牛源金黄色葡萄球菌的耐药性及耐甲氧西林金黄色葡萄球菌的检测

【目的】了解内蒙古地区奶牛乳房炎金黄色葡萄球菌耐药性和耐甲氧西林金黄色葡萄球菌（MRSA）感染的情况，为奶牛乳房炎的防治提供理论依据。【方法】采用K-B纸片扩散法，检测分离自内蒙古地区38株金黄色葡萄球菌对17种药物的敏感性，同时用琼脂稀释法检测苯唑西林、万古霉素对金黄色葡萄球菌的最小抑菌浓度（MIC）；再用头孢西丁、苯唑西林纸片扩散法、苯唑西林盐琼脂筛选法和PCR方法扩增mecA耐药基因对分离菌株进行全面MRSA检测。【结果】分离菌株对每种抗生素都有不同程度抗性，对氨苄西林、头孢拉丁、青霉素、复方新诺明、新生霉素和链霉素的耐药率都高于45%，而对氧氟沙星、丁胺卡那霉素、万古霉素、环丙沙星、庆大霉素和头孢唑林的敏感性高于90%，2株细菌的万古霉素MIC≥16 μg•mL-1；其中8株细菌的苯唑西林MIC≥8 μg•mL-1，而其它菌株的苯唑西林MIC≤2 μg•mL-1；分离菌株多重耐药情况严重，耐受3种及3种以上药物的菌株占84.21%，其中4株细菌能同时耐受9种不同抗菌药物；16（42.11%）株细菌被检测携带mecA耐药基因，而仅有其中7株的苯唑西林MIC≥4 μg•mL-1；头孢西丁、苯唑西林纸片扩散法和苯唑西林盐琼脂筛选法分别检出7株、10株和7株表型为MRSA的菌株。【结论】分离菌株的耐药性和多重耐药现象较为严重，被调查地区奶牛场中已经存在MRSA和OS-MRSA感染情况，且感染率高。

Antimicrobial Resistance Analysis and Detection of Methicillin-Resistant Staphylococcus aureus (MRSA) Among Staphylococcus aureus Strains Isolated from Bovine Mastitis

【Objective】The aim of the study is to investigate the antimicrobial resistance of S. aureus (Science) and to detect the presence of methicillin-resistant S.aureus (MRSA) among S.aureus strains isolated from bovine mastitis in Inner Mongolia, and to provide credible theory evidence for prevention and treatment of bovine mastitis. 【Method】 K-B disk diffusion method was used to test drug sensitivity of 38 total strains of S.aureus to 17 commonly used antibiotics. Meanwhile, agar screen was performed to identify the minimum inhibitory concentration of oxacillin and vancomycin to all strains. Cefoxitin, oxacillin disk diffusion and oxacillin agar screen were used to detect the phenotype of MRSA, and PCR assay was generated the genotype of MRSA as well. 【Result】 The isolates had different degrees of antimicrobial resistance to each antibiotic, the frequency of resistance to ampicillin, cefradine, penicillin, cotrimoxazole, novobiocin and streptomycin was more than 45%, yet keeping sensitive to ofloxacin, vancomycin, amikacin, ciprofloxacin, gentamicin and cefazolin was over 90%. Two of the strains with vancomycin MIC were ≥16 μg•mL-1. The MICs of oxacillin for eight of total strains were ≥ 8 μg•mL-1, others with oxacillin MICs were ≤2 μg•mL-1. The multidrug resistance was severe, 84.21% of the strains were resistant to at least 3 kinds of antimicrobial agent, four of the total strains can survive in the presence of night various antibiotics. 16(42.11%) S.aureus strains carried mecA gene detected by PCR assay. However, there were only seven of them have the minimum inhibitory concentration over 4 μg•mL-1. When cefoxitin, oxacillin disk diffusion and oxacillin agar screen methods were generated the phenotype of MRSA, only 7, 10 and 7 strains of each were identified. 【Conclusion】 The antimicrobial resistance and multidrug resistance of S aureus were serious. High incidence of MRSA and OS-MRSA has been associated with bovine mastitis in the surveyed region.