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

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. 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 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. Results A 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-48 a 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 IS Shes2 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 .