A retrospective study of the prevalence of OmpA-RFLP patterns among US field strains of Haemophilus parasuis as correlated to clinical signs and serotype

摘要

To date, no specific virulence factors of Haemophilus parasuis have been clearly identified. Solid homologous protection against some strains using autogenous bacterins has been demonstrated. However, cross protection against heterogenous serovars ismuch less frequently observed. Therefore, the use of serotyping alone may not be the most appropriate method when selecting isolates for vaccine production. Recent studies have shown that the virulence of H. parasuis may be best relate to the presence ofcertain proteins, such as outer membrane protein A (OmpA), which demonstrate a tropism for certain cell types. Within the realm of H parasuis, OmpA is a highly conserved domain and studies have demonstrated that the presence of anti-OmpA antibodies correlate with protection against H. parasuis following challenge1. The aim of the present study was to investigate the prevalence of the OmpA gene by its PCR-RFLP pattern among clinical strains. The correlation of OmpA-RFLP pattern to clinical signs, and the correlation of serotype to clinical signs were also investigated.