Helicobacter pylori populations in Peruvian patients. Clin. Infect. Dis

Helicobacter pylori is an extremely diverse species. The characterization of strains isolated from individual patients should give insights into colonization and disease mechanisms and bacterial evolution. We studied H. pylori isolates from patients in the Japanese-Peruvian Polyclinic in Lima, Peru, by determining metronidazole susceptibility or resistance and by random amplified polymor-phic DNA (RAPD) fingerprinting (a measure of overall genotype). Strains isolated from several biopsy specimens from each of 24 patients were studied. Both metronidazole-susceptible and-resistant strains were isolated from 13 patients, whereas strains of more than one RAPD type were isolated from only seven patients. We propose that the homogeneity in RAPD fingerprints for strains isolated from most persons reflects selection for particular H. pylori genotypes during chronic infection in individual hosts and the human diversity in traits that are important to this pathogen. Carriage of related metronidazole-resistant and-susceptible strains could reflect frequent metronida-zole use in Peru and alternating selection for resistant and susceptible phenotypes during and after metronidazole therapy. Helicobacter pylori causes chronic infections in the human cially apparent in childhood. About one-half of Peruvian chil-gastric mucosa that can last for years or decades despite in- dren become infected with H. pylori during their first years of flammatory and immune responses and changes in gastric phys- life, and most others become infected within the next one t