Clinical microbiologists, Infection Preventionists and Infectious Disease experts all agree that multidrug-resistant gram-negative bacteria pose the greatest risk to public health. The reasoning is 2-fold. First, resistance development occurs faster in gram-negative bacteria than gram-positive bacteria, but perhaps most importantly there are fewer new antibiotics coming to market that are active against gram-negative bacteria. If we combine this with the fact that over the past decade we have been able to prove that the environment plays a large role in the spread of most of the key hospital-associated infections, this means that we need to better understand the ability of these key pathogens to survive on surfaces and infect our patients.
CRE in particular is a concern due to the fact that CRE infections are difficult to treat with mortality rates of 40% - 50%! Due to CRE's impact as a public health threat, Weber et al conducted a study that investigated the frequency and location of environmental contamination of CRE and the ability of CRE to survive on surfaces.
For the first part of the study, the researchers sampled surfaces such as bed rails, overbed tables, chair arms, sinks, toilets, bathroom floor, supply/medicine carts and the tops of the linen hampers in 15 rooms of patients colonized or infected with CRE. The cultures found 6 different strains of Enterobacter spp. and a strain of Klebsiella pneumoniae and found that only 8.4% of the surfaces were contaminated, with bed rails, sinks and toilets being associated with the most frequently contaminated.
The second part of the study looked at the survival ability of CRE strains of K. pneumoniae, E.coli and Enterobacter sp. when inoculated on overbed tables, vinyl surfaces, stainless steel, Formica and cloth. With the exception of Klebsiella on Formica, all 3 pathogens showed <15% survival rate at the 24 hr mark, <5% at the 48 hr mark and 0% at 72hrs. Further E. coli did not survive as well as K. pneumoniae or Enterobacter spp.
Overall, the study showed that CRE is infrequently isolated from environmental surfaces in rooms of infected patients, and if isolated, is only found in small numbers. These results suggests that CRE does not survive well in the environment in comparison with other key hospital-associated pathogens such as MRSA, VRE, C.diff, MDR Acinetobacter spp and MDR Pseudomonas.
Without a doubt, CRE is a growing concern and significant public health threat, however we may be able to breathe a little easier knowing that it appears the environment may play a less important role in the transmission of CRE. It's certainly not conclusive.....but it could be a glimmer of a light at the end of a long and dark tunnel in understanding how to manage CRE.