comparative study of M.I.C evaluator test with the broth microdilution method for antimicrobial susceptibility testing of enterobacter cloacae isolated from cooked food

Agar dilution and broth microdilution are widely recommended quantitative antimicrobial susceptibility test methods, but they are tedious and time consuming to implement as routine tests in many clinical laboratories. Therefore, this study aimed at comparing the broth microdilution and the M.I.C Evaluator method which has been validated for its high accuracy and easy performance for routine diagnostic use. Twenty Enterobacter cloacae strains were isolated following microbiological procedures and confirmation of the isolates used the API 20E test. The strains were evaluated for their susceptibility to seven antimicrobials using the broth microdilution and MIC Evaluator methods. The doubling dilution difference [essential agreement] in the MIC result was derived from: log[2] [MIC by BMD] -log[2] [MIC by M.I.C Evaluator method]. The categorical agreement, interpreted as breakpoints of sensitive and resistance strains was also noted. Categorical agreement between M.I.C Evaluator strip and broth microdilution for amoxicillin, metronidazole and erythromycin was 100%: while categorical agreement for ciprofloxacin was 90%. The essential agreement for erythromycin, ciprofloxacin and tetracycline were 90%, 70% and 15% respectively. Results indicate a high efficiency of the M.I.C Evaluator strip method in determination of minimum inhibitory concentration as compared to broth microdilution method. However, further analysis regarding the suitability of the M.I.C Evaluator for testing Enterobacter cloacae is warranted considering that no consensus guidelines exist for the use of this method with the organism.

Inhibitory and bactericidal activity of selected South African honeys and their solvent extracts against clinical isolates of Helicobacter pylori

The growing problem of antibiotic resistance by Helicobacter pylori demands the search for novel compounds, especially from natural sources. We evaluated the anti-H. pylori activity of six local honeys at different concentrations as well as their solvent extracts by the Hole Plate diffusion method. The minimum inhibitory concentration [MIC[50]] of the two most active extracts of each honey was determined by the broth microdilution method, and the time kill assay of the most active extract of each honey determined by viability studies. Data were analyzed by one-way ANOVA test at 95% significance level. All the honey varieties as well as their solvent extracts demonstrated varying levels of antibacterial activity based on different mean zone diameters [16.0mm [crude] to 22.2mm [extract]] and percentage susceptibilities [73.3% [crude] to 93.3% [extract]] of the test isolates. The chloroform extracts of Pure Honey [PH] and Champagne Royal Train [CRT] recorded MIC[50] ranges of 0.01-10% and 0.625-10% [v/v] respectively; that were not significantly different [P > 0.05] from amoxicillin [0.001-1.25mg/mL], the positive control. The most potent bactericidal effect against the test isolates was obtained with 5% v/v [1/2 MIC] concentration of chloroform extract of PH from 42-72hrs. In conclusion, these honeys and their extracts could be leads for further investigation in the discovery of new natural anti-H. pylori compounds