Antibiotic susceptibility of Helicobacter pylori clinical isolates:: Comparative evaluation of disk-diffusion and E-test methods

Antimicrobial susceptibility of 25 Helicobacter pylori strains isolated from patients with acid peptic diseases were tested for in vitro sensitivity to commonly used antibiotics using disk-diffusion and E-test, methods. All strains tested were susceptible to tetracycline by E-test, with the minimum inhibitory concentration (MIC) values being < 0.125 mu g/ml for all strains except for 6 (< 0.023 mu g/ml). However 1 strain was resistant by disk-diffusion method. One strain was resistant to clarithromycin both by disk diffusion and E-test (MIC < 48 mu g/ml), and 1 strain was resistant only by disk diffusion. Only one strain was resistant to amoxicillin by disk diffusion and E-test (MIC > 256 mu g/ml). For ciprofloxacin, three strains were resistant by disk diffusion and two by E-test (MIC < 32 mu g/ml). Sixteen strains were resistant to metronidazole by disk diffusion and E-test (MIC >= 8 mu g/ml), and 1 was resistant only by E-test (MIC < 48 mu g/ml). Overall, 64% of the strains were resistant to metronidazole. The MIC for metronidazole was also tested by agar-dilution method, and metronidazole resistant strains had an, MIC > 8 mu g/ml. The disk-diffusion method showed excellent correlation with E-test results; there was 100% agreement for amoxicillin a other antibiotics showed 90% to 95% accuracy. Disk diffusion is cheaper than E-test (approximately 2.6 cents vs. US$2.60), is easy to perform, and is a reliable method for testing H. pylori susceptibility to antimicrobial agents in the clinical microbiology laboratory.