Improved terminal disinfection using hydrogen peroxide vapour (HPV) or bleach to control C. diff

January 30, 2013 Jon Otter (@jonotter) C. difficile, Disinfection bleach, C. difficile, disinfection, HPV, intervention study, NTD

A prospective before-after study at the 900 bed St. John’s Mercy Medical Center evaluated the impact of an HPV intervention focused on the terminal disinfection of rooms used by patients with multidrug-resistant organisms and C. difficile. HPV was introduced on a priority scale accounting for the target pathogen and the risk associated with the unit. Due to local prevalence, most of the rooms decontaminated using HPV were vacated by patients with C. difficile infection (CDI). Hence, the authors evaluated the impact of introducing HPV on the rates of CDI.

The rate of CDI was static prior to the introduction of HPV, with no significant change in rate from 2007 to 2008 (Figure). Hence, this study was performed in a truly endemic setting in contrast to a previous study of a similar design by Boyce et al., which was performed in a “hyper-endemic” setting. When HPV was introduced in 2009 (along with enhanced conventional methods comprising quadruple bleach disinfection for rooms that could not be disinfected using HPV), the rate of CDI fell by 37% from 0.9 to 0.5 cases per 1000 patient days (p<0.0001) (see chart below).

Chart showing the rate of C. difficile infection before and after the implementation of HPV or quadruple bleach disinfection for the terminal decontamination of patient rooms.

Recent data have shown that patients admitted to rooms previously occupied by a patient with C. difficile are at an increased risk of developing C. difficile infection. Thus, it seems logical that improving the efficacy of terminal disinfection would result in reduced rates of CDI. Furthermore, the scale of reduction in CDI incidence was remarkably similar to the study by Boyce et al. (37% vs. 39%), though in this previous study, the 39% hospital wide reduction was not statistically significant.

The major criticism of the study is that HPV and quadruple bleach disinfection were implemented more or less simultaneously so it’s not possible to attribute the reduction to HPV alone. This is complicated by the fact that quadruple bleach disinfection was implemented for all C. difficile rooms in mid-2008, 6 months prior to the introduction of HPV. So, it is possible in theory to do a sub-analysis of corresponding months during the period when quadruple bleach disinfection alone compared with HPV plus quadruple bleach disinfection was in operation. However, this sub-analysis was not performed. A previous study by the same group showed that quadruple bleach disinfection was necessary to eliminate A. baumannii and MRSA from surfaces, and that HPV was microbiologically superior to quadruple bleach disinfection. Thus, since HPV has time and efficiency savings compared with quadruple bleach disinfection, it is cost effective to use HPV in this setting.

The authors undertook a careful evaluation of hand hygiene and glove / gowning compliance, showing that these were not significantly different comparing the pre-intervention and intervention periods. They also evaluated the use of key antimicrobial agents and found that there were small but statistically significant changes in antimicrobial usage, which may have confounded the association with improved disinfection. However, levofloxacin use (one of the high risk CDI drugs) increased significantly in 2009 and there was still a significant reduction in CDI.

The paper includes some useful data on feasibility and safely aspects of implementing HPV, and the ‘priority scale’ (Appendix) for deciding which rooms were disinfected using HPV is rational and will help other hospitals decide on a similar priority scale.

Several other points of interest are reported. For example, the significant reduction in CDI was achieved whilst adhering to US C. difficile control guidelines, which recommend the use of gloves and alcohol based hand products (rather than hand washing with soap and water) for treating patients with CDI in endemic settings. They also held patients who had CDI in contact precautions for the duration of their stay, not just until symptoms resolved.

This study shows that more effective removal of C. difficile spores from the rooms of patients when they are discharged through enhanced conventional methods combined with the implementation of HPV reduces the hospital-wide incidence of CDI. The authors conclude: ‘implementation of an enhanced hospital-wide terminal cleaning program revolving around HPV decontamination of targeted hospital rooms was practical, safe, and associated with a significant reduction in the endemic rate of CDI at our hospital.’

Article citation: Manian FA, Griesnauer S, Bryant A. Implementation of hospital-wide enhanced terminal cleaning of targeted patient rooms and its impact on endemic Clostridium difficile infection rates. Am J Infect Control in press.

Where the wild things are

January 22, 2013 Jon Otter (@jonotter) Contamination, CRE contamination, CRE, sampling

Carbapenem-resistant Enterobacteriaceae (CRE) are a major threat to public health worldwide and Israel is among the countries with the highest rates of these pathogens. A concerted campaign has done a good job of bringing the national outbreak under control, but problems persist¹. An Israeli hospital investigated the extent of environmental contamination with CRE in the vicinity of 34 CRE-carriers using two different sampling methods; contact plates and swabs (with or without enrichment). Pilot sampling was performed to identify the five sites that were most likely to be contaminated (pillow, crotch and leg area on the bed, personal bedside table and infusion pump). To investigate the effect of cleaning on the recovery of CRE, the five sites were sampled at two different times; 4 and 24 hr after rooms were cleaned and patient cloths and sheets were changed.

The study detected CRE in the surrounding environment of most (88%) of the patients sampled, showing that a high proportion of carriers shed these pathogens into their environment which can then be transmitted. Recovery was highest in the carrier’s immediate environment with the patient bed being the most contaminated. Not surprisingly, recovery of CRE from the environment was reduced when sampling was done 4 hr after cleaning compared to 24 hr after cleaning (21% of sites contaminated vs 27%). However these results also highlight the speed by which the patient environment is re-contaminated with CRE after cleaning. The study also showed that the choice of the detection method is also important and reported that contact plates were more efficient at recovering CRE than swabs even with enrichment broth.

The high rate of recovery of CRE from the environment in this study is surprising. Hence, hospitals with CRE-carriers should expect the environment in the vicinity of these patients to be contaminated. Regular and thorough cleaning of the patient environment and equipment should be an integral part of the hospital’s infection control strategy to reduce the spread of these pathogens.

Article citation:

Lerner A, Adler A, Abu-Hanna Jet al.Environmental contaminationby carbapenem-resistantenterobacteriaceae. J Clin Microbiol 2013;51:177-81.

References

1. Schwaber MJ, Lev B, Israeli Aet al. Containment of a country-wide outbreak of carbapenem-resistant Klebsiella pneumoniae in Israeli hospitals via a nationally implemented intervention. Clin Infect Dis 2011; 52: 848-855.

Hydrogen peroxide at war with catalase

January 17, 2013 Jon Otter (@jonotter) Disinfection, MRSA catalase, disinfection, MRSA

A study published by the UK Health Protection Agency highlights the fact that MRSA dried on surfaces appears to be less susceptible to hydrogen peroxide vapour (HPV) than bacterial endospores in the form of commercially produced biological indicators. This is a surprise because bacterial endospores are generally considered to be close to the top of the tree in terms of resistance to disinfection and sterilization. The answer lies in the enzyme catalase. Catalase breaks down hydrogen peroxide and is produced by MRSA but not by the metabolically inert spores. A previous study also showed that catalase-producing bacteria were less susceptible to HPV than bacteria that did not produce catalase and metabolically inert spores.

Bacterial endospore biological indicators (BIs) are typically used to monitor the efficacy of HPV systems. Does the finding that MRSA and probably other catalase-producing bacteria are less susceptible to HPV, “cell for spore”, than bacterial endospores challenge the use of BIs to monitor decontamination using HPV? In vitro susceptibility is important, but the resistance of a ‘system’ to HPV will be determined by a number of factors including the relative susceptibility of the organisms, suspending medium, substrate and inoculum. Thus, you’ll never get a “one-size-fits-all” monitoring system for HPV. BIs provide a stringent, repeatable, consistent and safe method to monitor the efficacy of HPV. Whilst they may not be top of the tree in terms of efficacy, BIs provide a useful yard-stick for monitoring efficacy.

Article citation: Pottage T, Macken S, Walker JT, Bennett AM. Meticillin-resistant Staphylococcus aureus is more resistant to vaporized hydrogen peroxide than commercial Geobacillus stearothermophilus biological indicators. J Hosp Infect 2012; 80:41-5.

Mitigating the increased risk from the prior room occupant through HPV room disinfection

January 2, 2013 Jon Otter (@jonotter) Disinfection HPV, intervention study, MDRO, NTD, prior room occupant

The role of surface contamination is increasingly recognised in the transmission of certain nosocomial pathogens¹. The most compelling evidence comes from the finding that admission to a room previously occupied by a patient infected or colonised with some multidrug-resistant organisms (MDROs) increases the risk of acquiring that MDRO for the subsequent room occupant by a factor of two or more^1-3. Conventional cleaning and disinfection does not reliably remove all environmental MDROs^4,5. Hence, it seems that inadequate terminal disinfection of hospital rooms explains the association with the increased risk of acquisition from the prior room occupant. It follows, then, that improvements in terminal disinfection should reduce the levels of residual contamination and the transmission of pathogens through this route. A recent study from Johns Hopkins Hospital tested this hypothesis through the introduction of hydrogen peroxide vapour (HPV) terminal disinfection of selected patient rooms⁶.

A 30-month prospective cohort intervention study was performed on 6 high-risk units (5 ICUs). HPV was implemented on 3 of the units following a 12-month pre-intervention phase. Clinical impact was assessed by a cohort study. Each patient admitted to any study unit during both phases was included in one of three cohorts:

‘MDRO-standard’ Patients admitted to a room where the prior room occupant had an MDRO and the room was disinfected using standard methods.
‘MDRO-HPV’Patients admitted to a room where the prior room occupant had an MDRO and the room was decontaminated using HPV
‘No MDRO-standard’ Patients admitted to a room where the prior room occupant was not known to have an MDRO and the room was disinfected using standard methods.

The key finding was that patients admitted to rooms decontaminated using HPV were 64% less likely to acquire any MDRO (incidence rate ratio [IRR] of the MDRO-HPV vs. MDRO-standard cohorts = 0.36, confidence interval CI=0.19-0.70, p<0.001) (see chart below).

Chart showing the MRDO acquisition rate in the three patient cohorts.

‘MDRO-standard’ = Patients admitted to a room where the prior room occupant had an MDRO and the room was disinfected using standard methods. ‘MDRO-HPV’ = Patients admitted to a room where the prior room occupant had an MDRO and the room was decontaminated using HPV.

‘No MDRO-standard’ = Patients admitted to a room where the prior room occupant was not known to have an MDRO and the room was disinfected using standard methods.

The difference between cohorts was adjusted for patient level variables such as length of stay, morbidities and other variables that could explain the difference. This means that the difference between cohorts is attributable to HPV alone. When broken down into individual MDROs, the largest reduction was shown for VRE (a 75% reduction, p<0.0001). HPV provided a protective effect for the other MDROs assessed (C. difficile, MRSA and MDR-Gram-negative rods), but differences for these individual pathogens were not statistically significant.

Surprisingly, even when the prior room occupant was not known to have an MDRO, HPV reduced the risk of acquisition by 51% (comparing the MDRO-HPV with the No MDRO-standard cohort). You’d expect the acquisition rate in the ‘MDRO-HPV’ cohort to match the ‘No MDRO-standard cohort’. In fact, it is lower. This is likely due to survival of contamination from previous occupants, unrecognised colonisation or introduction by healthcare workers.

Environmental impact was assessed by sampling each patient room on all units monthly for the last 3 months of the pre-intervention phase and the first 6 months of the intervention phase. Swabs were collected from all patient rooms, occupied or unoccupied, regardless of patient status. The overall percentage of rooms contaminated with one or more MDRO was reduced significantly when HPV was in operation. Further, rooms contaminated with multiple MDROs, occasions when the MDRO from room differed from the room occupant’s known MDRO and MDROs cultured from empty rooms were less likely when HPV was in operation.These changes are due to improved terminal disinfection using HPV.

Whilst this study is one of the few to evaluate patient outcomes in addition to environmental impact of a no-touch automated room disinfection system⁷. it does have several limitations, some of which are highlight in an accompanying editorial⁸. Firstly, the rooms or units were not randomized to an intervention arm, which could have introduced bias. Secondly, whilst the conventional disinfection methods were optimized prior to the introduction of HPV, more could have been done to improve the efficacy of conventional methods which may have over-estimated the impact of HPV. Thirdly, the low prevalence of acquisition (especially for MDROs besides VRE) made detecting changes in incidence difficult. Fourthly, whilst the infection rates in the three cohorts did not change significantly with study phase and the clinical impact on an individual patient level was impressive, overall unit level changes in rates of infection were not reported.

The study has important implications for the proportion of transmission that is likely to involve contaminated surfaces. Extrapolating unadjusted data from the study indicates that 16.7% of the acquisitions that occurred during the study were attributable directly to the prior room occupant. This figure most likely underestimates the total contribution of contaminated surface to nosocomial transmission because contaminated surfaces are likely to be involved indirectly in transmission during the stay of affected patients¹.

In summary, HPV disinfection significantly reduced the risk of patients acquiring MDROs from previous room occupants in high-risk settings. Furthermore, HPV also provides a protective effect even when the prior room occupant was not known to be infected or colonised with an MDRO. These clinical findings are supported by environmental data showing that HPV disinfection improves the efficacy of terminal disinfection, thus reducing environmental contamination. Whilst the study is not without its limitations, it takes the question of how to tackle hospital environmental contamination forward a pace or two.

Article citation: Passaretti CL, Otter JA, Reich NG et al. An evaluation of environmental decontamination with hydrogen peroxide vapor for reducing the risk of patient acquisition of multidrug-resistant organisms. Clin Infect Dis 2013; 56: 27-35.

References:

1. Otter JA, Yezli S, French GL. The role played by contaminated surfaces in the transmission of nosocomial pathogens. Infect Control Hosp Epidemiol 2011; 32: 687-699.

2. Drees M, Snydman D, Schmid Cet al. Prior environmental contamination increases the risk of acquisition of vancomycin-resistant enterococci. Clin Infect Dis 2008; 46: 678-685.

3. Huang SS, Datta R, Platt R. Risk of acquiring antibiotic-resistant bacteria from prior room occupants.Arch Intern Med 2006; 166: 1945-1951.

4. Manian FA, Griesenauer S, Senkel Det al. Isolation of Acinetobacter baumannii complex and methicillin-resistant Staphylococcus aureus from hospital rooms following terminal cleaning and disinfection: can we do better? Infect Control Hosp Epidemiol 2011; 32: 667-672.

5. 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.

6. Passaretti CL, Otter JA, Reich NGet al. An evaluation of environmental decontamination with hydrogen peroxide vapor for reducing the risk of patient acquisition of multidrug-resistant organisms. Clin Infect Dis2013; 56: 27-35.

7. Otter JA, Yezli S, Perl TM, Barbut F, French GL. Is there a role for “no-touch” automated room disinfection systems in infection prevention and control? Submitted. J Hosp Infect 2013; 83: 1-13.

8. McDonald LC, Arduino M. Climbing the evidentiary hierarchy for environmental infection control. Clin Infect Dis 2013; 56: 36-9.