Genotyping of Haemophilus parasuis Isolated from the Northwest of China Using PCR-RFLP Based on ompA Gene

抄録

Outer membrane proteins (OMPs) are the major virulent factors of Haemophilus parasuis. PCR-RFLP targeting the ompA gene was conducted to investigate the possibility of genotyping of H. parasuis in this study. Fifteen reference strains and 49 isolates from pig farms in the northwest of China were genotyped by the PCR-RFLP with a pair of specific primers. The results indicated that both the 15 reference strains and 49 isolates could be classified as 8 different genotypes by the PCR-RFLP, respectively. Seven genotypes including AA, BB, BA, CA, BC, BD and CD were existed simultaneously in the reference strains and the isolates, but genotype CB only existed in the isolated strains. Interestingly, genotype BA, CD and CA were only found in diseased pigs and accounted for 38.8, 22.4 and 18.4% in the isolates, respectively. While strains isolated from apparently healthy pigs were classified into the genotype AA, BB, BC and CB. However, the virulent reference serovar 1 strain has an AA genotype and the fact that nearly all strains from the healthy pigs belong to serovars classed as virulent suggests that these genotypes might also include virulent strains and further validation with more field strains is needed. The capability of the RFLP-PCR method based on ompA gene for genotyping of H. parasuis isolates indicates that this method may be a useful tool for epidemiogical study.