Somatic cell scores and clinical signs following experimental intramammary infection of dairy cows with a Staphylococcus aureus small colony variant (S. aureus SCV) in comparison to other bovine strains
Somatic cell scores and clinical signs following experimental intramammary infection of dairy cows with a Staphylococcus aureus small colony variant (S. aureus SCV) in comparison to other bovine strains
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DOI：
10.1016/j.vetmic.2009.01.027
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发表时间：
2009-06-12
影响因子：
3.3
通讯作者：
Mallard, Bonnie
中科院分区：
文献类型：
--
作者：
Atalla, Heba;Gyles, Carlton;Mallard, Bonnie
最近分离的牛金黄色葡萄球菌小菌落变异体（SCV）被证明在培养的内皮细胞内持续存在。然而，S.金黄色葡萄球菌SCV在乳腺持续感染中的作用尚不清楚。这里检验的假设是一种天然存在的牛沙门氏菌。金黄色葡萄球菌SCV Heba 3231和人工产生的SCV Newbould hemB突变体将建立轻度乳房内感染，并诱导与其同基因亲本菌株3231和Newbould 305相比不同的宿主应答。4组临床健康奶牛（5头奶牛/处理组）通过乳房内途径感染SCV Heba 3231、菌株3231、hemB突变体或菌株Newbould 305。每头奶牛的四分之三乳腺用类似于5000菌落形成单位的细菌进行攻毒，第四个四分之一输注PBS。监测奶牛，并根据直肠温度、食欲、产奶量、乳房均匀度、乳汁外观、前乳样品的细菌培养和体细胞评分（SCS），在攻毒后前5天分配临床评分。检查所有奶牛的慢性感染，直至攻毒后第36天。用SCV菌株攻毒的奶牛发生乳腺炎，与亲本菌株诱导的乳腺炎相比，乳腺炎较轻。用菌株3231攻毒的奶牛发生了最严重的临床型乳房炎。与攻击前第0天相比，所有处理组的SCS在感染后第2-5天和第14-36天显著（P < 0.05）更高。这种较温和的宿主对SCV的反应可能代表了S.金黄色葡萄球菌对乳腺环境的影响。(C)2009 Elsevier B. V.保留所有权利。
A recently isolated bovine Staphylococcus aureus small colony variant (SCV) was shown to persist within cultured endothelial cells. However, the clinical importance of S. aureus SCV in persistent infection of the mammary gland is unknown. The hypothesis tested here was a naturally occurring bovine S. aureus SCV, Heba3231, and a Newbould hemB mutant that was an artificially created SCV would establish mild intramammary infection and induce a different host response compared to their isogenic parental strains, 3231 and Newbould 305. Four groups of clinically healthy cows, 5 cows/treatment group, were infected by the intramammary route with SCV Heba3231, strain 3231, the hemB mutant or strain Newbould 305. Three quarters of the mammary gland of each cow were challenged with similar to 5000 colony-forming units of bacteria and the fourth quarter was infused with PBS. Cows were monitored and assigned clinical scores for the first 5 days post-challenge based on rectal temperature, appetite, milk yield, udder uniformity, milk appearance, bacterial culture of foremilk samples and somatic cell score (SCS). All cows were examined for chronic infection up to day 36 post-challenge. Cows challenged with SCV strains developed mastitis that was mild compared with that induced by the parent strains. Cows challenged with strain 3231 developed the most severe clinical mastitis. SCS from all treatment groups were significantly (P < 0.05) higher at days 2-5 and 14-36 post-infection compared to day 0 before challenge. This milder host response to SCVs may represent an adaptation of S. aureus to the mammary gland environment. (C) 2009 Elsevier B.V. All rights reserved.