中华鳖3种细菌的鉴定及致病性研究

针对一例中华鳖(Trionyx sinensis)爆发性死亡疾病，本研究旨在寻找其致病因子，明确分离菌的生物学地位、致病性和耐药特征。从患病中华鳖体内获得菌株C1、C2 和C3，经人工回归感染健康鳖，测定分离菌的致病作用；经形态学观察、生理生化鉴定及16S rRNA测序，结合系统发育学分析，做菌种的归类判定；用琼脂扩散(K-B)法测定菌株对抗生素药物的敏感性。分离纯培养的3 株菌分别为弗氏柠檬酸杆菌(Citrobacter freundii)、摩氏摩根氏菌(Morganella morganii)、肺炎克雷伯氏菌(Klebsiella pneumoniae)；能引起中华鳖急性感染性疾病，3 种菌共同致病死亡率最高，可达100%。药敏试验结果显示：弗氏柠檬酸杆菌对头孢他啶、头孢曲松、左氧氟沙星高度敏感，对万古霉素等17 种药物耐药；摩氏摩根氏菌对头孢他啶和头孢曲松高度敏感，对克林霉素等17 种药物耐药；肺炎克雷伯氏菌对恩诺沙星等13 种药物敏感，对青霉素等6 种药物耐药。本研究所检出的弗氏柠檬酸杆菌、摩氏摩根氏菌和肺炎克雷伯氏菌为该例中华鳖爆发性死亡疾病的病原菌，3 菌混合致病力强于单一菌液。弗氏柠檬酸杆菌和摩氏摩根氏菌呈现高度多重耐药，肺炎克雷伯氏菌耐药趋势异于前两者，表现为弱耐药株。

Three Bacteria Isolated from Trionyx sinensis: Identification and Pathogenicity

Due to the outbreak of a deadly disease on Chinese turtle (Trionyx sinensis), this study aims to find out the pathogenic factor, and identify the biological status, the etiology and drug resistance characteristics of isolated bacteria. Three pathogenic bacteria assigned as C1, C2, C3 were isolated from the diseased Chinese turtle (Trionyx sinensis). The pathogenic effect of the isolated bacteria was determined through artificial regression on healthy Chinese turtle. Species of bacteria were classified through morphological observation, physiological and biochemical identification, 16S rRNA sequencing and phylogenetic analysis. Kirby-Bauer agar diffusion method was used for the drug sensitivity test. The three isolated bacteria strains were classified as Citrobacter freundii, Morganella morganii, and Klebsiella pneumoniae. Isolated bacteria could cause acute infectious disease on healthy Chinese turtle, and the mix of 3 species of bacteria could lead to almost 100% mortality. Drug- sensitivity tests showed that Citrobacter freundii were highly sensitive to Ceftazidime, Ceftriaxone and Levofloxacin, while extremely resistant to 17 kinds of drugs such as Vancomycin; Morganella morganii were very sensitive to Ceftriaxone, Ceftriaxone and highly resistant to 17 kinds of drugs such as Clindamycin; Klebsiella pneumoniae were hypersensitive to 13 kinds of drugs such as Enrofloxacin and extremely resistant to 6 kinds of drugs such as Penicillin. This study showed that Citrobacter freundii, Morganella morganii and Klebsiella pneumoniae were the pathogenic bacteria which caused the deadly disease outbreak on the Chinese turtle. The pathogenicity of the 3 mixed isolate bacteria was stronger than any single bacteria strain. Citrobacter freundii and Morganella morganii showed a high degree of multi-drug resistance, while resistant tendency of Klebsiella pneumoniae is different from the others, which was a weak resistant strain.