First report from Bangladesh on genetic diversity of multidrug-resistant Pasteurella multocida type B:2 in fowl cholera

Background and Aim: Fowl cholera (FC) caused by Pasteurella multocida is a highly contagious bacterial disease of global importance for poultry production. The severity and incidence of FC caused by P. multocida may vary considerably depending on several factors associated with the host (including species and age of infected birds), the environment, and the bacterial strain. This study aimed to investigate the genetic diversity of multidrug-resistant P. multocida strains isolated from FC outbreaks in laying hens from commercial farms of Bangladesh. Materials and Methods: We collected 57 samples of suspected FC, including 36 live and 21 dead laying hens. P. multocida isolates were characterized by biochemical and molecular-biological methods. Results: Twenty-two strains of P. multocida were isolated from these samples through phenotypic and genotypic characterization. The strains were grouped into two distinct random amplification of polymorphic DNA (RAPD) biotypes harboring a range of pathogenic genes; exbB, ompH, ptfA, nanB, sodC, and hgbA. In this study, 90.90% and 81.82% P. multocida strains were multidrug-resistant and biofilm formers, respectively. Whole-genome sequencing of the two representative RAPD phylotypes confirmed as P. multocida type B: L2:ST122, harboring a number of virulence factors-associated genes (VFGs), and antimicrobial resistance (AMR) genes (ARGs). In addition, pan-genome analysis revealed 90 unique genes in the genomes of P. multocida predicted to be associated with versatile metabolic functions, pathogenicity, virulence, and AMR. Conclusion: This is first-ever report on the association of P. multocida genotype B: L2:ST122 and related VFGs and ARGs in the pathogenesis of FC in laying hens. This study also provides a genetic context for future researches on the evolutionary diversity of P. multocida strains and their host adaptation