Twelve weaned piglets (3-week-old) were divided into three groups according to the time of feed change and observed for diarrhea during the time they were 3 to 8 weeks of age. A total of 553 strains of Escherichia coli were isolated from rectal fecal samples and examined for heat-labile (LT) and heat-stable (ST) enterotoxins, pilus antigens (K88, K99, and 987P), hemolysin (Hly), raffinose utilization (Raf) and drug resistance. Enterotoxigenic and/or hemolytic E. coli strains appeared in the rectal feces of 5-to 6-week-old piglets with diarrhea in connection with feed change and changing temperatures. Most of the isolates showed multiple drug resistance to sulfonamides (Sa), streptomycin (Sm), chloramphenicol (Cp), tetracycline (Tc), kanamycin (Km), spectinomycin (Sp), ampicillin, and/or mercury. Enterotoxigenic E. coli isolates represented four phenotypes: K88+.LT+.Hly+.Raf+.(SaSmCpTcKmSp) (12 strains), K99+.ST+.Raf+. (TcKm) (7 strains), ST+.Raf+.(TcKm) (7 strains), and ST.+(SaSmKm) (25 strains). The drug resistance determinants were transferable concurrently and some of them mobilized the determinants for K88, LT, Hly, and Raf to an E. coli C strain.Enterotoxigenic Escherichia coli (ETEC) is now recognized as a cause of diarrheal disease in animals and man. Since early reports by Smith and Halls (27, 28), many reports have been published on ETEC (14,19,21,22,26,32), enterotoxins (2, 12), pilus antigens (15, 17), and their plasmids (4,13,24,31,34). The recent knowledge of E. coli diarrhea was adequately reviewed by the World Health Organization (36). However, the epidemiology of ETEC disease needs to be investigated in different geographical areas. Not many investigations on ETEC disease in animals have been published in Japan. The present study reports the appearance of ETEC in feces of piglets with diarrhea in connection with adverse factors of feed changes and temperature changes during the winter.IPresent address:
