Dataset Information

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 ?-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 ?-lactamase RbiA, OXY-2-4 with overproduce-type promoter. Moreover, we performed the isoelectric focusing (IEF) of ?-lactamases, and the determination of the MICs of ?-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 ?-lactamase. E. coli HB101 (pKOB23) and all 12 isolates demonstrated equally resistance to piperacillin/tazobactam (MICs, >128 ?g/ml). The phenotypic confirmatory test after the initial screening test for ESBLs can discriminate ?-lactamase RbiA-producing K. oxytoca from ?-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 ?-lactamase RbiA that conferred resistance to piperacillin/tazobactam. In order to detect K. oxytoca isolates that produce RbiA to promote research concerning ?-lactamase RbiA-producing K. oxytoca, the phenotypic confirmatory test after the initial screening test for ESBLs would be useful.

SUBMITTER: Fujita A

PROVIDER: S-EPMC4634934 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Characterization of Piperacillin/Tazobactam-Resistant Klebsiella oxytoca Recovered from a Nosocomial Outbreak.

Fujita Ai A Kimura Kouji K Yokoyama Satoru S Jin Wanchun W Wachino Jun-Ichi J Yamada Keiko K Suematsu Hiroyuki H Yamagishi Yuka Y Mikamo Hiroshige H Arakawa Yoshichika Y

PloS one 20151105 11

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 perf ...[more]

PMID: 26539828

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Project description:Klebsiella pneumoniae is emerging as an important nosocomial pathogen due to its rapidly increasing multidrug resistance, which has led to a renewed interest in polymyxin antibiotics, such as colistin, as antibiotics of last resort. However, heteroresistance (i.e., the presence of a subpopulation of resistant bacteria in an otherwise susceptible culture) may hamper the effectiveness of colistin treatment in patients. In a previous study, we showed that colistin resistance among extended-spectrum-beta-lactamase (ESBL)-producing K. pneumoniae isolates emerged after the introduction of selective digestive tract decontamination (SDD) in an intensive care unit (ICU). In this study, we investigated heteroresistance to colistin among ESBL-producing K. pneumoniae isolates by using population analysis profiles (PAPs). We used whole-genome sequencing (WGS) to identify the mutations that were associated with the emergence of colistin resistance in these K. pneumoniae isolates. We found five heteroresistant subpopulations, with colistin MICs ranging from 8 to 64 mg/liter, which were derived from five clonally related, colistin-susceptible clinical isolates. WGS revealed the presence of mutations in the lpxM, mgrB, phoQ, and yciM genes in colistin-resistant K. pneumoniae isolates. In two strains, mgrB was inactivated by an IS3-like or ISKpn14 insertion sequence element. Complementation in trans with the wild-type mgrB gene resulted in these strains reverting to colistin susceptibility. The MICs for colistin-susceptible strains increased 2- to 4-fold in the presence of the mutated phoQ, lpxM, and yciM alleles. In conclusion, the present study indicates that heteroresistant K. pneumoniae subpopulations may be selected for upon exposure to colistin. Mutations in mgrB and phoQ have previously been associated with colistin resistance, but we provide experimental evidence for roles of mutations in the yciM and lpxM genes in the emergence of colistin resistance in K. pneumoniae.

Dataset Information

Characterization of Piperacillin/Tazobactam-Resistant Klebsiella oxytoca Recovered from a Nosocomial Outbreak.

Publications

Characterization of Piperacillin/Tazobactam-Resistant Klebsiella oxytoca Recovered from a Nosocomial Outbreak.

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