广西鸡大肠杆菌的分离与鉴定

THE ISOLATION AND IDENTIFICATION OF AVIAN ESCHERICHIA COLI IN GUANGXI

从广西6个代表性鸡场分离出132株大肠杆菌,分离率平均为37.82％,其中81.82％的菌株分离自2～8周龄的鸡;经血清学鉴定,流行的血清型主要有11种,其中O_(50)、O_(133)、O_(15)、O_(90)、O_(146)、O_(92)及O_(84)等7种属首次报道;分离物经10项生化指标试验,有99.24％的菌株在醋酸铅琼脂上有轻度的H _2S产生,其余9项反应均符合典型大肠杆菌的特征;经电镜观察,发现O_1、O_(50)、O_(78)、O_(84)、O_(88)、O_(90)和O_(92)等7种血清型有菌毛,在培养72小时后,菌毛的数量及长度均比培养24小时者有所增加;主要血清型分别对鸡进行皮下和气管内两种途径的致病性试验,结果有10种是致病性的,而且还证实菌毛与呼吸道感染的致病性有直接的关系。

132 isolates of Eseheriehia coli were isolated from six broiler farms in Guangxi. The mean isolation percentage was 37.82％. 81.82％ of the isolates were obtained from the broiler chickens between 2～8 weeks of age. Serotyping efforts demonstrated that O_(50), O_(88), O_(133), O_8, O_(78), O_(15), O_(90), O_(148), O_(84), O_(92), and O_1 serogroaps were predominant. Among the eleven serogroups, O_(50), O_(133), O_(15), O_(90), O_(146), O_(92), and O_(84), were firstly reported. 99.24％ of the isolates produced H_2S on lead acetate agar slant. Results of 9 out of 10 biochemical reactions tested were typical for E. coll. Transmision electron microscopy was performed to identify the presence of somatic pili on the main 11 serogoups of E.coli. They were cultured in veal infusion and incubated at 37℃. The cultures were examined for the expression of pili at 24 and 72 hours of incubation. Pili were on the strains of O_1, O_(50), O_(78), O_(84), O_(88), O_(90) and O_(92) serogroups. The number and length of pili per cell were found to be increased while the incubation time prolonged to 72 hours. The pathogenicity of the isolates belonging to the eleven serogrups were evaluated in day-old susceptive chickens through inoculated subcutaneously or intratracheally. The results demonstrated that O_1, O_(15), O_(50), O_(78), O_(84), O_(88), O_(90), O_(92),O_(133) and O_(146) serogroups were pathogenic. It was confirmed that pili have a direct relationship with the pathogenicity of E.coIi when inoculated through intratracheal.