副猪嗜血杆菌国内流行血清型菌株的致病性比较研究

Comparative study on pathogenicity of the most prevalent serovars of Haemophilus parasuis isolates in China

对我国最为流行的血清4、5、12、13和14型副猪嗜血杆菌进行了豚鼠和仔猪毒力试验的比较研究。豚鼠毒力试验结果表明,对豚鼠毒力最强的是12和14型菌株,其LD50均低于3.5×10^8 CFU;其次是5型,其LD50介于1.0×10^9-1.9×10^9 CFU之间;毒力最弱的是13型,其LD50介于4.0×10^9-4.1×10^9 CFU之间。4型的毒力差异较大,强毒菌株与5型接近,弱毒菌株与13型接近。与我们前期报道的小鼠毒力试验结果相比,豚鼠接种副猪嗜血杆菌后具有更长的发病死亡周期,且具有纤维素性渗出和败血症等副猪嗜血杆菌病的病变特征,表明豚鼠较小鼠更适合作为该病的替代实验动物。进一步的仔猪毒力试验结果与豚鼠毒力试验结果相一致。剖检发现,所有5、12和14型菌株以及4型强毒菌株均能导致严重的败血症性病理变化,表明副猪嗜血杆菌强毒菌株能导致猪的系统感染和全身性疾病;而所有13型菌株和4型弱毒株则不能。这表明国内流行的5、12和14型副猪嗜血杆菌的毒力与国外已有报道一致,均为强毒菌株;而4和13型则不同,具有明显的地域特征。

In this study,we compared the pathogenicity of the most prevalent Haemophilus parasuis serovars 4,5,12,13 and 14 in China in guinea pig and pig models. Serovars 12 and 14 were the most highly virulent in guinea pigs,LD50s of no more than 3.5 ×10^8 CFU,followed by serovar 5 with LD50s of 1.0× 10^9-1.9× 10^9 CFU. Serovar 13 was the lowest virulent, LD50s 4.0 × 10^9-4.1 ×10^9 CFU. Furthermore,2 of 4 serovar 4 strains were highly virulent,but the remaining 2 strains were low virulent. Compared to mouse model in our previous report, septicemia, pericarditis, pleu- ritis and death were apparent in Haemophilus parasuis-infected guinea pigs, suggesting that these animals may be useful as a laboratory model. Furthermore, these serovars produced similar results in the piglet models to that in the guinea pig models following intraperitoneal inoculation. Out of serovar 13 strains all serovars 12,14,5 and part of serovar 4 strains, were highly virulent in piglets, causing moribidity or death,indicating that under appropriate conditions Haemophilus parasuis can invade and cause severe systemic disease, characterized by fibrinous polyserositis, arthritis and meningitis.