罗非鱼源蜡样芽孢杆菌分离、鉴定及药敏特性研究

从福建漳州某养殖场患出血病死亡的罗非鱼肝脏、肾脏及脾脏分离到一株致病性菌株FJLF。对该菌进行了形态特征观察、理化特性测定及16S rRNA序列分子鉴定。生理生化特征和16S rRNA基因序列分析结果显示,分离到的FJLF株为蜡样芽孢杆菌(Bacillus cereus)。人工感染该菌后发病鱼出现与自然发病类似症状,且从病灶中分离到与原感染菌一致菌株。腹腔注射后该菌株对罗非鱼的半致死剂量LD_(50)=2.30×10~6CFU/g。FJLF株对诺氟沙星、头孢噻肟、新霉素及卡那霉素等8种抗生素高度敏感;对环丙沙星、痢特灵、红霉素及链霉素中度敏感;对苯唑西林、青霉素、头孢拉定及阿莫西林等10种抗生素耐药。

Isolation,identification and antibiotic sensitivity of Bacillus cereus from tilapia

Bacterial strain FJLF was isolated from diseased tilapia suffered from serious hemorrhage disease at a fish farm in Zhangzhou,Fujian Province,and it was identified as Bacillus cereus based on biochemical reaction characters and 16S rRNA gene sequence analyses.Artificial affected fish by intraperitoneal FJLF-injection showed the same clinic signs as the diseased fish in ponds.Therefore,the isolated B.cereus was proved as the main pathogen,and its LD50 to tilapia was determined as 2.30×106CFU/g using the probabilistic graphical method.The antibiotic sensitivity test showed that the isolated was very sensitive to norfloxacin,cefotaxime,neomycin,kanamycin,etc.,less sensitive to ciflox,furazolidone,erythrocin,streptomycin1,and not sensitive to oxacillin,penicillin,cefadroxil,amoxicillin etc.