specialist technicians to operate, today as the technology has improved, hospital staff can be trained to perform decontaminations safely and effectively.
How it works:
1. After the patient has vacated housekeeping remove the bed linens and trash.
2. Set up the room and equipment.
3. Enter user password in control panel.
4. Select "parametric cycle" on control panel.
5. Select the room being sterilised from the menu.
6. Start the process.
7. When the control panel tells you the process is complete confirm the concentration is less than 1ppm.
8. Remove the equipment and return the room to service.
HPV fills the space in the room distributing evenly through the space regardless of the room configuration; this allows the vapour to work around corners in shadow areas and behind equipment and other obstructions. Once the saturation vapour pressure of peroxide is reached a micro-condensation layer of hydrogen peroxide is deposited on to all the surfaces in the room.
The micro-condensation layer is a highly concentrated hydrogen peroxide producing a rapid kill of all micro-organisms; one feature of the micro-condensation process is that the kill rate is independent of the concentration of peroxide in the air, typical time dose relationships do not apply using this method. The micro-condensation process provides a full three-dimensional kill.
Following a dwell time to allow a full six-log kill the aeration unit is activated. Hydrogen peroxide vapour is drawn in to the aeration unit and the peroxide is broken down in to oxygen and water vapour. This leaves the room free from pathogens and much safer for the next occupant.
Regarding consumables, a number of studies have shown that the exterior packaging of unopened supplies in rooms occupied contact precautions patients will become contaminated with pathogens shed by the patient.16 As a result of this contamination, standard practice is to dispose of unused consumables when the patient is discharged. It costs the hospital money to replace the unused items and the materials must be disposed of, possibly explaining why healthcare is the second largest user of landfill in the country.
Micro-condensation HPV systems have been shown to safely decontaminate the packaging of unopened consumables items in the patient room being sterilised.16 This has been shown to produce tangible cost-benefit for the hospitals.
This process has been applied to hospitals throughout the world to reduce infection rates; in the US alone more than 1,500 rooms a month are treated using this process. As the number of published studies showing reduced infection rates increases, the level of acceptance of the process is increasing.(17 HPV is now regularly deployed to stop outbreaks and prevent infections in some of America’s busiest hospitals. Many hospitals have benefited from the major savings available from the application of HPV due to reduced infection rates.
1. Yukoe, et al. A Compendium of Strategies to Prevent Healthcare Associated Infections in Acute Care Hospitals. Infect Control Hosp Epidem. October 2008.
2. Guide to the Elimination of Clostridium difficile in Healthcare Settings. APIC. 2008.
3. Management of Multidrug-Resistant Organisms In Healthcare Settings. CDC. 2006.
4. Hirai Y. Survival of bacteria under dry conditions; from a view of nosocomial infection. J Hosp Infect. 1991;19:191-200.
5. Wagenvoort JHT, Sluijsmans W, Penders RJR. Better environmental survival of outbreak vs. sporadic MRSA isolates. J Hosp Infect. 2000;45:231-234.
6. Bonilla HF, Zervos MJ, Kauffman CA. Long-term survival of vancomycin-resistant Enterococcus faecium on a contaminated surface. Infect Cont Hosp Epidemiol 1996;17:770-772.
7. Huang SS, Datta R, Platt R. Risk of Acquiring Antibiotic-Resistant Bacteria From Prior Room Occupants. Arch Intern Med. Vol. 166. Oct. 9, 2006.
8. Drees M, Snydman D, Schmid C, et al. Prior Environmental Contamination Increases the Risk of Acquisition of Vancomycin-Resistant Enterococci. Clin Infect Dis. 2008;46:678-685.
9. Hayden MK, Bonten MJ, Blom DW, Lyle EA, van de Vijver DA and Weinstein RA. Reduction in Acquisition of Vancomycin-Resistant Enterococcus after Enforcement of Routine Environmental Cleaning Measures. Clin Infect Dis. June 2006:42.
10. Dancer SJ. Importance of the environment in methicillin-resistant Staphylococcus aureus acquisition: the case for hospital cleaning. Lancet. Vol. 7. December 2007.
11. French GL, Otter JA, Shannon KP, Adams NM, Watling D, Parks MJ. Tackling contamination of the hospital environment by methicillin-resistant Staphylococcus aureus (MRSA): a comparison between conventional terminal cleaning and hydrogen peroxide vapour decontamination. J Hosp Infect. 2004;57:31-37.
12. Boyce JM, Havill NL, Otter JA, et al. Impact of hydrogen peroxide vapor room decontamination on Clostridium difficile environmental contamination and transmission in a healthcare setting. Infect Control Hosp Epidemiol. 2008;29:723-729.
13. Passaretti K, et al, Adherence to Hydrogen Peroxide Vapor (HPV) Decontamination Reduces VRE Acquisition in High Risk Units, ICAAC 2008. 2009.
14. Schouten MA, Otter JA, van Zanten AR, Houmes-Zielman G, Nohlmans-Paulssen MK. Environmental decontamination of an intensive care unit to control outbreaks of multidrug-resistant Gram-negative rods using hydrogen peroxide vapor (HPV). Int J Antimicrob Agents. 2007;29 Suppl. 2:S479.
15. Manian, et al. Impact of an Intensive Terminal Cleaning and Disinfection (C/D) Program Involving Selected Hospital Rooms on Endemic Nosocomial Infection (NI) Rates of Common Pathogens at a Tertiary Care Medical Center; SHEA 2010.
16. Otter, et al. Decontamination of unused, packaged consumables contaminated with vancomycin-resistant enterococci (VRE) using hydrogen peroxide vapour (HPV); SHEA 2010.
17. Rutala, et al. Dinsinfection, Sterilization and Antisepsis 2010 Edition APIC.
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