Antimicrobial susceptibility patterns of the A and T types of Pasteurella haemolytica

Differentiation of Pasteurella haemolytica biotypes A and T with growth inhibitors

“…The basis for this is found in Smith's first descriptions and A and T types, in which he showed that type T strains were more resistant to a number of antibiotics than type A cultures (17). These differences have recently been quantitated and shown to be of sufficient magnitude in the case of penicillin to suggest a basis for a differential test (5). In view of the emergence of antibiotic-resistant strains, which would limit the usefulness of such a test, the inclusion of inhibitory dyes, which have been useful in the characterization of other bacteria (11,12,14), appeared as a possible alternative.…”