食品中单核细胞增生李斯特菌株生物被膜形成、药敏试验及毒力基因检测

Biofilm formation,antimicrobial susceptibility test and virulence gene detection of Listeria monocytogenes in food

目的分析食品中单核细胞增生李斯特菌株生物被膜形成、药敏试验及毒力基因,为临床感染防治提供依据。方法选择分离自宣城地区各类检测食品的单核细胞增生李斯特菌株作为研究对象;考察不同温度、BHI培养基浓度、培养时间、pH值、NaCl浓度、葡萄糖浓度对生物被膜形成的影响;采用微量肉汤稀释法对食品中单核细胞增生李斯特菌株进行药敏试验;采用PCR对毒力基因进行检测。结果随着培养时间延长及BHI培养基浓度升高,生物被膜形成率呈明显升高趋势,差异有统计学意义(P<0.05)。pH值为7.5、NaCl浓度为5 g/L、葡萄糖浓度为22 g/L、温度为37℃时生物被膜形成率最高,差异均有统计学意义(P<0.05)。单核细胞增生李斯特菌对氨苄西林、美罗培南、青霉素及万古霉素的敏感率均为100.00%,而对复方磺胺甲噁唑、环丙沙星、红霉素、四环素则表现出不同的耐药性,其中对四环素耐药率最高,差异均有统计学意义(P<0.05)。单核细胞增生李斯特菌毒力基因iap和inlA的阳性率均为100.00%,而prfA、hlyA、plcB的阳性率均不足100.00%,其中plcB阳性率最低,差异均有统计学意义(P<0.05)。结论在该研究试验条件下,随着培养时间的延长及BHI培养基浓度升高,单核细胞增生李斯特菌生物被膜形成率呈明显升高趋势,pH值为7.5、NaCl浓度为5 g/L、葡萄糖浓度为22 g/L、温度为37℃时生物被膜形成率最高,单核细胞增生李斯特菌对四环素耐药率最高,毒力基因plcB阳性率最低。

Objective To analyze the biofilm formation,antimicrobial susceptibility test and virulence gene of Listeria monocytogenes in food,to provide evidence for clinical infection prevention and treatment.Methods The Listeria monocytogenes strains isolated from various foods in Xuancheng area were selected as the research object.The effects of different temperature,BHI culture tested medium concentration,culture time,pH value,NaCl concentration and glucose concentration on the formation of biofilm were investigated.The antimicrobial susceptibility test of Listeria monocytogenes in food was tested by micro broth dilution method.The virulence genes were detected by PCR.Results With the prolongation of culture time and the increase of BHI culture medium concentration,the formation rate of biofilm increased significantly,and the differences were statistically significant(P<0.05).When the pH value was 7.5,the NaCl concentration was 5 g/L,the glucose concentration was 22 g/L,and the temperature was 37℃,the biofilm formation rate was the highest,and the differences were statistically significant(P<0.05).The susceptibility rates of Listeria monocytogenes to ampicillin,meropenem,penicillin and vancomycin were all 100.00%,but to compound sulfamethoxazole,ciprofloxacin,erythromycin and tetracycline the drug resistance were different,among which the resistance rate to tetracycline was the highest,and the differences were statistically significant(P<0.05).The positive rates of the virulence genes iap and inlA of Listeria monocytogenes were both 100.00%,while the positive rates of prfA,hlyA,and plcB were all less than 100.00%,and the positive rate of plcB was the lowest,and the differences were statistically significant(P<0.05).Conclusion Under the experimental conditions of this study,with the prolongation of culture time and the increase of BHI culture medium concentration,the biofilm formation rate of Listeria monocytogenes increase significantly.When the pH value is 7.5,the NaCl concentration is 5 g/L,the glucose concentration is 22 g/L,and the temperature is 37℃,the biofilm formation rate is the highest,and the resistance rate of Listeria monocytogenes to tetracycline is the highest,the detection rate of the virulence gene plcB is lowest.