ANTIBIOTIC RESISTANCE PATTERNS OF HEAVY METAL TOLERANT BACTERIA ISOLATED FROM A WETLAND INUNDATED BY URBAN RUNOFF

In this study, the heavy metal tolerance and antibiotic resistance patterns of bacteria isolated from Oroma wetland in Port Harcourt, Nigeria were investigated. The response of bacterial species isolated from the wetland to some selected heavy metals (zinc, lead, copper and iron) was investigated on basal medium containing different concentrations of the metals.  The isolated bacteria were identified based on their colonial, microscopic and biochemical characteristics and belonged to following genera; Bacillus, Staphylococcus, Enterococcus, Escherichia, Pseudomonas, Citrobacter and Proteus. All the isolates showed resistance to the test heavy metals at lower concentrations (0.1 mg/L ‒ 0.5 mg/L) except Bacillus species which showed resistance to lead at 0.25 mg/L. Generally, the isolates were highly sensitive to lead (Citrobacter species showed the highest MIC value for lead at 0.1 mg/L) and more resistant to iron with Escherichia species showing MIC values up to 2.5 mg/L. However. In the control plate (consisting of a metal deficient medium) there was profuse microbial growth. Antimicrobial susceptibility testing (Kirby-Bauer standard disc diffusion) was performed using augmentin, tetracycline, amoxicillin, gentamicin, nitrofurantoin, cotrimazole, nalixidic acid and ofloxacin on Mueller-Hinton agar according to the BSAC recommendations. The isolates exhibited high resistance to most of the antibiotics like augumentin and amoxicillin where there was complete resistance by all the isolates. This co-selection of metal tolerance and antibiotic resistance in bacteria poses a potential public health hazard as diseases become increasingly difficult to treat with antibiotics resulting in complications and administration of a more expensive and most likely, a more toxic drug.

Key words: heavy metal, tolerance, antibiotics, resistance, bacteria, wetland,