Phenotypic and molecular characterization and antimicrobial susceptibility pattern of Pasteurella and Mannheimia species obtained from cattle and sheep with pneumonia

Among the heterogeneous Pasteurellaceae family, Pasteurella multocida and Mannheimia haemolytica are the pathogenic species that cause enzootic pneumonia in cattle and sheep. This study aimed to characterise Pasteurella and Mannheimia species obtained from pneumonia cases in cattle and sheep. 100 cattle and 100 sheep lungs diagnosed with infectious pneumonia as a result of histopathological examination were analyzed for Pasteurellaceae members by phenotypic methods, VITEK 2 Compact system and PCR. Antibiotic susceptibilities and phylogenetic analysis of the isolates were done by VITEK 2 Compact System and 16S rRNA-PCR, respectively. Seven Pasteurella multocida and 9 Mannheimia haemolytica were identified. All strains were resistant to ampicillin and trimethoprim/sulfamethoxazole. High susceptibility to ceftiofur (100%, 7/7 and 88.89%, 8/9) and doxycycline (85.71%, 6/7 and 100%, 9/9) was detected among the P. multocida and M. haemolytica isolates, respectively. MIC for gentamicin was in the epidemiologic cut-off limits (ECV) (https://mic.eucast.org/search/). The diversity of resistance genes (TEM, OXA-58, AadB, AadA25, Tet H and Sul 2) was high and their frequency ranged from 22.22% to 100% (16/16) among the strains. MDR was detected as 100% (7/7) for P. multocida and 33.33% (3/9) for M. haemolytica strains. Based on the MDR, six resistotypes (A to F) were determined, with more among the P. multocida strains. An approach called “antibiotic resistance marker-based genotyping” was introduced based on the presence of antibiotic resistance genes, and 8 genotypes (I to VIII) were determined, with more profiles (I to V) among the P. multocida strains. The strains positioned in two main phylogenetic clusters with the 16S rRNA gene sequencing, and P. multocida strains were found to be more genetically close. Bacterial behaviors related to antimicrobial susceptibility may help communicate with producers and veterinarians regarding appropriate antimicrobial stewardship. Phylogenetic clustering of strains can increase country-specific sequence data and create new taxa from a universal perspective.