Seixas R, Santos J P, Bexiga R, Vilela C L, Oliveira M
Immunology and Microbiology Laboratory, Interdisciplinary Centre of Research in Animal Health (CIISA)/Faculdade de Medicina Veterinária da Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal.
Immunology and Microbiology Laboratory, Interdisciplinary Centre of Research in Animal Health (CIISA)/Faculdade de Medicina Veterinária da Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal.
J Dairy Sci. 2014;97(1):340-4. doi: 10.3168/jds.2013-7130. Epub 2013 Nov 13.
Methicillin-resistant staphylococci (MRS) have already been reported as mastitis agents. Such bacterial species are a public health concern, and the characterization of their antimicrobial resistance and virulence profile is important to better control their dissemination. The present work evaluated the distribution of methicillin-resistance among 204 staphylococci from clinical (n=50) and subclinical (n=154) bovine mastitis. The presence ofthe mecA gene was determined by PCR. Phenotypic expression of coagulase, DNase, lipase, gelatinase, hemolytic enzymes, and biofilm production was evaluated. The presence of biofilm-related genes, icaA, icaD, and bap, was also determined. Antimicrobial resistance patterns for aminoglycosides, lincosamides, macrolides, fluoroquinolones, sulphonamides, tetracyclines, and fusidic acid were determined. Nineteen (9.3%) isolates were identified as MRS, and the presence of mecA in these isolates was confirmed by PCR. Virulence factors evaluation revealed that gelatinase was the most frequently detected (94.7%), followed by hemolysins (73.7%) and lipase (68.4%); 84.2% of the MRS isolates produced biofilm and icaA and icaD were detected in almost half of the MRS isolates (52.6%), but all were bap-negative. Resistance against other antimicrobial agents ranged from 0 (fusidic acid, ciprofloxacin, norfloxacin, enrofloxacin) to 100% (nalidixic acid). Resistance to nalidixic acid and nalidixic acid-tetracycline were the most common antimicrobial resistance profiles (31.6%). This study confirms that despite the low prevalence of MRS, isolates frequently express other virulence traits, especially biofilm, that may represent a serious challenge to clinicians.
耐甲氧西林葡萄球菌（MRS）已被报道为乳腺炎病原体。这类细菌是公共卫生问题，对其抗菌耐药性和毒力特征进行表征对于更好地控制其传播很重要。本研究评估了204株来自临床（n = 50）和亚临床（n = 154）牛乳腺炎葡萄球菌的耐甲氧西林分布情况。通过PCR检测mecA基因的存在。评估了凝固酶、DNA酶、脂肪酶、明胶酶、溶血酶的表型表达以及生物膜的产生情况。还检测了生物膜相关基因icaA、icaD和bap的存在。测定了对氨基糖苷类、林可酰胺类、大环内酯类、氟喹诺酮类、磺胺类、四环素类和夫西地酸的抗菌耐药模式。19株（9.3%）分离株被鉴定为MRS，通过PCR证实这些分离株中存在mecA。毒力因子评估显示，明胶酶检测频率最高（94.7%），其次是溶血素（73.7%）和脂肪酶（68.4%）；84.2%的MRS分离株产生生物膜，近一半的MRS分离株（52.6%）检测到icaA和icaD，但所有分离株均为bap阴性。对其他抗菌药物的耐药率从0（夫西地酸、环丙沙星、诺氟沙星、恩诺沙星）到100%（萘啶酸）不等。对萘啶酸和萘啶酸 - 四环素的耐药是最常见的抗菌耐药模式（31.6%）。本研究证实，尽管MRS的患病率较低，但分离株经常表达其他毒力特征，尤其是生物膜，这可能对临床医生构成严峻挑战。
