Helicobacter pylori: characteristics, pathogenicity, detection methods and mode of transmission implicating foods and water

Identification of novel Helicobacter species in pig stomachs by PCR and partial sequencing

Evidence of infection with Helicobacter species in pig stomach was investigated by the use of a PCR with Helicobacter genus-specific primers. Forty pig stomachs, each of four different ulcer lesion grades, 0, 1, 2, and 3 in the pars esophagea area, were collected from a slaughterhouse in Minnesota. Of 160 stomach samples examined, 102 (63.8%) were positive by the PCR assay. The 40 samples each of lesion grades 0, 1, 2, and 3 showed 22.5, 52.5, 85.0, and 95.0% PCR-positive results, respectively. There was a significant trend (P < or = 0.01) in the proportions of PCR-positive cases relative to severity of the lesion. About 80% of the 16S rRNA gene was amplified, and PCR-restriction fragment length polymorphism (RFLP) patterns were analyzed. Of 102 PCR-positive samples, the PCR-RFLP patterns resulted in four different types, 32 samples being classified into type MN 1, 16 samples into type MN 2, 43 samples into type MN 3, and 11 samples into type MN 4. When the sequences of each RFLP type were compared to those reported in databases by using BLAST software, types MN 1, MN 2, MN 3, and MN 4 showed homologies of 97.3, 95.4, 96.7, and 99.5% with the 16S ribosomal DNA of Helicobacter flexispira taxon 3, Helicobacter sp. strains MIT 94-022 and MZ 640285, and Helicobacter suis, respectively. None of the 102 samples positive for the Helicobacter genus were positive with a primer set specific for Helicobacter pylori. Attempts to culture the organisms from selected stomachs in vitro were unsuccessful.

Disinfectant activity against different morphological forms of Helicobacter pylori: first results

The pathogenic bacterium Helicobacter pylori, which has infected more than one-half of the world's human population, exists in two morphological forms; the viable helical form and the disputed viable-but-not-culturable coccoid form. Infection by the helical form proceeds through the oral-oral route, while that by the coccoid form, if possible at all, is by the faecal-oral and/or the oral-oral route. The present pilot study addresses the question of disinfectant efficacy against both forms of the bacterium.

Mechanism for Helicobacter pylori stimulation of interleukin-8 production in a gastric epithelial cell line (MKN 28): roles of mitogen-activated protein kinase and interleukin-1beta

Although it is known that the pathogenic mechanism of Helicobacter pylori involves the stimulated production of interleukin-8 (IL-8) as an inflammatory mediator, the details of the pathway remain unclear. The role of mitogen-activated protein kinase (MAPK) in IL-8 production by H. pylori has been examined in an in vitro study. IL-8 mRNA expression in gastric epithelial cells (MKN 28) was determined by reverse transcriptase-polymerase chain reaction (RT-PCR). IL-8 production was examined by ELISA. The activation of p38 MAPK was assessed by western blotting. Neither IL-8 mRNA nor activated p38 MAPK or p44/42 MAPK was detected in cells not treated with H. pylori. In contrast, incubation of cells with H. pylori, or IL-1beta, or both, clearly stimulated the expression of IL-8 mRNA within 60 min in a concentration-dependent manner. Phosphorylation of p38 MAPK and p44/p42 MAPK, as well as IL-8 production, occurred within 30 min and 24 hr after co-culturing MKN 28 cells with H. pylori and IL-1beta, respectively. Pretreatment of cells with MAPK inhibitors [1-[7-(4-fluorophenyl)-1,2,3,4-tetra-hydro-8-pyridylpyrazolo[5,1-c][1,2,4]triazin-2-yl]-2-phenylethanedione sulfate monohydrate (FR167653), 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)imidazole (SB203580), or 2-(2'-amino-3'-methoxyphenyl)-oxanaphthalen-4-one (PD98059)] significantly inhibited IL-8 production stimulated by H. pylori or IL-1beta or both. The combination of H. pylori and IL-1beta additively stimulated IL-8 production. The additive effect of H. pylori and IL-1beta on IL-8 production was inhibited by treatment with a p38 MAPK inhibitor. It was revealed that the culturing of MKN 28 cells with H. pylori significantly stimulates IL-8 production to a degree sufficient for induction of neutrophil chemotaxis via activation of p38 and p44/42 MAPK.

Survival of Helicobacter pylori in ready-to-eat foods at 4 degrees C

The survival of Helicobacter pylori (NCTC 11638) in various semiprocessed and fresh, ready-to-eat foods, and one raw chicken was studied at 4 degrees C and under aerobic conditions by experimentally inoculating these with 10(4) CFU. Cells were concentrated by two centrifugation cycles followed by plating onto selective blood agar medium made from Wilkins-Chalgren agar supplemented with 5% whole horse blood, and 30 mg/l colistin methanesulfonate, 100 mg/l cycloheximide, 30 mg/l nalidixic acid, 30 mg/l trimethoprim, and 10 mg/l vancomycin. H. pylori was recovered from spiked pasteurized milk and tofu samples up to 5 days and from spiked leaf lettuce and raw chicken up to 2 days. H. pylori could not be recovered from yogurt after any length of storage time. H. pylori is unlikely to grow in foods; however, it may survive in low acid-high moisture environments under refrigeration and pose a possible risk for transmission of infection via foods.

Does enterohemorrhagic Escherichia coli O157:H7 enter the viable but nonculturable state in salted salmon roe?

An outbreak caused by salted salmon roe contaminated with enterohemorrhagic Escherichia coli O157 occurred in Japan in 1998. Since about 0.75 to 1.5 viable cells were estimated to cause infection, we presumed that O157 might enter the viable but nonculturable (VNC) state in salted salmon roe and consequently that viable cell numbers might be underestimated. Although patient-originating O157 cells could not grow on agar plates after 72 h of incubation in 13% NaCl, they were resuscitated in yeast extract broth, and more than 90% of the cells were shown to be viable by fluorescent staining, suggesting that almost all of them could enter the VNC state in NaCl water. Roe-originating O157 was resistant to NaCl because it could grow on agar after 72 h of incubation in NaCl water, but about 20% of cells appeared to enter the VNC state. Therefore, germfree mice were infected with O157 to examine the resuscitation of cells in the VNC state and the retention of pathogenicity. O157 that originated in roe, but not patients, killed mice and was isolated from the intestine. However, these isolates had become sensitive to NaCl. O157 cells of roe origin incubated in normal media also killed mice and were isolated from the intestine, but they also became transiently NaCl sensitive. We therefore propose that bacterial cells might enter the VNC state under conditions of stress, such as those encountered in vivo or in high salt concentrations, and then revive when those conditions have eased. If so, the VNC state in food is potentially dangerous from a public health viewpoint and may have to be considered at the time of food inspection. Finally, the establishment of a simple recovery system for VNC cells should be established.