Author: Jon Otter (@jonotter)

No need to worry about environmental contamination with Enterobacteriaceae…or is there?

Jon Otter (@jonotter) Contamination, CRE , , , , ,

It was once thought that only bacterial endospores would survive on dry hospital surfaces for extended periods (measured in days and weeks rather than hours). Microbiological data indicates that a range of vegetative bacteria can survive on dry surfaces for extended periods. Whilst differing testing methods and conditions make comparison of survival times between studies difficult, it is clear that non-fermenting Gram-negative bacteria (such as Acinetobacter baumannii and Pseudomonas aeruginosa) survive considerably longer than the Enterobacteriaceae (such as Klebsiella pneumoniae and Escherichia coli).  However, the Enterobacteriaceae can survive for more than a month on dry surfaces. Indeed, a 2009 laboratory study highlighted substantial strain variation in the survival of K. pneumoniae, with the survival of three strains ranging from a 6-log reduction inside 3 weeks to a 1-log reduction over six weeks.

Several recent studies have evaluated environmental contamination with ESBL-producing Enterobacteriaceae. One French study evaluated surface contamination on five standardized sites surrounding patients infected or colonized with ESBL-producing Klebsiella spp. (n=48) or ESBL-producing E. coli (n=46). Environmental contamination was significantly more likely in the rooms of Klebsiella spp. patients (31% of 48 rooms positive; 6% of 240 sites positive) vs. E. coli patients (4% of 46 rooms positive; 1% of 230 sites sites). Multiple regression identified carriage of ESBL-producing K. pneuomiae as the only independent predictor of ESBL environmental contamination (adjusted odds ratio=10.38, 95% confidence interval = 1.24-228.58). Surprisingly, only 52% of the ESBL-producing isolates were identical to the patients in the room, suggesting survival of ESBL-producing bacteria from prior occupants or importation into the room. Another French study with a similar design identified comparable rates of contamination, and also found that contamination was significantly more likely with K. pneumoniae than with E. coli.

environmental sampling

Environmental contamination with C. difficile spores, VRE and non-fermenting Gram-negative bacteria is now a well-established route of transmission. Whilst the same cannot be said for the Enterobacteriaceae, these studies combined with an Israeli article recently featured on this Micro Blog, show that environmental contamination with Enterobacteriaceae may be more important than previously thought. These findings are particularly important in light of the recent global spread of carbapenemase-producing K. pneumoniae.

Article citations:

Guet-Revillet H, Le Monnier A, Breton N et al. Environmental contamination with extended-spectrum beta-lactamases: is there any difference between Escherichia coli and Klebsiella spp? Am J Infect Control 2012; 40: 845-848.

Gbaguidi-Haore H, Talon D, Hocquet D, Bertrand X. Hospital environmental contamination with Enterobacteriaceae producing extended-spectrum β-lactamase. Am J Infect Cont 2013; Jan 18 [Epub ahead of print].

What does it take to prevent the transmission of C. difficile from environmental surfaces?

Jon Otter (@jonotter) C. difficile , ,

Infected patients shed pathogens into the environment, resulting in increased risk of infection for the subsequent occupant of the room by a factor or two or more.1 For example, in one study, patients admitted to rooms previously occupied by patients with C. difficile infection (CDI) were 2.8 times more likely to develop CDI than patients admitted to rooms disinfected using conventional methods. Thus, most agree that more needs to be done to reduce contamination with C. difficile spores in order to interrupt transmission. However, what level of disinfection is required to prevent the transmission of C. difficile?

A consideration of data relating to the infectious dose of C. difficile is a useful first step. In hamster studies, Larson and Borriello showed that only one or two spores of C. difficile were sufficient to initiate infection in clindamycin-treated hamsters.2  This indicates that very low levels of C. difficile spores can initiate infection.

Lawley, et al.3 developed a murine model that provides useful background data on infectious dose. A dose-response relationship was established between the concentration of contamination in the cages and the proportion of healthy mice that developed CDI. All mice became infected when exposed to 100 spores/cm2 and 50 percent of mice became infected when exposed to 5 spores/cm2.  The point at which none of the mice became infected was a concentration of less than one spore per cm2. The mice were exposed to the contaminated cages for one hour. In the healthcare environment, room exposure times are usually measured in days and so these estimates are likely to be conservative. Although translating data from animal models to meaningful clinical practice is difficult, it appears from these animal models that a low concentration of contamination is able to transmit spores to a susceptible host, as is the case with other healthcare-associated pathogens such as norovirus. 4

The low infectious dose of C. difficile is not the only challenge to disinfection. Bacterial endospores can survive on surfaces for many months5 and are resistant to several commonly used disinfectants.6 Patients with CDI result in widespread fecal contamination with C. difficile present in the feces of infected individuals at concentrations in excess of 106 spores per gram.7

Lawley, et al. examined which disinfectants were able to interrupt the transmission of C. difficile and established a relationship between the level of inactivation of C. difficile spores in vitro and the degree to which transmission was interrupted (figure).

Cdiff_log_reduction

Figure. Correlation between in vitro log reduction and interruption of transmission of C. difficile spores in a murine model.3

The oxidizing agents sodium hypochlorite (bleach) and hydrogen peroxide vapour (HPV) were the only agents tested that achieved a 6-log reduction on C. difficile spores in vitro and completely interrupted the transmission of C. difficile. Notably, both bleach and HPV disinfection can reduce the incidence of CDI in healthcare applications.8-9  Based on these findings, the CDC recommends that surfaces potentially contaminated with C. difficile spores should be disinfected using EPA-registered sporicidal agent (such as bleach) or sterilants.

Recent data highlight the fact that agents with in vitro efficacy may not effectively eradicate hospital pathogens from surfaces due to limitations with achieving adequate distribution and contact time using conventional cleaning methods.1,10 The emergence of ‘no-touch’ automated disinfection methods provide an alternative to reliance on a manual operator for the inactivation of pathogens on surfaces.  HPV is an EPA-registered sterilant that achieves a 6-log reduction on C. difficile spores in vitro, eradicates C. difficile spores from surfaces and reduces the incidence of CDI and successfully mitigates the increased risk from the prior room occupant. 5, 9, 11-13

In summary, given the fact that a small number of C. difficile spores are sufficient to cause CDI in susceptible individuals, disinfectants with an EPA-registered sporicidal claim or sterilants should be used for disinfecting rooms used by patient with CDI. ‘No-touch’ methods, such as HPV, remove reliance on the operator to achieve adequate distribution and contact time and are appropriate for the terminal disinfection of rooms used by patients with CDI.

References:
1. Otter JA, Yezli S, French GL. The role played by contaminated surfaces in the transmission of nosocomial pathogens. Infect Control Hosp Epidem. 2011; 32:687-99.
2. Larson HE, Borriello SP. Quantitative study of antibiotic-induced susceptibility to Clostridium difficile enterocecitis in hamsters. Antimicrob Agents Chemother 1990; 34:1348-53.
3. Lawley TD, Clare S, Deakin LJ, et al. Use of purified Clostridium difficile spores to facilitate evaluation of health care disinfection regimens. Appl Environ Microbiol 2010; 76:6895-900.
4. Yezli S, Otter JA. Minimum infective dose of the major human respiratory and enteric viruses transmitted through food and the environment. Food Environ Microbiol 2011; 3:1-30.
5. Otter JA, French GL. Survival of nosocomial bacteria and spores on surfaces and inactivation by hydrogen peroxide vapor. J Clin Microbiol 2009; 47:205-7.
6. Humphreys PN. Testing standards for sporicides. J Hosp Infect 2011; 77:193-8.
7. Al-Nassir WN, Sethi AK, Nerandzic MM, Bobulsky GS, Jump RL, Donskey CJ. Comparison of clinical and microbiological response to treatment of Clostridium difficile-associated disease with metronidazole and vancomycin. Clin Infect Dis 2008; 47:56-62.
8. Mayfield JL, Leet T, Miller J, Mundy LM. Environmental control to reduce transmission of Clostridium difficile. Clin Infect Dis 2000; 31:995-1000.
9. 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 Epidem. 2008; 29:723-9.
10. Manian FA, Griesenauer S, Senkel D, et 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; 32:667-72.
11. 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..
12. 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 2012..
13. Cooper T, O’Leary M, Yezli S, Otter JA. Impact of environmental decontamination using hydrogen peroxide vapour on the incidence of Clostridium difficile infection in one hospital trust. J Hosp Infect 2011; 78:238-40.

MDR-Acinetobacter baumannii beats MRSA in the war for ICU predominance

Jon Otter (@jonotter) Acinetobacter, Contamination, MRSA , , , , ,

A. baumannii is a notorious nosocomial pathogen due to a combination of its environmental resilience, its association with antimicrobial resistance and its outbreak potential. Colonized patients and contaminated environments are thought to be the primary reservoirs for the nosocomial transmission of this pathogen.

A recent study from China suggests that carriers of MDR A. baumannii (MDR-AB) show stronger ability to contaminate their immediate environment than those carrying MRSA and that MDR-AB spreads more easily and rapidly among inpatients compared with MRSA. The 20-month study was conducted in a respiratory ICU (RICU) where active screening of patients and targeted environmental screening for MRSA and MDR-AB were performed. The environmental samples were collected from 6 sites on patients’ bed linens.

High levels of carriage and nosocomial acquisition were found among the 175 patients admitted to the RICU where 44% of the patients were MDR-AB positive (80% of which were hospital acquired) and 24% of patients were MRSA carriers (60% of which were hospital acquired). Interestingly, 15.4% of the patients were co-carriers of MRSA and MDR-AB.

Researchers found that bed linens were commonly contaminated with MRSA and MDR-AB and that the contamination rate for MDR-AB was significantly higher than that of MRSA. Of the 576 MRSA samples, 26.6% were positive, and 51.6% of the 1,176 MDR-AB swabs were positive. This is surprising given the strict daily extensive cleaning practices, thrice daily bed linen changes and stringent terminal sterilization immediately after discharge of carriers. Researchers used the weekly colonisation pressure adjusted by degree of bed linen contamination (WCPe) and weekly acquisition rate (WAR) as parameters to evaluate the potential spread of these pathogens among inpatients. They found a positive significant correlation between the WCPe and WAR values for both organisms but both the WCPe and WAR of MDR-AB were significantly higher than for MRSA.

This study shows that environmental contamination with MDR-AB and the rate of its nosocomial acquisition is significantly higher than those for MRSA, which may explain why MDR-AB is able to spread among inpatients more rapidly. Although the study found positive significant correlation between the WCPe and WAR in the subsequent weeks, this correlation does not necessarily indicate causality. Nevertheless, the authors conclude that reduction of environmental contamination close to MDR-AB positive patients is crucial in controlling MDR-AB transmission.

Article citation:

Sui W, Wang J, Wang H et al. Comparing the transmission potential of Methicillin-resistantStaphylococcus aureus and multidrug-resistant Acinetobacter baumannii among inpatients using target environmental monitoring. Am J Infect Control. 2012. doi: 10.1016/j.ajic.2012.08.007

Keep your hands to yourself

Jon Otter (@jonotter) Hand hygiene ,

An article in the American Journal of Infection Control evaluates the acquisition of Clostiridium difficile spores on the gloved hands of healthcare personnel (HCP) following contact with environmental surfaces and patients. The work was performed by Guerrero et al. in Curtis Donskey’s team at the Cleveland VA hospital. The prospective study included 30 patients with C. difficile infection. The hands of HCP were effectively used to sample surfaces on patients’ skin and from the inanimate environment. The key findings is that there was no significant difference between the rate of contamination of HCP hands when touching the patient as compared with touching environmental surfaces (50% for both). Although the concentration of spores acquired on the hands was lower for environmental surfaces than for patient sites, there was not a significant difference.

The study evaluated the proportion of various environmental and patient sites that transferred C. difficile spores to the gloved hands of HCP, which ranged from 20% to 50% for both patient and environmental contacts.

This study follows other that have examined the proportion of contacts with either patients or surfaces that result in HCP hand contamination. These studies have shown that the risk of acquiring hand contamination when touching a patient or a surface is approximately equal for MRSA and VRE.

hand_washing_photo

These studies highlight the complex interplay between the hands of HCP, patients and their inanimate environment. It seems likely that a substantial proportion of transmission between patients occurs indirectly through contact with environmental surfaces. For example, a study published in 2000 evaluated the spread of a non-microbial marker (plant DNA) designed to model the spread of pathogens from hospitals surfaces. The marker was inoculated onto a single telephone handle in one of six 8-cot ‘pods’ in a neonatal intensive care unit. The spread of the marker was remarkable: within four hours it was identified from environmental surfaces and staff hands across the unit including all six pods. While the spread of plant DNA does not necessarily accurately represent the spread of a pathogenic micro-organism, it does present a picture of dynamic and rapid transmission involving both environmental surfaces and staff hands.

There has been much discussion around whether to focus on improving environmental cleaning and disinfection or compliance with hand hygiene. These studies demonstrate that there is a need to improve both environmental and hand hygiene in order to maximize patient safety.

Article citation: Guerrero DM, Nerandzic MM, Jury LA, Jinno S, Chang S, Donskey CJ. Acquisition of spores on gloved hands after contact with the skin of patients with Clostridium difficile infection and with environmental surfaces in their rooms. Am J Infect Control 2012;40:556-558.

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

Jon Otter (@jonotter) C. difficile, Disinfection , , , , ,
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.
Micro Blog Jan 2013
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

Jon Otter (@jonotter) Contamination, CRE , ,

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.

12-PDR-A290-278

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

Jon Otter (@jonotter) Disinfection, MRSA , ,

Methicillin-resistant_Staphylococcus_aureus_b2340183_1

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

Jon Otter (@jonotter) Disinfection , , , ,

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 more1-3. Conventional cleaning and disinfection does not reliably remove all environmental MDROs4,5. 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.

MRDO acquisition rates

‘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.

It’s time to give MRSA the red card

Jon Otter (@jonotter) MRSA , ,

red_card

A remarkable study published by a German group found that countries whose national football team performed badly on a fair play indicator had a higher proportion of methicillin-resistance amongst bloodstream isolates. The team investigated the countries who qualified for the 2008 European Football Championship and gave each a ‘fair play indicator’ score (red or yellow cards / 100 min). They then used methicillin resistance data for S. aureus from the European Antimicrobial Resistance Surveillance System (EARSS) programme to plot against the fair play indicator score. The proportion of S. aureus resistant to methicillin correlated with the fair play indicator score (correlation coefficient of 0.632, p=0.038). Greece, Turkey, Italy and Romania clustered together with a high proportion of MRSA and a poor fair play indicator score. The Netherlands and Sweden had a low MRSA rate and a better fair play indicator score.

Does this study highlight cultural differences that influence the national rate of MRSA? Or is this a statistical fluke? Repeating the approach on past or future European challenges (or perhaps even broadening the net to the Football World Cup) will help to confirm the association. But either way, it’s a great study for a football fan!

Article citation: Meyer E, Gastmeier P, Schwab F. National MRSA rates run along with fair play of national football teams: a cross-national data analysis of the European Football Championship, 2008. Infection 2012 Aug 5. [Epub ahead of print]

What is “community-associated” MRSA?

Jon Otter (@jonotter) MRSA , , ,

Community_associated_Methicillin-resistant_Staphylococcus_aureus_b2340183

A study in this month’s ICHE highlights the problems with using epidemiological definitions to designate MRSA as “nosocomial”. The study evaluated the impact of different numerators and denominators on the rate of apparent hospital-onset MRSA across 32 hospitals in California. The time that patients were hospitalized before being considered hospital-onset varied from 48 to more than three days and denominators were also variable. The particular combination of numerator and denominator used resulted in significant differences in the proportion of MRSA cases designated hospital-onset. This has clear implications for comparing rates of hospital-attributable MRSA in the era of public reporting.

The paper raises a wider problem of how to define healthcare- and community-associated MRSA in the era of CA-MRSA strains as a cause of healthcare-associated infections. A recent review in JHI (Otter & French 2012) made the case for a genotypic definition of CA-MRSA. Epidemiological definitions were useful for differentiating CA-MRSA and HA-MRSA strain types in the past. However, although HA-MRSA strain types are rarely transmitted in the community, CA-MRSA strains have now begun to be transmitted in healthcare facilities, so epidemiological definitions are breaking down. CA-MRSA are community strains of S. aureus that have acquired mecA. They are distinct from HA-MRSA and should be defined genetically. Carriage of the Panton-Valentine leukocidin (PVL) or antimicrobial susceptibly profiles can be useful indicators of CA-MRSA but should not be used to define them. For the full assessment of their epidemiology, MRSA infections should now be characterised as (1) caused by HA- or CA-MRSA strain types; (2) acquired in community or healthcare settings; and (3) onset in the community or healthcare facility. (This review made the 10 ten list of the JHI Editors choice and is freely available online here.)

Article citations:

Datta R, Kuo King M, Kim D et al. What Is Nosocomial? Large Variation in Hospital Choice of Numerators and Denominators Affects Rates of Hospital-Onset Methicillin-Resistant Staphylococcus aureus. Infect Control Hosp Epidemiol 2012; 33: 1166-9.

Otter JA, French GL. Community-associated meticillin-resistant Staphylococcus aureus: the case for a genotypic definition. J Hosp Infect 2012; 81: 143-8.