Helicobacter pylori release from yeast as a vesicle-encased or free bacterium.

BACKGROUND Yeast has been suggested as a potent reservoir of H pylori that facilitates bacterial spread within human populations. What mechanism ensures effective H pylori release from yeast? Here, H pylori release from yeast as a vesicle-encased or free bacterium was studied. MATERIALS AND METHODS Liquid culture of Candida yeast was examined by light, fluorescence and transmission electron microscopy methods to observe the released vesicles. Vesicles were isolated and examined by TEM. Immunogold labeling was used for detection of H pylori-specific proteins in vesicles' membrane. Free bacterial cells, released from yeast, were separated by immunomagnetic separation and observed by field emission scanning electron microscopy (FESEM). DNA of bead-bound bacteria was used for amplification of H pylori-16S rDNA. Viability of bead-bound bacteria was examined by live/dead stain and cultivation on Brucella blood agar. RESULTS Microscopic observations showed that vesicles contained bacterium-like structures. Thin sections showed release of vesicle-encased or free bacterium from yeast. Immunogold labeling revealed occurrence of H pylori proteins in vesicles' membrane. FESEM showed attachment of H pylori cells to magnetic beads. Sequencing of 521 bp PCR product confirmed the identity of bead-bound H pylori. Live/dead staining showed viability of bead-bound H pylori but the result of culture was negative. CONCLUSIONS Escape of intracellular H pylori from yeast as a membrane-bound or free bacterium indicates that H pylori uses safe exit mechanisms that do not damage the host which is the principle of symbiotic associations. In human stomach, certain conditions may stimulate yeast cells to release H pylori as a vesicle-encased or free bacterium.