北京市售酸奶中益生菌的分离鉴定及耐药性检测

目的对北京市售酸奶中添加的益生菌种类及浓度、益生菌酸奶分离株对6种抗生素(青霉素、氨苄青霉素、庆大霉素、万古霉素、克林霉素及红霉素)的耐药性进行检测。方法采用直接稀释法分离酸奶样品中的益生菌并进行活菌计数,对分离到的菌株进行革兰染色和生化反应鉴定,同时采用肉汤稀释法测定分离菌株对6种抗生素的最小抑菌浓度。结果用MRS培养基、(36±1)℃、厌氧培养条件下从31种北京市售酸奶样品中共分离出52株菌,其中革兰氏阳性杆菌37株,革兰阳性球菌15株。生化反应鉴定结果将52株菌分为乳酸杆菌和嗜热链球菌2大类共6个种;活菌计数结果显示,12份样品(38.7%)中益生菌计数低于国家标准规定的1×106cfu/ml(g);19份样品(61.3%)中活菌计数符合国家标准规定;所有酸奶样品分离菌株对青霉素,氨苄青霉素均敏感,而对庆大霉素的敏感性较低,1株菌对克林霉素和红霉素耐药,4株菌对万古霉素耐药。结论采集的北京市售酸奶样品大部分产品中添加的益生菌种类及活菌数符合国家标准规定,部分产品生产用菌种对一种或多种抗生素耐药。

Isolation and identification of probiotics from yoghourt in Beijing

Objective To carry out isolation and the viable plate count of probiotics from yoghourt.To investigate the antimicrobial susceptibility of strains to penicillin,gentamicin,ampicillin,vancomycin,clindamycin and erythromycin.Methods Probiotics were recovered and counted from yoghourt by plate count method.The recovered isolates were characterized by Gram's stain,biochemical test,antimicrobial susceptibility test.Results MRS medium and(36±1)℃ were the optimum condition of culture.In total,52 probiotic isolates were recovered from 31 yoghourt products,12(38.7%) products showed a lower probiotic quantity than 1×106 cfu /ml of the national stantard,and 19(61.3%) products were higher than 1×106 cfu /ml.Gram's stain showed that 37 isolates were gram positive bacilli and 15 isolates were positive coccus.These 52 isolates were grouped into six species by biochemical method,including L.bulgaricus,S.thermophilus,L.acidophilus,L.casei,L.delbrueckii and L.fermentum.All 52 isolates were susceptible to penicillin and ampicillin,one isolate was resistant to both clindamycin and erythromycin,four isolates were resistant to vancomycin.Conclusion Most of yoghourt products contained sufficient viable probiotics as required by the national standard.A small quantity of isolates were resistant to some antimicrobials and multi -drug resistant isolates were also found.