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 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.
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].