Distribution of multi-resistant Gram-negative versus Gram-positive bacteria in the hospital inanimate environment
Introduction
The increasing emergence and spread of multi-resistant bacteria in hospitals is of great concern and continues to challenge infection control and hospital epidemiology practice worldwide.1., 2., 3., 4. The frequency of cross-transmission varies between 13 and 34.6%, and is especially high in intensive care units (ICUs).5., 6., 7., 8. Rigorous isolation guidelines have been proposed to prevent cross-transmission of multi-resistant bacteria, without distinguishing between Gram-positive and Gram-negative organisms.9., 10., 11., 12., 13., 14. Contamination of the hospital inanimate environment by Gram-positive pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant enterococci (VRE), especially in an epidemic situation, has been frequently addressed.15., 16., 17., 18., 19. Micro-organisms in the inanimate hospital environment are said to contribute only negligibly to endemic nosocomial infections.20., 21., 22., 23. However, limited data are available concerning the degree of contamination of the hospital environment of patients harbouring multi-resistant Gram-negative organisms compared with Gram-positive organisms. Strict isolation is time-consuming, expensive and causes considerable discomfort for patients and hospital personnel.4., 24. Therefore, in order to improve the current situation these recommendations must be evaluated by prospective studies. The aim of this study was: (1) to assess the degree of contamination of hospital rooms and the patients' inanimate environment with multi-resistant Gram-negative and Gram-positive bacteria; (2) to discuss the role played by these bacteria in cross-transmission; and (3) to evaluate current isolation precautions in light of these findings.
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Setting
The University Hospital Aachen is a tertiary care teaching hospital with around 1500 beds. Annually, approximately 48 000 patients are admitted and account for 470 000 patient bed-days. This study was performed in nine ICUs (anaesthetics, burns unit, cardiac surgery, internal medicine, neurology, neurosurgery, paediatric and general surgery) with 101 beds. Additionally, all the general wards (GWs) were studied. Surfaces in the ICUs (floor, walls and all easily accessible items) were disinfected
Results
One hundred and ninety patients who were either colonized or infected with MRSA, VRE or multi-resistant Gram-negative bacteria were consecutively enrolled and monitored during the study. Fifty-four patients (28.4%) harboured multi-resistant Gram-positive bacteria and 136 (71.6%), multi-resistant Gram-negative bacteria (see Table I). The mean hospital stay before the microbiological isolation and the environmental sampling was 7.3 and 19.4 days for Gram-positive and Gram-negative isolates,
Discussion
We have clearly demonstrated that the degree of environmental contamination with multi-resistant Gram-positive organisms (e.g. MRSA and VRE) was much more extensive than for multi-resistant Gram-negative pathogens (24.7 versus 4.9%, P<0.0001). During the study period, the average prevalence for MRSA was 0.13 MRSA-positive patients per 1000 patient days. As no outbreak or cluster was observed during this time, this extremely low prevalence suggests that the environmental samples found were
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