Antibiotic resistance patterns of coliform bacteria isolated from food

308 strains of coliform bacteria isolated from food of various origin were identified and their resistance patterns were studied. The strains belonged to 10 different species and Escherichia coli was the most common. Coliforms isolated from samples incubated at 44 degrees C were more often identified as E. coli than coliforms isolated from samples incubated at 37 degrees C. Klebsiella and Enterobacter spp. taken together were, on the contrary, mor often isolated at 37 degrees C than at 44 degrees C. E. coli was most frequently isolated from raw meat and egg products. Klebsiella dn Enterobacter spp. more often in other types of products. 54% of the strains were resistant to at least one of the 9 antibiotics tested. Resistance to nitrofurantoin and sulphaisodimidine was most frequent (30 and 25% respectively). No strain resistant to streptomycin, neomycin or trimethoprim/sulphamethoxazole was registered. 40% of the resistant strains were multiresistant. The lowest number of resistant strains was recorded from custards and desserts and from raw meat products (42 and 46% respectively) and the highest from ice-cream (89%). Multiresistant strains were recorded most frequently from pasteurized milk products, custards and desserts. None of the 66 multiresistant strains tested could transfer the resistance to E. coli in vitro. The results do not indicate that food of animal origin in Sweden represents a source for bacteria with transferable resistance determinants.