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ABSTRACT
Antimicrobial susceptibility testing (AST) is the standard procedure for the susceptibility testing of bacterial isolates. The validity of AST depends on rigid standardization of every feature of the test, including but not limited to the composition of the medium used. This study was carried out to evaluate the AST of three bacterial isolates on other media along with Mueller Hinton agar. Mueller-Hinton agar (MHA), nutrient agar (NA), Columbia blood agar base (CBA), tryptone soya agar (TSA) and a combination of peptone water and bacteriological agar (PWA) were prepared according to manufacturer’s specification in triplicates. Bacterial isolates in triplicates were also standardized according to 0.5 McFarland’s standard and were streaked on the plate before introduction of antibiotics. The results were read following guidelines by clinical laboratory standard institute. Data were analysed using statistical package for social scientist and Microsoft excel. Results revealed that for Chromobacterium, MHA had a mean inhibition zone of 24.25±1.03 mm for meropenem, while the mean zones of inhibition for other media were 25.50±0.50 mm (NA), 27.00±0.57 mm (TSA), 23.00±0.57 mm (PWA) and 21.75±0.47 mm (CBA). For Salmonella marked differences in the zones of inhibition were observed for ciprofloxacin as the standard MHA had 36.00±0.00 mm while other media had inhibition zones of 34.00±1.15 (MHA), 34.00±1.15 (CBA), 34.50±0.95 (TSA) and 32.25±0.75 (PWA). All media had similar interpretation for all antibiotics as well as similar cumulative antibiogram and MAR index in the study. It was clear that a strong positive relationship (relatedness) {0.98} was found in the susceptibility of Salmonella on NA and MHA. More so, it was obvious that 97 % of the values for NA fits the regression analysis model for MHA. This therefore implies that 97 % of the values obtained for NA are similar to the values obtained for MHA with a standard error of 2.08. The probability value (p value) at 95 % confidence shows that there is no statistical difference in the zones of inhibition on NA and MHA for Salmonella. More so, there was also a strong positive relationship between other media and the gold standard as the coefficient of determination {R2} for CBA {0.99}, TSA {0.97} and PWA {0.94} in reference to the standard MHA.
