Aims: In this study, we analyzed the molecular epidemiology of extended-spectrum β-lactamase (ESBL)-producing Proteus mirabilis isolates collected from the central region of Japan.
Materials and methods: Between 2005 and 2012, 820 clinical P. mirabilis isolates were obtained from ten acute care hospitals in Japan. We characterized ESBL confirmatory test-positive isolates by sequencing the ESBL genes and their flanking regions, detecting plasmid replicons, and performing pulsed-field gel electrophoresis (PFGE).
Results: Ninety-six isolates (12%) were positive according to the ESBL confirmatory test; all these isolates possessed blaCTX-M-2 with the same flanking structure of upstream ΔISEcp1 and a downstream region identical to downstream blaKLUA-1. IncT was the prevalent, and only, replicon found in 63 isolates. PFGE analysis detected eight clusters with more than one isolate, among which three included 56 isolates and six included isolates from multiple hospitals.
Conclusion: CTX-M-2-producing P. mirabilis with an identical genetic structure flanking blaCTX-M-2 is dominant in this Japanese region, and there is evidence for the clonal spread of isolates.
Keywords: CTX-M-2; ESBLs; IncT; Proteus mirabilis; clonal spread.