Strain Typing and Molecular Characterization of CTX-M-1 Group ESBL in Clinical Klebsiella pneumoniae Isolated from Children

Extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae is rapidly spreading worldwide, creating serious problems in clinical settings.

The aim of this study was to describe the molecular and epidemiological characteristics of CTX-M-1 group ESBL-producing K. pneumoniae.

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 blaCTX-M-1 was analyzed by polymerase chain reaction (PCR) mapping and sequencing, and the transferability of blaCTX-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).

All 17 isolates carried the blaCTX-M-15 gene. IncL/M was the most common replicon type (82.3%). The conjugation experiment showed that blaCTX-M-15 was carried on transferable plasmids. In all of the studied isolates, the mobile element ISEcp1 was found upstream and orf477 downstream of blaCTX-M-15, whereas IS26 was not found. PFGE identified 11 different profiles and one major clone.

The findings of this study suggest that among the K. pneumoniae strains isolated from samples of children, dissemination of the blaCTX-M-15 gene is due to clonal spread and to the dissemination of mobile genetic elements bearing blaCTX-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.