title: Frequency of virulence genes in mixed infections with Helicobacter pylori strains from a Mexican population.
abstract: 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.
  
  
  OBJECTIVE
  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.
authors.affiliation: Laboratorio de Hematología Especial, Instituto Mexicano del Seguro Social CMN-La Raza, Hospital de Especialidades, México D.F., México; Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, México D.F., México.
authors.forename: R
authors.initials: R
authors.lastname: González-Vázquez
authors.affiliation: Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, México D.F., México.
authors.forename: M G
authors.initials: MG
authors.lastname: Córdova-Espinoza
authors.affiliation: Laboratorio de Urgencias y Servicio de Transfusiones, Instituto Mexicano del Seguro Social CMN-La Raza, Hospital General, México D.F., México; Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, México D.F., México.
authors.forename: A
authors.initials: A
authors.lastname: Escamilla-Gutiérrez
authors.affiliation: Departamento de Infectología e Inmunología Perinatal, Instituto Nacional de Perinatología «Isidro Espinosa de los Reyes», México D.F., México.
authors.forename: I
authors.initials: I
authors.lastname: Morales-Méndez
authors.affiliation: Laboratorio de Bacteriología Intestinal, Hospital Infantil de México «Federico Gómez», México D.F., México.
authors.forename: S A
authors.initials: SA
authors.lastname: Ochoa-Pérez
authors.affiliation: Departamento de Zoología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, México D.F., México.
authors.forename: F
authors.initials: F
authors.lastname: Armendáriz-Toledano
authors.affiliation: Departamento de Endoscopias Pediátricas, Instituto Mexicano del Seguro Social CMN-La Raza, México D.F., México.
authors.forename: J
authors.initials: J
authors.lastname: Fonseca-Nájera
authors.affiliation: Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, México D.F., México. Electronic address: sgiono@yahoo.com.
authors.forename: S
authors.initials: S
authors.lastname: Giono-Cerezo
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004269:DNA, Bacterial / Q000235:genetics; D005260:Female; D005838:Genotype; D016481:Helicobacter Infections / Q000453:epidemiology* / Q000382:microbiology*; D016480:Helicobacter pylori / Q000235:genetics*; D006801:Humans; D008297:Male; D008800:Mexico / Q000453:epidemiology; D008875:Middle Aged; D016896:Treatment Outcome; D037521:Virulence Factors / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial; D037521:Virulence Factors
keywords: ADN polimórfico amplificado al azar; Factores de virulencia; Genotipificación; Genotyping; Helicobacter pylori; Infección mixta; Mixed infection; Random Amplified Polymorphic DNA; Virulence factors