RESUMO
<p><b>OBJECTIVE</b>To investigate the prevalence of kanamycin (kan) and ampicillin (amp) resistant bacteria in public drinking water.</p><p><b>METHODS</b>Bacteria containing kan and amp resistant genes were amplified by PCR and further characterized by colony hybridization and transformation studies. The genus of kan and amp resistant bacteria was determined with standard methods.</p><p><b>RESULTS</b>Among the 625 drinking water samples, 400 contained kan and amp resistant bacteria and the percentage was 42.5% and 57.5%, respectively, which was further confirmed by the amplification of a 810 bp kan resistant gene and a 850 bp amp resistant gene. Of the 170 kan resistant bacteria, 90 were Gram negative and 80 were Gram positive. Of the 230 amp resistant bacteria, 160 were Gram negative while 70 were Gram positive. Salmonella, Shigella, Staphylococcus, Streptococcus, and E.coli were detected as 13%, 11%, 17%, 30%, and 29%, respectively. Bacterial strain DH5alpha transformed with plasmids isolated from kan and amp resistant bacteria confirmed that the antibiotic resistant genes were mediated by plasmids.</p><p><b>CONCLUSION</b>Drinking water is contaminated with kan and amp resistant bacteria due to poor sanitary conditions.</p>