In order to gain insight into the relative importance of several virulence factors of Bacteroides gingivalis, 8 strains with a varying virulence were studied. The virulence of B. gingivalis was determined in a mouse model. Strains HG 66, HG 76 and HG 184 were very virulent causing phlegmonous abscesses with lesions and necrosis. The strains HG 405 and HG 462 caused phlegomonous abscesses with pus. Strains HG 91, HG 94 and HG 185 were less virulent and induced gravity abscesses. In vitro strains HG 66, HG 76 and HG 184 induced low amounts of chemiluminescence by polymorphonuclear leucocytes. All other strains including HG 405 and HG 462 caused a relatively high chemiluminescence. Most strains displayed a high sensitivity to the bactericidal activity of fresh serum except for the highly virulent strains HG 66, HG 76 and HG 184. No differences in extracellular proteolytic activity on Azocoll, production of volatile fatty acids and ammonia were found between the B. gingivalis strains studied. In conclusion, differences in virulence were shown within the species B. gingivalis; the relative importance of several virulence factors was investigated.

The in vitro binding of surface-exposed material and outer membrane proteins of Helicobacter pylori to high-molecular-weight salivary mucin was studied. We identified a 16-kDa surface protein which adhered to high-molecular-weight salivary mucin. This protein binds specifically to sulfated oligosaccharide structures such as sulfo-Lewis a, sulfogalactose and sulfo-N-acetyl-glucosamine on mucin. Sequence analysis of the protein proved that it was identical to the N-terminal amino acid sequence of neutrophil-activating protein. Moreover, this adhesin was able to bind to Lewis x blood group antigen.

Helicobacter pylori is able to colonize gastric epithelia, causing chronic active gastritis, gastric and duodenal ulcers and presumably gastric malignancies. Attempts to identify the natural reservoir for this microorganism other than the stomach have been unsuccessful. It is suspected that H. pylori can be transmitted orally, since the microorganism has been detected at various sites of the oral cavity. The aim of the present study was to determine whether H. pylori can bind to salivary mucins, which in vivo coat the oral epithelia, and characterize further the interaction. Binding of salivary mucins and of synthetic oligosaccharides was studied in ELISA and immunoblotting, using specific mono- and polyclonal antibodies, and synthetic neoglycoconjugates. H. pylori bound most avidly to a highly sulfated subpopulation of high molecular weight salivary mucins, secreted from the palatine salivary glands, and with less avidity to mucin species secreted by the sublingual and submandibular salivary glands, which are less sulfated. Binding was strongly enhanced upon decreasing pH from 6.0 to 5.0. Using synthetic polyacrylamide coupled oligosaccharides it was found that SO3-3-Gal and the SO3-3-Lewis(a) blood group antigen bound to H. pylori. In contrast, binding of sialylated Lewis(a) and Lewis(b) antigens was much weaker. This study indicates that sulfated oligosaccharides on salivary mucins may provide receptor structures for adhesion of H. pylori to oral surfaces.

The presence of Helicobacter pylori in the oral cavity (6 sites), oesophagus, stomach and bowel of 20 dyspeptic patients was investigated. Samples were cultured on three selective media and analyzed by 16S rDNA polymerase chain reaction (PCR) and southern hybridization. Helicobacter pylori DNA was detected by PCR from oral-cavity samples of three (20%) and from faeces samples of only one (7%) of the patients whose stomach biopsies were positive for Helicobacter pylori. When culture was used, the microorganism's rate of recovery from the oral cavity and faeces was 13% and 7%, respectively. One patient had a Helicobacter pylori-like organism in samples collected from the tongue and palate. Both strains were urease, catalase and oxidase positive and grew microaerophilically but were negative on PCR analysis. This demonstrates the possibility of false identification of Helicobacter pylori by use of routine enzyme reactions. Interestingly, specimens collected from the cheeks of three patients were positive for Helicobacter pylori by PCR analysis. This is the first instance of detection of this microorganism in the cheek.

The vacA and cagA geno- and phenotypes of two mouse-adapted strains of Helicobacter pylori, SS1 and SPM326, were determined. The SS1 strain, which had thecagA + and vacA s2-m2 genotype, induced neither vacuole formation in HeLa cells nor interleukin-8 (IL-8) production in KATO III cells. In contrast, H. pyloriSPM326, with the cagA + and vacAs1b-m1 genotype, induced vacuoles as well as IL-8 production in vitro. Furthermore, a spontaneous mutant of SPM326, which produced a vacuolating cytotoxin but was not able to induce IL-8 production (SPM326/IL-8−), was detected. C57Bl/6 and BALB/c mice were infected with these three strains to investigate the colonization pattern and the effect on the immune response in vivo. The SS1 strain colonized the stomachs of all mice in large numbers which remained constant over time. Colonization with the SPM326/IL-8+ and SPM326/IL-8− strains was lesser, or even absent, and decreased over time. At 5 weeks postinoculation all three H. pylori strains induced a mild increase of neutrophil count in the gastric corpus of C57Bl/6 mice, which disappeared by 12 weeks. At both 5 and 12 weeks postinoculation C57Bl/6 mice colonized with SPM326/IL-8+ showed an increased expression of major histocompatibility complex (MHC) class II antigen in the cardia which was accompanied by an increased number of T cells. C57Bl/6 mice that were infected with SS1 and SPM326/IL-8− did not show chronic inflammation. BALB/c mice colonized with SS1 and SPM326/IL-8− also showed an increase in neutrophil count at 5 weeks, which normalized again by 12 weeks postinoculation. At this time point SS1-infected mice showed inflammation in the corpus and antrum. At these sites an increased expression of MHC class II antigens and an increased number of T cells were observed. Although small lymphoid follicles were already observed 5 weeks after inoculation with SS1, their incidence as well as their number was increased at 12 weeks. These results show that inflammation induced by H. pyloridepends both on the bacterial strain and the host.