Università degli Studi di Milano, Department of Health, Animal Science and Food Safety, via Celoria 10, 20133 Milano, Italy.
J Dairy Sci. 2013 Jun;96(6):3799-805. doi: 10.3168/jds.2012-6275. Epub 2013 Mar 30.
In many parts of the world, coagulase-negative staphylococci (CNS) are the predominant cause of intramammary infections (IMI) in dairy cows and in water buffaloes, as well. A longitudinal field study was carried out on one well-managed dairy water buffalo herd to determine the prevalence and distribution of CNS and a recently described CNS-species, Staphylococcus rostri, in milk samples to explore its relevance for buffaloes' udder health throughout lactation, and to gain insight into the susceptibility of the latter species toward commonly used antimicrobials. Twice weekly quarter milk samples from a cohort of 11 lactating water buffaloes were collected over an 8-mo period. The CNS (n=109; 76.2% of all culture-positive samples) were the predominant pathogens causing IMI, followed by Corynebacterium bovis (n=11; 7.6%) and Streptococcus spp. (n=9; 6.2%) other than Stretococcus uberis (n=2; 1.4%). Thirty-seven hemolytic staphylococci suspected to be Staphylococcus aureus were further differentiated using transfer DNA-intergenic spacer-PCR and rpoB-gene sequencing because they were coagulase-negative. Thirty-three of those isolates were identified as Staph. rostri, whereas 2 others were identified as Staphylococcus epidermidis. None of the Staph. rostri isolates displayed resistance to the antimicrobial agents tested. Mean quarter milk somatic cell count (qSCC) of all samples collected throughout lactation was 20,970 cells/mL. The qSCC at sampling of quarters infected with Staph. rostri (34,466 cells/mL) and CNS other than Staph. rostri (34,813 cells/mL) were significantly higher than the qSCC of noninfected quarters (20,287 cells/mL), yet not significantly different from each other. These findings provide novel insight into the prevalence and distribution, antimicrobial susceptibility, and relevance of Staph. rostri compared with other CNS species causing IMI in water buffaloes. Further studies are needed to pinpoint the relevance, niches, and transmission routes of Staph. rostri, as well as other CNS in water buffaloes.
在世界许多地区，凝固酶阴性葡萄球菌（CNS）是奶牛和水牛乳腺炎的主要病原体。本研究对一个管理良好的水牛奶牛群进行了纵向现场研究，以确定 CNS 和最近描述的 CNS 物种罗司氏葡萄球菌在牛奶样本中的流行率和分布，以探讨其与水牛泌乳期乳房健康的相关性，并深入了解后者对常用抗生素的敏感性。在 8 个月的时间里，每周两次从 11 头哺乳期水牛的四个乳区采集奶样。CNS（n=109；所有培养阳性样本的 76.2%）是引起 IMI 的主要病原体，其次是牛棒状杆菌（n=11；7.6%）和链球菌属（n=9；6.2%），除了停乳链球菌（n=2；1.4%）。因为它们是凝固酶阴性的，所以用转移 DNA 基因间 spacer-PCR 和 rpoB 基因测序进一步区分了 37 株疑似金黄色葡萄球菌的溶血葡萄球菌。其中 33 株被鉴定为罗司氏葡萄球菌，另外 2 株被鉴定为表皮葡萄球菌。没有一株罗司氏葡萄球菌分离株对测试的抗菌药物显示耐药性。整个泌乳期采集的所有样本的平均乳区体细胞计数（qSCC）为 20,970 个细胞/ml。感染罗司氏葡萄球菌（34,466 个细胞/ml）和非罗司氏葡萄球菌 CNS（34,813 个细胞/ml）的乳区 qSCC 明显高于未感染乳区（20,287 个细胞/ml），但彼此之间无显著差异。这些发现为罗司氏葡萄球菌与引起水牛乳腺炎的其他 CNS 物种的流行率和分布、抗菌药物敏感性以及相关性提供了新的认识。需要进一步研究以确定罗司氏葡萄球菌以及水牛其他 CNS 的相关性、生态位和传播途径。
