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Revista médica de Chile

Print version ISSN 0034-9887


WORMWOOD, Tracy et al. Frequency of CagA-positive Helicobacter pylori strains in 160 patients subjected to endoscopy. Rev. méd. Chile [online]. 2018, vol.146, n.5, pp.596-602. ISSN 0034-9887.


Helicobacter pylori is the most significant pathogen associated with gastric diseases, including gastric cancer. Infected patients with strains that are CagA-positive generally have worse outcomes than those infected with CagA-negative strains. Patients infected with CagA-positive strains have a higher risk for developing gastric cancer.


To determine the prevalence of CagA-positive H. pylori strains in fecal samples of patients from the Coquimbo Region of Chile, using a non-invasive, nested-qPCR method.

Material and Methods:

We evaluated 160 patients with gastrointestinal symptoms subjected to an upper gastrointestinal endoscopy. DNA was extracted from fecal samples and tested for the presence of H. pylori using nested-qPCR for the ureC gene, and subsequently compared with the results of histology-Giemsa stain from the patients' endoscopic biopsies. When H. pylori was found, the presence of CagA-positive strains was determined via nested-qPCR.


The histology-Giemsa stain was positive for H. pylori infection in 123 patients (76.9%), while the analysis of fecal samples detected H. pylori in 129 patients (80.6%). The sensitivity and specificity of nested-qPCR to detect the bacterium was 96.7 and 73.0% respectively. Among patients with the infection, 25% had CagA-positive strains.


In this sample of patients, there is a low prevalence of CagA-positive H. pylori strains.

Keywords : Bacterial infections; Feces; Helicobacter pylori; Molecular Epidemiology.

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