Mahato Sudipta, Mistry Hiral U, Chakraborty Shalini, Sharma Paresh, Saravanan R, Bhandari Vasundhra
National Institute of Animal BiotechnologyHyderabad, India.
Department of Animal Genetics and Breeding, Veterinary College and Research InstituteNamakkal, India.
Front Microbiol. 2017 Jul 31;8:1446. doi: 10.3389/fmicb.2017.01446. eCollection 2017.
Methicillin resistant causing bovine mastitis has been very well investigated worldwide. However, there are only limited reports on the characterization of methicillin resistant and sensitive coagulase negative staphylococci (CoNS) across the globe. Hence, in the present study, we aim to determine the phenotypic traits based on antimicrobial susceptibility profile and genotypic characterization by verifying the presence of resistance determinants, virulence and toxin genes present in the CoNS causing clinical mastitis. We obtained 62 CoNS isolates from 167 mastitic milk samples collected from three different states of India. The 62 isolates comprises of 10 different CoNS species , , , s, , , , , and . Susceptibility screening against 11 antibiotics determined 45.16% isolates as multidrug resistant (resistant to more than two class of antibiotic), 46.74% resistant (one or two antibiotic class) and 8.06% isolates were pan-sensitive (sensitive to all drugs). High resistance was observed against oxacillin and cefoxitin, whereas all isolates were susceptible toward vancomycin and linezolid. Fifty three isolates were methicillin resistant and 9 isolates were sensitive as determined by oxacillin susceptibility assay. The methicillin resistance gene, was found in 95.16% isolates and staphylococcal cassette chromosome (SCC) typing predominantly revealed Type III ( = 34) and Type V ( = 18). Interestingly, 11.9% of positive isolates were oxacillin susceptible and referred as oxacillin susceptible positive staphylococci (OS-MRS). Additionally, genes encoding for enterotoxin, () toxic shock syndrome (), exfoliatin () and virulence () were also screened. Of all the genes examined, 67.74% of isolate were positive for the gene, followed by the gene in 25.8% whereas in none of the isolates the and the gene was amplified. The study also highlights the incidence of clinical isolates of CoNS, which are harboring the toxin and the virulence genes rendering them as a more potential threat. This is the first report of animal origin OS-MRS from India, which emphasizes on the inclusion of both the genetic and phenotypic test for proper characterization of CoNS and preventing resistant strain misidentification.
耐甲氧西林引起牛乳腺炎的情况在全球范围内已得到充分研究。然而，关于全球范围内耐甲氧西林和敏感凝固酶阴性葡萄球菌（CoNS）特性的报道却很有限。因此，在本研究中，我们旨在通过验证引起临床乳腺炎的CoNS中耐药决定因素、毒力和毒素基因的存在，根据抗菌药物敏感性谱和基因特征来确定其表型特征。我们从印度三个不同邦采集的167份患乳腺炎牛奶样本中获得了62株CoNS分离株。这62株分离株包括10种不同的CoNS菌种，分别为 、 、 、 、 、 、 、 、 和 。针对11种抗生素的敏感性筛选确定45.16%的分离株为多重耐药（对两类以上抗生素耐药），46.74%为耐药（对一类或两类抗生素耐药），8.06%的分离株对所有药物敏感。观察到对苯唑西林和头孢西丁的耐药性较高，而所有分离株对万古霉素和利奈唑胺敏感。通过苯唑西林敏感性试验确定53株分离株耐甲氧西林，9株敏感。95.16%的分离株中发现了耐甲氧西林基因 ，葡萄球菌盒式染色体 （SCC）分型主要显示为III型（ = 34）和V型（ = 18）。有趣的是，11.9%的 阳性分离株对苯唑西林敏感，被称为苯唑西林敏感 阳性葡萄球菌（OS-MRS）。此外，还筛选了编码肠毒素（ ）、毒性休克综合征毒素（ ）、剥脱毒素（ ）和毒力（ ）的基因。在所有检测的基因中，67.74%的分离株 基因呈阳性，其次是25.8%的 基因呈阳性，而在所有分离株中均未扩增出 和 基因。该研究还强调了携带毒素和毒力基因的CoNS临床分离株的发生率，这使其成为更具潜在威胁的因素。这是来自印度的动物源OS-MRS的首次报道，强调了同时进行基因和表型检测以正确鉴定CoNS并防止耐药菌株误判的重要性。
