Ongoing dissemination of OXA-244 carbapenemase-producing Escherichia coli in Switzerland and their detection

OXA-244 is a derivative of OXA-48 showing weaker carbapenemase activity, compromising the detection of corresponding producers in clinical laboratories. Since 2017, the Swiss National Reference Center for Emerging Antibiotic Resistance noticed an increased identification of OXA-244-producing Escherichia coli (n=15) within the country. Different methods (biochemical and immunoassay tests, screening culture media) were tested for the detection of OXA-244 producers. Whole genome sequencing was used to investigate the genetic relatedness between the isolates and the genetic structures at the origin of the acquisition of the bla(OXA-244) gene. The mSuperCARBA (R) medium and the NG-Test CARBA5 assay were found to be suitable tools for detecting all OXA-244-producing isolates.Other selective media did not perform optimally. Among the fifteen strains, live sequence types were identified, with ST38 being predominant. The bla(OXA-244) gene was located on the chromosome for all isolates. Overall, detection of OXA-244 producers is challenging and specific: guidelines must be followed. (C) 2020 The Authors. Published by Elsevier Inc.