一株岩原鲤源致病性ST-251型嗜水气单胞菌的分离与生物学特性研究

为探究宜宾某岩原鲤(Procypris rabaudi)养殖场以体表出血为特征的流行性疾病的病因,通过生理生化特性检测与16S rDNA、致病性试验、多位点序列分型(MLST)、纸片扩散法(K-B)明确该流行病的病原及其生物学特性。结果显示,从病鱼的肝、肾分离获得一株病原菌(YYL),鉴定其为嗜水气单胞菌(Aeromonas hydrophila),在水温(24±1)℃时,该菌对体重为(12.6±0.8)g的岩原鲤半数致死量(LD₅₀)为5.8×10⁴ CFU·g^-1;药物敏感性试验表明,该菌对头孢他定、庆大霉素、多西环素、恩诺沙星、氟苯尼考等敏感,对亚胺培南、罗红霉素、复方新诺明、磺胺异恶唑、克林霉素耐药;MLST分子分型其属于ST-251型,并携带aerA、hlyA、aphA、act、ast等毒力基因。该研究从体表出血为特征的发病岩原鲤分离到ST-251型嗜水气单胞菌,该菌株携带多种毒力因子,致病力强,在岩原鲤的养殖中应加强对该病原感染的预防与控制。

Isolation and biological characteristics of a pathogenic ST-251 Aeromonas hydrophila from Procypris Rabaudi (rock carp)

To explore the causes of epidemic diseases characterized by body surface bleeding in a Procypris rabaudi farm in Yibin, the pathogen and its biological characteristics were identified by physiological and biochemical characteristics,research on the pathogenesis,16S rDNA, multilocus sequence typing (MLST) and Kirby-Bauer (K-B). A pathogenic bacterium (YYL) was isolated from liver and kidney of diseased fish, and identified as Aeromonas hydrophila.When the water temperature was (24±1) ℃, its median lethal dose (LD₅₀) was 5.8 × 10 ⁴ CFU·g^-1 for rock carp weight of (12.6±0.8) g. Drug sensitivity test showed that the YYL was sensitive to many drugs, such as ceftazidime, gentamicin, doxycycline, enrofloxacin, florfenicol, but resistant to imipenem, roxithromycin, compound sulfamethoxazole, clindamycin. The isolated A. hydrophila belonged to ST-251 type by multilocus sequence typing (MLST), and carried virulence genes aerA, hlyA, aphA, act, ast. In this study, ST-251 A. hydrophila was isolated from the diseased rock carp characterized by body surface hemorrhage. This strain carried a variety of virulence factors and had strong pathogenicity. Therefore, it was necessary to strengthen the prevention and control of this pathogen infection in the cultivation of rock carp.