Molecular characteristics of extended-spectrum lactamase-producing Escherichia coli in Japan: emergence of CTX-M15 in Japanese clinical isolates of E.coli ST131

Abstract number: P632

Yano H., Hitoshi K., Hirakata Y., Arai K., Endo S., Kanamori H., Ogawa M., Shimojima M., Ishibashi N., Aoyagi T., Hatta M., Yamada M., Nishimaki K., Tokuda K., Kitagawa M., Kunishima H., Kaku M.

Objectives: The prevalence of extended-spectrum b-lactamase (ESBL) has recently been increasing worldwide. In this study, we investigated the molecular epidemiology and characteristics of ESBL-producing Escherichia coli and plasmid-mediated quinolone resistance (PMQR) determinants among these isolates in Japan.

Methods: A total of 101 clinical isolates of ESBL-positive E. coli collected from 11 institutes in eastern Japan between June 2008 and November 2009 were studied. Antimicrobial susceptibilities of the strains were determined. PCR was performed to identify b-lactamase genes blaTEM, blaSHV, and blaCTX-M. For CTX-M-positive strains, PCR was performed to identify CTX-M-1, CTX-M-2, and CTX-M-9 group-specific primers. PCR products of TEM, SHV, CTX-M-1 group, CTX-M-2 group, and CTX-M-9 group genes were sequenced. These isolates were also analyzed by multilocus sequence typing (MLST). Detection of PMQR gene (qnrA, qnrB, qnrC, qnrS, and qepA) and aac(6')-Ib gene was performed by PCR. aac(6')-Ib amplicons were sequenced to confirm the -cr variant.

Results: All 101 strains were intermediate or resistant to ampicillin, piperacillin, cefpodoxime, cefotaxime, aztreonam, and cefepime, and 97 (96.0%) of them were to levofloxacin. Of the 101 strains, 97 (96.0%) were positive for CTX-M, while 47 (46.5%) and two (2.0%) were positive for TEM and SHV, respectively. Among the 97 CTX-M-positive strains, 18 were CTX-M-1 group; four were CTX-M-2 group; and 75 were CTX-M-9 group. Sequencing results revealed that CTX-M-14 was the most prevalent (49/101: 48.5%), following by CTX-M-27 (22/101: 21.8%) and CTX-M-15 (8/101: 7.9%). Both of two CTX-M-2 group-positive strains were CTX-M-2. All of the 47 TEM-positive strains were TEM-1, and the two SHV-positive strains were SHV-12. Based on MLST, seven of eight CTX-M-15-producing isolates belonged to sequence typing (ST) 131. One and two isolates carried qnrB and qnrS, respectively, while there were no qnrA nor qnrC-positive isolates. Sequencing revealed that nine of 13 aac(6')-Ib-positive strains were -cr variant. Six of eight CTX-M-15-producing isolates were positive for aac(6')-Ib-cr.

Conclusion: Our results suggest that CTX-M-14 was the most prevalent in ESBL-producing E. coli and ST131 producing CTX-M-15 has emerged in Japan. To our knowledge, this is the first report of CTX-M-15-producing E. coli ST131 in Japan.

Session Details

Date: 07/05/2011
Time: 00:00-00:00
Session name: Abstracts of 21st ECCMID / 27th ICC
Location: Milan, Italy, 7 - 10 May 2011
Presentation type:
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