Helicobacter pylorivacAandcagAGenotypes in Mexican Adults and Children

Abstract

Studies examining associations between Helicobacter pylori virulence markers and disease have concentrated on adults in developed countries. This study assessed adults and children in Mexico. Ninety patients were recruited, 56 adults (37 with active peptic ulceration and 19 with no ulcers) and 34 children (all with recurrent abdominal pain and no ulcers). H. pylori was cultured from gastric biopsy specimens, and vacA alleles and cagA were typed by use of polymerase chain reaction from multiple colony sweeps. Multiple vacA types were common in single-biopsy isolates and were more frequent in adults with ulcers (95%) than in adults without ulcers (37%; P<.001) or in children (52%; P<.01). vacA s1b and cagA+ strains were more frequent in adults than in children. vacA s1 and cagA+ strains had similar frequencies in adults with and without ulcers. In conclusion, infection with multiple H. pylori strains, defined by different vacA genotypes, is common in Mexico. Such mixed infection is associated with ulcer disease. Strain populations infecting Mexican adults and children differ.

Age and Severity of Mucosal Lesions Influence the Performance of Serologic Markers in Helicobacter pylori–Associated Gastroduodenal Pathologies

“…Although we assessed infection with H. pylori cagA+ strains indirectly by measuring antibodies against CagA, previous studies have shown a close correlation between the detection of antibodies to CagA and the detection of the cagA gene in the isolated strain (13,14). In fact, in previous studies in Mexican adults with peptic ulcer, serologic response to CagA was 83.7% (3), whereas cagA+ H. pylori strains were detected in 81% of the patients (34).…”

Novel vacA s1d signal sequence found in Helicobacter pylori from Mexican Children with Recurrent Abdominal Pain

“…This variability strongly impacts the virulence of the bacterium. Specific genotypes have been associated with the development of gastritis, peptic ulcers and stomach cancer [5][6][7][9][10][11][12][13][14][15]22]. The difference between genotypes of this bacterium is given by the presence or lack of gene blocks in the accessory genome within the plasticity zones of the chromosome and by the polymorphism of the nucleotide sequences in structural genes, such as the vacA gene, which encodes for the vacuolating cytotoxin [19][20][21].…”

“…Several studies show that infection by this microorganism is really a multicolonization of the gastric mucosa by different H. pylori strains with different genotypes. Therefore, it is not possible to attribute a particular genotype to disease outcome [11][12][13][14][15]. These same studies also indicate the presence of strains that were not characterized according to their signal sequence, referring to these strains as being non-typeable.…”

“…It is known that the prevalence of H. pylori infection among populations in different parts of the world varies with the highest levels being seen in developing countries where the infection is acquired during childhood. Epidemiological studies show that H. pylori infection is of mixed origin with strains of different genotypes of vacA, cag and iceA [11][12][13][14][15]. The coexistence of different strains in a bacterial population sharing only one niche leads to high rates of recombination, generating new genotypes among strains of the same species or different genders, which are better adapted to micro-environmental conditions [2,18,31,32].…”

Seropositividad a Helicobacter pylori entre estudiantes universitarios y sus familias: Estudio comparativo

“…La infección se adquiere con mayor frecuencia durante la niñez (1 a 5 años), persistiendo en forma crónica probablemente durante toda la vida de los individuos (12,13).…”