Abstract
Seventy-nine strains of enterotoxigenic Escherichia coli (ETEC) isolated from 35 diarrheic piglets (aged one to 43 days) reared on 22 farms in Okinawa Prefecture between 1989 and 1998 were submitted to PCR investigations for serotypes, biochemical characteristics, fimbrial adhesions, entrotoxin production, and the presence of virulence genes. The isolates belonged to 6 serogroups: 0149 (57), 0141 (8), 020 (7), 09 (3), 0141 (3), and 064 (1). All of the 0149 strains demonstrated β hemolytic activities, whereas the remaining 0 serogroups did not. On the basis of 20 biochemical features noted in all isolates, characteristic isolate patterns were divided into 10 distinct types: 40 isolates (50.6%) were classified as one type. The F4 (K88) ac fimbrial gene was detected in 64 strains (81.0%); the F5 (K99) gene in 3 strains (3.8%); and the F6 (987P) gene in 11 strains (13.9%). One strain (1.3%) was negative for all 4 of the adhesive genes. Thirty-six strains (45.6%) were shown to possess 4 enterotoxin genes (LT I, ST I, ST II, and EAST 1). LT I, ST II, and EAST 1 were present in 22 strains; ST I in 10 strains; ST I and ST II in 5 strains; ST I, ST II, and EAST 1 in 4 strains; and ST I and EAST 1 in 2 strains. These results indicate the dominance of the serogroup 0149 harboring 4 enterotoxin genes (LT I, ST 1, ST II, and EAST 1) and the F4ac fimbrial gene.
