大口黑鲈(Micropterus salmoides)致病性维氏气单胞菌的分离鉴定及其特性分析

ISOLATION AND IDENTIFICATION OF PATHOGENIC AEROMONAS VERONII IN MICROPTERUS SALMOIDES

大口黑鲈(Micropterus salmoides)是我国重要的淡水养殖经济鱼类品种,目前包括细菌性疾病在内的诸多因素影响了其养殖业的健康发展。维氏气单胞菌是引起淡水鱼败血症和溃疡综合征的重要病原菌。从患病大口黑鲈肝脏组织中分离到1株病原菌,通过形态学观察、生理生化特性分析、16S rRNA序列和特定毒力基因分析对其进行鉴定,并通过人工回归感染试验和药敏试验分析其致病性和耐药性。结果表明该菌为致病性维氏气单胞菌(Aeromonas veronii),含有aer、act、lip、fla、gcaT和OMPA I等毒力基因;药敏试验显示其对头孢曲松、氯霉素、氟苯尼考、强力霉素、四环素、多粘菌素、复方新诺明、左氟沙星等8种抗生素高度敏感,对新霉素、恩诺沙星、庆大霉素、链霉素、阿齐霉素、环丙沙星等6种抗生素中度敏感,对其他8种抗生素具有一定耐药性;人工回归感染实验表明该菌具有较高的致病性,对大口黑鲈的半致死浓度为1.4×10^(6) CFU/mL。维氏气单胞菌是水产养殖中的条件性致病菌,研究结果揭示了该菌株的部分生物学特性,有利于丰富维氏气单胞菌属的基础数据,同时也为鲈鱼养殖过程中的病害防控提供了一定的参考依据。

In China,Micropterus salmoides is an important economic freshwater farmed fish species.At present,the healthy development of M.salmoides aquaculture industry has been affected by many factors,including bacterial diseases.Aeromonas veronii is an important pathogen causing septicemia and ulcer syndrome in freshwater fish.A bacterial strain was isolated and identified from liver of diseased M.salmoides by morphological,physiological,and biochemical approaches,and 16S rRNA sequence and specific virulence gene analysis.The pathogenicity and drug resistance were analyzed by artificial regression infection test and drug sensitivity test.Results show that the strain was pathogenic A.veronii,and it contained virulence genes such as aer,act,lip,fla,gcaT,and OMPA I.The strain was highly sensitive to 8 antibiotics(ceftriaxone,chloramphenicol,florfenicol,doxycycline,tetracycline,polymyxin,cotrimoxazole,and levofloxacin),moderately sensitive to 6 antibiotics(neomycin,enoxacin,gentamicin,streptomycin,azithromycin,and ciprofloxacin),and was resistance to other 8 antibiotics,as revealed in our drug sensitivity test.The bacterium was pathogenic to M.salmoides,and the median lethal dose was 1.4×10^(6) CFU/mL as shown in our artificial regression infection experiment.A.westermani is a conditional pathogen in aquaculture,and some biological characteristics of this strain were documented,which is beneficial to enrich the basic data of A.westermani,and provides some scientific basis and reference for the prevention and control of diseases in M.salmoides culture.