Abstract

This study reports the survey of the level of efficacy of some brands of the antibiotics sold in Calabar, Nigeria. This survey was carried out using the agar diffusion technique. Ten brands of 5 different antibiotics were bought from different pharmacy shops in Calabar metropolis and tested against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus pyogenes to determine their efficacies. The test antibiotics were 2 brands each of ampicillin, chloramphenicol, erythromycin, septrin and vancomycin. This survey measured the ability of these antibiotics to inhibit bacterial growth in vitro. The potency or activity per milligram of a chemotherapeutic agent is expressed on the basis of the lowest concentration of minimal inhibitory concentrations (MICs) or higher zones of inhibition. From the results, the overall mean zones of inhibition for the test organisms ranged from 20.2 – 33.3 mm, with 21.9 mm for E. coli, 26.4 mm for K. pneumoniae, 20.2 mm for P. aeruginosa, 33.3 mm for S. aureus and 21.7 mm for S. pyogenes. Our study showed that there were no significant differences (P > 0.05) between the mean zones of inhibition of the test antibiotics and standard controls tested against the test organisms except for P. aeruginosa and K. pneumoniae. The 2 brands of ampicillin and erythromycin were significantly (P = 0.027; P = 0.038) less effective against P. aeruginosacompared to the standard controls while for K. pneumoniae, the 2 brands of chlorampenicol and erythromycin were significantly (P = 0.049; P = 0.057) less effective compared to the standard controls. The results showed that the level of potency of these antibiotics vary according to the different manufacturers. Indeed, the findings of this survey confirm that some of the brands of antibiotics (ampicillin, chloramphenicol and erythromycin) sold in Nigeria may be fake or adulterated and do not contain the acclaimed quantity of active ingredients, which is a reflection of what goes on in many developing countries, in particular, in sub-Saharan Africa.

Key words: Active ingredients, antibiotics, efficacy, quality, selective toxicity, survey, zones of inhibition.