Discovery of blaOXA-199, a Chromosome-Based blaOXA-48-Like Variant, in Shewanella xiamenensis

Abstract

Introduction bla OXA-48 is a globally emerging carbapenemase-encoding gene. The progenitor of bla OXA-48 appears to be a Shewanella species. The presence of the bla OXA-48-like gene was investigated for two Shewanella xiamenensis strains.MethodsStrain WCJ25 was recovered from post-surgical abdominal drainages, while S4 was the type strain of S. xiamenensis. Species identification for WCJ25 was established by sequencing the 16S rDNA and gyrB genes. PCR was used to screen the bla OXA-48-like genes and to obtain their complete sequences. A phylogenetic tree of the bla OXA-48-like genes was constructed. The genetic context of the bla OXA-48-like gene in strain WCJ25 was investigated by inverse PCR using self-ligated AseI- or RsaI-restricted WCJ25 DNA fragments as template, while that in strain S4 was determined by PCR mapping using that in WCJ25 as template.ResultsA new bla OXA-48 variant, designated bla OXA-48b, with four silent nucleotide differences from the bla OXA-48 (designated bla OXA-48a) found in the Enterobacteriaceae was identified in strain S4. Strain WCJ25 had a new bla OXA-48-like variant, bla OXA-199, with five nucleotide differences from bla OXA-48a and bla OXA-48b. The OXA-199 protein has three amino acid substitutions (H37Y, V44A and D153G) compared with OXA-48. Both bla OXA-48b and bla OXA-199 were found adjacent to genes encoding a peptidase (indicated as orf), a protein of unknown function (sprT), an endonuclease I (endA), and a ribosomal RNA methyl transferase (rsmE) upstream and to transcriptional regulator gene lysR and an acetyl-CoA carboxylase-encoding gene downstream. In addition, the insertion sequence ISShes2 was found inserted downstream of bla OXA-199 but not of bla OXA-48b. The 26 bp sequences upstream and 63 bp downstream of bla OXA-48a, bla OXA-48b and bla OXA-199 were identical.Conclusions bla OXA-48a, bla OXA-48b and bla OXA-199 might have a common origin, suggesting that the bla OXA-48a gene found in the Enterobacteriaceae could have originated from the chromosome of S. xiamenensis.