Detection of OXA-181-producing Pseudomonas aeruginosa in Germany

Objectives

To report the detection of the class D carbapenemase OXA-181 in an MDR clinical Pseudomonas aeruginosa isolate in Germany.

Methods

Carbapenemase detection was performed by using several phenotypic tests such as the modified Hodge test, a combined disc test with boronic acid, EDTA or cloxacillin, a lysate-based inhibition assays and by PCR for common and rare carbapenemase genes. Antibiotic susceptibilities were determined by broth microdilution. The genetic environment of bla_OXA-181 in the clinical P. aeruginosa isolate was characterised by Illumina and MinION sequencing.

Results

An multidrug-resistant P. aeruginosa was isolated from a tracheal swab in 2019 and was sent to the German National Reference Centre for multidrug-resistant Gram-negative bacteria for carbapenemase detection. Several phenotypic tests indicated the presence of a carbapenemase which was not inhibited by EDTA nor by boronic acid. PCRs for common and rare carbapenemase genes revealed the presence of a bla_OXA-181 gene. WGS data confirmed that the gene was located on the chromosome as part of a Tn2013 transposon. The genetic organisation of bla_OXA-181 has already been described in a P. aeruginosa isolate from England, but both isolates differed significantly in their sequence types (ST111/ST235). Analysis of the genetic environment of the bla_OXA-181 gene also revealed high homology to a plasmid from a Klebsiella pneumoniae isolate.

Conclusions

To our knowledge, this is the first report of bla_OXA-181 in a clinical P. aeruginosa isolate in Germany which emphasises the ongoing spread of yet unusual carbapenemases among different Gram-negative species and therefore complicating their detection in routine laboratories.