Comparison of E-test with other conventional susceptibility testing methods for ciprofloxacin and gentamicin against gram negative enteric bacilli

Abstract

Background: Increasing antibiotic resistance in Gram negative bacteria has led to the need for a faster and reliable method for determining antimicrobial susceptibility testing. In a resource poor setting like ours, it's also important to look for methods that will be clinically and economically beneficial to the patient. /Wm;This study was aimed at evaluating the Epsilometer test (E-test) and conventional methods for determining antimicrobial susceptibility of isolates of Gram-negative enteric bacteria to ciprofloxacin and gentamicin. Methods: Disc diffusion, E-test, broth dilution and agar dilution methods were performed on 54 bacterial isolates. Results: Using the E-test, 88.9 % of bacterial isolates were resistant to ciprofloxacin, 92.6 % were resistant using broth microdilution, 96.3 % were resistant using agar dilution and 72.2 % were resistant using disc diffusion. Minimum Inhibitory Concentration (MIC50 of isolates for gentamicin showed significant difference for all the techniques (p < 0.05) while MIC90 for gentamicin and MlC50and MIC90 for ciprofloxacin for all the techniques had no significant difference (p > 0.05). Both E-test and broth dilution methods showed high levels of agreement (p > 0.05), there were low levels of agreement between E-test and agar dilution method (p < 0.05), especially at MIC50. Conclusion: The E-test can therefore be considered a reliable method to determine antimicrobial susceptibility testing and it gives results which are at least as accurate as those obtained by the broth dilution method