Advanced Milk Testing Research Laboratory, Postgraduate Institute of Veterinary Education and Research, Rajasthan University of Veterinary and Animal Sciences at Bikaner, B-2 Bypass, Shiprapath, Mansarovar, Jaipur, 302020, Rajasthan, India.
Sawai Man Singh Medical College, Jaipur, 302004, Rajasthan, India.
Ann Clin Microbiol Antimicrob. 2017 Sep 20;16(1):65. doi: 10.1186/s12941-017-0242-9.
Staphylococcus aureus is the predominant bacterium responsible for various diseases in animals and humans. Preventive strategies could be better implemented by understanding the prevalence, genetic patterns, and the presence of enterotoxin and biofilm-producing genes along with the antibiotic susceptibility of this organism. This study was conducted in Rajasthan, the northwestern state of India, holding the largest population of cattle that makes it the second largest milk producer in India and no such prior information is available on these aspects.
A total of 368 individual quarter bovine raw milk samples were collected from 13 districts of Rajasthan, and screened for the presence of S. aureus. Microbiological and molecular approaches were followed for bacterial identification. Genetic diversity was determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of coagulase gene (coa), whereas enterotoxin and biofilm-producing genes were studied by PCR analysis. Antibiotic strips were employed to study the antibiotic resistance among strains.
In all, 73 S. aureus strains were obtained from 368 bovine raw milk samples out of that only 30 showed the presence of coa. Nine types of coa patterns ranging from 730 to 1130 bp were observed among these isolates. PCR-RFLP of coa distinguished the isolates into 15 genotypic patterns, of which patterns I, IV, V, and VI were predominant. Of the isolates, 30% were positive for sec, 10% for sea, and 3.3% for seb; these genes are responsible for enterotoxin production, whereas all isolates were found positive for icaAD and eno. The prevalence rates of other biofilm-producing genes fnbA, clfB, ebpS, sasG, fnbB, sasC, cna, bap, fib and, bbp were 97, 93, 90, 80, 80, 77, 53, 27, 10, and 6.6%, respectively. Twenty-seven (90%) strains were multidrug resistant, of which 15 were methicillin resistant. Maximum sensitivity was reported for kanamycin and it could be considered as a drug of choice for controlling S. aureus mediated cattle infections in the studied regions.
Overall, these strains could cause several diseases to humans, insisting the need for developing a stricter hygiene program for improving milking practices and animal health.
金黄色葡萄球菌是导致动物和人类各种疾病的主要细菌。通过了解该生物的流行情况、遗传模式、肠毒素和生物膜产生基因的存在以及抗生素敏感性，可以更好地实施预防策略。本研究在印度西北部的拉贾斯坦邦进行，该邦拥有最大的牛群，是印度第二大牛奶生产国，但目前尚无关于这些方面的信息。
从拉贾斯坦邦的 13 个地区共采集了 368 份个体牛 quarters 生奶样本，用于筛选金黄色葡萄球菌的存在。采用微生物学和分子方法进行细菌鉴定。采用聚合酶链反应-限制性片段长度多态性（PCR-RFLP）分析凝固酶基因（coa）确定遗传多样性，通过 PCR 分析研究肠毒素和生物膜产生基因。采用抗生素条研究菌株的抗生素耐药性。
从 368 份牛 quarters 生奶样本中共获得了 73 株金黄色葡萄球菌，其中只有 30 株显示 coa 的存在。在这些分离株中观察到 coa 长度为 730-1130bp 的 9 种 coa 模式。coa 的 PCR-RFLP 将分离株分为 15 种基因型模式，其中模式 I、IV、V 和 VI 占优势。分离株中有 30%为 sec 阳性，10%为 sea 阳性，3.3%为 seb 阳性；这些基因负责产生肠毒素，而所有分离株均为 icaAD 和 eno 阳性。其他生物膜产生基因 fnbA、clfB、ebpS、sasG、fnbB、sasC、cna、bap、fib 和 bbp 的检出率分别为 97%、93%、90%、80%、80%、77%、53%、27%、10%和 6.6%。27 株（90%）为多药耐药株，其中 15 株为耐甲氧西林。对卡那霉素的敏感性最高，可考虑作为控制研究地区金黄色葡萄球菌介导的牛感染的首选药物。
总的来说，这些菌株可能会导致人类患上多种疾病，因此需要制定更严格的卫生计划，以改善挤奶操作和动物健康。
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