Phenotypic and Molecular Characterization of the Capsular Serotypes of Pasteurella Multocida Isolates From Bovine Respiratory Disease Cases in Ethiopia

Abstract

Background: Pasteurella multocida is a heterogeneous species and opportunistic pathogen that causes bovine respiratory disease. This disease is one of an economically important disease in Ethiopia. Losses due to mortality and associated expenses are estimated to be higher in the country. Studies revealed that limited information is available regarding the capsular types, genotypes, and antimicrobial sensitivity of P. multocida isolates circulating in the country. This suggests, further molecular advances to understand the etiological diversity of the pathogens representing severe threats to the cattle population. Results: Bacteriological analysis of nasopharyngeal swab and pneumonic lung tissue samples collected from a total of 400 samples revealed isolation of 61 (15.25%) P. multocida subspecies multocida. 35 (20.59%) were isolated from calves and 26 (11.30%) from adult cattle. Molecular analysis using PCR assay targeting KMT1 gene (~460 bp) amplification was shown in all presumptive isolates. Capsular typing also confirmed the presence of serogroup A (hyaD-hyaC) gene (~1044 bp) and serogroup D (dcbF) gene (~657 bp) from 56 (91.80%) and 5 (8.20%) isolates, respectively. The biovar typing identified 48 (78.69%) isolates of biovar 3. Phylogenetic analysis based on the hyaD-hyaC gene nucleotide sequences showed that P. multocida serogroup A are genetically closely related to the different P. multocida isolates retrieved from the GenBank. Antibiogram of isolates revealed high sensitivity towards chloramphenicol (100%), amoxicillin (95.08%), and amikacin (90.16%). Resistance was observed in cloxacillin (88.52%) and Penicillin-G (77.05%). Conclusions: In the present study, P. multocida capsular type A biovar 3 was predominantly isolated from pneumonic cases in cattle in the study areas. The finding provides useful information for further research and choice of antimicrobials for treatment. Hence, further comprehensive molecular epidemiological investigation is proposed covering wider areas of the country to identify pathogens associated with BRD for an effective control strategy.