Comparative molecular characterization of Corynebacterium pseudotuberculosis of different origin

Ribotyping and susceptibility to 17 antimicrobial agents were used to compare 37 isolates of Corynebacterium pseudotuberculosis (28 from horses, 1 from cattle, 3 from sheep and 5 from goats) derived from various types of lesions, and different geographic locations. According to the presence of nitrate reductase, all but one isolate from horses reduced nitrate (nitrate-positive), whereas all isolates from sheep and goats were unable to reduce nitrate (nitrate-negative). The ribotype of the nitrate-negative isolate from a horse with ulcerative lymphangitis was identical to all the other isolates from horses, and different than the ribotype of nitrate-negative isolates from sheep and goats. Ribotyping with one of the restriction endonucleases, Apa 1, revealed differences between, but not within, the two biotypes. However, ribotyping with Pst 1 endonuclease revealed one variant within the equine biotype and one variant within the ovine biotype. The minimum inhibitory concentration (MIC; microgram/ml) of antimicrobial agents against isolates from nitrate-negative and nitrate-positive groups was very similar, with the exception of isolates from sheep and goats which had a higher MIC for amikacin than isolates from horses and cattle.