Carbapenem-Susceptible OXA-23-Producing Proteus mirabilis in the French Community

Abstract

Nineteen Proteus mirabilis isolates producing the carbapenemase OXA-23 were recovered over a 2-year period in 19 French hospitalized patients, of whom 12 had community onset infections. The isolates exhibited a slightly reduced susceptibility to carbapenems. Whole-genome analysis revealed that all 19 isolates formed a cluster compared to 149 other P. mirabilis isolates. Because of its susceptibility to carbapenems, this clone may be misidentified as a penicillinase producer while it constitutes a reservoir of the OXA-23-encoding gene in the community.

Keywords: OXA-23; Proteus mirabilis; carbapenemase; clonality; spread.

FIG 1

Phylogenetic network of the genomes of 168 P. mirabilis isolates. The genomic comparison included the 19 bla_OXA-23 isolates collected at the University Hospital of Besançon (France) and 149 P. mirabilis isolates available in the NCBI database (Table S1). The core genome was defined as genes shared by ≥95% of the selected genomes (≥160/168 genomes). It was composed of 2,660 genes of the 3,686 genes annotated in reference strain P. mirabilis HI4320. The network was built using core genome multilocus sequence typing (cgMLST) distances with the neighborNet method in SplitTree4 (17). OXA-23- and CMY-2-positive P. mirabilis clusters are surrounded by a rectangle and a triangle, respectively. Circles represent two additional genomic branches evolving from a common ancestor.

FIG 2

Schematic representation of bla_OXA-23 insertion in the PmOXA23 clone. Genes are represented by light gray arrows indicating the direction of transcription. The predicted functions of genes are shown under the arrows. Gray boxes and black triangles represent insertion sequences and direct repeats, respectively. The OXA-23-carrying transposon-like structure of strain PmOXA23-13 (GenBank accession number SLUF00000000) was compared to that of an OXA-58-positive P. mirabilis 1091 isolate (accession number MCOR00000000).