Dwars R Marius, Matthijs Mieke G R, Daemen Angeline J J M, van Eck Jo H H, Vervelde Lonneke, Landman Wil J M
Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
Vet Immunol Immunopathol. 2009 Jan 15;127(1-2):65-76. doi: 10.1016/j.vetimm.2008.09.019. Epub 2008 Oct 2.
The progression of Escherichia coli lesions was studied in the respiratory tract of 4-week-old commercial broilers. Lesions were induced after a single intratracheal E. coli infection, and after an infection with E. coli preceded 5 days earlier by an oculo-nasal and intratracheal infectious bronchitis virus (IBV) infection of either the virulent M41 strain or the H120 vaccine strain. Trachea, lung and thoracic airsac lesions were examined macroscopically and microscopically. Tissue samples were taken at 3h post-inoculation (hpi), and 1, 2, 4 and 7 days post-inoculation (dpi) with E. coli. The location of both pathogens was assessed by immunohistochemistry. Single E. coli inoculation induced pneumonia and airsacculitis; in case it was preceded by IBV infection, the same macroscopical lesions and also viral tracheitis were found. No clear difference existed between the single and dual infected birds with respect to inflammatory reactions in the lung, which had disappeared within 7 days, except for the presence of more follicles in dual infected birds. IBV antigen was detected in secondary bronchi and airsacs up to 2 dpi and in the trachea up to 4 dpi. E. coli bacteria were found in the tracheal lumen included in purulent material, the parabronchi and airsacs. In lung tissue E. coli antigen was found up to 4 dpi. No clear difference existed between single and dual inoculated birds regarding the presence of E. coli in the lung. In the airsacs, a few bacteria were found from 0.5 hpi up to 4 dpi in E. coli and IBV-E. coli inoculated birds. Although both pathogens were cleared beyond detection at 7 dpi, in IBV-E. coli inoculated birds lesions in the airsac persisted, in contrast to broilers inoculated with E. coli only. In the present study it is shown that 4-week-old broilers are not resistant to intratracheal E. coli inoculation, however, these birds can overcome the induced E. coli infection within a short time span. Moreover, a preceding infection with vaccine or virulent IBV does not seem to impair the clearance of E. coli in the respiratory tract of broilers, but rather induces an exaggerated inflammatory response in the airsacs only, which seems to be the mechanism behind the pattern of airsacculitis in commercial poultry in the field.
在4周龄的商品肉鸡呼吸道中研究了大肠杆菌病变的进展情况。在单次气管内接种大肠杆菌后，以及在眼鼻和气管内接种强毒M41株或H120疫苗株传染性支气管炎病毒（IBV）5天前接种大肠杆菌后诱导病变。对气管、肺和胸气囊病变进行了宏观和微观检查。在接种大肠杆菌后3小时（hpi）、1、2、4和7天（dpi）采集组织样本。通过免疫组织化学评估两种病原体的定位。单次接种大肠杆菌可诱发肺炎和气囊肿炎；如果在此之前有IBV感染，则会出现相同的宏观病变以及病毒性气管炎。在肺内的炎症反应方面，单次感染和双重感染的鸡之间没有明显差异，炎症反应在7天内消失，只是双重感染的鸡中有更多的滤泡。在接种后2 dpi内可在次级支气管和气囊中检测到IBV抗原，在接种后4 dpi内可在气管中检测到。在脓性物质、副支气管和气囊中的气管腔内发现了大肠杆菌。在肺组织中，直到4 dpi都能发现大肠杆菌抗原。在肺内大肠杆菌的存在方面，单次接种和双重接种的鸡之间没有明显差异。在气囊中，在接种大肠杆菌和IBV-大肠杆菌的鸡中，从0.5 hpi到4 dpi都发现了少量细菌。尽管在7 dpi时两种病原体均被清除至检测不到，但与仅接种大肠杆菌的肉鸡相比，接种IBV-大肠杆菌的鸡气囊中的病变仍然存在。在本研究中表明，4周龄的肉鸡对气管内接种大肠杆菌没有抵抗力，然而，这些鸡可以在短时间内克服诱发的大肠杆菌感染。此外，先前感染疫苗或强毒IBV似乎不会损害肉鸡呼吸道中大肠杆菌的清除，而是仅在气囊中诱导过度的炎症反应，这似乎是田间商品家禽气囊肿炎模式背后的机制。
