菜市场中食源性大肠杆菌耐药性及其传播风险分析

Antimicrobial Resistance and Transmission Risk of Foodborne Escherichia coli in Wet Markets

摘要:

【目的】为评估菜市场中食源性大肠杆菌的耐药性及其传播风险，对浙江杭州3个菜市场市售猪肉、水产品、蔬菜以及污水进行大肠杆菌分离。【方法】通过16S rRNA测序鉴定菌株，纸片扩散法鉴定大肠杆菌的耐药表型，使用PCR技术检测分离株的耐药基因型和整合子，分析大肠杆菌耐药情况，并通过接合转移评估耐药传播特性，共现网络分析分离菌株耐药性传播风险。【结果】从180份样品中共分离得到68株大肠杆菌，K-B法药敏试验表明，大肠杆菌分离株大多数为多重耐药菌。其中阿莫西林、四环素和磺胺异噁唑的耐药率均在50%以上。PCR扩增耐药基因结果表明，四环素类耐药基因tetA的检出率最高，其次为sul1、blaTEM和tetB。此外，与菜市场A和菜市场C相比，菜市场B大肠杆菌耐药基因检出更严重。整合子检出率最高的基因是intI1（高达30.88%），整合子阳性菌中共8株菌携带基因盒。接合转移结果显示，3株菌株中四环素耐药基因tetA可通过质粒接合作用，转移到受体菌EC600中。共现网络分析显示，在大肠杆菌分离株中耐药基因和可移动元件之间有较高的共传播风险。【结论】作者调查了浙江杭州3个菜市场中大肠杆菌的耐药情况和传播风险，为保障菜市场食品安全提供理论依据。

Abstract:

[Objective]To evaluate the antimicrobial resistance and transmission risk of foodborne Escherichia coli in wet markets, this study isolated E. coli from pork, aquatic products, vegetables, and wastewater collected from three wet markets in Hangzhou, Zhejiang.[Method]The isolates were identified by 16S rRNA sequencing, and their antimicrobial resistance phenotypes were determined via the disk diffusion method. PCR was employed to detect antimicrobial resistance genes and integrons in the isolates. The antimicrobial resistance characteristics of E. coli were analyzed, and conjugation experiments were performed to assess the potential for horizontal transfer of antimicrobial resistance genes. Co-occurrence network analysis was conducted to evaluate the transmission risk of antimicrobial resistance among the isolates.[Result]A total of 68 E. coli strains were isolated from 180 samples. The Kirby-Bauer (K-B) test revealed that most E. coli isolates were multidrug-resistant (MDR). The resistance rates to amoxicillin, tetracycline, and sulfisoxazole exceeded 50%. PCR amplification revealed that the tetracycline resistance gene tetA had the highest detection rate, followed by sul1, blaTEM, and tetB. Moreover, E. coli isolates from the wet market B exhibited higher prevalence of antimicrobial resistance genes than those from wet markets A and C. The detection rate of the integrase gene intI1 was the highest at 30.88%, and eight intI1-positive strains carried gene cassettes. Conjugation experiments demonstrated that in three donor strains, tetA could be transferred via plasmid-mediated conjugation into the recipient strain EC600. Co-occurrence network analysis revealed a strong co-transmission relationship between antimicrobial resistance genes and mobile genetic elements among E. coli isolates.[Conclusion]The author investigates the antimicrobial resistance profiles and dissemination risk of E. coli isolated from three wet markets in Hangzhou, Zhejiang, providing a theoretical basis for ensuring the food safety in wet markets.