动物性食品源大肠杆菌质粒介导喹诺酮的耐药机制研究

本研究以动物性食品源大肠杆菌为研究对象,采用琼脂二倍稀释法调查菌株对抗生素的药物敏感性,通过PCR扩增及产物测序检测质粒介导喹诺酮耐药(PMQR)基因的分布以及喹诺酮耐药决定区(QRDR)靶基因突变,旨在更好的了解食源性大肠杆菌对喹诺酮类药物产生耐药性的分子机制。645份动物性食品样品中共检出大肠杆菌179株,总检出率为27.7%。179株动物性食品源大肠杆菌对15种抗生素均表现出不同程度的耐药性,其中对四环素、链霉素、萘啶酸和复方新诺明的耐药水平较高。PMQR基因阳性菌株共14株,占受试菌株的7.8%,其中有11株能通过接合转移将PMQR基因转移至受体菌中。QRDR靶位突变在PMQR阳性菌株中普遍存在,介导菌株对喹诺酮的高水平耐药。研究结果表明,动物性食品可能成为耐药菌株的潜在"蓄水池",并通过食物链将耐药性传递给人类,从而引起人类的感染以及耐药菌株的流行。

Mechanism of Plasmid-mediated Quinolone Resistance in Escherichia coli Isolated from Animal-derived Food

Escherichia coli was isolated from animal-derived food samples and the antibiotic susceptibility of isolated strains was investigated by agar dilution method. The distribution of plasmid-mediated quinolone resistance (PMQR) genes and mutations in the quinolone resistance-determining region (QRDR) were analyzed by the polymerase chain reaction (PCR) amplification and product sequencing. A total of 179 strains of E. coli were detected (27.7%) in 645 animal-derived food samples. The resistance of these isolates to 15 different antibiotics was observed, with high level of resistance to streptomycin, tetracycline, nalidixic acid, and trimethoprim/sulfamethoxazole. Fourteen strains were PMQR-gene positive, accounting for 7.8% of the test strains, and 11 of the PMQR-positive strains could transfer quinolone resistance to the recipient through conjugation. Mutations in QRDR were prevalent among the PMQR-positive isolates, which could be responsible for the high-level resistance to quinolone. Our results demonstrate that animal-derived food may act as a reservoir for drug-resistant strains and can be a channel for transfer of resistant genes to humans via the food chain, thus causing human infection and a possible outbreak of drug-resistant strains.