Activity of antibiotics and azole antimycotics against Helicobacter pylori

The bacteristatic and bactericidal activities of six antibiotics from different substance classes against Helicobacter pylori were determined. Ampicillin, imipenem, tetracycline, and amikacin inhibit the growth of all isolates at concentrations achievable in serum. Cefpirome and ofloxacin are ineffective against three and two of 41 strains, respectively. However, the minimum bactericidal concentrations (MBC) of the substances are two- to sixteen-fold higher than the minimum inhibitory concentrations (MIC). There is sufficient bactericidal activity of ampicillin and imipenem against all strains, but amikacin, ofloxacin, tetracycline, and cefpirome are unable to kill 2, 8, 12, and 18 of 25 strains, respectively, at concentrations achievable in serum. Differences between MIC and MBC of antibiotics may contribute to the explanation of therapy failures. In addition, the inhibitory activity of seven nitroimidazole antimycotics and the triazole fluconazole was evaluated. The nitroimidazole MICs range from 2 to 64 mg/l, with tioconazole, miconazole, bifonazole, and ketoconazole as the most active substances. Fluconazole, however, was ineffective at concentrations < or = 128 mg/l. The efficacy of the nitroimidazole antimycotics against H. pylori in vivo should be tested in a clinical trial.