High Prevalence of OXA-23 Carbapenemase-Producing Proteus mirabilis among Amoxicillin-Clavulanate-Resistant Isolates in France

Abstract

In this multicentric study performed in 12 French hospitals, we reported that 26.9% (14/52) of the amoxicillin-clavulanate-resistant Proteus mirabilis isolates produced the OXA-23 carbapenemase. We found that an inhibition zone diameter of <11 mm around the amoxicillin-clavulanate disc was an accurate screening cutoff to detect these OXA-23 producers. We confirmed by whole-genome sequencing that these OXA-23-producers all belonged to the same lineage that has been demonstrated to disseminate OXA-23 or OXA-58 in P. mirabilis.

Keywords: Acinetobacter; OXA-23; Proteae; carbapenemase; epidemiology; infectious clones.

FIG 1

Characteristics of the 52 amoxicillin-clavulanate-resistant P. mirabilis isolates. (A) Geographic distribution and clinical samples. (B) Distribution of the amoxicillin-clavulanate zone inhibition diameters. (C) Distribution of the amoxicillin-clavulanate minimal inhibition concentrations.

FIG 2

(A) Phylogenetic relationship of the 14 OXA-23-producing P. mirabilis isolates with the 145 reference genomes of P. mirabilis reported by Bonnin et al. (10). This comparison was performed on 17.83% of the genome of OXA-23-producing P. mirabilis VAC used as a reference. (B) Phylogenetic relationship of the OXA-23/OXA-58-producing P. mirabilis isolates. This comparison was performed on 57.36% of the genome of OXA-23-producing P. mirabilis VAC used as a reference. OXA-23-producing P. mirabilis from this study are marked by a black point. Scale bar on tree indicates the number of single-nucleotide polymorphisms per position of common sequences.