Clarithromycin

There are no accepted standardized methods for testing H. pylori antimicrobial susceptibilities and the protocols used in this study were based on recently published guidelines [16 ] and also those of Performance Standards for Antimicrobial Susceptibility Testing- Clinical and Laboratory Standards Institute - NCCLS, 2007 [17 ]. Briefly, bacterial suspensions were adjusted to the 0.5 McFarland standard (equivalent to 1–2 × 10⁸ cfu/ml) and were used to inoculate Muller Hinton agar plates (Merck, Germany). Antimicrobial disks (ampicillin (10 μg), levofloxacin (5 μg), metronidazole (5 μg), clarithromycin (2 μg), amoxicillin (10 μg), streptomycin (10 μg), cefsulodin (30 μg), erythromycin (5 μg), tetracycline (30 μg), trimethoprim (25 μg), furazolidone (1 μg), rifampin (30 μg), and spiramycin (100 μg) (Oxoid, UK)) were applied and the plates were incubated under microaerophilic conditions at 35 °C for 16–18 h. The zones of growth inhibition produced by each antibiotic were measured and interpreted by standard procedure. Reference strains NCTC 13206 (CCUG 38770) and NCTC 13207 (CCUG 38772) were included as quality controls [18 (link)].

Chemicals and solvents used in all experiments were of analytical grade. Solvents, including ethanol (EOH) and Dimethyl sulfoxide (DMSO), were purchased from LABCHEM (USA) and Fisher chemical (UK), respectively. Sterile blank disks of 6-mm diameter and disks with standard antibiotics (clarithromycin 15 μg, metronidazole 5 μg, ciprofloxacin 5μ g, and tetracycline 30 μg) were purchased from Oxoid (UK).