辽宁某牛场奶牛隐性乳房炎源链球菌耐药性研究

Susceptibility test on Streptococcus isolated from dairy cow with subclinical mastitis

为了解辽宁阜新某奶牛场奶牛隐性乳房炎发生情况,采用体细胞计数法对奶牛场中94头临床表现健康的奶牛进行隐性乳房炎筛查,对检测后的阳性乳样进行链球菌的分离鉴定,并采用微量肉汤稀释法对分离所得的链球菌进行药敏试验。结果显示：该牛场奶牛隐性乳房炎的检出率为48.94%;对34株奶牛隐性乳房炎链球菌分离株进行体外药敏试验,发现菌株对头孢氨苄、磺胺间甲氧嘧啶和磺胺甲基异恶唑耐药率最高（100%）;对苯唑西林、阿奇霉素、林可霉素、多西环素、土霉素、红霉素的耐药率均在82.4%以上;对氨苄西林、阿莫西林和环丙沙星较敏感,敏感率分别为44.1%、50.0%及52.9%。结果表明：该奶牛场隐性乳房炎源链球菌多重耐药现象严重。

In order to investigate the occurrence of dairy subclinical mastitis,milk samples collected from 94 cows on a dairy farm in Fuxin,Liaoning Province and somatic cell counting was used to perform the investigation. Streptococcus was isolated and identified from milk samples which were determined as positive,and the susceptibility test on Streptococcus isolates was carried out using the micro-broth dilution method. The results showed that the occurrence rate of subclinical mastitis in dairy cows was 48. 94%. The susceptibility test showed that the Streptococcus isolates possessed the highest resistance rates（ 100%） to cephalexin,sulfamethoxine and sulfamethoxazole,and the resistance rates to oxacillin,azithromycin,lincomycin,doxycycline,oxytetracycline,and erythromycin were all above 82. 4%. Conversely,the isolates showed lower resistance rates to ampicillin,amoxicillin,and ciprofloxacin,of 44. 1%,50. 0%,and 52. 9%,respectively. To sum up,Streptococcus isolates in this dairy farm had a variety of resistance phenotypes,indicating emergence of multi-drug resistance. It is advisable that the dairy farm should select antimicrobial agents possessing high susceptibility against Streptococcus to cure subclinical mastitis in the cows there.