Most multidrug-resistant Pseudomonas aeruginosa isolates from hospitals in eastern France belong to a few clonal types

Abstract

This study aimed to determine the genetic diversity of clinical multidrug-resistant Pseudomonas aeruginosa. We used pulsed-field gel electrophoresis and multilocus sequence typing to analyze 187 strains isolated in different French hospitals. To illustrate the diversity of resistance mechanisms to antibiotics in a given clone, we identified β-lactamases with an extended spectrum by using phenotypic and genotypic methods. Typing results showed that the majority of our multidrug-resistant isolates belong to a few clonal types (ST235, ST111, and ST175) that are already spreading worldwide. These successful international clones sporadically produced extended-spectrum β-lactamase-encoding genes but mostly became extensively resistant to β-lactams after derepression of intrinsic resistance mechanisms (i.e., AmpC cephalosporinase). Our results indicate that cross-transmission plays a major role in the spread of multidrug-resistant P. aeruginosa in hospital settings.

Fig. 1

Dendrogram of the percent similarity between DraI-digested genomic DNAs from multidrug-resistant P. aeruginosa isolates. B, Besancon University Hospital; D, Dijon University Hospital; N, Nancy University Hospital; S, Strasbourg University Hospital; R, Reims University Hospital.

Fig. 2

Distribution of epidemic lineages of P. aeruginosa in eastern France (A) (this study), Europe (B), and worldwide (C). For maps B and C, the β-lactamase content is specified in brackets when available, according to references , , , to , , , and and the MLST database (http://pubmlst.org/paeruginosa).