Proyecto De Reciclaje De Plastico

MDR-2010-0154-Ayala_1P.3d

01/18/11

7:29pm

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MDR-2010-0154-Ayala_1P Type: research-article

MICROBIAL DRUG RESISTANCE Volume XX, Number XX, 2011 ª Mary Ann Liebert, Inc. DOI: 10.1089/mdr.2010.0154

MECHANISMS

Resistance to Antibiotics and Characterization of Helicobacter pylori Strains Isolated from Antrum and Body from Adults in Mexico
1 1 1 1 Guadalupe Ayala, MarciaGalvan, Lilia Chihu, Geny Fierros, Alejandro Sanchez, ´ 1 ´ 1 2 1 1 Berta Carrillo, Adolfo Roman, Lizbeth Lopez-Carrillo, Jesus Silva-Sanchez, and Study Group* ´ ´ ´

Background and Aims: Resistance to antibiotics is common in patients with Helicobacter pylori infection in more than one anatomic stomach site. We assessed whether the antibiotic resistance varies according to virulence factors of thebacteria as well as to the age and gender of individuals infected in two anatomic sites. Methods: H. pylori strains were isolated from an antral and corpus biopsy from 90 patients with gastric ambulatory who had not received any previous therapy. Susceptibility to metronidazole and clarithromycin was assessed by E-test, and vacA and cagA genotypes were determined by polymerase chain reaction.Results: Dual resistance to metronidazole and clarithromycin was 3.3% in antrum and 4.4% in the corpus; heteroresistance was 19% and 5.5% for metronidazole and clarithromycin, respectively. Clarithromycin resistance significantly increased with age. Women showed a twofold increased risk for metronidazole-resistant strains in antrum (odds ratio ¼ 2.85, 95% confidence interval 1.09 to 7.42). Virulencefactors were not associated with antimicrobial resistance. Conclusion: Prevalence of resistance to clarithromycin may be increasing in this country. Antimicrobial susceptibility tests from different biopsy sites deserve attention.

Introduction elicobacter pylori is implicated in the etiology of gastric diseases ranging from superficial gastritis to gastric cancer, and it has been classified as a groupI carcinogen.28 In developing countries such as Mexico, more than 80% of adults are colonized with H. pylori, and there is no difference between urban and rural populations.30 Colonization generally persists throughout life, except in those people effectively treated with antibiotics or in those who develop atrophic gastritis, usually late in life.14,32 Eradication of H. pylori prevents pepticulcer25 and gastric adenocarcinoma,6 promotes AU1 c the healing of early low-grade MALT lymphoma,5 and possibly provides relief for nonulcer dyspepsia.17,24 In general, the guidelines for treating patients in whom H. pylori infections were diagnosed consisted of traditional clarithromycincontaining triple therapy in combination with a proton pump inhibitor (PPI). However, recently results regardingH. pylori eradication treatments follow this regimen point to the fact that they do not reliably offer a !80% cure rate, due mainly to the increased prevalence of antibiotic resistance. Recently,

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alternative treatments have been proposed.15 These new treatments usually consist of a PPI in combination with two or three antibiotics, among which amoxicillin, clarithromycin, metronidazole, andtetracycline are included. The primary resistance rate to the two most commonly used antibiotics, clarithromycin and metronidazole, is an important factor to be considered.27 Thus, the choice of drug regimen should be made based on the knowledge of recent data on the resistance rates to these antibiotics in a given geographical area. Another factor that could affect the success of therapy is thefact that an individual might have a mixed H. pylori infection with differing antimicrobial susceptibilities in different parts of the stomach.19,21,33 However, in our country, there is still very little information on the prevalence of antimicrobial-resistant H. pylori strains isolated from gastric biopsies from different anatomical sites of the stomach. We assessed whether clarithromycin,...