Pathology, virulence-associated gene profiling, antimicrobial susceptibility, and pathogenicity of untypeable capsular serotypes of Pasteurella multocida isolated from slaughtered pigs of India.

This article focuses on the molecular characterization, pathology, antimicrobial susceptibility, and pathogenicity of untypeable capsular serotypes of *Pasteurella multocida* isolated from slaughtered pigs in India. The study found a 27.17% prevalence of *P. multocida* by PCR, with untypeable capsular serotypes predominating over known serotypes A, D, B, E, and F. These untypeable isolates uniformly carried key virulence genes (exbB, nanB, sodC, plpB, oma87) and exhibited higher resistance to antibiotics such as ampicillin, amoxicillin, and penicillin. Mouse pathogenicity tests confirmed the virulence of untypeable isolates, and histopathological and immunohistochemical analyses linked these strains to bronchopneumonia and tonsillitis in pigs. The findings highlight the potential threat posed by these untypeable, antibiotic-resistant *P. multocida* strains to pig health and underscore the need for targeted preventive measures and vaccine development.