The dissemination of multidrug-resistant Enterobacter cloacae throughout the UK and Ireland

Abstract

Enterobacter cloacae is a clinically important Gram-negative member of the Enterobacteriaceae, which has increasingly been recognized as a major pathogen in nosocomial infections. Despite this, knowledge about the population structure and the distribution of virulence factors and antibiotic-resistance determinants of this species is scarce. In this study, we analysed a systematic collection of multidrug-resistant E. cloacae isolated between 2001 and 2011 from bloodstream infections across hospitals in the UK and Ireland. We found that the population is characterized by the presence of multiple clones formed at widely different time periods in the past. The clones exhibit a high degree of geographical heterogeneity, which indicates extensive dissemination of these E. cloacae clones across the UK and Ireland. These findings suggest that a diverse, community-based, commensal population underlies multidrug-resistant E. cloacae infections within hospitals.

Figure 1

A) Histogram of pair-wise SNP distance between the core genome sequences of isolates. B) Maximum Likelihood tree for the isolates. The colours of the isolates correspond to hospitals of isolation.

Figure 2

A) Detected clusters (CLs) represented on the phylogenetic tree. The intensity of branch colour corresponds to the bootstrap support (SH support). B) MLST sequence type (ST) composition of each of the clusters. Each colour signifies one ST. C) Hospitals from which isolates in each cluster were identified. D) Distribution of pairwise geographical distance for each cluster compared with the distribution of the whole population. The notched area shows the 95% confidence interval around the median. E) Distribution of the time of isolation for isolates in each cluster. The boxes in D) and E) give the interquartile range, the whiskers indicate the boundary of 1.5 times the interquartile range, and the points beyond that are outliers.