Exposure to Metronidazole In Vivo Readily Induces Resistance in Helicobacter pylori and Reduces the Efficacy of Eradication Therapy in Mice

Abstract

The Helicobacter pylori SS1 mouse model was used to characterize the development of resistance in H. pyloriafter treatment with metronidazole monotherapy and to examine the effect of prior exposure to metronidazole on the efficacy of a metronidazole-containing eradication regimen. Mice colonized with the metronidazole-sensitive H. pyloriSS1 strain were treated for 7 days with either peptone trypsin broth or the mouse equivalent of 400 mg of metronidazole once a day or three times per day (TID). In a separate experiment,H. pylori-infected mice were administered either peptone trypsin broth or the mouse equivalent of 400 mg of metronidazole TID for 7 days, followed 1 month later by either peptone trypsin broth or the mouse equivalent of 20 mg of omeprazole, 250 mg of clarithromycin, and 400 mg of metronidazole twice a day for 7 days. At least 1 month after the completion of treatment, the mice were sacrificed and their stomachs were cultured for H. pylori. The susceptibilities of isolates to metronidazole were assessed by agar dilution determination of the MICs. Mixed populations of metronidazole-resistant and -sensitive strains were isolated from 70% of mice treated with 400 mg of metronidazole TID. The ratio of resistant to sensitive strains was 1:100, and the MICs for the resistant strains varied from 8 to 64 μg/ml. In the second experiment, H. pylori was eradicated from 70% of mice treated with eradication therapy alone, compared to 25% of mice pretreated with metronidazole (P < 0.01). Mice still infected after treatment with metronidazole and eradication therapy contained mixed populations of metronidazole-resistant and -sensitive isolates in a ratio of 1:25. These results demonstrate thatH. pylori readily acquires resistance to metronidazole in vivo and that prior exposure of the organism to metronidazole is associated with failure of eradication therapy. H. pylori-infected mice provide a suitable model for the study of resistance mechanisms inH. pylori and will be useful in determining optimal regimens for the eradication of resistant strains.

Host Adaptation and Immune Modulation Are Mediated by Homologous Recombination inHelicobacter pylori

“…Serum samples were tested for H. pylori antigen-specific IgA, IgM, IgG, IgG1, and IgG2a antibodies by an ELISA technique [16]. Ninety-six-well Maxisorp plates (Nunc) were coated with 25 mg of a sonicated whole-cell extract of H. pylori SS1.…”

“…Mice were killed up to 70 days after infection. Colonization with H. pylori was assessed by quantitative culture, as described elsewhere [16]. The stomach tissue was washed in PBS; divided so that each fragment contained cardia, body, and antrum; and placed in BHI broth/0.2% cyclodextrin.…”

Helicobacter pylori Current Chemotherapy and New Targets for Drug Design

“…Due to the high potential for H. pylori to develop antibiotic resistance, monotherapy is not recommended for H. pylori infections [155,169].…”

“…The acid pH of the stomach appears to be of little or no consequence to the antimicrobial activity of this antibiotic. Unfortunately, metronidazole is highly susceptible to bacterial resistance [155].…”

Synthesis and in vitro anti-Helicobacter pylori activity of 2-[(chlorobenzyl)thio]-5-(5-nitro-2-furyl)-1,3,4-thiadiazoles

“…Although there have been conflicting reports concerning the clinical impact of metronidazole resistance in H. pylori, many studies have demonstrated that resistance to this class of antibiotics does reduce the efficacy of metronidazolecontaining eradication regimens (Jenks et al, 1999;Graham, 1998;Jenks et al, 2000).…”