Clarithromycin resistance in Helicobacter pylori: prevalence in untreated dyspeptic patients and stability in vitro

Abstract

Susceptibilities to clarithromycin and metronidazole of 444 Helicobacter pylori isolates cultured from antral biopsies of 444 dyspeptic patients were determined by disc diffusion tests (15 mu g disc for clarithromycin, 5 mu g disc for metronidazole). Susceptibility of 46 of these isolates to erythromycin (5 mu g disc) was also tested. Minimal inhibitory concentrations (MICs) of clarithromycin for 42 selected isolates were determined by a plate dilution method. A zone diameter of 30 mm was defined as a 'cut-off' size differentiating susceptibility and resistance of the organism to clarithromycin, by comparing results obtained with the two methods. Of the 444 isolates, 424 (95.5%) were highly sensitive to clarithromycin, with zone diameters ranging from 30 to 98 mm. Twenty isolates (4.5%) were defined as resistant to clarithromycin, with zone diameters ranging between 6 and 28 mm. The incidence of clarithromycin resistance was similar in men and women and in different age groups, and was not significantly different between patients with peptic ulcer and non-ulcer dyspepsia. Among the 444 isolates, 168 (37.8%) were metronidazole resistant. There was cross resistance between clarithromycin and erythromycin, but not between clarithromycin and metronidazole. Stability of clarithromycin resistance was evaluated by the disc diffusion test and confirmed by the plate dilution method. Among the 20 clarithromycin-resistant isolates, nine (45%) reverted to be sensitive after 25 subcultures on drug-free agar. The findings in this study indicate that the incidence of clarithromycin-resistant H. pylori in untreated dyspeptic patients is low. Cross-resistance occurs between macrolides and resistance to clarithromycin in some strains is reversible.

Macrolide Resistance in Campylobacter jejuni and Campylobacter coli : Molecular Mechanism and Stability of the Resistance Phenotype

“…These studies found that H. pyloriresistant isolates carrying an A2142G mutation in the target gene showed a higher rate of instability of the resistance phenotype than those with an A2143G mutation (3,8,52). The data on the stability of Ery r in Campylobacter isolates might suggest that the rate of detection of the A2058G mutation could be underestimated in macrolide-resistant isolates due to the subcultures performed from the first isolation to the moment of susceptibility test performance.…”

Triple therapy with clarithromycin, amoxicillin and omeprazole for Helicobacter pylori eradication in children and adolescents

“…Thus, the non-inclusion of nitroimidazole seems very important on account of prior low rates of Hp eradication in children of our country. Clarithromycin resistance ranges from 5% to 15%, in European studies (23,30) and is increasing in children because of the widespread use in pediatric practice, mainly in developed countries.…”

Susceptibility of Helicobacter pylori isolates to metronidazole, clarithromycin and amoxycillin in vitro and in clinical treatment in Japan

“…21,23,24 The incidence of CLAR resistance was 9.1% (29/320), which is higher than the incidence in Switzerland (0%), Australia (1.9%) and the Netherlands (3%), almost equal to that in France (9.3%), and lower than that in the United States (11%), Belgium (11%) and Africa (14%). 17,26 Resistance is probably linked to the previous use of antibiotics. In Japan, MNZ and other nitroimidazoles are used almost solely for the treatment of Trichomonas vaginalis and recently for H. pylori infection, because we rarely encounter patients with amoebiasis and giardiasis, unlike the incidence of these diseases in developing countries.…”

“…It has been reported that the incidence of MNZ-resistant H. pylori isolates is increasing year by year. 17,31 Not only MNZ but CLAR resistance will also be selected and spread by the use of unsuccessful treatment regimens using these antibiotics. Regimens with high cure rates should be used to prevent the generation of acquired resistance to antibiotics.…”