Helicobacter pylori colonization in children with gastritis and peptic ulcer. II. Ultrastructural change of the gastric mucosa

Lipid and Protein Oxidation during in Vitro Gastrointestinal Digestion of Pork under Helicobacter pylori Gastritis Conditions

Helicobacter pylori gastritis affects gastric pH and concentrations of ascorbic acid, hydrogen peroxide, hypochlorite, ammonia and urea, pepsin, and mucin. First, the separate effects of each of these altered factors on oxidation of pork were investigated during in vitro gastrointestinal digestion. Lipid and protein oxidation increased (range 23-48%) in duodenal digests of pork previously exposed to elevated (6.1) versus normal acidic stomach pH (2.3 to 3.5) conditions. Salivary nitrite reduced the formation of lipid and protein oxidation products (range 14-20%) under normal acidic but not elevated stomach pH conditions. Higher amounts of hydrogen peroxide and lower amounts of ascorbic acid decreased concentrations of lipid oxidation products in duodenal pork digests, whereas ammonia slightly stimulated protein oxidation during digestion. Second, two H. pylori gastritis-duodenal digestion models were installed using a set of altered compound concentrations at normal acidic or elevated stomach pH. The elevated pH-gastritis-duodenal digestion model increased pork protein oxidation compared with the normal pH-gastritis and the normal digestion model (14.3 ± 2.1 vs 8.2 ± 1.0 nmol DNPH/mg protein, P < 0.001). Compared with the other models, protein oxidation was also increased when nitrite-cured pork was exposed to the elevated pH-gastritis-duodenal digestion model (10.8 ± 1.4 vs 5.9 ± 0.8 nmol DNPH/mg protein, P < 0.001), but no significant effect of the model was observed when the pork was seasoned with herbs. Lipid oxidation was not or was marginally affected by the installed model.

Important bacterial gastrointestinal pathogens in children: a pathogenesis perspective

This article focuses on the five most common bacterial enteropathogens of the developed world--Helicobacter pylori, Escherichia coli, Shigella, Salmonella, and Campylobacter--from the perspective of how they cause disease and how they relate to each other. Basic and recurring themes of bacterial pathogenesis, including mechanisms of entry, methods of adherence, sites of cellular injury, role of toxins, and how pathogens acquire particular virulence traits (and antimicrobial resistance), are discussed.

Helicobacter pylori enter and survive within multivesicular vacuoles of epithelial cells

Although intracellular Helicobacter pylori have been described in biopsy specimens and in cultured epithelial cells, the fate of these bacteria is unknown. Using differential interference contrast (DIC) video and immunofluorescence microscopy, we document that a proportion of cell-associated H. pylori enter large cytoplasmic vacuoles, where they remain viable and motile and can survive lethal concentrations of extracellular gentamicin. Entry into vacuoles occurs in multiple epithelial cell lines including AGS gastric adenocarcinoma, Caco-2 colon adenocarcinoma and MDCK kidney cell line, and depends on the actin cytoskeleton. Time-lapse microscopy over several hours was used to follow the movement of live H. pylori within vacuoles of a single cell. Pulsed, extracellular gentamicin treatments show that the half-life of intravacuolar bacteria is on the order of 24 h. Viable H. pylori repopulate the extracellular environment in parallel with the disappearance of intravacuolar bacteria, suggesting release from the intravacuolar niche. Using electron microscopy and live fluorescent staining with endosomal dyes, we observe that H. pylori-containing vacuoles are similar in morphology to late endosomal multivesicular bodies. VacA is not required for these events, as isogenic vacA- mutants still enter and survive within the intravacuolar niche. The exploitation of an intravacuolar niche is a new aspect of the biological life cycle of H. pylori that could explain the difficulties in eradicating this infection.