Prevalence of plasmid-mediated quinolone resistance genes in Klebsiella pneumoniae strains in pediatrics in China / 中华微生物学和免疫学杂志

ABSTRACT

Objective To investigate the prevalence of plasmid-mediated quinolone resistance (PMQR) genes among clinical isolates of Klebsiella pneumoniae (K.pneumoniae) in pediatrics.MethodsA total of 131 non-duplicate clinical isolates of K.pneumoniae were collected in the Affiliated Children′s Hospital of Capital Institute of Pediatrics from 2010 to 2012.PMQR genes [qnrA, qnrB, qnrS, aac(6′)-Ⅰb-cr and qepA], mutations in the quinolone resistance-determining region (QRDR) and extended spectrum β-lactamases (ESBLs) genes in those strains were analyzed by PCR.Minimum inhibitory concentrations (MIC) of different antibiotics against those K.pneumoniae strains were determined by broth microdilution method and E-test according to the guidelines issued by the Clinical and Laboratory Standards Institute (CLSI).Transferability of the PMQR genes was examined by conjugation test with the sodiumazide-resistant Escherichia coli J53.Results Among the 131 isolates, 9.92% were resistant to quinolone and 30.5% were positive for PMQR genes, including 6.87% harboring qnrB gene, 22.9% harboring qnrS gene and 4.58% harboring aac(6′)-Ⅰb-cr gene.Neither qnrA-positive nor qepA-positive strain was detected.Among these PMQR genes-positive isolates, 90% were ESBLs-producing strains and two presented mutations in gyrA and parC genes.Conjugation test showed that these PMQR genes could be transferred horizontally and the ciprofloxacin resistance increased 2 to 32 folds in transconjugants.Conclusion This study indicates that the PMQR gene-carrying rate is high in K.pneumoniae strains isolated in paediatrics in China.Most of the PMQR gene-positive strains are also ESBLs-producing strains.The PMQR genes could be transferred horizontally in bacteria.