南京地区某渔场嗜水气单胞菌流行菌株的鉴定及分子分型

为确定南京地区某渔场异育银鲫出血性败血症的病原体,采集该渔场3个饲养塘口患病鱼脏器进行细菌分离培养,基于气单胞菌DNA促旋酶B亚单位(gyr B)基因序列设计引物,PCR扩增后测序进行细菌鉴定;同时,对病原菌生物学特性如溶血性、蛋白酶活性、生物被膜形成能力、运动能力以及对斑马鱼的毒力等进行分析,并进行多位点序列分型(MLST)。结果在3个饲养塘口均分离到嗜水气单胞菌,分别命名为GL-15、GL-17和GL-18;MLST分型显示三株分离菌均为ST251型;生物学特性实验表明,均有溶血性、蛋白酶活性以及运动性,生物被膜形成能力较强,OD595均超过0.5,对斑马鱼的LD50在1.4×103~3.9×103 CFU/尾,属强毒株。本研究为有效防控南京地区嗜水气单胞菌引发的出血性败血症的暴发流行提供了依据。

Identification and molecular typing of the epidemic Aeromonas hydrophila strains in one farm of Nanjing

Aeromonias hydrophila is a Gram-negative bacterium, which is widely distributed in the water environment. Pathogenic strains can cause sepsis in a variety of aquatic animals. In Sep.2015, crucian carp (Carassius carassius) in one farm of Nanjing showed symptoms of haemorrhagic septicaemia. Samples from diseased fish in three ponds were collected and the pathogenic bacteria were isolated. Three A. hydrophila isolates were identified based on sequencing of the housekeeping gene gyrB, and named GL-15, GL-17 and GL-18, respectively. Then the three A. hydrophila strains were typed using multilocus sequence typing (MLST) based on six housekeeping genes. Also, all three isolates were analyzed for hemolytic and proteolytic characterizations and pathogenicity in zebrafish. The results showed that all the three strains presented hemolytic and proteolytic activities, and the abilities of biofilm formation and swarming and swimming. And they were highly virulent stains, with the LD50 values of 1.4×10₃ to 3.9×10₃ CFU. This study provides a basis for control of MAS caused by A. hydrophila in Nanjing area.