Strain typing and molecular characterization of CTX-M-1 group ESBL in clinical klebsiella pneumoniae isolated from children
Shahin Najar Peerayeh
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© 2016, Pediartric Infections Research Center. Background: Extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae is rapidly spreading worldwide, creating serious problems in clinical settings. Objectives: The aim of this study was to describe the molecular and epidemiological characteristics of CTX-M-1 group ESBL-producing K. pneumoniae. Methods: Seventeen CTX-M-1 group ESBL-producing K. pneumoniae isolates found among 31 K. pneumoniae isolates in samples collected from three hospitals in Tehran, Iran between May and December 2011 were included in the present study for further characterization and determination of clonal relationships. The genetic environment of bla CTX-M-1 was analyzed by polymerase chain reaction (PCR) mapping and sequencing, and the transferability of bla CTX-M-1 was evaluated through the use of a conjugation assay. PCR-based replicon typing (PBRT) was used to identify plasmid replicons. The isolates were typed using pulsed-field gel electrophoresis (PFGE). Results: All 17 isolates carried the bla CTX-M-15 gene. IncL/M was the most common replicon type (82.3%). The conjugation experiment showed that bla CTX-M-15 was carried on transferable plasmids. In all of the studied isolates, the mobile element ISEcp1 was found upstream and orf477 downstream of bla CTX-M-15 , whereas IS26 was not found. PFGE identified 11 different profiles and one major clone. Conclusions: The findings of this study suggest that among the K. pneumoniae strains isolated from samples of children, dissemination of the bla CTX-M-15 gene is due to clonal spread and to the dissemination of mobile genetic elements bearing bla CTX-M-15 , such as ISEcp1. Genotyping of K. pneumoniae is indispensable for monitoring the spread of ESBL-producing strains, for initiating the implementation of suitable infection control measures, and for general epidemiology purposes.