Isolation and Molecular Detection of Mannheimia haemolytica and Pasteurella multocida from Clinically Pneumonic Pasteurellosis Cases of Bonga Sheep Breed and Their Antibiotic Susceptibility Tests in Selected Areas of Southwest Ethiopian Peoples Regional State, Ethiopia.

Background: Pneumonic pasteurellosis is a respiratory system disease of sheep caused by Mannheimia haemolytica, Pasteurella multocida, and Bibersteinia trehalosi responsible for the low productivity and economic loss resulting from death and treatment costs. This study was conducted to isolate and molecularly detect causative agents and antibiotic susceptibility tests from a nasal swab sample of the Bonga sheep breed that was suspected to have pneumonic pasteurellosis in selected areas of Southwest Ethiopian Peoples Regional State.

Methods: A cross-sectional study design was used along with purposive sampling of nasal swab samples from sheep that were brought to veterinary clinics during the study period. Bacterial isolation and phenotypic characterization were carried out using microbiological and biochemical tests that followed standard microbiological techniques. To molecularly confirm the isolates, PHSSA and KMT1, species-specific PCR primer genes were used. Using the disc diffusion method, molecularly confirmed isolates were subjected to an in vitro antibiotic susceptibility test.

Results: The 85 samples that were scrutinized had an overall isolation rate of 31.76%, whereas the isolates of Pasteurella multocida and Mannheimia haemolytica had species compositions of 40.7% and 59.25%, respectively. Overall, 12.5% of the Mannheimia haemolytica and 18.18% of the Pasteurella multocida species were verified from phenotypical isolates using the species-specific PCR primer genes PHSSA and KMT1, respectively. An in vitro antibiotic susceptibility test was carried out on all four PCR-confirmed isolates for seven commonly used antibiotics used to treat ovine pasteurellosis in the study area. It was found that both bacterial species were resistant to chloramphenicol and penicillin G.

Conclusion: Using phenotypic and molecular diagnostic techniques, the results of our current inquiry revealed that Pasteurella multocida and Mannheimia haemolytica are the causative agents of ovine pneumonic pasteurellosis in the study area.