title: Characterization of Piperacillin/Tazobactam-Resistant Klebsiella oxytoca Recovered from a Nosocomial Outbreak.
abstract: We characterized 12 clinical isolates of Klebsiella oxytoca with the extended-spectrum β-lactamase (ESBL) phenotype (high minimum inhibitory concentration [MIC] values of ceftriaxone) recovered over 9 months at a university hospital in Japan. To determine the clonality of the isolates, we used pulsed-field gel electrophoresis (PFGE), multi-locus sequence typing (MLST), and PCR analyses to detect blaRBI, which encodes the β-lactamase RbiA, OXY-2-4 with overproduce-type promoter. Moreover, we performed the isoelectric focusing (IEF) of β-lactamases, and the determination of the MICs of β-lactams including piperacillin/tazobactam for 12 clinical isolates and E. coli HB101 with pKOB23, which contains blaRBI, by the agar dilution method. Finally, we performed the initial screening and phenotypic confirmatory tests for ESBLs. Each of the 12 clinical isolates had an identical PFGE pulsotype and MLST sequence type (ST9). All 12 clinical isolates harbored identical blaRBI. The IEF revealed that the clinical isolate produced only one β-lactamase. E. coli HB101 (pKOB23) and all 12 isolates demonstrated equally resistance to piperacillin/tazobactam (MICs, >128 μg/ml). The phenotypic confirmatory test after the initial screening test for ESBLs can discriminate β-lactamase RbiA-producing K. oxytoca from β-lactamase CTX-M-producing K. oxytoca. Twelve clinical isolates of K. oxytoca, which were recovered from an outbreak at one university hospital, had identical genotypes and produced β-lactamase RbiA that conferred resistance to piperacillin/tazobactam. In order to detect K. oxytoca isolates that produce RbiA to promote research concerning β-lactamase RbiA-producing K. oxytoca, the phenotypic confirmatory test after the initial screening test for ESBLs would be useful.
authors.affiliation: Department of Bacteriology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
authors.forename: Ai
authors.initials: A
authors.lastname: Fujita
authors.affiliation: Department of Bacteriology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
authors.forename: Kouji
authors.initials: K
authors.lastname: Kimura
authors.affiliation: Department of Bacteriology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Yokoyama
authors.affiliation: Department of Bacteriology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
authors.forename: Wanchun
authors.initials: W
authors.lastname: Jin
authors.affiliation: Department of Bacteriology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Wachino
authors.affiliation: Department of Bacteriology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Yamada
authors.affiliation: Department of Clinical Infectious Diseases, Aichi Medical University Graduate School of Medicine, 1-1 Yazakokarimata, Nagakute, Aichi 480-1195, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Suematsu
authors.affiliation: Department of Clinical Infectious Diseases, Aichi Medical University Graduate School of Medicine, 1-1 Yazakokarimata, Nagakute, Aichi 480-1195, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Yamagishi
authors.affiliation: Department of Clinical Infectious Diseases, Aichi Medical University Graduate School of Medicine, 1-1 Yazakokarimata, Nagakute, Aichi 480-1195, Japan.
authors.forename: Hiroshige
authors.initials: H
authors.lastname: Mikamo
authors.affiliation: Department of Bacteriology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
authors.forename: Yoshichika
authors.initials: Y
authors.lastname: Arakawa
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D003428:Cross Infection / Q000188:drug therapy / Q000382:microbiology*; D004196:Disease Outbreaks; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000382:microbiology; D005260:Female; D006801:Humans; D007564:Japan; D007710:Klebsiella Infections / Q000188:drug therapy / Q000382:microbiology; D041121:Klebsiella oxytoca / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D008297:Male; D008826:Microbial Sensitivity Tests / Q000379:methods; D008875:Middle Aged; D058885:Multilocus Sequence Typing / Q000379:methods; D010397:Penicillanic Acid / Q000031:analogs & derivatives* / Q000627:therapeutic use; D010878:Piperacillin / Q000627:therapeutic use*; D000078142:Tazobactam; D001618:beta-Lactamases / Q000235:genetics; D047090:beta-Lactams / Q000627:therapeutic use
chemical_list: D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D010397:Penicillanic Acid; D001618:beta-Lactamases; D000078142:Tazobactam; D010878:Piperacillin