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Characterization of quinolone resistance mechanisms in lactic acid bacteria isolated from yogurts in China

Jiang, Xiaobing, Yu, Tao, Zhou, Danlei, Ji, Shengdong, Zhou, Chune, Shi, Lei, Wang, Xuannian
Annals of microbiology 2016 v.66 no.3 pp. 1249-1256
Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus, amino acids, ciprofloxacin, genes, lactic acid bacteria, minimum inhibitory concentration, mutation, polymerase chain reaction, reserpine, resistance mechanisms, thermophilic microorganisms, transporters, yogurt, China
Twenty-five strains of ciprofloxacin-resistant lactic acid bacteria (LAB; 14 Lactobacillus spp. and 11 Streptococcus thermophiles spp.) isolated from commercial yogurts in China were analyzed in this study. For each of these strains, amino acid changes associated with quinolone resistance-determining regions (QRDRs) were investigated using PCR-based detection methods. The same methodology was used to identify the presence of plasmid-mediated quinolone resistance (PMQR) genes in LAB. Sequencing analyses and an efflux pump inhibition test (using reserpine) were also performed as part of the analysis. Our results showed that typical mutations corresponding to quinolone resistance were found in the QRDRs of LAB strains. Detected mutations included Ser80Leu in parC, and Ser83Leu and Glu87Asp in gyrA. In addition, a Tyr74Phe substitution in parC, which had not previously been reported to be associated with quinolone resistance, was observed in two Lactobacillus delbrueckii subsp. bulgaricus strains. For each of the tested strains, the presence of the efflux pump inhibitor, reserpine, resulted in a two- to eightfold reduction in the minimum inhibitory concentrations (MICs) of ciprofloxacin. However, PMQR genes were not observed in any of the strains analyzed. Our results suggest that mutations in the QRDRs or efflux pump could be involved in ciprofloxacin resistance, and that a combination of these mechanisms may lead to increased ciprofloxacin resistance in LAB strains.