长春地区鸡源奇异变形杆菌的分离鉴定及毒力分析

【背景】奇异变形杆菌(Proteus mirabilis)是一种机会致病菌，广泛存在于周围环境中，常导致动物和人类感染。【目的】探究吉林省长春地区某养鸡场病鸡死亡原因，为疾病防控提供参考。【方法】从病死青年鸡脏器分离到病原菌TSA-1，通过革兰氏染色、生化试验和16S rRNA基因序列鉴定，并进行药敏试验、毒力基因检测、细胞毒性和黏附性试验、大蜡螟攻毒试验研究。【结果】分离株TSA-1在镜下呈短杆状、球状的革兰氏阴性菌，生化特性与奇异变形杆菌相一致，16S rRNA基因序列比对显示与奇异变形杆菌相似度为100%；药敏试验结果显示分离株TSA-1对氨苄西林、四环素、卡那霉素、头孢唑林等14种药物耐药，对环丙沙星、恩诺沙星等7种药物敏感；分离株还具有较强的生物被膜形成能力，携带ireA、ucaA、pmfA、atfA、ptA、zapA、hpmA和flhC这8种毒力基因，并对巨噬细胞RAW264.7表现出细胞毒性，而且对Caco-2细胞具有很强的黏附作用；同时对大蜡螟幼虫表现出比禽致病性大肠杆菌(avian pathogenic Escherichia coliO78，APEC-O78)更强的致死作用。【结论】从病死鸡脏器分离得到的奇异变形杆菌TSA-1具有多重耐药性，并携带多种毒力基因，对细胞和大蜡螟幼虫表现出强毒性作用，说明该菌是引起病鸡死亡的主要致病菌之一，应引起重视。

Isolation, identification, and virulence analysis of a Proteus mirabilis strain from chicken in Changchun

[Background] Proteus mirabilis is an opportunistic pathogen ubiquitous in the environment and often causes infections in animals and humans. [Objective] To explore the cause of death of sick chickens in a chicken farm in Changchun city, Jilin province, and provide reference for disease prevention and control. [Methods] The pathogenic bacterial strain TSA-1 was isolated from the organs of dead young chickens and identified by Gram staining, biochemical tests, and 16S rRNA gene sequencing. Furthermore, drug sensitivity test, virulence gene detection, cytotoxicity and adhesion tests, and challenge in larvae of Galleria mellonella were performed for this strain. [Results] TSA-1 was a short rod-shaped or spherical Gram-negative bacterium, with the biochemical properties consistent with those of P.mirabilis. The 16S rRNA sequence alignment showed that TSA-1 shared the similarity of 100% with P.mirabilis. The drug susceptibility test results showed that TSA-1 was resistant to 14 antibiotics including ampicillin, tetracycline, kanamycin, and cefazolin and sensitive to 7 antibiotics including ciprofloxacin and enrofloxacin. The strain had strong biofilm formation ability and carried 8 virulence genes: ireA, ucaA, pmfA, atfA, ptA, zapA, hpmA and flhC. It showed cytotoxicity to RAW 264.7 macrophages and had strong adhesion to Caco-2 cells. In addition, it had stronger lethal effect on larvae of G.mellonella than avian pathogenic Escherichia coli O78. [Conclusion] P.mirabilis TSA-1 isolated from the organs of dead chickens has multi-drug resistance and carries a variety of virulence genes. It is the one of the major pathogenic bacteria causing chicken death and deserves more attention.