Método nao invasivo para detecção de Helicobacter pylori

Abstract

The discovery of Helicobacter pylori by Barry J. Marshall and J. R. Warren in the eighties and the posterior association of this bacterial species with gastric, peptic ulcer and lately with gastric câncer, brougth about a crescent interest in new methods, specially non-invasive ones that could be used by molecular epidemiology to elucidate the infection of H. pylori in population at risk. Salivas were collected in a shantytown (University Park) in a pilot study in a survey from early childhood (2 years) to adolescence (14 years). The salivas were colected in weekends when the mother could give all the necessary information and cooled in ice in a stirofoam box. At the laboratory they were centrifuged at 3000G for 15minutes and thereafter frozen at -20°C, prior to analysis. IgG, IgA, total protein and albumins were determined; immunoglobulins by specific ELISA and the rest by spectrophotometric methods. The ELISA was done by a specific kit used for sorologic determination and adapted in our laboratory for saliva analyses. The comercial kit contained microtritation plates, goat antibody human anti-IgG conjugated with fosfatase as a marker, BSA bloking solution dissolved in physiological saline, glycerol at 50 %, dietanolamine buffer and H. pylori antigen prepared from community strains. The cases were considered positives when optical densities between the ratios of positives and negatives were equal or superior to 2. This index was calculatcd as a result of the quotient between the averages of positives and negatives. These data were compared with the ones obtained by breath tests and fecal PCR. When compared with the positive ones there was a confirmation of 79% with breath tests and 83% of the serum positives. The comparisons of these data in saliva with the different methods demonstrate that this tecnique is a good and easy tool for the use in molecular epidemiology. Preliminary experiments were first done with adults known as soropositives to H. pylori and some negative Controls, regarding IgA. Among 44 children studied at least 10 were considered positives and 34 negatives to IgA at the saliva dilution of 1:200. As for IgG, 19 children were positives at this same dilution; the same study was conducted in 14 mothers, and 7 were positive for IgA while 10 were IgG positives. An outside positive control goup from 10 patients chosen from the gastroenterology clinic of a General Hospital in Fortaleza, showed 2 positives patients for IgA and a maximum of 8 positives for IgG.The comparison of these saliva data were done with serum IgG, breath test and fecal PCR.