市售即食食品中非致病菌的耐药性及耐药基因转移的研究

Antibiotic resistance analysis and the AR gene transfer in non-pathogens isolated from ready-to-eat food

目的了解西安市即食食品中的非致病菌的耐药性分布、耐药程度及耐药基因的转移情况,分析潜在的食品安全问题。方法对西安市的几家大型超市零售的熟肉、果盘、凉拌菜3大类即食食品样品进行食源性非致病菌的红霉素和氨苄青霉素耐药性分析、耐药基因转移、菌株16 S rRNA序列测序鉴定等。结果 42.5%的分离株具有不同程度的红霉素耐药性,47.5%的分离株具有不同程度的氨苄青霉素耐药性,21.2%的分离株同时具有2种抗生素耐药性;11.3%的红霉素耐药株耐药性高达160 mg/L,6.3%的氨苄青霉素耐药株耐药性高达500 mg/L。随机挑选的部分耐药株在无抗生素培养基中连续传代1000代以后,60%的氨苄青霉素耐药株和45%的红霉素耐药株的耐药性消失。部分耐药株的耐药基因可水平转移至非耐药株中。这些耐药株多为肠球菌、葡萄球菌、芽孢杆菌、假单胞菌等。结论即食食品中的非致病菌有潜在的风险,耐药基因在细菌间的转移可能对人体敏感肠道菌群和致病菌有一定影响。

Objective To elucidate the antibiotic-resistance （AR） distribution, AR level and the transfer of AR genes in non-pathogens isolated from ready-to-eat food in Xi＇an, and evaluate the potential food safety risk. Methods The erythromyein and ampieillin resistance, the AR gene transfer, 16S rRNA gene sequence analysis were performed on the bacteria from ready-to-eat food samples collected from supermarkets of Xi＇an, including cooked meat, fruit slices and Chinese salads. Results 42.5% of the isolates were erythromycin resistant, 47.5% were ampicillin resistant, while 21.2% were resistant to both antibiotics. 11.3% of Ermr strains could grow under 160mg/L Ermthromycin, 6.3% of Ampr strains could grow under 500mg/L ampieillin. After 1000 generations on medium without antibiotic, 60% and 45% of randomly selected Ampr and Ermr strains lost their antibiotic resistance. Within these strains, the Ermr and Ampr fragments could be transferred from the antibiotic-resistant strains into the negative strains. Most antibiotic-resistant strains belonged to Enterocoecus, Staphylococcus, Bacillus and Pseudomonas. Conclusion There was a potential food safety risk of non-pathogens in ready-to-eat food, and the transfer of AR genes might have some impact on the human intestinal flora and pathogenic bacteria.