Capsular types, LPS genotypes, and virulence-associated genes of Pasteurella multocida strains isolated from pigs

Pasteurella multocida (P. multocida), an opportunistic zoonotic pathogen associated with high morbidity and mortality in livestock, shows significant temporal and geographical variation in its serotype distributions and phenotypic characteristics. The aim of this study was To investigate capsular types, lipopolysaccharide (LPS) genotypes, and virulence-associated genes of P. multocida strains isolated from pigs. A total of 801 samples (lungs, tonsils, nasal swabs) were collected from slaughterhouses and various regions of the Hunan province. P. multocida strains were isolated from various samples, classified, and virulence-associated genes were detected by polymerase chain reaction (PCR). 124 P. multocida strains were assigned to six groups based on both capsular type and LPS genotype, namely A: L3 (capsular type A and LPS genotype 3, 64/124); A: L6 (16/124); D: L6 (38/124); F: L3 (4/124); L3 (1/124) and 1 untypable strain. Of the 23 virulence-associated genes investigated in this study, 14 were highly expressed in 98% to 100% of the 124 strains. While tbpA was undetectable in any of the isolated strains, hsf-1, pfhA, tadD, toxA, pmHAS, hgbA, hgbB, and nanB showed differential distribution among the strain groups. Interestingly, pfhA (Mutation or inactivation of pfhA was reported to decrease the virulence of P. multocida) was found in 46% of group A: L3 strains and in 100% of group F: L3 strains, but not found in other groups. Further investigation is needed to determine whether strains in group A: L3show greater virulence than the A: L6 P. multocida strains.