ANTIBIOTIC-RESISTANCE OF ESCHERICHIA-COLI O157-H7 AND O157-NM ISOLATED FROM ANIMALS, FOOD, AND HUMANS

Antibiotic resistance was determined for 118 E. coli O157:H7 and 7 O15 7:NM isolates from animals, foods, and humans. Among the 125 isolates, 30 (24%) were resistant to at least one antibiotic and 24 (19%) were resistant to three or more antibiotics. Cattle isolates had the highes t rate (34%) of antibiotic resistance. The seven resistant food isolat es were all from ground beef. The most frequent resistance type overal l was streptomycin-sulfisoxazole-tetracycline, which accounted for ove r 70% of the resistant strains. Two E. coli O157:NM isolates from catt le were resistant to six antibiotics: ampicillin, kanamycin, sulfisoxa zole, streptomycin, tetracycline, and ticarcillin. Streptomycin was th e most common antibiotic to which E. coli O157:H7 and O157:NM were res istant (29 out of 30 isolates), followed by tetracycline (26 isolates) . This study suggests that E. coli O157:H7 and O157:NM have developed resistance to antibiotics. Research is needed to define mechanisms of antibiotic resistance in E. coli O157:H7 and to minimize the developme nt of resistance.