Sharma Sanjita, Sharma Vishnu, Dahiya Dinesh Kumar, Khan Aarif, Mathur Manisha, Sharma Amit
Advanced Milk Testing Research Laboratory, Post Graduate Institute of Veterinary Education and Research , Mansarovar, Jaipur, Rajasthan, India .
Foodborne Pathog Dis. 2017 Mar;14(3):132-140. doi: 10.1089/fpd.2016.2118. Epub 2017 Jan 13.
Listeriosis is a serious foodborne disease of a global concern, and can effectively be controlled by a continuous surveillance of the virulent and multidrug-resistant strains of Listeria monocytogenes. This study was planned to investigate prevalence of L. monocytogenes in bovine raw milk samples. A total of 457 raw milk samples collected from 15 major cities in Rajasthan, India, were analyzed for the presence of L. monocytogenes by using standard microbiological and molecular methods. Five of the 457 samples screen tested positive for L. monocytogenes. Multiplex serotyping showed that 3/5 strains belonged to serotype 4b followed by one strain each to 1/2a and to 1/2c. Further virulence potential assessment indicated that all strains possessed inlA and inlC internalins, and, in addition, two strains also possessed the gene for inlB. All strains were positive for Listeriolysin O (LLO) and showed phosphatidylinositol-specific phospholipase C (PI-PLC) activity on an in vitro agar medium with variations in production levels among the strains. A good correlation between the in vitro pathogenicity test and the chick embryo test was observed, as the strains showing higher LLO and PI-PLC activity were found to be lethal to fertilized chick embryos. All strains were resistant to the majority of antibiotics and were designated as multidrug-resistant strains. However, these strains were susceptible to 9 of the 22 tested antibiotics. The maximum zone of inhibition (mm) and acceptable minimum inhibitory concentration were observed with azithromycin, and thus it could be the first choice of a treatment. Overall, the presence of multidrug-resistant L. monocytogenes strains in the raw milk of Rajasthan region is an indicator of public health hazard and highlighting the need of consumer awareness in place and implementation of stricter food safety regulations at all levels of milk production.
李斯特菌病是一种全球关注的严重食源性疾病，通过对单核细胞增生李斯特菌的强毒株和多重耐药菌株进行持续监测可有效控制该病。本研究旨在调查牛生鲜乳样本中单核细胞增生李斯特菌的流行情况。采用标准微生物学和分子方法，对从印度拉贾斯坦邦15个主要城市采集的457份生鲜乳样本进行了单核细胞增生李斯特菌检测分析。457份样本中有5份经筛查检测出单核细胞增生李斯特菌呈阳性。多重血清分型显示，5株菌中有3株属于4b血清型，其次各有1株属于1/2a和1/2c血清型。进一步的毒力潜力评估表明，所有菌株均具有inlA和inlC内化素，此外，还有两株菌也具有inlB基因。所有菌株的李斯特菌溶血素O（LLO）均呈阳性，并且在体外琼脂培养基上显示出磷脂酰肌醇特异性磷脂酶C（PI-PLC）活性，各菌株的活性水平有所差异。体外致病性试验与鸡胚试验之间观察到良好的相关性，因为LLO和PI-PLC活性较高的菌株对受精鸡胚具有致死性。所有菌株对大多数抗生素均耐药，被指定为多重耐药菌株。然而，这些菌株对22种受试抗生素中的9种敏感。阿奇霉素的抑菌圈最大（毫米）且最低抑菌浓度可接受，因此它可能是首选治疗药物。总体而言，拉贾斯坦邦地区生鲜乳中存在多重耐药的单核细胞增生李斯特菌菌株表明存在公共卫生危害，凸显了提高消费者意识以及在牛奶生产各环节实施更严格食品安全法规的必要性。
