一株凡纳滨对虾源维氏气单胞菌的分离鉴定及药敏特性

【目的】凡纳滨对虾(Litopenaeus vannamei)是世界范围内最主要的对虾养殖品种之一,2017年5-6月上海某凡纳滨对虾养殖场出现不明原因的死亡病例,发病急,死亡率高。从患病凡纳滨对虾体内分离到一株优势菌AVZ01,旨在确定病因并筛选出敏感药物,为今后凡纳滨对虾维氏气单胞菌(Aeromonas veronii)的防治提供参考。【方法】从患病凡纳滨对虾肝胰腺和肠道中分离致病菌,通过理化特性及16S r RNA基因序列分析进行鉴定,通过人工感染试验确定病原,使用Bliss法计算出半数致死剂量(LD50),并通过纸片扩散法进行药敏试验。【结果】从患病凡纳滨对虾体内分离到一株优势菌AVZ01,进行人工回归感染试验后,对虾发病症状与自然发病症状相似,凡纳滨对虾的LD50为8.7×105 CFU/m L。根据该菌株的形态特征、理化特性、16S r RNA基因序列分析,综合判断该病原菌为维氏气单胞菌。药敏试验结果显示,该菌株对米诺环素、诺氟沙星、庆大霉素等16种抗生素高度敏感,对青霉素、苯唑西林、头孢氨苄等9种抗生素耐药。【结论】分离菌株AVZ01对凡纳滨对虾有较强的致病性,养殖过程中可选用庆大霉素及新霉素等药物进行防控。

Isolation, identification and antibiotic sensitivity of Aeromonas veronii from Litopenaeus vannamei

Objective] Litopenaeus vannamei is one of the most important species of shrimp farming in the world, with high output and value and strong market demand. From May to June of 2017, Litopenaeus vannamei was found to have unexplained high morbidity and mortality in one shrimp farm in Shanghai. To determine and identify the cause of death for Litopenaeus vannamei and screen out sensitive drugs, a dominant bacterium strain AVZ01 was isolated from sick L. vannamei. The aim of this study was to provide reference for further prevention and treatment of Aeromonas veronii in China. Methods] The pathogenic bacteria were isolated from the hepatopancreas and intestinal tract of dead L. vannamei. The LD50 assay was carried out by Bliss method. According to morphological, biochemical characteristics and 16S rRNA gene sequence analysis, the isolated strain was identified. Antibiotic susceptibility test was carried out by K-B methods. Results] After the artificial infection test with strain AVZ01 from the diseased shrimp, the symptoms of shrimp were similar to those of natural disease, the LD50 was counted to 8.7×105 CFU/mL. According to the morphological characteristics, biochemical characteristics and 16S rRNA gene sequence analysis, the pathogen was identified as A. veronii. The results of antibiotic sensitivity test showed that the AVZ01 strain is highly sensitive to 16 antibiotics, such as metolycins, norfloxacin and gentamicin, etc, and resistant to 9 antibiotics, such as penicillin, oxacillin and cephalexin, etc. Conclusion] The isolated strain AVZ01 has strong pathogenic to L. vannamei, and the gentamicin and neomycin could be used for the control and treatment in the future.