Evaluation of the Quality of Commercial Antibacterial Discs Available in Nigeria

Aims: This study was undertaken to compare the quality and efficacy of six brands of antibacterial discs that are commercially available in Nigeria.
Methodology: The brands evaluated include two foreign brands (Oxoid and Abtek) and four local brands (Optudisc, Polydisc, Maxidisc and Jirehdisk). The brands were analyzed by antibiotic susceptibility testing (AST) using laboratory isolates of Staphylococcus aureus and Escherichia coli to measure the antimicrobial performances of the brands; and UV-Vis spectrophotometry to measure the absorbances of antibiotics extracted from antibiotic discs of the various brands.
Results: All of the brands of antibacterial discs of under study exhibited variations in their antimicrobial performances and UV-absorbances. This was observed where some of the discs with lower stated potencies produced inhibition zones and absorbances far greater than similar discs from other brands with higher stated potencies. Also, discs of the same stated potencies showed variable results in both the antibiotic susceptibility testing (AST) and UV-Vis spectrophotometric analyses. Coefficients of variation greater than 5%, which indicates high disc-to-disc variation and unsatisfactory reproducibility, were recorded highest among the local brands during the AST. All the brands with multidisc panels, except the Abtek and Polydisc brands, produced some zones of inhibition that are unreadable. Of all the zones of inhibition that were unreadable, Optudisc brand recorded the highest rate (36∙7%), while 6∙7% of discs of Jirehdisk brand and 6∙7% of discs of Maxidisc brand produced inhibition zones that were unreadable.
Conclusion: All brands of susceptibility discs evaluated in this study except the Oxoid and Abtek brands manifested poor quality and performed below expected standard, though one of the local brands (Polydisc) performed closest to the foreign brands. With further improvement in quality, these brands may be recommended for use in Nigeria.