Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Utrecht, 3584 CL, the Netherlands.
M-Team and Mastitis and Milk Quality Research Unit, Department of Reproduction, Obstetrics, and Herd Health, Faculty of Veterinary Medicine, Ghent University, Merelbeke, B-9820, Belgium.
J Dairy Sci. 2012 Sep;95(9):5075-5084. doi: 10.3168/jds.2012-5615.
Coagulase-negative staphylococci (CNS) are the most commonly isolated bacteria from goat milk. The goal of this study was to explore and describe differences between CNS species in persistence of intramammary infection (IMI) and in effect on somatic cell count (SCC) and milk yield (MY). Milk samples were collected from 530 does from 5 Dutch dairy goat herds on 3 occasions during 1 lactation. Coagulase-negative staphylococci species were identified at the species level by transfer RNA-intergenic spacer PCR (tDNA-PCR) followed by capillary electrophoresis. The most prevalent CNS species were Staphylococcus caprae, Staphylococcus epidermidis, Staphylococcus simulans, and Staphylococcus xylosus, but large differences were seen in species distribution between herds. Staphylococcus caprae and Staph. xylosus appeared to be more persistent than other species, but confidence intervals were overlapping. The effect of IMI caused by the 4 most prevalent CNS species on SCC and on MY was determined with linear regression models, and Staph. aureus and Corynebacterium bovis were included in the analyses as reference organisms. Most species were associated with a significantly higher SCC than noninfected udder halves, but the effect of CNS species on SCC was much smaller than the effect of Staph. aureus on SCC. We found a significant positive association between infection with Staph. caprae and MY. Intramammary infection caused by Staph. xylosus, on the other hand, had a negative association with milk yield, comparable to the effect of Staph. aureus, but these effects were not significantly different from zero. Intramammary infections with CNS species have a high prevalence in goats and are persistent, but have a limited effect on SCC compared with IMI with Staph. aureus. The effect of CNS species on MY differed between species, but differences were nonsignificant because limited numbers per species were available for analysis. Therefore, CNS species appear to behave as minor pathogens in goats, but larger studies are needed to give better estimates for the effect on MY.
凝固酶阴性葡萄球菌（CNS）是从山羊奶中分离出的最常见细菌。本研究的目的是探索和描述 CNS 物种在持续性乳腺炎（IMI）和对体细胞计数（SCC）和产奶量（MY）的影响方面的差异。在一个泌乳期内，从 5 个荷兰乳用山羊场的 530 只母羊中采集了 3 次奶样。通过 tRNA 基因间隔区 PCR（tDNA-PCR）结合毛细管电泳鉴定 CNS 物种。最常见的 CNS 物种是表皮葡萄球菌、腐生葡萄球菌、模仿葡萄球菌和木糖葡萄球菌，但在不同的牛场中，物种分布存在很大差异。葡萄球菌和木糖葡萄球菌似乎比其他物种更具持续性，但置信区间重叠。通过线性回归模型确定了 4 种最常见的 CNS 物种引起的 IMI 对 SCC 和 MY 的影响，并将金黄色葡萄球菌和牛棒状杆菌纳入分析作为参考生物。大多数物种与 SCC 显著升高相关，但 CNS 物种对 SCC 的影响远小于金黄色葡萄球菌对 SCC 的影响。我们发现感染表皮葡萄球菌与产奶量呈显著正相关。另一方面，感染木糖葡萄球菌与产奶量呈负相关，与金黄色葡萄球菌的影响相当，但这些影响与零无显著差异。山羊中 CNS 物种引起的乳腺炎感染率很高，具有持续性，但与金黄色葡萄球菌引起的 SCC 相比，对 SCC 的影响有限。CNS 物种对 MY 的影响因物种而异，但由于每个物种的可用数量有限，差异无统计学意义。因此，CNS 物种在山羊中似乎表现为次要病原体，但需要更大的研究来更好地估计对 MY 的影响。
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