鲟致病性类志贺邻单胞菌的鉴定及药物敏感性

Identification and drug sensitivity of a Plesiomonas shigelloides isolated from diseased sturgeons

摘要:

摘要:【目的】2012年夏季北京地区多地养殖的鲟鱼发病，主要临床症状为肛门红肿、伴有黄色分泌物，腹腔内有大量腹水，腹腔内壁有出血点，肝脏点状出血，脾脏肿大等，累计死亡率达60%。本文目的为研究其病原。【方法】从具有临床症状的濒死鱼中分离病原菌，分析病原菌的形态特征、理化特性、分类地位及药物敏感性等特性，经过人工感染及引起的组织病理确认致病性。【结果】结果显示病原菌的16S rDNA 序列构建的进化树，与类志贺邻单胞菌同源性最高，在99%以上;结合其生理生化特征和API细菌鉴定系统的结果，确认为类志贺邻单胞菌。该菌对鲟鱼的半致死量LD50为1.0×105.8 CFU/mL，引起肝、肾和脾组织病变。胞外产物不具有淀粉酶、蛋白酶、脂肪酶和明胶酶活性，也无溶血性，推测其毒性可能来源于内毒素。该菌对恩诺沙星、盐酸多西环素、氟苯尼考和甲枫霉素敏感，药物敏感浓度均小于2μg/mL;而对试验的其它抗菌药物不敏感。【结论】确认类志贺邻单胞菌是引起北京地区鲟鱼发生上述临床症状疾病的主要致病菌，可优选盐酸多西环素、氟苯尼考和恩诺沙星进行防治。

Abstract:

Abstract:［Objective］In 2012，the cumulative mortality of farmed sturgeons in Beijing was almost 60% with various symptoms，including the reddening of the anus with yellow exudation，ascities in the peritoneal cavity，petechial haemorrhages in liver and internal muscle wall，and the swollen spleen．［Methods］We isolated the pathogen from the dying sturgeons with significant pathological signs，and then analyzed its morphological，physiological and biochemical characteristics，taxonomic status，and drug sensitivity． Moreover，the pathogenic characteristic of presumptive pathogens was identified by artificial infection．［Results］The 16S rDNA sequence of the pathogen was more than 99% homology with that of Plesiomonas shigelloides，suggesting that the pathogen was P．shigelloides，which was also demonstrated by the results of biochemical tests．The LD50 of the pathogen to sturgeon was 1.0×105.8 CFU/mL，and it also can cause liver，kidey and spleen to lesions. There were no activities of amylase，caseinase，lipase，gelatinase and haemolysis of extracellular products of P. shigelloides，and its toxicity might be from endotoxin．In addition，the bacterium was specific sensitive to enrofloxacin，doxycyline hyclate，florfenicol and thiamphenicol with MIC less than 2μg/mL．［Conclusion］P. shigelloides was the main pathogen to cultured sturgeons in Beijing area，and enrofloxacin，doxycyline hyclate and florfenicol can be used against the disease.