We examined the effects of human whole salivary supernatant and parotid fluid on glucose uptake by Streptococcus mutans, Streptococcus sanguis, Streptococcus mitis, Actinomyces viscosus, Staphylococcus aureus , and Escherichia coli. The following three effects of saliva were observed: (i) inhibition of glucose uptake ( S. mutans, S. sanguis ), (ii) promotion of a transient, rapid (0 to 30 s) burst of glucose uptake ( S. mutans, S. sanguis ), and (iii) enhancement of glucose uptake ( S. mitis, A. viscosus, S. aureus, E. coli ). We observed no differences between the effects of whole salivary supernatant and the effects of parotid fluid. Heat treatment (80°C, 10 min) of saliva or the addition of dithiothreitol abolished inhibition of glucose uptake. Supplementation of saliva with H 2 O 2 potentiated inhibition of glucose uptake. S. mitis and A. viscosus , which were stimulated by saliva alone, were inhibited by H 2 O 2 -supplemented saliva; 50% inhibition of glucose uptake by S. mutans and S. mitis required ca. 10 μM H 2 O 2 in 50% (vol/vol) saliva. Loss of the inhibitory action of saliva occurred at about 5% (vol/vol) saliva. Supplementation of saliva dilutions with SCN − and H 2 O 2 extended the inhibitory activity to solutions containing ca. 0.2% (vol/vol) saliva. We suggest that the salivary lactoperoxidase-SCN − -H 2 O 2 system is responsible for the inhibitory activity of saliva reported here. Furthermore, we concluded that lactoperoxidase and SCN − are present in saliva specimens in concentrations that exceed minimal inhibitory levels by factors of ca. 500 and 10 to 20, respectively. The resistance of A. viscosus, S. aureus , and E. coli to the inhibitory potential of saliva alone was probably due to the production of catalase by these organisms. The resistance of S. mitis may have been due to special effects of saliva on H 2 O 2 accumulation by this organism compared with S. mutans and S. sanguis. The basis of saliva-dependent enhancement of glucose uptake and the basis of promotion of a transient, rapid burst of glucose uptake are unknown. The role of the salivary lactoperoxidase-SCN − -H 2 O 2 system in the oral microbial ecosystem is discussed.

The adherence of [3H]thymidine-labeled Streptococcus sanguis strains to bare hydroxyapatite and to hydroxyapatite coated with a range of concentrations of lysozyme, poly-L-lysine, poly-L-glutamic acid, whole saliva supernatant, and combinations of some of the above was studied. Adherence of several strains of S. sanguis to bare hydroxyapatite and saliva-coated hydroxyapatite was compared. Saliva present as a pellicle on the hydroxyapatite inhibited adherence of some strains (903, M-5, 73X11) and stimulated that of others (S35, B-4, 66X49). Strains 903 and S35 were chosen for further study. Adherence of both strains was stimulated up to fivefold by the presence of adsorbed lysozyme or poly-L-lysine on the hydroxyapatite, whereas poly-L-glutamic acid inhibited adherence (80 to 95%). Adherence of strain S35 to hydroxyapatite coated with combinations of saliva and (i) lysozyme, (ii) poly-L-lysine, or (iii) poly-L-glutamic acid was unaffected compared with adherence to hydroxyapatite coated with saliva alone. In contrast, adherence of strain 903 to hydroxyapatite coated with combinations of saliva and either lysozyme or poly-L-lysine was inhibited up to ca. 90% compared with hydroxyapatite coated with saliva alone. Strain 903 was also unaffected by combinations of poly-L-glutamic acid and saliva on the hydroxyapatite. Adherent cells of both strains were completely (greater than 90%) eluted with high-ionic-strength buffer from either bare hydroxyapatite or hydroxyapatite coated with lysozyme alone. Adherent cells of strain S35 were only poorly eluted (25%) from hydroxyapatite coated with either saliva alone or saliva and lysozyme. Strain 903 elution from hydroxyapatite coated with either saliva alone or saliva and lysozyme was essentially complete. These observations were taken to indicate that the two test strains adhered to saliva-coated hydroxyapatite by different mechanisms. Protein-coated hydroxyapatite was shown not to be saturated under the conditions described here. Examination by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the variously supplemented salivary pellicles formed on the hydroxyapatite demonstrated that major changes in salivary protein composition did not occur when lysozyme, poly-L-lysine, or poly-L-glutamic acid was used to supplement saliva. Lysozyme-dependent aggregation of strain 903 was shown not to occur under the conditions of our experiments. We suggest that the basis for stimulation of adherence to hydroxyapatite coated only with lysozyme is an increase in the cationic surface area available for electrostatic adherence of the microorganisms.(ABSTRACT TRUNCATED AT 400 WORDS)

A simple and rapid method is described for the removal of lysozyme from human whole salivary supernatant. Saliva specimens were adsorbed with Micrococcus lysodeikticus. The saliva so treated was depleted of 95% of the lysozyme activity. Changes in total protein, lactoperoxidase, lactoferrin, immunoglobulin A, and the proportions of several anionic proteins were less than 10%. It is concluded that adsorption of saliva with M. lysodeikticus is a suitable procedure for the preparation of saliva that is selectively deficient in lysozyme.

Glucose uptake was examined by using whole-cell suspensions of Streptococcus mutans (strains BHT, Ingbritt, and GS-5), Streptococcus mitis (strains 9811 and 72X41), and Actinomyces viscosus (strains T6 and WVU626) incubated for up to 90 min in 0 to 82% (vol/vol) human whole salivary supernatant. Glucose uptake by the S. mutans strains was completely inhibited at all saliva concentrations. Dithiothreitol (DTT), present during saliva incubation, prevented saliva inhibition. Glucose uptake was also restored when saliva-inhibited cells were subsequently exposed to DTT. The inclusion of catalase in the saliva incubation mixtures resulted in protection equal to that obtained with DTT. The S. mitis strains were also inhibited by saliva but to a far lesser extent that S. mutans. DTT and catalase also protected S. mitis from saliva inhibition. Both A. viscosus strains were completely refractory to saliva inhibition of glucose uptake. Based on (i) the sensitivity of the catalase-negative streptococci and the resistance of catalase-positive actinomyces to saliva inhibition and (ii) the equal and complete protection to saliva inhibition afforded by DTT and catalase, we conclude that the lactoperoxidase-SCN-H202 system in saliva was the only antibacterial system expressed under our experimental conditions. The relative resistance of S. mitis 9811 (compared with S. mutans BHT) to saliva inhibition was shown not to result from poor H202 production in either glucose-supplemented buffer or saliva solutions. S. mitis produced inhibitory quantities of H202 that equaled or exceeded S. mutans H202 accumulation. It is suggested that S. mitis might possess a greater ability to repair lactoperoxidase-mediated damage than does S. mutans. Every organism studied exhibited a saliva concentration-dependent, cell growth-independent stimulation of glucose uptake after 60 to 90 min of incubation. The A. viscosus and S. mitis strains showed saliva stimulation (or stabilization) of glucose uptake with unsupplemented saliva. In the case of S. mutans, saliva stimulation was only observed when DTT was present. The possible role of salivary lactoperoxidase as a modulator of the intraoral site specificities exhibited by S. mutans is discussed.

The fluoride (F) sensitivity of glucose uptake by whole cell suspensions of Streptococcus mutans in the presence and absence of human whole salivary supernatant was studied. It was observed that dithiothreitol (DTT) and other thiols markedly reduced the F sensitivity of cells when saliva (50%, vol/vol) was present during glucose uptake. In the absence of saliva, cells were sensitive to 2 to 2.5 mM F regardless of the presence of thiols. Supplementation of cells in phosphate or tris(hydroxymethyl)aminomethane-hydrochloride buffers with physiological concentrations of calcium or phosphate had no effect on the F sensitivity of the organism. Experiments with permeabilized cells suggested that thiols themselves had no direct effect on the F sensitivity of enolase (a principal F target). Cells pretreated with DTT subsequently exhibited decreased F sensitivity when examined in the presence of saliva but not in the absence of saliva. Cells pretreated with whole salivary supernatant were found to be subsequently less sensitive to F in the absence of saliva during glucose uptake. Furthermore, in cases where cells were pretreated with saliva, subsequent additions of DTT were unnecessary to obtain maximal reduction in the F sensitivity of glucose uptake. It was concluded that the saliva-dependent reduction in F sensitivity of glucose uptake was not due to sequesteration of available F by salivary constituents. The data suggest that a salivary component(s) interacts directly with the microorganism in some manner which results in reduced F sensitivity of the process under study. Possible mechanisms of saliva action are discussed. 'Dialyzed for 18 h at 4°C against 200 volumes of distilled water. INFECT. IMMUN.