Effects of modified Cary and Blair medium on recovery of nonhemolytic Pasteurella haemolytica from Rocky Mountain bighorn sheep (Ovis canadensis canadensis) pharyngeal swabs.

Modified Cary and Blair transport medium (MCB) was evaluated for recovery of Pasteurella spp. from pharyngeal swabs of healthy Rocky Mountain bighorn sheep (Ovis canadensis canadensis). In experiment one, three pharyngeal swabs were collected from each of 25 bighorns. Pasteurella haemolytica was recovered from 21 of 25 swabs tested almost immediately and from 16 of 25 swabs held in MCB medium at about 22 C for 24 hr before testing (P > 0.10). Recovery of P. haemolytica decreased (P < 0.005) to 1 of 25 when swabs were held in MCB medium at about 22 C for 48 hr before testing. In experiment two, four pharyngeal swabs were collected from each of ten bighorns and held in MCB medium at about 5 C for < or = 5, 24, 48, or 72 hr prior to testing. Recovery was unaffected by storage at 5 C; P. haemolytica was isolated from all 40 of these samples. All Pasteurella spp. isolates were nonhemolytic P. haemolytica. In experiment one, most isolates were serotype 4; in experiment two, serotype 3 was most common. We propose that MCB medium is effective for transporting bighorn sheep pharyngeal swabs for P. haemolytica screening because it imposes minimal or no effect on recovery when held < or = 24 hr at 22 C or < or = 72 hr at 5 C.