Antibiotic and heavy metal tolerance in bacteria isolated from drinking water sources in Nsukka metropolis, Enugu state, Nigeria

Résumé fourni par la source

Resistance to antimicrobial agents and heavy metals is inevitable as a result of natural consequence of bacterial cell adaptation to exposure to antimicrobials and heavy metals in the environment. Heavy use of bioactive substances in the medical and agricultural sectors has led to increasing resistance to those substances. This study was carried out to demonstrate antibiotic and heavy metal tolerance in bacteria isolated from drinking water supplies in Nsukka, Southeast, Nigeria. Fresh water samples were collected from different sources in different locations in Nsukka metropolis from where bacterial isolates were obtained. The isolates were assessed for their antibiotic and heavy metal tolerance by the agar disc diffusion assay. Determination of the maximum tolerable concentrations (MTC) of the metal salts was carried out by the broth dilution method. Six bacterial isolates obtained and identified tentatively based on their cultural, morphological and biochemical characteristics were Escherichia coli, Citrobacter spp., Bacillus cereus, Micrococcus varians, Proteus mirabilis and Salmonella spp. The antibiotic resistance assay revealed that Salmonella spp. and Proteus mirabilis were resistant to all antibiotics tested and fifty percent of all the isolates were sensitive to sulphafurazole and furazolidone. It was observed that Bacillus cereus had MTC values for Pb2+ (800 µg/mL), Cu2+ (700 µg/mL) and Cr6+ (200 µg/mL) while Citrobacter spp. had the least MTC value for Cr6+. There was a significant difference (p ≤ 0.05) in the effect of heavy metal concentration on the sensitive isolates. We, therefore, conclude that the water environment in Nsukka, Southeast Nigeria is a potential reservoir of antibiotic and heavy metal tolerance determinants.