The Potency Of Locally Prepared Antibiotic Discs Compared To The Commercially Available Dics On Staphylococcus Aureus And Escherichia Coli Isolates

Locally prepared antibiotic discs are becoming widely used in both private and public hospital laboratories in developing countries. Data on their quality is scarce. To provide data, locally manufactured antibiotic discs were prepared to have the same disc content with their corresponding commercially sold antibiotic discs and their potency compared on S.aureus and E.coli isolates. Erythromycin, Ciprofloxacin, Levofloxacin, Ampicillin, Co-trimoxazole, Tetracycline, Cloxacillin, Amoxyclav, Cefixime tablets and powders of Amikacin, Chloramphenicol, Ceftriaxone, Cefotaxime and Gentamicin were used in the preparation of locally manufactured antibiotic discs following a standard operating procedure. Their corresponding commercial antibiotic discs of the same brand were purchased from GEOCHIM SARL, Bamenda. Suspension standards of pure isolates of Staphylococcus aureus and Escherichia coli were prepared and standardized with 0.5 McFarland standard. Both discs were tested on the isolates following the modified Kirby-Bauer antimicrobial susceptibility testing method. After 18 hours of incubation at 35-37oC in ambient air, their diameters of inhibition zones were measured (in millimeters), compared and interpreted as susceptible, intermediate or resistant using the Clinical and Laboratory Standard Institute interpretation table. Locally prepared antibiotic discs were found to be more effective (had larger diameters of inhibition zones) compared to the commercially sold antibiotic discs. There was no significant statistical difference (p-value = 0.157) between the diameters of inhibition zones of the locally prepared antibiotic discs compared to the commercially sold ones. We recommend that antibiotic discs should be prepared locally from antibiotic tablets and used for routine antimicrobial susceptibility testing hence saving scarce foreign exchange required for importation of commercially sold antibiotic discs