Does prolonged exposure to antibiotic-resistant bacteria increase the rate of antibiotic-resistant infection?

The magnitude of the risk of acquiring infections due to antibiotic-resistant bacteria, as a consequence of prolonged contact with such bacteria, is unclear. We compared antibiotic resistance patterns of Escherichia coli isolated from the urine of bacteriuric female abattoir workers with resistance patterns of E. coli cultured from 190 poultry taken from the processing line. We found E. coli in 181 (95%) of the poultry cultures; 96% of the isolates were resistant to one or more antibiotics, and 87% were multiply resistant. Of the 649 women whose urine was cultured and who had not recently received antibiotic therapy, 69 (10.6%) had positive urine cultures, with E. coli accounting for 67% of the isolates. Of the 46 E. coli isolates, 8 (17.4%) were resistant to one or more antibiotics. All of the antibiograms of the urinary isolates were unique, and only one, a strain with resistance only to streptomycin, matched those of any of the poultry isolates. Of the women tested for bacteriuria, 74 had taken antibiotics within 3 months of culture, and these women were analyzed separately. Among the recent antibiotic users, six (8.1%) had positive urine cultures, all with E. coli. Four of these isolates were resistant to at least one antibiotic; all had patterns that matched at least one of the poultry isolates. Therefore, in a population of female abattoir workers who were not receiving antibiotic therapy, despite a high exposure to resistant microorganisms of animal origin, infections were infrequently caused by organisms with resistance patterns characteristic of the livestock to which the women were heavily exposed.