Antimicrobial resistance in Escherichia coli strains isolated from pigs with diarrhea.

Antimicrobial sensitivities were determined for 1,037 Escherichia coli isolates cultured from the intestines of pigs with diarrhea. In vitro resistance by at least 1 isolate of E coli was demonstrated to each antimicrobial tested. Isolates from suckling pigs were more often resistant to chloramphenicol than were those from weaned pigs. Significantly more E coli from weaned pigs were resistant to kanamycin and neomycin than were those from suckling pigs. Escherichia coli that were the primary cause of diarrhea (colibacillosis isolates) were significantly more resistant to kanamycin, neomycin, and spectinomycin than were noncolibacillosis isolates. The opposite was true for ampicillin.