Bacterial Disease Division, Animal and Plant Quarantine Agency, 177 Hyeksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, Republic of Korea.
Laboratory of Veterinary Pharmacokinetics and Pharmacodynamics, College of Veterinary Medicine, Kyungpook National University, Bukgu, Daegu 41566, Republic of Korea.
J Dairy Sci. 2019 Dec;102(12):11439-11448. doi: 10.3168/jds.2019-17028. Epub 2019 Sep 20.
Coagulase-negative staphylococci (CNS) are one of the most common bovine mastitis pathogens found worldwide. In this study, we investigated the prevalence and distribution of CNS species in mastitis milk samples and further characterized the methicillin-resistant (MR) CNS. A total of 311 CNS were isolated from 3,692 quarter milk samples from 1,373 dairy cattle at 81 farms between 2013 and 2017. Further evaluation of the CNS isolates revealed 14 CNS species among the samples and 3 predominant species-namely, Staphylococcus chromogenes, Staphylococcus simulans, and Staphylococcus epidermidis. Resistance was higher in S. epidermidis than in other CNS species except for resistance against oxacillin in Staphylococcus sciuri. Resistance to β-lactams was the most common in all CNS species (8.4% in ampicillin, 21.2% in oxacillin, and 13.5% in penicillin). Conversely, only minimal resistance to cephalothin, ceftiofur, and pirlimycin/novobiocin was found. Twenty-one isolates from 4 species were mecA-carrying MRCNS strains, including 18 S. epidermidis and 1 each of S. sciuri, Staphylococcus equorum, and Staphylococcus hominis. The majority of the mecA-carrying MRCNS isolates were produced in the biofilm. Furthermore, multidrug-resistant sequence type 179 isolate produced the strongest biofilm. Seven genotypes were detected in the 18 MR S. epidermidis strains, the most predominant of which persisted on a farm for 2 yr. Our findings for the antimicrobial susceptibility profiles and genotypic characterization of the MRCNS isolates could provide valuable information for controlling the spread of resistance and the selection of appropriate antimicrobial therapies for mastitis in the future. Further, strategic antibiotic use for mastitis treatment and hygienic management practices aimed at the prevention of the growth of resistant bacteria are urgently needed on dairy farms.
凝固酶阴性葡萄球菌（CNS）是全球范围内最常见的奶牛乳腺炎病原体之一。在本研究中，我们调查了乳腺炎奶样中 CNS 种的流行和分布情况，并进一步对耐甲氧西林的 CNS（MRCNS）进行了特征描述。在 2013 年至 2017 年间，从 81 个农场的 1373 头奶牛的 3692 个乳区奶样中分离出了 311 株 CNS。对 CNS 分离株的进一步评估表明，在样本中存在 14 种 CNS 种，其中 3 种为主要种，分别为：变色葡萄球菌、模仿葡萄球菌和表皮葡萄球菌。表皮葡萄球菌的耐药性高于其他 CNS 种，除了对青霉素的耐药性低于松鼠葡萄球菌外。所有 CNS 种对β-内酰胺类药物的耐药性最为常见（氨苄西林为 8.4%，苯唑西林为 21.2%，青霉素为 13.5%）。相反，对头孢噻呋、头孢替呋和吡利霉素/新生霉素的耐药性则很小。在 4 种种的 21 个分离株中，发现携带 mecA 的 MRCNS 菌株，包括 18 株表皮葡萄球菌和 1 株松鼠葡萄球菌、马胃葡萄球菌和人葡萄球菌。携带 mecA 的 MRCNS 分离株主要在生物膜中产生。此外，多药耐药性序列型 179 分离株产生的生物膜最强。在 18 株耐甲氧西林表皮葡萄球菌菌株中检测到 7 种基因型，其中最主要的基因型在一个农场持续了 2 年。我们对 MRCNS 分离株的抗生素药敏谱和基因特征的研究结果，可以为未来控制耐药性传播和选择适当的抗乳腺炎治疗方法提供有价值的信息。此外，在奶牛场中，急需战略性地使用抗生素治疗乳腺炎和实施卫生管理措施，以防止耐药菌的生长。
