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Category: Bacterial Pathogenesis
Antibiotic Susceptibility and Resistance, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555818005/9781555812133_Chap42-1.gif /docserver/preview/fulltext/10.1128/9781555818005/9781555812133_Chap42-2.gifAbstract:
Many therapies for peptic ulcer disease have been tried, with the conclusion that multiple drug combinations are at present essential to the achievement of acceptable outcomes; cure of infection in >80% of patients is based on intention to treat. One class of drugs, which has been a constant from the early work of Marshall and Warren, is the 5-nitroimidazoles, principally tinidazole and metronidazole, agents that had been used in the treatment of anaerobic bacterial and selected protozoan infections. Two other drugs were also used with success subsequently: a macrolide compound, clarithromycin, and a β-lactam compound, amoxicillin. The issues relating to drug selection and antibiotic resistance as well as the prospect of using genomics for drug discovery is reviewed in this chapter. Resistance to 5-nitroimidazole is widespread. In the developed countries, it varies between 10 and 50% whereas in developing countries it may concern virtually all strains. Resistance to β-lactam antibiotics by gram-negative bacteria is most commonly due to the production of β-lactamase, either chromosomally encoded, or, more often, plasmid media. The methods used for H. pylori susceptibility testing can be divided into standard phenotypic methods on the basis of diffusion or dilution, and genotypic methods. In summary, despite the significant progress that has been made with respect to development of tests to detect antimicrobial resistance, additional work is needed to optimize the performance of the susceptibility testing methods of H. pylori, especially for metronidazole.
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Chemical structure of the prodrug metronidazole. Metronidazole is activated by the reduction of the nitro group (arrow) leading to the generation of a reactive radical.
Chemical structure of the prodrug metronidazole. Metronidazole is activated by the reduction of the nitro group (arrow) leading to the generation of a reactive radical.
Binding of labeled erythromycin on increasing concentrations of H. pylori ribosomes.
Binding of labeled erythromycin on increasing concentrations of H. pylori ribosomes.
Suggested modifications of standard methods for susceptibility testing of H. pylori
Suggested modifications of standard methods for susceptibility testing of H. pylori
Evaluation of the disk diffusion agar method for metronidazole susceptibility testing of H. pylori
Evaluation of the disk diffusion agar method for metronidazole susceptibility testing of H. pylori
Correlation of the E-test and agar dilution for metronidazole susceptibility testing
Correlation of the E-test and agar dilution for metronidazole susceptibility testing