Comparing different isolates of Pasteurella haemolytica from beef calves using their in vitro antimicrobial sensitivity patterns

In vitro studies, using disc diffusion and agar dilution techniques, were carried out to compare susceptibilities to selected antimicrobial agents of 30 isolates of Pasteurella haemolytica from healthy calves and 30 isolates from calves with transit fever. There was no difference in susceptibility patterns between isolates from healthy calves and isolates from diseased calves or between isolates of serotype A1 and isolates of serotype A2. Penicillin resistance was associated with production of beta-lactamase.