产色葡萄球菌和松鼠哺乳动物球菌在3个具有不同垫料系统的中国奶牛场中奶牛、农场环境和工作人员间的分布

摘要(中文译文)

非金黄色葡萄球菌和哺乳动物球菌（NASM）是牛乳腺炎中最常检出的病原体之一，但其优势菌种、在牛-人-环境界面上的分布、牛群内种群结构以及潜在的流行病学联系在中国仍未得到充分描述。我们在3个采用不同垫料系统的中国商业化奶牛场（粪渣固体[MNS]、新砂[NS]和锯末）开展了一项横断面调查。样本采集自泌乳牛和喂奶犊牛（多个身体部位）、乳腺炎牛奶（临床型和亚临床型）、牧场环境以及工作人员。NASM通过MALDI-TOF MS和tuf测序进行鉴定，并对分离频率最高的2种NASM菌种进一步采用核心基因组多位点序列分型（cgMLST）进行特征分析。乳腺炎牛奶中NASM的检出率在不同牛场间存在差异，MNS牛场最高，NS牛场最低。从牛奶中共分离出11种NASM菌种，其中产色葡萄球菌（Staphylococcus chromogenes）和松鼠哺乳动物球菌（Mammaliicoccus sciuri）为分离频率最高的2种NASM菌种。产色葡萄球菌（产色葡萄球菌与松鼠哺乳动物球菌：27.5% vs. 19.5%）在宿主相关样本中检出率更高，而松鼠哺乳动物球菌（松鼠哺乳动物球菌与产色葡萄球菌：34.7% vs. 10.4%）在环境样本中富集；直肠和垫料分别是产色葡萄球菌（38.3%）和松鼠哺乳动物球菌（44.3%）的主要携带部位。牛场层面的分布模式各具特点：MNS牛场各来源均以松鼠哺乳动物球菌为主（牛：45.6%；环境：69.1%；人：13.9%），而NS牛场（牛：18.6%；环境：13.2%；人：11.9%）和锯末牛场（牛：43.9%；环境：21.1%；人：16.7%）均以产色葡萄球菌为主。乳腺炎牛奶中松鼠哺乳动物球菌的检出情况与其在各牛场环境中的出现情况相一致，而产色葡萄球菌在所有牛场的乳腺炎牛奶中均为最常见的菌种。核心基因组MLST显示两种菌种均具有显著的遗传多样性，并在牛、人和环境来源中检出了相关分离株。此外，在牛奶和垫料样本之间检出了相同的产色葡萄球菌分离株对，在一头喂奶犊牛和一头泌乳牛的鼻前庭之间检出了相同的松鼠哺乳动物球菌分离株对。总体而言，这2种优势NASM菌种在采用不同垫料系统的牛场间呈现出明显的牛场特异性分布模式，凸显了针对关键来源和管理措施进行菌种靶向防控的重要性。

Abstract

Non-aureus staphylococci and mammaliicocci (NASM) are among the most frequently detected pathogens in bovine mastitis, yet their dominant species, distribution across the cow-human-environment interface, within-herd population structure, and potential epidemiologic links remain incompletely described in China. We conducted a cross-sectional survey in 3 commercial Chinese dairy herds using distinct bedding systems (manure solids [MNS], new sand [NS], and sawdust). Samples were collected from lactating cows and milk-fed calves (multiple body sites), mastitic milk (clinical and subclinical), the farm environment, and workers. The NASM were identified by MALDI-TOF MS and tuf sequencing, and the 2 most frequently isolated NASM species were further characterized by core-genome multilocus sequence typing (cgMLST). Detection of NASM in mastitic milk differed across herds, being highest in the MNS herd and lowest in the NS herd. Eleven NASM species were isolated from milk, with Staphylococcus chromogenes and Mammaliicoccus sciuri as the 2 most frequently isolated NASM species. Staphylococcus chromogenes (S. chromogenes vs. M. sciuri: 27.5% vs. 19.5%) was more frequently detected in host-associated samples, whereas M. sciuri (M. sciuri vs. S. chromogenes: 34.7% vs. 10.4%) was enriched in environmental samples; the rectum and bedding represented the main carriage sites for S. chromogenes (38.3%) and M. sciuri (44.3%), respectively. Herd-level patterns were distinct: the MNS herd was dominated by M. sciuri across sources (cattle: 45.6%; environment: 69.1%; humans: 13.9%), whereas the NS (cattle: 18.6%; environment: 13.2%; humans: 11.9%) and sawdust (cattle: 43.9%; environment: 21.1%; humans: 16.7%) herds were dominated by S. chromogenes. Detection of M. sciuri from mastitic milk mirrored its environmental occurrence across herds, whereas S. chromogenes remained the most common species in mastitic milk in all herds. Core-genome MLST revealed substantial genetic diversity in both species, with related isolates detected among bovine, human, and environmental sources. In addition, identical S. chromogenes isolate pairs were detected between milk and bedding samples, and identical M. sciuri isolate pairs were detected between the nasal vestibules of a milk-fed calf and a lactating cow. Overall, the 2 dominant NASM species had marked herd-specific distribution patterns across herds with distinct bedding systems, underscoring the importance of species-targeted control focused on key sources and management practices.

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