Burriel A R
Department of Farm Animal and Equine Medicine and Surgery, Royal Veterinary College Potters Bar.
Vet Rec. 1997 Apr 19;140(16):419-23. doi: 10.1136/vr.140.16.419.
Over an entire lactation 891 milk samples were collected from 99 ewes in a well-managed dairy flock. Coagulase-negative staphylococci were isolated from 53 (5.9 per cent) of the samples, with 13 (6.6 per cent) of the glands giving coagulase-negative staphylococci in two or more consecutive samples. When a somatic cell count threshold of 6 x 10(5)/ml of milk was adopted as an indication of inflammation, 30 of the milk samples collected during early and mid-lactation, which contained coagulase-negative staphylococci, were considered to come from glands suffering subclinical mastitis. In five glands subclinical mastitis persisted for the entire lactation. A comparison of somatic cell counts measured with the fossomatic or Coulter counters suggested that the former gave the most reliable values, particularly in late lactation. After the experimental infection of 20 glands of meat breeds with coagulase-negative staphylococci, five glands remained infected for all 49 days of observation and seven glands excreted bacteria intermittently. Irrespective of the presence of coagulase-negative staphylococci in the sample, the composition of the milk from the challenged glands was significantly modified (P < 0.0001 for the infected, and P < 0.01 for the uninfected glands). Fat and protein concentrations were increased and lactose decreased, suggesting that although coagulase-negative staphylococci could not always be isolated, they persisted in many of the challenged glands and continued to influence the physiology of the gland. This possibility was supported by the presence of severe damage to the udder tissue of glands in which bacteria had been shown to be present for long periods.
在一个管理良好的奶牛羊群中，从99只母羊身上采集了891份整个泌乳期的乳样。从53份（5.9%）乳样中分离出凝固酶阴性葡萄球菌，13个乳腺（6.6%）在两个或更多连续乳样中检测出凝固酶阴性葡萄球菌。当采用每毫升牛奶6×10⁵个体细胞数的阈值作为炎症指标时，在泌乳早期和中期采集的、含有凝固酶阴性葡萄球菌的30份乳样被认为来自患有亚临床乳腺炎的乳腺。在5个乳腺中，亚临床乳腺炎持续了整个泌乳期。用fossomatic或库尔特计数器测量体细胞数的比较表明，前者给出的值最可靠，尤其是在泌乳后期。在用凝固酶阴性葡萄球菌对20个肉用品种的乳腺进行实验感染后，在49天的观察期内，有5个乳腺一直处于感染状态，7个乳腺间歇性地排出细菌。无论乳样中是否存在凝固酶阴性葡萄球菌，受挑战乳腺的乳汁成分都有显著改变（感染的乳腺P<0.0001，未感染的乳腺P<0.01）。脂肪和蛋白质浓度增加，乳糖减少，这表明尽管并非总能分离出凝固酶阴性葡萄球菌，但它们在许多受挑战的乳腺中持续存在，并继续影响乳腺的生理功能。在长期存在细菌的乳腺的乳房组织出现严重损伤的情况下，这种可能性得到了支持。
