Transferable antibiotic resistance in Escherichia coli isolated from healthy Nigerian school children

Three hundred and ninety-six E. coli isolates obtained from apparently healthy school children in Ile-Ife, Nigeria, were tested for their susceptibility to 11 different antibiotics. Of these, only gentamicin, cefotaxime and nalidixic acid were found to have significant in vitro activity against most of the isolates. The incidence of antibiotic resistances encountered varied between 24% for trimethoprim and 55.5% for the sulphonamide. It was further observed that 47.5% of the isolates were identified as being multiply resistant, since they were simultaneously resistant to at least three different antibiotics. The 86 trimethoprim-resistant isolates tested were found to be able to transfer this resistance trait together with resistance genes of to other antibiotics, into a plamidless strain of E. coli by conjugation. Seventy-seven of the trimethoprim-resistant isolates were also found to be classifiable into the types of dihydrofolate reductases responsible for the observed resistance on the basis of hybridization experiments. The results of this study indicate that there is a large reservoir of antibiotic resistances within the community, and that the resistance genes were easily transferable to other strains even without direct exposure to antibiotics.