中国两大奶牛场肺炎克雷伯菌乳腺炎疫情的遗传多样性和分子流行病学研究。
Genetic diversity and molecular epidemiology of outbreaks of Klebsiella pneumoniae mastitis on two large Chinese dairy farms.
机构信息
Department of Clinical Veterinary Medicine, College of Veterinary Medicine, China Agricultural University, Beijing 100193, P.R. China.
Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada, N1G 2W1.
出版信息
J Dairy Sci. 2021 Jan;104(1):762-775. doi: 10.3168/jds.2020-19325. Epub 2020 Nov 25.
Klebsiella pneumoniae is an opportunistic and environmental mastitis-causing pathogen, with potential for contagious transmission. Repetitive element sequence-based PCR was used to determine genetic diversity and explore potential transmission and reservoirs for mastitis caused by K. pneumoniae on 2 large Chinese dairy farms. A total of 1,354 samples was collected from the 2 dairy farms, including milk samples from cows with subclinical and clinical mastitis, bedding, feces, feed, teat skin, and milking liners. Environmental samples were collected from all barns and milking parlors and extramammary samples from randomly selected dairy cows on both farms. In total, 272 and 93 K. pneumoniae isolates were obtained from Farms A and B, respectively (with ~8K and 2K lactating cows, respectively). Isolation rates from clinical mastitis (CM), subclinical mastitis (SCM), and environmental or extramammary samples were 34, 23 and 37%, respectively for Farm A and 42, 3, and 34% for Farm B. The K. pneumoniae isolated from CM milk and extramammary or environmental sources had high genetic diversity (index of diversity >90%) on the 2 farms and from SCM on Farm A. However, on Farm B, 9 SCM isolates were classified as 2 genotypes, resulting in a relatively low index of diversity (Simpson's index of diversity = 0.39; 95% CI = 0.08-0.70). Genotypes of K. pneumoniae causing mastitis were commonly detected in feces, bedding, and milking liners (Farm A), or from teat skin, sawdust bedding, and feed (Farm B). Based on its high level of genetic diversity, we inferred K. pneumoniae was an opportunistic and environmental pathogen causing outbreaks of CM on these 2 large Chinese dairy farms. Nevertheless, that only a few genotypes caused SCM implied some strains had increased udder adaptability and a contagious nature or a common extramammary source. Finally, control of intramammary infections caused by K. pneumoniae on large Chinese dairy farms must consider farm-level predictors, as the 2 outbreaks had distinct potential environmental sources of infection.
肺炎克雷伯菌是一种机会性和环境性乳腺炎病原体，具有传染性传播的潜力。我们使用重复元件序列基 PCR 来确定遗传多样性，并探索在中国的 2 个大型奶牛场中由肺炎克雷伯菌引起的乳腺炎的潜在传播和储源。从这 2 个奶牛场共采集了 1354 个样本，包括患有亚临床和临床乳腺炎的奶牛的奶样、垫料、粪便、饲料、乳头皮肤和挤奶衬垫。环境样本从所有牛舍和挤奶厅采集，从这 2 个奶牛场的随机选择的奶牛采集非乳腺样本。从农场 A 和 B 分别获得了 272 和 93 株肺炎克雷伯菌（分别有~8000 和 2000 头泌乳奶牛）。从临床乳腺炎（CM）、亚临床乳腺炎（SCM）和环境或非乳腺样本的分离率分别为农场 A 中的 34%、23%和 37%，以及农场 B 中的 42%、3%和 34%。从 CM 牛奶和非乳腺或环境来源分离的肺炎克雷伯菌在这 2 个农场以及农场 A 的 SCM 中具有很高的遗传多样性（多样性指数>90%）。然而，在农场 B 中，9 个 SCM 分离株被分为 2 种基因型，导致多样性指数相对较低（辛普森多样性指数=0.39；95%置信区间=0.08-0.70）。引起乳腺炎的肺炎克雷伯菌的基因型在粪便、垫料和挤奶衬垫中（农场 A）或在乳头皮肤、木屑垫料和饲料中（农场 B）普遍存在。基于其高水平的遗传多样性，我们推断肺炎克雷伯菌是一种机会性和环境病原体，导致这 2 个中国大型奶牛场爆发 CM。然而，只有少数基因型引起 SCM 表明某些菌株具有增加的乳房适应性和传染性或共同的非乳腺源。最后，在中国大型奶牛场控制由肺炎克雷伯菌引起的乳腺炎感染必须考虑农场级别的预测因子，因为这 2 次暴发有明显不同的潜在感染环境源。
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