Effect of lysozyme on glucose fermentation, cytoplasmic pH, and intracellular potassium concentrations in Streptococcus mutans 10449

DexA70, the Truncated Form of a Self-Produced Dextranase, Effectively Disrupts Streptococcus mutans Biofilm

Billions of people suffer from dental caries every year in spite of the effort to reduce the prevalence over the past few decades. Streptococcus mutans is the leading member of a specific group of cariogenic bacteria that cause dental caries. S. mutans forms biofilm, which is highly resistant to harsh environment, host immunity, and antimicrobial treatments. In this study, we found that S. mutans biofilm is highly resistant to both antimicrobial agents and lysozyme. DexA70, the truncated form of DexA (amino acids 100–732), a dextranase in S. mutans, prevents S. mutans biofilm formation and disassembles existing biofilms within minutes at nanomolar concentrations when supplied exogenously. DexA70 treatment markedly enhances biofilm sensitivity to antimicrobial agents and lysozyme, indicating its great potential in combating biofilm-related dental caries.

Rubidium-containing mesoporous bioactive glass scaffolds support angiogenesis, osteogenesis and antibacterial activity

In this study, rubidium-containing mesoporous bioglass (Rb-MBG) scaffolds were formed with the investigation of the influence of Rb addition on angiogenic and osteogenic differentiation abilities of hBMSC. The phase composition, microstructure, pore size distribution, ion release, biological activity, drug loading rate, and release rate of Rb-MBG were characterized. The proliferation and differentiation of hBMSC, the markers of bone formation (ALP, COL-1) and angiogenesis (VEGF, HIF-1α), and wnt/β-catenin related-signaling pathway gene were studied by cell culture. Rb-MBG loaded with antibacterial agents enoxacin (ENX), coliforms and Staphylococcus aureus were cultured together to study the antibacterial effects. The results indicate that the samples have a 350-550 μm large pore structure and 4.5-5.5 nm mesoporous size. Adding Rb can increase the activity of ALP, the secretion of VEGF and COLI, and the expression of HIF-1α of hBMSCs. Rb containing MBG is likely to enhance the proliferation and differentiation of hBMSCs through the influence of Wnt/ß-catenin signal path. Rb-MBG scaffold can load effectively and release Rb ions and ENX continuously to damage the bacterial cell membrane with the synergistic effect, and therefore achieve antibacterial results. In conclusion, adding Rb to MBG supports angiogenesis and osteogenesis of hBMSCs, as well as antibacterial activity.

Capacity of a hydroxyapatite-lysozyme combination against Streptococcus mutans for the treatment of dentinal caries

Background:

One current strategy for the treatment of carious lesions is the use of biomaterials with antimicrobial activity.

Aims:

The aim of this study was to evaluate a combination of hydroxyapatite and lysozyme for the treatment of dentinal caries by measuring Streptococcus mutans counts before carious tissue sealing, and 24 h, 1 month, and 6 months after treatment.

Materials and Methods:

Forty permanent third molars were selected, and flat dentin surfaces were prepared. The teeth were exposed to a cariogenic challenge with S. mutans. After challenge, the dentinal caries were collected from five specimens. The remaining specimens were treated with a mixture of hydroxyapatite and lysozyme in sodium laureth sulfate and sealed with composite resin. S. mutans counts were obtained 24 h, 1 month, and 6 months after sealing.

Statistical Analysis:

The results were evaluated by descriptive statistics and Wilcoxon signed-rank test.

Results:

a significant reduction in S. mutans (CFU/mL) was observed in dentinal lesions 1 month after treatment with hydroxyapatite/lysozyme in sodium laureth sulfate (P = 0.0254). Comparison of S. mutans counts obtained 24 h, 1 month, and 6 months after treatment revealed reductions only at the 1-month time point (P = 0.0318).

Conclusions:

the combination of hydroxyapatite and lysozyme may be an alternative for reducing the S. mutans burden in dentinal caries.

Innate Humoral Defense Factors

Although innate immunity came into the research spotlight in the late 1990s when its instructive role in the adaptive immune response was recognized, innate humoral defense factors have a much older history. The exocrine secretions of the body contain a plethora of distinct soluble factors (lysozyme, lactoferrin, peroxidases, proline-rich proteins, histatins, etc.) that protect the body from mucosal microbial pathogens. More recent studies have established that the humoral arm of innate immunity contains a heterogeneous group of pattern-recognition molecules (e.g., pentraxins, collectins, and ficolins), which perform diverse host-defense functions, such as agglutination and neutralization, opsonization, control of inflammation, and complement activation and regulation. These pattern-recognition molecules, which act as functional predecessors of antibodies (“ante-antibodies”), and the classic soluble innate defense factors form an integrated system with complementary specificity, action, and tissue distribution, and they are the subject of this chapter.

Antibacterial activity of licochalcone A against spore-forming bacteria

Licochalcone A was isolated from the roots of licorice, Glycyrrhiza inflata, which has various uses in the food and pharmaceutical industries; isolation was followed by extraction with ethanol and column chromatography with silica gel. In this study, the activities of licochalcone A against some food contaminant microorganisms were evaluated in vitro. The vegetative cell growth of Bacillus subtilis was inhibited in a licochalcone A concentration-dependent manner and was completely prevented by 3 micrograms of licochalcone A/ml. Licochalcone A showed a high level of resistance to heating at 80 to 121 degrees C for 15 min. Licochalcone A did not inhibit the germination of heat-treated spores of B. subtilis induced by L-alanine. Licochalcone A showed effects against all gram-positive bacteria tested and especially was effective against all Bacillus spp. tested, with MICs of 2 to 3 micrograms/ml, but was not effective against gram-negative bacteria or eukaryotes at 50 micrograms/ml. Although the cationic antimicrobial peptides protamine and epsilon-poly-L-lysine resulted in the loss of antimicrobial activity in the presence of either 3% (wt/vol) NaCl or protease at 20 micrograms/ml, the antibacterial activity of licochalcone A was resistant to these conditions. Thus, licochalcone A could be a useful compound for the development of antibacterial agents for the preservation of foods containing high concentrations of salts and proteases, in which cationic peptides might be less effective.

Effects of pH, potassium, magnesium, and bacterial growth phase on lysozyme inhibition of glucose fermentation by Streptococcus mutans 10449

The effects of physiological (saliva and plaque fluid) concentrations of potassium and magnesium and growth phase on lysozyme inhibition of glucose fermentation by S. mutans 10449 were investigated. Glucose fermentations were carried out in a pH-stat at pH 7.0 or 5.5. Cells were at least two times more sensitive to lysozyme in the early-to-middle exponential phase compared with the stationary phase. S. sobrinus 6715 exhibited three-fold greater lysozyme resistance than S. rattus BHT or S. mutans 10449. The concentration of potassium which reduced lysozyme inhibition of S. mutans 10449 fermentation by 50% was 0.2 and 10 mmol/L for stationary and exponential phase cells, respectively. Corresponding values for magnesium were < or = 0.01 and 0.50 mmol/L. Potassium and magnesium exhibited little pH dependence in their reduction of lysozyme inhibition of fermentation by exponential- or stationary-phase S. mutans 10449. The results suggest that: (i) lysozyme interaction with stationary-phase cells involves more non-inhibitory modes than with exponential-phase cells, and (ii) lysozyme may be more effective as an antibacterial agent in saliva than in plaque fluid.

Acquisition of manganous ions by mutans group streptococci

The cariogenic bacteria Streptococcus sobrinus and S. cricetus were shown to have an absolute requirement for manganous ion in order to bind glucans or to adhere to glass in the presence of sucrose. The bacteria possessed a reasonably high affinity transport system for 54Mn2+, yielding a Km of about 12 microM. The Vmax for uptake of 54Mn2+ in S. sobrinus was increased when the bacteria were grown in Mn-depleted medium, but the Km remained the same. There was no evidence for two Mn2+ uptake systems, commonly observed for many bacteria. Ions such as Ca2+, Co2+, Co3+, Cu2+, Fe2+, Fe3+, Hg2+, Mg2+, Ni2+, and Zn2+ did not inhibit the uptake of 54Mn2+ by the bacteria, although Cd2+ was a potent inhibitor. Fractionation experiments showed that manganese was distributed in protoplasts (67%) and in the cell wall (33%). Approximately 80% of the 54Mn2+ in S. sobrinus was rapidly exchangeable with nonradioactive Mn2+. Electron spin resonance experiments showed that all of the manganese was bound or restricted in mobility. Proton motive force-dissipating agents increased the acquisition of 54Mn2+ by the streptococci, probably because the wall became more negatively charged when the cell could no longer produce protons.

Lysozyme enhances the inhibitory effects of the peroxidase system on glucose metabolism of Streptococcus mutans

The combined effect of the salivary peroxidase system and lysozyme on the glucose uptake of Streptococcus mutans NCTC 10449 was investigated. The bacteria were grown to late-exponential phase, washed, re-suspended in buffer at pH6, and incubated with (1) 50 micrograms/mL lysozyme from human milk for 60 min; (2) 7-15 mumol/L hypothiocyanous acid/hypothiocyanite for 10 min; and (3) lysozyme for 60 min prior to addition of and incubation with hypothiocyanous acid/hypothiocyanite for 10 min. Glucose uptake was initiated by adding the bacterial suspensions to 10 mL of pre-warmed 50 mumol/L glucose containing 0.98 mumol/L D-(U-14C-)-glucose, and the mixture was incubated in a shaking water-bath at 37 degrees C. Samples were withdrawn at various time intervals, rapidly filtered through 0.45-microns membranes, washed with ice-chilled buffer, and the incorporated radioactivity determined. Lysozyme stimulated S. mutans glucose uptake slightly, but significantly inhibited S. rattus glucose metabolism. A 20-30% inhibition of radiolabeled glucose incorporation was observed with hypothiocyanous acid/hypothiocyanite alone. Incubation of the bacteria with lysozyme prior to addition of hypothiocyanous acid/hypothiocyanite containing peroxidase resulted in a total inhibition of the glucose uptake. In contrast, lysozyme in combination with hypothiocyanous acid/hypothiocyanite without peroxidase gave only a 30-50% inhibition. The addition of 5 mmol/L dithiothreitol after incubation with lysozyme and hypothiocyanous acid/hypothiocyanite eliminated the inhibition of the bacterial glucose uptake. The viability of S. mutans was not affected by treatment with any of the components used. Our results indicate that physiological concentrations of lysozyme and the salivary peroxidase system components have a synergistic effect which results in a significant inhibition of glucose metabolism by S. mutans.