Enhanced cleaning of intensive care unit rooms did a better job of reducing the overall risk of acquiring methicillin-resistant S. aureus than it did of reducing the risk of acquiring vancomycin-resistant enterococci.
The findings from a retrospective cohort study, published March 28 in the Archives of Internal Medicine, showed that a cleaning intervention lowered MRSA acquisition by 49% and VRE acquisition by 29% for patients admitted to rooms previously occupied by carriers of either organism, in any of 10 ICUs in a 750-bed academic medical center.
The cleaning intervention consisted of frequently immersing cleaning cloths in buckets containing an ammonium agent. The adequacy of cleaning was measured by the presence of a tracking marker that was visible under UV light. Based on measures of the marker, staff were given targeted feedback designed to improve their cleaning technique.
The intervention paid off in reduced transmissions, but "the impact of this intervention depends on the prevalence of pathogens in hospitals," Rupak Datta, the lead author of the study (Arch. Intern. Med. 2011;171:491-4), said in an interview.
Further, "environmental contamination makes up a small fraction of overall transmission" of antibiotic-resistant organisms in hospitals, noted Mr. Datta of the University of California, Irvine. The majority of MRSA and VRE transmissions are the result of suboptimal handwashing by hospital staff, he said.
Mr. Datta and the research group had formerly shown that admission to rooms previously occupied by a MRSA-positive or a VRE-positive patient increased by 40% the odds of MRSA and VRE acquisition (Arch. Intern. Med. 2006;166:1945-51). Cleaning interventions were undertaken as a result of that finding. In addition, other investigators had reported that "increasing the volume of disinfectant applied to environmental surfaces, providing education for Environmental Services staff, and instituting feedback with a black-light marker improved cleaning and reduced the frequency of MRSA and VRE contamination" (Infect. Control Hosp. Epidemiol. 2008;29:593-9).
In the current study, the group evaluated the impact of the cleaning interventions on patient risk of acquiring MRSA or VRE from the prior room occupants.
The researchers compared hospital occupancy data during the 2 years when the enhanced cleaning intervention was implemented (Sept. 1, 2006, through April 30, 2008) with baseline data from the 2 years prior to the implementation (Sept. 1, 2003, through April 30, 2005).
For MRSA detection, there were 10,151 eligible room stays at baseline, and 11,849 at intervention. There were 10,349 eligible room stays for VRE detection at baseline, and 11,871 at intervention.
The MRSA acquisition rate decreased from 3% (305 of 10,151) at baseline to 1.5% (182 of 11,849) at intervention. The VRE acquisition rate fell from 3% (314 if 10,349) at baseline to 2.2% (256 of 11,871) at intervention.
Patients at baseline who were admitted to rooms previously occupied by MRSA carriers had a 3.9% risk of MRSA acquisition, compared with 2.9% for patients admitted to rooms previously occupied by MRSA-negative patients. After the cleaning intervention, the risk of MRSA acquisition was 1.5% for all patients, regardless of whether the previous room occupant had MRSA.
Patients admitted at baseline to rooms previously occupied by VRE carriers had a 4.5% risk of VRE acquisition, compared with a 2.8% risk when the previous room occupant was not a VRE carrier. After the intervention, the risk of acquiring VRE was 3.5% when the previous room occupant was a VRE carrier and 2% when the previous room occupant wasn’t a carrier.
"We were surprised" by the difference in the results between MRSA and VRE, said Mr. Datta.
The authors cited several explanations for this difference, including the "generally higher burden of VRE contamination and evidence that room contamination may be a major factor in VRE transmission." They added that "VRE contamination has been shown to persist through three standard room cleanings."
The study’s limitations include lack of data on antibiotic use, which is associated with increased VRE shedding and acquisition.
"Additional studies are needed to evaluate the differential effect of enhanced cleaning on MRSA vs. VRE. This may be particularly relevant for hospitals with high VRE prevalence, where the burden of VRE contamination may demand more rigorous cleaning methods," the authors wrote.
The authors reported no financial conflicts.