| The pulsed field gel electrophoresis (PFGE) method was applied for molecular
typing of 130 Mannheimia haemolytica serotype A1 isolates obtained from 13 prefectures in Japan. These isolates
were divided into 15 ApaI PFGE profiles that formed 6 distinct clusters (cluster A to F). Fifty-three
(40.7%) isolates were classified in cluster B, and 20.0%, 13.8%, 12.3%,
6.9% and 6.1% of isolates were in cluster E, A, F, D, and C, respectively.
The isolates of cluster B were differentiated into 7 subtypes (B1 to B7)
and subtype B5 contained 34 isolates. We associated the PFGE clusters with
the year of isolation and the geographical origin. Before 1994 all isolates
were grouped into clusters A, B or C. The numbers of isolates belonging
to clusters D to F have increased since 1994, and since 1997 half of the
isolates belong to these groups. There was no relationship between molecular
typing and geographic origin of these isolates. These results indicate
that isolates of M. haemolytica A1 strain with various molecular profiles have already spread in Japan
and may have caused sporadic infections. (Environmental Hygiene Section,
Shichinohe Research Unit TEL +81-176-62-5115) |