Chowdhury Md Shahidur Rahman, Hossain Hemayet, Uddin Md Bashir, Rahman Md Matiur, Altaf Hossain Ferdaus Mohd, Islam Md Rafiqul, Hoque M Nazmul, Rahman Md Masudur, Hossain Md Mukter, Rahman Md Mahfujur
Department of Medicine, Sylhet Agricultural University, Sylhet, Bangladesh.
Department of Anatomy and Histology, Sylhet Agricultural University, Sylhet, Bangladesh.
PLoS One. 2025 Jun 17;20(6):e0324920. doi: 10.1371/journal.pone.0324920. eCollection 2025.
Subclinical mastitis (SCM) poses a significant threat to the global dairy industry, particularly in Bangladesh, where it remains a major constraint in buffalo dairy farming. The rising prevalence of antimicrobial resistant pathogens complicates disease management, resulting reduced milk yield, increased veterinary expenses, compromised animal welfare and potential risk to public health. This study investigated the prevalence and resistance profiles of multidrug-resistant (MDR) and extensively drug-resistant (XDR) Staphylococcus and Streptococcus species in raw buffalo milk from SCM cases in Bangladesh. A total of 1,540 quarter milk samples from 385 buffaloes were analyzed, revealing SCM prevalence rates of 67.9% (1046/1540; 95% CI: 65.6-70.3) at the quarter level and 80.8% (311/385; 95% CI: 76.5-84.6) at the animal level. Notable regional variations were observed, with Gowainghat showing the highest prevalence (88.1%; 141/160). This study did not identify any biologically plausible risk factors for the occurrence of SCM in buffalo. The Modified Whiteside Test and California Mastitis Test confirmed SCM, with culture and biochemical tests identifying 789 (51.2%) Staphylococcus spp. and 424 (27.5%) Streptococcus spp. isolates. Polymerase Chain Reaction (PCR) analysis indicated that 72.7% (456/627) of Staphylococcus isolates were Staphylococcus aureus, while the predominant Streptococcus species included Streptococcus uberis (32.3%) and Streptococcus dysgalactiae (14.9%). Resistance gene detection revealed a high prevalence of antimicrobial resistant genes (ARGs), particularly aac-3(iv) and tetA, across different buffalo quarters and habitats. Antibiogram profiling demonstrated high susceptibility to tetracycline (80.9; 83.1) and trimethoprim-sulfamethoxazole (87.4; 81.9), while significant resistance was noted against ampicillin (88.8; 87.1) and nalidixic acid (68.1; 62.1). MDR was observed in 76.4% (479/627) of Staphylococcus spp. and 67.3% (167/248) of Streptococcus spp. isolates, with 10.37% (65/627) and 10.48% (26/248) classified as possible XDR, respectively. These findings explored high antimicrobial resistance level among Staphylococcus and Streptococcus species in subclinical mastitis, highlighting the need for improved management practices and surveillance to mitigate public health risks posed by contaminated milk.
亚临床型乳腺炎（SCM）对全球乳制品行业构成重大威胁，在孟加拉国尤为如此，它仍是该国水牛养殖的主要制约因素。抗菌药物耐药病原体的流行率不断上升，使疾病管理变得复杂，导致牛奶产量下降、兽医费用增加、动物福利受损以及对公众健康构成潜在风险。本研究调查了孟加拉国SCM病例中生鲜水牛奶中多重耐药（MDR）和广泛耐药（XDR）葡萄球菌和链球菌属的流行情况及耐药谱。共分析了来自385头水牛的1540份乳区奶样，结果显示乳区水平的SCM流行率为67.9%（1046/1540；95%置信区间：65.6 - 70.3），动物水平为80.8%（311/385；95%置信区间：76.5 - 84.6）。观察到显著的区域差异，戈温加特的流行率最高（88.1%；141/160）。本研究未发现水牛发生SCM的任何生物学上合理的风险因素。改良怀特赛德试验和加利福尼亚乳腺炎试验确诊了SCM，培养和生化试验鉴定出789株（51.2%）葡萄球菌属和424株（27.5%）链球菌属分离株。聚合酶链反应（PCR）分析表明，72.7%（456/627）的葡萄球菌分离株为金黄色葡萄球菌，而主要的链球菌种类包括乳房链球菌（32.3%）和停乳链球菌（14.9%）。耐药基因检测显示，不同水牛乳区和栖息地中抗菌药物耐药基因（ARGs）的流行率很高，尤其是aac - 3(iv)和tetA。药敏谱分析表明，对四环素（80.9；83.1）和甲氧苄啶 - 磺胺甲恶唑（87.4；81.9）高度敏感，而对氨苄西林（88.8；87.1）和萘啶酸（68.1；62.1）有显著耐药性。在76.4%（479/627）的葡萄球菌属和67.3%（167/248）的链球菌属分离株中观察到MDR，分别有10.37%（65/627）和10.48%（26/248）被归类为可能的XDR。这些发现揭示了亚临床型乳腺炎中葡萄球菌和链球菌属的高抗菌药物耐药水平，突出了改进管理措施和监测以减轻受污染牛奶对公众健康风险的必要性。
