血鹦鹉鱼木糖葡萄球菌的分离鉴定和耐药性研究

Identification and Drug Resistance of Staphylococcus xylosus Isolated from Cichlid Cichlasoma var.

自患病血鹦鹉鱼肾脏分离获得优势菌CVSX1,做分离纯化培养、生化与分子鉴定、人工感染试验和药敏试验,以期对该病有效预防和治疗。分离菌株血液培养菌落呈圆形,表面光滑,边缘整齐,颜色灰白色至略黄,周围有弱溶血环。经过涂片染色镜检,该菌株革兰氏染色为阳性圆形球菌,直径约为0.8～1.0μm,多数成堆,少数散在、成对或四联状排列。该菌株无荚膜或鞭毛,亦无芽孢,根据形态和生理、生化性状可初步鉴定为木糖葡萄球菌。菌株的16SrDNA序列比对表明,菌株CVSX1与已登录GenBank数据库的木糖葡萄球菌16SrDNA序列的相似性〉99%,聚类分析结果表明菌株CVSX1与葡萄球菌属的木糖葡萄球菌遗传距离最小。通过人工感染试验证明木糖葡萄球菌CVSX1对血鹦鹉幼鱼有较强的致病性。应用临床常用的抗生素对木糖葡萄球菌CVSX1进行药敏检测,菌体CVSX1对磺胺嘧啶、青霉素G、诺氟沙星、四环素高度耐药,对红霉素、丁胺卡那敏感,对环丙沙星、氧氟沙星表现为中介。

The pathogenic bacteria were isolated from the kidney of diseased Cichlid Cichlasoma var.and made physiological,biochemical and molecular biological identification.Furthermore,drug sensitive tests and artificial infection experiments were performed in order to develop effective control and prevention measures.After 24 hours,the bacteria cultured on blood agar and clones were circular with smooth and neat edges and a weak zone of hemolysis around.The bacteria were Gram positive coccobacteria and had the diameter about 0.8—1.0μm,most of which were acervate,a few scattered pairs or quadruple-like arrangement,without capsule or flagella and no spores either.Based on physiological and biochemical characteristics,the strain was identified as Staphylococcus xylosus.Analysis of the 16 SrDNA sequence of the strain showed that it belonged to Staphylococcus,and had farther distance with Streptococcus,and that the similarity to uploaded 16 SrDNA sequence of S.xylosusin GenBank database was 99%.Cluster analysis revealed that the bacteria had the smallest genetic distance with S.xylosus.Pathogenicity of the isolated strain was determined by artificial infection experiment and it was found that it had strong pathogenicity to Cichlasoma var.juveniles.The bacteria susceptibility test indicated that the bacterial strain was resistant to sulfadiazine,penicillin,norfloxacin,tetracycline,but sensitive to erythromycin,and amikacin,and moderately sensitivity intermediate with ciprofloxacin and ofloxacin.