Antibiotic sensitivity patterns and molecular characterization of P. multocida vaccine strain and field isolates

A study was conducted to compare in-vitro antimicrobial sensitivity patterns of the vaccine strain and field isolates of Pasteurella multocida. Three strains of P. multocida isolated from cattle and buffalo, were confirmed by biochemical tests and P. multocida specific Multiplex HSB-PCR. All the three field isolates belonged to P. multocida type B: 2 with amplified products of 460bp and 590 bp. The vaccine strain and isolates were tested against 17 different antibiotics by disc diffusion. Absolute resistance was observed among the field isolates to several antibiotics. The vaccine strain was resistant to amoxicillin, ofloxacin, sulfadiazine, streptomycin and cefuroxime. Isolate PB1 was resistant to sulfadiazine, streptomycin, cefoperazone, cephotaxime and oxytetracycline; PB2 was resistant to amoxicillin, ampicillin, sparfloxacin, ofloxacin, sulfadiazine, cefuroxime, cephotaxime, oxytetracycline and ciprofloxacin; PC1 was resistant to enrofloxacin, cefuroxime, cefperazone and cephotaxime. The most effective antibiotics against the vaccine and field strains were pefloxacin, ofloaxcin, trimethoprim and sparfloxacin. The study has revealed the emergence of multidrug resistant field strains of P. multocida.