Bacterial Disease Division, Animal and Plant Quarantine Agency, Gimcheon, Republic of Korea.
College of Veterinary Medicine and Institute for Veterinary Biomedical Science, Kyungpook National University, Daegu, Republic of Korea.
J Vet Med Sci. 2024 Dec 1;86(12):1219-1226. doi: 10.1292/jvms.24-0239. Epub 2024 Oct 11.
Staphylococcus spp. are one of the most predominant isolates in milk samples of dairy cows with mastitis worldwide. The aims of this study were to investigate the prevalence of bacterial pathogens in bovine mastitis milk samples in South Korea and the antimicrobial resistance profiles of staphylococcal isolates. In total, 1,245 strains were isolated from 1,260 mastitis quarter milk samples (with somatic cell counts ≥ 200,000 cells/mL) from 66 dairy farms between 2018 and 2022. The bacterial genus with the highest prevalence in bovine mastitis milk samples was Staphylococcus spp. (33.9%), followed by Streptococcus spp. (11.5%). S. aureus and non-aureus staphylococci (NAS) accounted for 11.0% and 89.0% of staphylococcal isolates, respectively. S. chromogenes was the most prevalent species among the 22 NAS species detected. S. aureus showed the highest resistance rates to penicillin (25.0%) and ampicillin (20.8%), whereas NAS showed the highest resistance rates to penicillin (18.3%), tetracycline (11.4%) and erythromycin (10.1%). Sixteen multidrug-resistant (MDR) isolates were only isolated from NAS, and the most commonly detected antimicrobial resistance gene in the 16 MDR isolates was mecA (75.0%), followed by tetK (62.5%), blaZ (50.0%), ermC (50.0%), and lnuA (43.8%). In conclusion, NAS were the most common isolates from mastitis milk in South Korea and MDR isolates carried a variety of antibiotic resistance genes. Our study suggests that continuous monitoring of the distribution and antimicrobial resistance in Staphylococcus spp., particularly NAS, is needed to improve the effectiveness of management and treatment strategies in dairy farms.
金黄色葡萄球菌是全世界乳腺炎奶牛牛奶样本中最主要的分离菌之一。本研究旨在调查韩国奶牛乳腺炎牛奶样本中细菌病原体的流行情况以及葡萄球菌分离株的抗生素耐药谱。在 2018 年至 2022 年期间，从 66 个奶牛场的 1,260 份乳腺炎四分体牛奶样本（体细胞计数≥200,000 个细胞/mL）中分离出 1,245 株细菌。在乳腺炎牛奶样本中，细菌属中葡萄球菌属的流行率最高（33.9%），其次是链球菌属（11.5%）。金黄色葡萄球菌和非金黄色葡萄球菌（NAS）分别占葡萄球菌分离株的 11.0%和 89.0%。在检测到的 22 种 NAS 中，S. chromogenes 是最常见的种。金黄色葡萄球菌对青霉素（25.0%）和氨苄西林（20.8%）的耐药率最高，而 NAS 对青霉素（18.3%）、四环素（11.4%）和红霉素（10.1%）的耐药率最高。仅从 NAS 分离出 16 株多药耐药（MDR）分离株，在 16 株 MDR 分离株中最常见的抗生素耐药基因是 mecA（75.0%），其次是 tetK（62.5%）、blaZ（50.0%）、ermC（50.0%）和 lnuA（43.8%）。总之，NAS 是韩国乳腺炎牛奶中最常见的分离菌，MDR 分离株携带多种抗生素耐药基因。我们的研究表明，需要持续监测金黄色葡萄球菌（特别是 NAS）的分布和抗生素耐药性，以提高奶牛场管理和治疗策略的有效性。
