Dietary calcium inhibits the intestinal colonization and translocation of Salmonella in rats.

Background & Aims: Dietary calcium decreases the cytotoxicity of intestinal contents and intestinal epitheliolysis by precipitating cytotoxic surfactants such as bile acids. A decreased luminal cytotoxicity might not only strengthen the barrier function of the gut mucosa but also reinforce the protective, endogenous microflora. We hypothesized, therefore, that dietary calcium increases the resistance to intestinal infections.

Identification of Clostridium tyrobutyricum as the causative agent of late blowing in cheese by species-specific PCR amplification.

Butyric acid fermentation, the late-blowing defect in cheese, caused by the outgrowth of clostridial spores present in raw milk, can create considerable loss of product, especially in the production of semihard cheeses like Gouda cheese, but also in grana and Gruyère cheeses. To demonstrate the causative relationship between Clostridium tyrobutyricum and late blowing in cheese, many cheesemaking experiments were performed to provoke this defect by using spores from several strains of the major dairy-related clostridia. A method of PCR amplification of a part of the 16S rRNA gene in combination with hybridization with species-specific DNA probes was developed to allow the specific detection of clostridial sequences in DNAs extracted from cheeses.

Genetic marking of Lactococcus lactis shows its survival in the human gastrointestinal tract.

A human feeding study was performed with Lactococcus lactis TC165.5, which is genetically marked by insertion of the sucrose-nisin conjugative transposon Tn5276 and chromosomal resistance to rifampin and streptomycin. The fate of strain TC165.

Detection and characterization of lactose-utilizing Lactococcus spp. in natural ecosystems.

The presence of lactose-utilizing Lactococcus species in nondairy environments was studied by using identification methods based on PCR amplification and (sub)species-specific probes derived from 16S rRNA sequences. Environmental isolates from samples taken on cattle farms and in the waste flow of a cheese production plant were first identified to the genus level, using a Lactococcus genus-specific probe. Isolates which showed a positive signal with this probe were further identified to the (sub)species level.

Nitric oxide-derived urinary nitrate as a marker of intestinal bacterial translocation in rats.

Background/aims: Bacterial translocation across the gut wall may lead to bacteremia and sepsis. Bacteriological analyses are laborious and time consuming, which precludes a rapid diagnosis of bacterial translocation. Synthesis of nitric oxide by macrophages is a primary response to bacterial infections.

Identification of mesophilic lactic acid bacteria by using polymerase chain reaction-amplified variable regions of 16S rRNA and specific DNA probes.

Specific DNA probes based on variable regions V1 and V3 of 16S rRNA of lactic acid bacteria were designed. These probes were used in hybridization experiments with variable regions amplified by using the polymerase chain reaction. In this way, a rapid and sensitive method was developed for the identification and classification of Lactococcus and Leuconostoc species.

Secretory IgA adsorption and oral streptococcal adhesion to human enamel and artificial solid substrata with various surface free energies.

In this paper, secretory IgA adsorption from a single component sIgA solution and from human whole saliva onto human enamel and artificial solid substrata with various surface free energies was studied as a function of time. ELISA indicated that screening or displacement of adsorbed sIgA by other salivary proteins occurred only on low surface free energy substrata, not on high surface free energy substrata such as enamel. In addition, the adhesion of three oral streptococcal strains (Streptococcus mitis BMS, S.

The influence of surface free energy and surface roughness on early plaque formation. An in vivo study in man.

Previous in vivo studies suggested that a high substratum surface free energy (s.f.e.

Surface hydrophobicity and surface free energy of Actinobacillus actinomycetemcomitans strains from human periodontitis.

The surface properties of five freshly isolated clinical strains of Actinobacillus actinomycetemcomitans and a non-sticky, non-cohesive colonial variant were characterized. On growth in serum-containing and serum-free media, the primary isolates had a high surface free energy, corresponding with the low hydrophobicity observed, using as assay adsorption to hexadecane. The dispersion component of the surface free energy was significantly lower upon growth in serum-free medium.

The influence of surface free-energy on planimetric plaque growth in man.

The purpose of this study was to examine the change in plaque area over nine days in vivo on four materials with different surface free-energies (s.f.e.

The effects of pellicle formation on streptococcal adhesion to human enamel and artificial substrata with various surface free-energies.

The influence of a pellicle on streptococcal adhesion was studied. A "ripened" two-hour salivary pellicle and an "early" five-minute salivary pellicle were formed on human enamel and artificial solid substrata with varying surface free-energies. Three strains of oral streptococci, also with widely different surface free-energies, were used for adhesion studies.

Zeta potential and the adhesion of oral streptococci to polymethylmethacrylate.

Adhesion of Candida albicans to the acrylic fitting surface of dentures can lead to the development of denture induced stomatitis and is suggested to be preceeded by the adhesion of indegeneous oral bacteria. Bacterial adhesion can be considered as a result of attractive van der Waals and repulsive electrostatic forces. In this paper we investigate the role of electrostatic interactions in the adhesion of oral streptococci to polymethylmethacrylate (PMMA), the most commonly employed denture-base material.

A comparison between the elemental surface compositions and electrokinetic properties of oral streptococci with and without adsorbed salivary constituents.

In order to characterize the functional cell surface, isoelectric points and elemental surface concentration, the ratios of nitrogen, oxygen and phosphorus to carbon of saliva-coated strains were determined by pH-dependent zeta potential measurements and X-ray photoelectron spectroscopy and compared with those of uncoated strains. The measurements of potential were carried out on completely hydrated cells, whereas the spectroscopy was on freeze-dried micro-organisms. The small increase in the nitrogen:carbon surface concentration ratio of saliva-coated streptococci in comparison to uncoated strains varied from 0.

Effect of zeta potential and surface energy on bacterial adhesion to uncoated and saliva-coated human enamel and dentin.

Physicochemical surface characteristics of early plaque-forming bacteria and of human tooth surfaces were measured to establish their role in bacterial adhesion to intact dental tissue slabs. In addition, the influence of an experimental salivary pellicle was evaluated. Strains of S.

Surface properties of Streptococcus salivarius HB and nonfibrillar mutants: measurement of zeta potential and elemental composition with X-ray photoelectron spectroscopy.

To characterize the functional cell surface, the zeta potentials and elemental surface composition of Streptococcus salivarius HB and a range of mutants with known molecular surface structures were determined. Zeta potentials of fully hydrated cells were measured as a function of pH in dilute potassium phosphate solutions, yielding isoelectric points of the strains. Elemental composition (O, C, N, and P) of the outer 2 to 5 nm of the freeze-dried cell surfaces were measured by X-ray photoelectron spectroscopy.

Comparison between the adhesion to solid substrata of Streptococcus mitis and that of polystyrene particles.

The adhesion of Streptococcus mitis to solid substrata from phosphate suspensions with various ionic strengths was studied and compared with the adhesion of polystyrene particles. At all ionic strengths, the interfacial free energy of adhesion governed the relative number of bacteria or polystyrene particles adhering at equilibrium, except that in a low-ionic-strength buffer, adhesion occurred less frequently because of increased electrostatic repulsion. Large differences between bacterial and polystyrene particle adhesion were observed, as indicated by the ratio of bacteria to polystyrene particles adhering, which decreased from 30 to 4 with a change from low to high ionic strength.

Monobacterial and mixed bacterial plaques of Streptococcus mutans and Veillonella alcalescens in an artificial mouth: development, metabolism, and effect on human dental enamel.

To gain greater understanding of the role of Streptococcus mutans and Veillonella in the caries process, studies of both aerobically and anaerobically grown plaques of S. mutans C67-1 and V. alcalescens V-1 on human enamel slabs were carried out in an artificial mouth.

Adhesion of oral streptococci from a flowing suspension to uncoated and albumin-coated surfaces.

A flow cell system was developed which allowed the study of bacterial adhesion to solid substrata at well-defined shear rates. In addition, the system enabled the solid surfaces to be coated with a proteinaceous film under exactly the same shear conditions. In this flow cell system, adhesion of three strains of oral streptococci from a phosphate-buffered solution onto three different substrata was studied as a function of time in the absence and presence of a bovine serum albumin (BSA) coating at a shear rate of 21 s-1.

Effect of the application of a mucin-based saliva substitute on the oral microflora of xerostomic patients.

A cross-sectional study among 46 xerostomic patients was carried out to determine the influence of a mucin-based artificial saliva on the microflora of standardized oral washings. Patient and non-xerostomic control groups were formed according to the use of saliva substitute (ad libitum or from an intraoral reservoir) and dentition (dentate, edentulous, full dentures). Only few differences were observed among the subgroups based on dentition within a specified salivary group.

Surface-free energy and bacterial adhesion. An in vivo study in beagle dogs.

Conflicting reports have been presented on the rôle of substratum surface free energy (s.f.e.

Relationship of cell surface morphology and composition of Streptococcus salivarius K+ to adherence and hydrophobicity.

The cell surfaces of a range of variants of Streptococcus salivarius HB, altered in cell wall antigen composition, were compared with those of the parent with respect to adherence, ability to adsorb to hexadecane, morphology, and exposure of lipoteichoic acid (LTA). Adherence to host surfaces was measured by using both saliva-coated hydroxyapatite beads and tissue-cultured HeLa cells, and interbacterial adherence was measured by using Veillonella alcalescens V1 cells. Progressive loss of the protease-sensitive fibril classes was generally associated with decreasing ability to adsorb to hexadecane.

Kinetics of adhesion of the oral bacterium Streptococcus sanguis CH3 to polymers with different surface free energies.

The kinetics of adhesion of Streptococcus sanguis CH3 from suspension to polymers with different surface free energies were studied by using three bacterial concentrations (2.5 X 10(7), 2.5 X 10(8), and 2.

Structural properties of fibrillar proteins isolated from the cell surface and cytoplasm of Streptococcus salivarius (K+) cells and nonadhesive mutants.

Most Streptococcus salivarius (K+) cells contain two protein antigens with different adhesive functions. The subcellular distribution and some structural properties of purified proteins were studied. Antigen B (AgB), a protein involved in interbacterial coaggregation with gram-negative bacteria, was present in the cell wall fraction only of the wild-type strain and was absent from the cells of a nonadhesive mutant.

Negative staining and immunoelectron microscopy of adhesion-deficient mutants of Streptococcus salivarius reveal that the adhesive protein antigens are separate classes of cell surface fibril.

The subcellular distribution of the cell wall-associated protein antigens of Streptococcus salivarius HB, which are involved in specific adhesive properties of the cells, was studied. Mutants which had lost the adhesive properties and lacked the antigens at the cell surface were compared with the parent strain. Immunoelectron microscopy of cryosections of cells labeled with affinity-purified, specific antisera and colloidal gold-protein A complexes was used to locate the antigens.