Antimicrobial susceptibility of Enterobacteriaceae isolated from vegetables

There is potential for the normal faecal flora of humans to be augmented by resistant strains of bacteria, acquired from food. The frequency of resist ance in the aerobic Gram-negative faecal flora is often very high. The purp ose of this study was to find out whether food strains contribute to this r esistance. One hundred and thirty-seven vegetable samples were studied, 48 of Finnish origin, and 89 imported. From these samples, 535 different strai ns of bacteria belonging to the family Enterobacteriaceae were isolated. En terobacter spp. were most frequent, Escherichia coli was rare. Sensitivity testing was undertaken only for isolates with different biotypes and antibi ograms. No resistance was found to cefotaxime, aztreonam, imipenem, gentami cin, nalidixic acid or ciprofloxacin. The frequency of trimethoprim resista nce was 0.2%, sulphamethoxazole resistance 1.3%, and tetracycline resistanc e 5.5%. These frequencies were much lower than those found in faecal flora. Chloramphenicol and cefuroxime resistance was found in 12% and 14% of isol ates, respectively. The only statistically significant differences between the Finnish and imported strains were for these two; the Finnish isolates w ere more resistant to cefuroxime, whereas the imported ones were more resis tant to chloramphenicol. Consequently, bacteria from vegetables are not res ponsible for the high prevalence of resistant Enterobacteriaceae in faecal flora in Finland; they are in fact unusually susceptible to the antibiotics studied. Multiresistance profiles, typical of strains associated with huma n activities, were not identified in these isolates.