Abstract
A total of 39 Mannheimia haemolytica from cattle in the Tokachi area from 1994 to 2006 were examined for serotyping, with an antibiotics sensitivity test and pulse field gel electrophoresis (PFGE). Twenty-one isolates (53.8%) were serotype 1, sixteen isolates (41%) were serotype 6 and two isolates were serotype 2 and untypable. Serotype 1 strains had been isolated continually, but had serotype 6 strains for the first time in 1999. Serotype 6 strains were isolated in greater number than serotype 1 strains starting 2004. Eighteen isolates of serotype 1 and 15 isolates of serotype 6 showed the same PFGE pattern. It was suggested that closely related isolates of serotype 1 and 6 were prevalent in the Tokachi area. Fifteen isolates of serotype 6 were multidrug resistant to antibiotics including SM, KM, CP, NA, ERFX. MIC90s of NA, ERFX and CP were also high in serotype 6 strains. Most of these multidrughresistance serotype 6 strains were isolated from Holstein or F1 (Holstein × Japanese Black Beef) calves for meat.
