Microbiological Assessment of Commercial Antibiotic Discs from selected Pharmacies in Bwari Area Council, Abuja, Nigeria

Aims: To assess the potency of two brands of locally prepared antibiotics against two bacterial species.

Place and Duration of Study: Department of Microbiology, Veritas University, Abuja, Nigeria, between September 2021 and February 2022.

Methodology: We purchased two brands of antibiotics and obtained our test isolates from General hospital in Bwari, Abuja. The test isolates were characterized both routinely and molecularly by Sanqer sequencing method to confirm the species. Agar diffusion method was employed to assess the effectiveness of the antibiotics on the test isolates. Finally, the results were compared with the Clinical and Laboratory Standards Institute (CLSI).

Results: The isolates obtained from the Bwari Genera l Hospital were characterized routinely and molecularly to identify the species. Disc - agar diffusion modified method was employed while the potencies of the discs were compared with approved standards of the Clinical and Laboratory Standards Institute (CLSI). The two brands which are locally made and available in multidisc panels, demonstrated performances against Staphylococcus sciuri and Proteus mirabilis but showed significant variations in concentrations and in their inhibitory zone diameters. Both brands containing Tarivid (10 µg) produced only a small zone against Proteus mirabilis, while Streptomycin (30 µg) and Gentamycin (10 µg) exhibited unreadable zones against Staphylococcus sciuri. Unreadable zones of inhibition, which implies large zones that merged together and exceeded plate diameters at the time of reading; were common with both brands and can lead to mis-information, increase in the susceptibility of resistant organisms and eventually, drug abuse.

Conclusion: The result of this assessment shows, that there is gross variation in these commercially available but locally prepared antibiotic discs. The disparity in the types of antimicrobial agents and their concentrations will pose a delicate problem to clinical microbiologists and subsequently in the diagnosis, administration of antibiotics and the likelihood of drug resistance.