Genotyping of Haemophilus parasuis isolated from northwest China using PCR-RFLP based on the ompA gene

Area of Science:

• Veterinary Microbiology
• Bacterial Genetics
• Molecular Epidemiology

Background:

• Outer membrane proteins (OMPs) are critical virulence factors in *Haemophilus parasuis*.
• Genotyping *H. parasuis* is essential for understanding its epidemiology and pathogenicity.
• The *ompA* gene is a potential target for differentiating *H. parasuis* strains.

Purpose of the Study:

• To evaluate the utility of PCR-restriction fragment length polymorphism (PCR-RFLP) targeting the *ompA* gene for genotyping *H. parasuis*.
• To characterize the genetic diversity of *H. parasuis* isolates from pig farms in northwest China.
• To explore the association between specific genotypes and clinical outcomes (diseased vs. healthy pigs).

Main Methods:

• DNA extraction from 15 reference strains and 49 field isolates of *H. parasuis*.
• PCR amplification of the *ompA* gene using specific primers.
• Digestion of PCR products with restriction enzymes and analysis by gel electrophoresis to determine genotypes via PCR-RFLP.

Main Results:

• PCR-RFLP successfully classified the *H. parasuis* strains into 8 distinct genotypes.
• Seven genotypes (AA, BB, BA, CA, BC, BD, CD) were common to both reference strains and isolates.
• Genotypes BA, CD, and CA were predominantly found in isolates from diseased pigs, while AA, BB, BC, and CB were found in isolates from healthy pigs.

Conclusions:

• PCR-RFLP targeting the *ompA* gene is a viable method for genotyping *H. parasuis* isolates.
• Specific *ompA* genotypes show potential correlation with disease status in pigs.
• Further studies with more field strains are warranted to confirm the virulence potential of identified genotypes and their epidemiological significance.