Antimicrobial susceptibility screening test of Mannheimia haemolytica and Pasteurella multocida (serogroup A) Moroccan strains isolated from ruminants

The present study is the first report aimed to determine the antibiotic susceptibility profiles of Mannheimia haemolytica and Pasteurella multocida serogroup A Moroccan isolates. Each isolate was tested for sensitivity to amoxicillin (A), amoxicillin/clavulanic acid (AMC), gentamicin (CN), streptomycin (STR), florfenicol (FFC), doxycycline (DO), erythromycin (E), spiramycin (SP), nalidixic acid (NA), flumequine (UB), enrofloxacin (ENF) and sulfamethoxazole (SXT). All isolates showed resistance to the antibiotics tested at a rate greater than 14%, except for one P. multocida isolate which had no resistance profile against AMC. The highest level of resistance was found against NA for P. multocida (100%) and against UB (82.4%) for M. haemolytica. The sensitivity rates for P. multocida were between 0 (against NA) and 85.7% (against STR, AMC, FFC), whereas sensitivity of M. haemolytica isolates ranged from 17.6% against UB and 79.4% against AMC. For both Pasteurellaceae species, the AMC was the most effective antimicrobial agent, however multi-drug resistance was observed in all isolates raising the interest to monitor the antimicrobial susceptibility of Pasteurellaceae species to determine appropriate antibiotic for treatment of pasteurellosis.