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

Abstract

Introduction: blaOXA-48 is a globally emerging carbapenemase-encoding gene. The progenitor of blaOXA-48 appears to be a Shewanella species. The presence of the blaOXA-48-like gene was investigated for two Shewanella xiamenensis strains. Methods: Strain 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 blaOXA-48-like genes and to obtain their complete sequences. A phylogenetic tree of the blaOXA-48-like genes was constructed. The genetic context of the blaOXA-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. Results: A new blaOXA-48 variant, designated blaOXA-48b, with four silent nucleotide differences from the blaOXA-48 (designated blaOXA-48a) found in the Enterobacteriaceae was identified in strain S4. Strain WCJ25 had a new blaOXA-48-like variant, blaOXA-199, with five nucleotide differences from blaOXA-48a and blaOXA-48b. The OXA-199 protein has three amino acid substitutions (H37Y, V44A and D153G) compared with OXA-48. Both blaOXA-48b and blaOXA-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 blaOXA-199 but not of blaOXA-48b. The 26 bp sequences upstream and 63 bp downstream of blaOXA-48a, blaOXA-48b and blaOXA-199 were identical. Conclusions: blaOXA-48a, blaOXA-48b and blaOXA-199 might have a common origin, suggesting that the blaOXA-48a gene found in the Enterobacteriaceae could have originated from the chromosome of S. xiamenensis. © 2012 Zhiyong Zong.