禽分枝杆菌对豚鼠的致病性分析

Pathogenicity of Mycobacterium avium to guinea pigs

摘要:

【背景】我国禽型结核菌素(avian tuberculin)的制造用菌株为CVCC 68201、CVCC 68202和CVCC 68203株，但目前仍未明确这3株菌的生物学特性及对豚鼠致病性的情况。【目的】探究禽分枝杆菌(Mycobacterium avium)的生物学特性及对动物机体的致病性，为禽结核病和牛结核病的防控工作提供技术支撑。【方法】对3株禽分枝杆菌基因组进行鉴定分析及核酸相似度分析；用3株禽分枝杆菌分别感染豚鼠，观察感染后的临床症状、病理学变化、体重增重情况分析、皮内变态反应结果、脏器系数变化等，进而分析3株禽分枝杆菌对豚鼠的致病力。【结果】种型鉴定和进化分析结果表明，CVCC 68201、CVCC 68202和CVCC 68203均为禽分枝杆菌，基因组与Mycobacterium avium subsp. avium FDAARGOS_1608最为相近；在感染前期、中期、后期对3株禽分枝杆菌感染豚鼠的体重增重情况分析发现，感染禽分枝杆菌影响豚鼠增重，主要表现为生长迟缓，感染第5周时，CVCC 68201、CVCC 68202组豚鼠的平均体重明显轻于未感染组；皮内变态反应试验结果显示，感染CVCC 68201组豚鼠的皮肤红肿面积明显大于其他2个感染组，CVCC 68201可引起机体更为强烈的迟发型变态反应；3株禽分枝杆菌感染后，豚鼠脾脏和肺脏存在不同程度的肿大与出血，其中感染CVCC 68201豚鼠的肺脏系数与未感染组相比差异显著(P<0.01)；病理学观察结果显示，豚鼠肺脏可见不同程度病变，其中CVCC 68201组更为严重，表现为肿大和轻微出血。各感染组豚鼠肺脏和脾脏组织切片抗酸染色均可见红色的分枝杆菌散在浸润。【结论】3株禽分枝杆菌对豚鼠均有一定程度的致病性，可引发局部病变。本研究为禽分枝杆菌的制备和鉴定提供依据，也为牛结核病的鉴别诊断方法研究提供参考。

Abstract:

[Background] The three strains, CVCC 68201, CVCC 68202, and CVCC 68203, are usually used to produce purified avian tuberculin in China, while their biological characteristics and pathogenicity to guinea pigs remain unclear. [Objective] To explore the biological characteristics of Mycobacterium avium and its pathogenicity to animals, so as to provide technical support for the prevention and control of avian tuberculosis and bovine tuberculosis. [Methods] The genomes of the three strains of M.avium were sequenced and the nucleotide similarity was determined. Guinea pigs were respectively infected with the three strains of M.avium. After that, we observed the clinical symptoms, pathological changes, and intradermal allergy and measured the weight gain and organ indexes to evaluate the virulence of the three strains to guinea pigs. [Results] CVCC 68201, CVCC 68202, and CVCC 68203 were all identified as M.avium, and their genomes had the highest similarity to that of M.avium subsp. avium FDAARGOS_1608. The infection with M.avium affected the weight gain of guinea pigs, which was mainly manifested as growth retardation. The average weight of the guinea pigs five weeks post infection with CVCC 68201 or CVCC 68202 was significantly lower than that of the uninfected guinea pigs. The results of the intradermal allergy challenge showed that the area of skin redness and swelling of the guinea pigs infected with CVCC 68201 was significantly larger than that of the other two infection groups, which indicated that CVCC 68201 caused more intense delayed-type allergy. The spleen and lungs of the guinea pigs had different degrees of swelling and hemorrhage after the infection, and the lung index of the guinea pigs infected with CVCC 68201 was different from that of the uninfected group (P<0.01). Different degrees of alveolar changes were observed in the lungs of the infected guinea pigs, which was severer in the CVCC 68201 infection group, as demonstrated by enlargement and slight bleeding. The acid-fast staining of lung and spleen tissue sections of infected guinea pigs showed scattered infiltration of red mycobacteria. [Conclusion] All the three strains are pathogenic to guinea pigs and can cause local lesions. This study provides a basis for the preparation and identification of M.avium and lays a foundation for the research on the method for differential diagnosis of bovine tuberculosis.