Comparison of the Etest and the Neo-Sensitabs method for antimicrobial susceptibility testing of Helicobacter pylori
Abstract number: P1179
Rasmussen L., Jonaitis L., Kupcinskas L., Andersen L.
Objectives: To assess the reliability of the E-test (AB BIODISK) compared with the Neo-Sensitabs (Rosco) method for antimicrobial susceptibility testing of Helicobacter pylori.
Methods:H. pylori strains were susceptibility tested by both the E-test and the Neo-Sensitabs method for ampicilin, metronidazole, ciprofloxacin, tetracycline and clarithromycin.
50 clinically isolated H. pylori strains were grown on chocolate agar plates and incubated at 37°C in a microaerobic gas chamber. The bacteria were harvested after 72 hours, suspended in API suspension medium (bioMérieux) and adjusted to a McFarland turbidity standard of 4 (109 CFU/ml). Inoculation was performed by applying 100 ml of the bacteria suspension to each plate (plates were room tempered before inoculation) and spread by drigalski loop. Before applying the E-test strips and the Neo-Sensitabs plates were left to dry for 15 minutes. The strips/tablets were applied using sterile forceps and only one strip/tablet per plate was applied. Incubation was conducted at 37°C in a microaerobic gas chamber and reading after 72 hours.
In order to allow a direct comparison of E-test and tablet results, MIC (Minimal inhibitory concentration) values were first log2 transformed and then converted to scores ranging from 1 to 15 . Correlations between scored MIC and zonesize were tested using Pearson's regression.
Figure 1. Correlation between metronidazole MIC values and zonesizes with 50 H. pylori isolates.
Results: Zonesize is plotted as a function of scored MIC of ampicilin, metronidazole, ciprofloxacin, tetracycline and clarithromycin and correlations calculated. The corresponding correlation coefficients are -0.49, -0.97, -0.89. -0.49 and -0.67 respectively. As an example Figure 1 shows the results of metronidazole.
Conclusion: Excellent correlation was demonstrated by statistical analysis between MIC score and zonesize values for metronidazole and ciprofloxacin while the correlation was acceptable for ampicilin, tetracycline and clarithromycin.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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