Oyem Ifeanyi Mirian^1,, Atuanya Ernest Ikenna²

The antibiotics sensitivity patterns and plasmid profiles of some selected bacteria isolated from septic tank sewage in the region under study was evaluated. Three replicate samples from Locations A, B and C representing Agbor, Benin and Sapele regions of Delta and Edo States, Nigeria respectively was collected from both the influent tank (raw sewage) and the effluent chamber (semi treated sewage) between November 2018 and January 2019 for testing. A composite sample was formed from the three samples collected. Antibiotic resistance testing was done to determine the resistance profile of the isolates using Mueller-Hinton agar plates which were prepared and appropriately labelled. These plates were inoculated with standardized microbial broth cultures by spread plate technique and left to dry for 30 minutes. Commercially available antibiotics discs containing varying concentrations of various types of commonly used antibiotics were placed at adequate distances on each of the seeded agar plates and incubated for 12h. Plasmid DNA from all tested strains was obtained by using alkaline lysis method. Cells were grown overnight at 37^oC in a nutrient broth in a 1.5 ml micro tube. The growth was harvested by centrifuging at 3,000 rpm for 10 minutes. The plasmid DNA was visualized by placing the gel in an ultraviolet transilluminator in a photo documentation system. The overall prevalence of antibiotic resistance was highest in Amoxicillin (90.5%) and least in Augmentin (40.5%). There was no significant difference (p>0.01) between antibiotic resistance in raw sewage and in the semi-treated sewage. Escherichia coli had the highest MAR index (0.9) while Proteus sp. had the lowest MAR index (0.4). Plasmid analysis of 9 bacterial isolates showed that 4 (44.4%) possessed plasmids each of molecular weight 23.1kb while 5 (56.6%) had no plasmid DNA.

antibiotics sensitivity, plasmid profiles, bacteria, sewage, septic tank