Plasmid-borne armA methylase gene, together with blaCTX-M-15 and blaTEM-1, in a Klebsiella oxytoca isolate from China

Abstract

An armA-producing Klebsiella oxytoca isolate, strain 157, was detected after screening of 447 extended-spectrum β-lactamase-producing Enterobacteriaceae isolates in China. K. oxytoca 157 was resistant to aminoglycosides, ciprofloxacin and most β-lactams. Resistance to aminoglycosides and β-lactams could be transferred to recipient Escherichia coli by conjugation. armA, blaCTX-M-15 and blaTEM-1 genes were detected in K. oxytoca 157 and transconjugant E. coli strain 600(pEC157). Mutation of aa 87 in GyrA was found in K. oxytoca 157. A plasmid of ∼55 kb was extracted from K. oxytoca 157(pKO157) and E. coli 600(pEC157). Southern blot hybridization confirmed that the armA, blaCTX-M-15 and bla TEM-1 genes were all located on this conjugative plasmid (pEC157). PCR mapping was also performed to investigate the genetic environment of armA. The armA gene was found to be flanked by the same putative transposable elements as reported previously in E. coli, Klebsiella pneumoniae and Citrobacter freundii isolates from different countries. © 2008 SGM.