Detection of genotypes of plasmid-mediated quinolone resistance in clinical isolates of Shigella / 中华传染病杂志

ABSTRACT

ObjectiveTo investigate the variations and distributions of the plasmid-mediated quinolone resistance genes in clinical isolates of Shigella and their resistance to antimicrobial agents. Methodsqnr, aac(6')-Ib-cr and qepA genes were identified by polymerase chain reaction (PCR) in 137 clinical isolates of Shigella.DNA sequencing of gene-positive strains were analyzed and the conjugation experiment was performed. The minimal inhibitory concentrations (MIC) of Shigella isolates, recipient strains and transconjugants were tested by agar dilution method for quinolones and other antimicrobial agents. The genotype of transconjugants were determined by PCR and sequencing. ResultsFour (2.9％) strains of the 137 Shigella isolates were qnr gene positive, including 3 qnrS2 positive and 1 qnrB4 positive (GenBank accession numbers of the complete sequence were JF261185 and HQ917003, respectively).Furthermore,five (3.6％) aac ( 6')-Ib-cr gene-positive strains (GenBank accession number JF261186 ) and one (0.7％) qepA gene-positive strain were identified in all isolates. The conjugation experiments were successfully carried out in six out of ten PCR-positive isolates. The MIC of transconjugants against quinolones and other antimicrobial agents increased differently compared to recipient strains. Conclusions The plasmid-mediated quinolone resistance genes are lowly prevalent in clinical isolates of Shigella. However, these resistance genes have the characteristic of horizontal transfer, which indicates that more attention should be paid to this phenomenon.