Institute for Agricultural and Fisheries Research (ILVO), Technology and Food Science Unit, 9090 Melle, Belgium.
J Dairy Sci. 2012 Dec;95(12):7027-38. doi: 10.3168/jds.2012-5400. Epub 2012 Sep 19.
The aim of this study was to investigate whether the main coagulase-negative staphylococci (CNS) species involved in bovine intramammary infections (IMI) possess specific characteristics that promote colonization of the udder. Virulence markers associated with biofilm formation, antimicrobial resistance, and biocide tolerance were compared between typically contagious CNS species (Staphylococcus chromogenes, Staphylococcus epidermidis, Staphylococcus haemolyticus, and Staphylococcus simulans) and those rarely causing IMI (Staphylococcus sciuri, Staphylococcus equorum, and others) to find possible associations with pathogenicity. Coagulase-negative staphylococci isolates (n=366) belonging to 22 different species were analyzed by PCR for the presence of the biofilm-associated genes bap and icaA, and the methicillin resistance gene mecA. A selection of 82 isolates was additionally tested for their susceptibility to 5 antibiotics and 2 commercial teat dip products. Minimum inhibitory concentrations of antimicrobials were determined by Etest (AB bioMérieux, Marcy l'Etoile, France), and a microdilution method was optimized to determine minimum biocidal concentrations of teat dips. The bap, icaA, and mecA genes were detected significantly more in isolates from CNS species typically living in the cows' environment than in isolates from IMI-causing species. Antimicrobial resistance was mainly against erythromycin (23%) or oxacillin (16%), and was detected more often in the environmental species. The isolates least susceptible to the teat dips belonged to the IMI-causing species Staph. chromogenes and Staph. simulans. We concluded that carriage of biofilm genes and antimicrobial resistance were not associated with the ability to colonize the mammary gland because free-living CNS species constituted a more significant reservoir of biofilm and resistance determinants than did IMI-causing species. In contrast, increased tolerance to biocides may favor the establishment of bovine IMI by some CNS species.
本研究旨在探讨是否主要凝固酶阴性葡萄球菌（CNS）种参与奶牛乳腺炎（IMI）具有促进乳房产物定植的特定特性。与生物膜形成、抗菌药物耐药性和杀生物剂耐受性相关的毒力标记物在通常传染性 CNS 种（金黄色葡萄球菌、表皮葡萄球菌、溶血葡萄球菌和模仿葡萄球菌）与那些很少引起 IMI（松鼠葡萄球菌、马胃葡萄球菌和其他）之间进行比较，以发现与致病性的可能关联。通过 PCR 分析了 366 株属于 22 个不同种的凝固酶阴性葡萄球菌分离株，以检测生物膜相关基因 bap 和 icaA 以及耐甲氧西林基因 mecA 的存在。另外选择了 82 株分离株，测试它们对 5 种抗生素和 2 种商业乳头浸渍产品的敏感性。通过 Etest（AB bioMérieux，Marcy l'Etoile，法国）测定抗菌药物的最低抑菌浓度，并优化了微稀释法以确定乳头浸渍的最低杀菌浓度。bap、icaA 和 mecA 基因在环境中常见的 CNS 种的分离株中检测到的比例明显高于 IMI 引起的种的分离株。主要对红霉素（23%）或苯唑西林（16%）耐药，在环境种中检测到的频率更高。对乳头浸渍最不敏感的分离株属于 IMI 引起的种 Staph.chromogenes 和 Staph.simulans。我们得出结论，生物膜基因和抗菌药物耐药性的携带与定植乳腺的能力无关，因为自由生活的 CNS 种比引起 IMI 的种构成了更大的生物膜和耐药决定因素的储存库。相比之下，对杀生物剂的耐受性增加可能有利于某些 CNS 种建立牛乳腺炎。
