Dissemination of blaOXA-58 in Proteus mirabilis isolates from Germany

Area of Science:

• Microbiology
• Genetics
• Antimicrobial Resistance

Background:

• Carbapenemase-producing Enterobacterales (CPE) are a significant global health threat.
• Proteus mirabilis is a common opportunistic pathogen, but carbapenem resistance is rarely reported.
• The bla OXA-58 gene encodes a carbapenemase primarily found in Acinetobacter species.

Purpose of the Study:

• To characterize Proteus mirabilis isolates carrying the bla OXA-58 gene.
• To investigate the genetic environment and plasmid context of bla OXA-58 in P. mirabilis.
• To assess the susceptibility profiles and diagnostic implications of bla OXA-58 in P. mirabilis.

Main Methods:

• Whole-genome sequencing (WGS) and Sanger sequencing were used to determine the genetic context of bla OXA-58.
• Pulsed-field gel electrophoresis (PFGE) was employed to assess strain clonality.
• Antimicrobial susceptibility testing (AST) was performed using microdilution according to EUCAST guidelines, and Carba NP testing was conducted.

Main Results:

• Four P. mirabilis strains from different German regions harbored bla OXA-58 on nearly identical plasmids (6219 and 6208 bp).
• An IS Aba 3-like transposase gene was located upstream of bla OXA-58.
• The P. mirabilis strains were not clonally related, and meropenem MICs were borderline or below EUCAST breakpoints, with variable Carba NP test results.

Conclusions:

• This is the first report of bla OXA-58 in Proteus mirabilis, carried on similar plasmids in non-clonal strains from diverse locations.
• The genetic environment of bla OXA-58 in P. mirabilis differs from that observed in Acinetobacter species.
• The low meropenem MICs and potential for false-negative Carba NP tests highlight the risk of overlooking bla OXA-58 in P. mirabilis infections.