Abstract

In this study, we identified extended-spectrum ß-lactamase (ESBL) and plasmid-mediated AmpC ß-lactamase which were associated with 16S rRNA methylase gene on the conjugative plasmid. Among 82 clinical isolates of Enterobacteriaceae that carry 16S rRNA methylase gene (64 strains, armA, and 18 strains, rmtB), blaSHV-12 was detected either alone or combined with blaDHA-1, blaCTX-M-3, and blaCTX-M-14 in 30 strains carrying armA and 6 strains carrying rmtB. The blaCTX-M-3 was detected in 13 of 64 strains carrying armA but no strains carrying rmtB. Whereas blaCTX-M-14 was detected in 15 of 18 strains carrying rmtB but only 2 of 64 strains carrying armA. Overall, blaSHV-12 and blaCTX-M-14 was the most common ESBL gene which was associated with armA and rmtB, respectively. In addition, we found that blaCTX-M-3 localized with armA on the same IncL/M plasmid and blaCTX-M-14 localized with rmtB on the same IncA/C plasmid. Restriction fragment length polymorphism of conjugative plasmids and pulsed-field gel electrophoresis of genomic DNAs revealed that intercellular horizontal transfer of conjugative plasmid and clonal transmission have been occurred at the same time.

• Keywords: 16S rRNA methylase; extended-spectrum beta-lactamase; IncL/M; IncA/C; Enterobacteriaceae