Frecuencia de genes de virulencia en infecciones mixtas con cepas de Helicobacter pylori de una población mexicana

Background Helicobacter pylori (H. pylori) is associated with gastroduodenal diseases. Virulence of clinical isolates is related to clinical outcome. Moreover, with microdiversity studies in clinical isolates from a single patient, but from a different origin (antrum or corpus), it is possible to demonstrate that there are simultaneous mixed infections. Aims To genotype H. pylori strains with multiplex PCR, according to their clinical virulence, and in this manner know the frequency of each genotype and relate it to clinical outcome in order to prevent the development of severe diseases. Methods A total of 210 patients with gastric alterations were studied. Virulence classification of H. pylori strains was carried out with multiplex PCR and 127 strains were identified as H. pylori by PCR (glmM and cagE). Genotype and clinical outcome were evaluated with the Fisher's exact test. In addition, RAPD-PCR was performed as a fingerprinting method to analyze mixed infections. Results The cagA, vacAs₁, and vacAm₁ genes were detected in all the clinical isolates. Strains were classified as: type i, 40.15% (51/127); type ii, 22.04% (28/127); and type iii, 28.4% (36/127), but two new different genotypes were also detected: (1) babA₂+, cagA+, vacAs₁+, 6.29% (8/127) and (2) babA₂+, cagA-, vacAs₂/m₂+, 3.14% (4/127). The cagE gene was detected in type i strains. Conclusions The Fisher's exact test did not support a significant association between clinical outcome and genotype. The main circulating genotypes in the Mexican population studied were: cagA+, vacAs₁, and vacAm₁. Multiplex PCR can be used as a screening test for H. pylori strains. Furthermore, the cagE gene is a good marker for identifying cag-PAI positive strains.