Executive Summary: Helicobacter pylori (H. pylori) is a Gram-negative bacterium that causes peptic ulcer and gastric cancer. In Ecuador, gastric cancer is among the five most commonly diagnosed types of cancer and is one of the leading causes of death from cancer. The prevalence of H. pylori infection varies between 20 and 80% in different regions of the world; however, only a small number of individuals develop any clinical picture.
Bacterial and host genetic factors are determining factors in the development of pathologies associated with this bacterium. H. pylori possesses virulence factors (cytotoxin A, Cac A, and vacuolating exotoxin, VacA) that facilitate gastric colonization. The geographic distribution of various strains of H. pylori would be associated with geographic differences in the distribution of gastric cancer. In Colombia, for example, the annual rate of gastric cancer in the Andes of Nariño is estimated to be 30/100,000 while in its coastal zone it is 6/100,000 despite the fact that the prevalence of H. pylori infection is similar in the Coast and in the Sierra. These differences could be due to the fact that the strains from the Sierra would have a different genotype and a European phylogeographic origin, while the strains from the Coast would have a European and African origin. In Ecuador there are few studies that have characterized the H. pylori genotypes present in different geographical regions, Coast, Sierra and Oriente. Consequently, the general objective of the present investigation is to compare the genotypes of different H. pylori strains obtained in gastric biopsy samples from symptomatic patients from the Zumbahua Parish in the Andean region with samples from patients from Sushufindi and Lago Agrio in the Amazon. Ecuadorians; and also to establish the in vitro culture of H. pylori with the purpose of conducting ancestry studies of the bacteria. This study has two phases: Phase I corresponds to the recruitment of patients, endoscopic examination, sampling, and pathological study. This phase of the study has already been carried out. Phase II concerns the genotyping of pathogenicity genes in samples taken in phase I and the isolation and cultivation of H. pylori strains in new gastric samples for ancestry analysis. For genotyping, the presence of pathogenicity genes cagA and vacA (s1,s2; m1,m2) will be studied by qPCR, while ancestry will be determined by "multi locus sequence typing" analysis. Seven housekeeping genes (atpA, efp, ureI, ppa, mutY, trpC and yphC) will be amplified using primers recommended by the Pasteur Institute in primary cultures of H. pylori. The sequences obtained will be analyzed in the database (http://pubmlst.org/helicobacter) to determine genotypes of each gene and type sequences of each strain. Subsequently, a phylogenetic analysis will be carried out to determine mating relationships and ancestry using Phyloviz. The results of this research will contribute to better management of patients infected with H. pylori. In addition, conditions will be established for the primary culture of this bacterium.
General Objectives: To compare the genotypes of different strains of H. pylori obtained in gastric biopsy samples from symptomatic patients from the Zumbahua Parish in the Andean region with samples from patients from Sushufindi and Lago Agrio in the Ecuadorian Amazon; and to establish the in vitro culture of H. pylori with the purpose of carrying out ancestry studies of this bacterium.
Specific objectives:
- To establish the sociodemographic and clinical characteristics of the patients participating in the study, from the Ecuadorian Sierra (Zumbahua) and Amazonia (Shushufindi and Lago Agrio).
- To compare the prevalence and macroscopic and microscopic characteristics of gastric lesions from biopsies of voluntary patients from the Ecuadorian Sierra (Zumbahua) and Amazonia (Shushufindi and Lago Agrio).
- To determine the presence of pathogenicity genes cagA, vacA (s1, m1, s2, m2) of H. pylori in gastric samples from patients from the Zumbahua Parish in the Andean region with samples from patients from Sushufindi and Lago Agrio in La Ecuadorian Amazon.
- To determine the ancestry of H. pylori cultures from gastric samples isolated from infected patients using genotyping techniques based on "Multilocus Sequence Typing" (MLST).
Participating Institutions:
UTE, USFQ, ESPOL.
Participants:
Director of the project Manuel E. Baldeón.
- Manuel E. Baldeon
- Paul Cardenas
- Patricia Manzano
Awarded budget: $50000
Project status: In progress.
