ABSTRACT

We compared the abilities of Enterococcus faecium strains (three vancomycin-resistant enterococci [VRE] and five vancomycin-susceptible enterococci [VSE]) and Enterococcus faecalis strains (one VRE and 10 VSE) to survive under dry conditions. Bacterial suspensions of the strains were inoculated onto polyvinyl chloride and stored under defined conditions for up to 16 weeks. All strains survived for at least 1 week, and two strains survived for 4 months. A statistical model was used to distribute the 19 resulting survival curves between two types of survival curves. The type of survival curve was not associated with the species (E. faecalis versus E. faecium), the source of isolation (patient versus environment), or the susceptibility to vancomycin (VRE versus VSE). Resistance to dry conditions may promote the transmissibility of a strain, but VRE have no advantages over VSE with respect to their ability to survive under dry conditions.

Since the first reported infection due to vancomycin-resistant enterococci (VRE) (10) many outbreaks of VRE infections or colonization have been reported (3, 4, 7–9, 11–14, 17, 18, 20). At least two of these outbreaks were traceable to environmental sources: one to contaminated rectal thermometers (12) and one to contaminated nursing bells (11).

According to earlier experiences with Staphylococcus aureus, resistant strains may survive longer under dry conditions than susceptible strains (19). These findings raised questions as to whether VRE can survive longer under dry conditions than vancomycin-susceptible enterococci (VSE). We therefore compared the abilities to survive under dry conditions of eight E. faecium strains (three VRE and five VSE) and 11 E. faecalis strains (one VRE and 10 VSE) (Table (Table1).1).

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