暹罗鳄致病性嗜水气单胞菌嗜水亚种的分离鉴定

Isolation and Identification of Pathogenic Aeromonas hydrophila spp. hydrophila from Crocodylus siamensis

对海南陵水某鳄鱼养殖场发病死亡鳄鱼进行病理解剖和病原分离鉴定,获得的分离菌株为革兰氏阴性杆菌,其培养特性、生化反应等与嗜水气单胞菌嗜水亚种生化特性基本一致,两者的16S rRNA基因序列同源性高达99.9%,在系统发育树中与嗜水气单胞菌嗜水亚种同属一发育分支。该菌的人工感染试验和药物敏感试验结果表明:分离菌株对NIH小鼠的半数致死量(LD50)为2.5×105/只,具有较强的致病作用;在耐药性上,该菌株对丁胺卡那霉素、环丙沙星、氟苯尼考等13种抗生素敏感,对红霉素、氨苄青霉素、青霉素、阿莫西林、链霉素、克林霉素及萘啶酸等9种抗生素有耐药性。

A dominant bacterial strain isolated from the lesion tissues of the inspected dead Crocodylus siamensis in Lingshui,Hainan Province was identified via morphological observation,and physiological and biochemical test.The results showed that this isolated strain was gram-negative and was almost identical in characteristics to Aeromonas hydrophila. The phylogenetic analysis based on 16 S rRNA gene sequences further indicated that the isolate was clustered in the genus Aeromonas,with its sequence having the maximum similarity（99. 9%） with that of Aeromonas hydrophila subsp. hydrophila. The artificial infection test showed that the isolate was highly morbigenous to NIH mice with the half median lethal dose of 2. 5 × 10^5 cfu·m L-1. The sensitivity tests of this isolate with 27 antibiotics demonstrated that the isolate was sensitive to 13 antibiotics,such as amikacin,ciprofloxacin,cefoperazone,etc,and resistant to 9 antibiotics such as erythromycin,ampicillin,streptomycin etc.