Antibacterial properties of silver-loaded gelatin sponges prepared with silver diamine fluoride

PURPOSE

To evaluate the antibacterial efficiency of silver-loaded gelatin sponges prepared from gelatin and silver diamine fluoride, Ag(NH3)2F.

METHODS

A series of novel silver-loaded gelatin sponges were prepared from gelatin and silver diamine fluoride. They were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The antibacterial activities against one oral bacteria model S. mutans were evaluated using the agar disk diffusion method and biofilm-grown bacteria assay. For the purpose of comparison, a second series of silver-loaded sponges were prepared using silver nitrate (AgNO3) as the silver source.

RESULTS

FT-IR, SEM and EDX results confirmed the successful preparation of silver-loaded gelatin sponges from both silver diamine fluoride and silver nitrate. Agar disk diffusion assays revealed that the antibacterial activity of silver-loaded sponges was strongly correlated with the silver content, and also depending on the silver source used in the preparation of sponges. Sustained inhibition of S. mutans in agar plates was observed for silver-loaded gelatin sponges containing about 5 wt% Ag or more. Biofilm assays showed different viabilities when treated with different formulations, with the viability of 11.4±3.1% for the sponges containing 5.30±1.18 wt% Ag prepared from silver diamine fluoride, and the viability of 15.4±3.1% for the sponges containing 29.13±10.34 wt% Ag prepared from silver nitrate.

CLINICAL SIGNIFICANCE

The silver loading contents had a significant effect on the antibacterial activities of silver-loaded gelatin sponges prepared with silver diamine fluoride. In addition, silver diamine fluoride was a superior silver source to prepare antibacterial silver-loaded gelatin sponges when compared with silver nitrate.

Modified Polymeric Nanoparticles Exert In Vitro Antimicrobial Activity Against Oral Bacteria

Polymeric nanoparticles were modified to exert antimicrobial activity against oral bacteria. Nanoparticles were loaded with calcium, zinc and doxycycline. Ions and doxycycline release were measured by inductively coupled plasma optical emission spectrometer and high performance liquid chromatography. Porphyromonas gingivalis, Lactobacillus lactis, Streptoccocus mutans, gordonii and sobrinus were grown and the number of bacteria was determined by optical density. Nanoparticles were suspended in phosphate-buffered saline (PBS) at 10, 1 and 0.1 mg/mL and incubated with 1.0 mL of each bacterial suspension for 3, 12, and 24 h. The bacterial viability was assessed by determining their ability to cleave the tetrazolium salt to a formazan dye. Data were analyzed by ANOVA and Scheffe’s F (p < 0.05). Doxycycline doping efficacy was 70%. A burst liberation effect was produced during the first 7 days. After 21 days, a sustained release above 6 µg/mL, was observed. Calcium and zinc liberation were about 1 and 0.02 µg/mL respectively. The most effective antibacterial material was found to be the Dox-Nanoparticles (60% to 99% reduction) followed by Ca-Nanoparticles or Zn-Nanoparticles (30% to 70% reduction) and finally the non-doped nanoparticles (7% to 35% reduction). P. gingivalis, S. mutans and L. lactis were the most susceptible bacteria, being S. gordonii and S. sobrinus the most resistant to the tested nanoparticles.

Effects of atmospheric non-thermal argon/oxygen plasma on biofilm viability and hydrophobicity of oral bacteria

PURPOSE

To evaluate the bactericidal effects of atmospheric non-thermal argon/oxygen plasma on in vitro oral biofilms constructed from S. mutans and/or S. sanguinis, and the influence of the plasma on the virulence properties of A. oris.

METHODS

In vitro oral biofilms were constructed in the wells of 48-well plates from S. mutans and/or S. sanguinis. The wells containing constructed biofilms and various amounts of phosphate-buffered saline (PBS) were treated with non-thermal argon/oxygen plasma brush for 2 minutes. The methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay and Live/Dead assay were used to evaluate the viability of biofilms in those wells after the plasma treatments. Meanwhile, A. oris suspensions were treated with the plasma and then evaluated for their virulence properties by measuring the hydrophobicity and co-aggregation capability of treated A. oris.

RESULTS

The MTT assay showed that exposure to non-thermal plasma for 2 minutes significantly reduced the viability of bacteria in both single-species and two-species biofilms of S. mutans and S. sanguinis with the reductions of up to 99%. Meanwhile, plasma treatment also altered the hydrophobicity of A. oris, and reduced their capability to co-aggregate with S. sanguinis.

CLINICAL SIGNIFICANCE

The results from this study demonstrated that atmospheric non-thermal argon/oxygen plasma could effectively deactivate oral bacteria biofilm by decreasing bacterial viability as well as reducing their hydrophobicity and co-aggregation capability.

Efficacy of 4 Irrigation Protocols in Killing Bacteria Colonized in Dentinal Tubules Examined by a Novel Confocal Laser Scanning Microscope Analysis

INTRODUCTION

The aim of this study was to determine the efficiency of 4 irrigation systems in eliminating bacteria in root canals, particularly in dentinal tubules.

METHODS

Roots of human teeth were prepared to 25/04, autoclaved, and inoculated with Enterococcus faecalis for 3 weeks. Canals were then disinfected by (1) standard needle irrigation, (2) sonically agitating with EndoActivator, (3) XP Endo finisher, or (4) erbium:yttrium aluminum garnet laser (PIPS) (15 roots/group). The bacterial reduction in the canal was determined by MTT assays. For measuring live versus dead bacteria in the dentinal tubules (4 teeth/group), teeth were split open and stained with LIVE/DEAD BackLight. Coronal, middle, and apical thirds of the canal dentin were scanned by using a confocal laser scanning microscope (CLSM) to determine the ratio of dead/total bacteria in the dentinal tubules at various depths.

RESULTS

All 4 irrigation protocols significantly eliminated bacteria in the canal, ranging from 89.6% to 98.2% reduction (P < .001). XP Endo had the greatest bacterial reduction compared with other 3 techniques (P < .05). CLSM analysis showed that XP Endo had the highest level of dead bacteria in the coronal, middle, and apical segments at 50-μm depth. On the other hand, PIPS had the greatest bacterial killing efficiency at the 150-μm depth in all 3 root segments.

CONCLUSIONS

XP Endo appears to be more efficient than other 3 techniques in disinfecting the main canal space and up to 50 μm deep into the dentinal tubules. PIPS appears to be most effective in killing the bacteria deep in the dentinal tubules.

Effect of glycated albumin and cranberry components on interleukin-6 and matrix metalloproteinase-3 production by human gingival fibroblasts

BACKGROUND AND OBJECTIVE

Gingival fibroblasts have the potential to participate in periodontal inflammation and breakdown, producing interleukin (IL)-6 and matrix metalloproteinase (MMP)-3. Advanced glycation end products (AGEs), formed during diabetic hyperglycemia, might aggravate periodontal inflammation. The cranberry contains anti-inflammatory polyphenols, which inhibit proinflammatory activities of lipopolysaccharide (LPS)- and IL-1β-stimulated human cells. Little is known of its effects on gingival fibroblast IL-6 or MMP-3 production stimulated by AGEs. The objectives were to determine cranberry effects on IL-6 and MMP-3 production by gingival fibroblasts exposed to the representative AGE, glycated human serum albumin (G-HSA), or LPS ± G-HSA.

MATERIAL AND METHODS

Cranberry high molecular weight non-dialyzable material (NDM), was derived from cranberry juice. Normal human gingival fibroblasts were incubated with G-HSA or normal HSA or Porphyromonas gingivalis LPS (1 μg/mL) ± G-HSA, in the presence or absence of preincubation with NDM. IL-6 and MMP-3 were measured by enzyme-linked immunosorbent assay. Data were analyzed using one-way analysis of variance and Scheffe's F procedure.

RESULTS

IL-6 production was stimulated by G-HSA or LPS (p < 0.01), which was inhibited in both cases by NDM (p < 0.002). [G-HSA+LPS] synergistically stimulated IL-6 production (p < 0.0001), which was inhibited by NDM. MMP-3 levels were not stimulated by G-HSA but were decreased by LPS (p < 0.02). [G-HSA+LPS] increased MMP-3 production significantly, vs. LPS (p = 0.0005). NDM inhibited MMP-3 levels in the presence of G-HSA or LPS, and in the presence of [G-HSA+LPS] (p < 0.0001).

CONCLUSIONS

G-HSA ± LPS may have differential effects on IL-6 and MMP-3 production by human gingival fibroblasts, but both are inhibited by NDM. The study suggests that cranberry phenols may be useful in regulating the host response and perhaps treating periodontitis in patients with poorly controlled diabetes.

In vitro comparison of commercial oral rinses on bacterial adhesion and their detachment from biofilm formed on hydroxyapatite disks

PURPOSE

This in vitro study was designed to assess the effectiveness of three oral rinses on bacterial adherence to epithelial cells and hydroxyapatite surfaces. The role of oral rinses on the detachment of bacteria from biofilm was also evaluated.

MATERIALS AND METHODS

The efficacy of three oral rinses, Acclean, Noplak and Prevention were tested against a wide range of oral bacteria. Oral rinse antimicrobial activity was determined by an MTT assay for bacterial viability, by live/ dead staining and by measuring the bacterial metabolic activity using an XTT assay.

RESULTS

The two oral rinses that contained 0.12% chlorhexidine had the greatest antibacterial activity on both planktonic and bio lm-grown organisms when compared to the Prevention oral rinse.

CONCLUSION

Both Acclean and Noplak were extremely effective in lowering the number of bacteria attached to buccal epithelial cells and pelllicles. In addition, these two oral rinses were also effective against the biofilm bacteria.

Effects of cranberry components on human aggressive periodontitis gingival fibroblasts

BACKGROUND AND OBJECTIVE

Aggressive periodontitis (AgP) causes rapid periodontal breakdown involving AgP gingival fibroblast production of cytokines [i.e. interleukin (IL)-6, a bone metabolism regulator], and matrix metalloproteinase (MMP)-3. Lipopolysaccharide upregulates fibroblast IL-6 and MMP-3, via transcription factors (i.e. NF-κB). Cranberry (Vaccinium macrocarpon) inhibits lipopolysaccharide-stimulated macrophage and normal gingival fibroblast activities, but little is known of its effects on AgP fibroblasts. Objectives of this study are to use AgP fibroblasts, to determine cytotoxicity of cranberry components or periodontopathogen (Fusobacterium nucleatum, Porphyromonas gingivalis) lipopolysaccharide ± cranberry components, and effects of cranberry components on lipopolysaccharide-stimulated NF-κB activation and IL-6 and MMP-3 production.

MATERIAL AND METHODS

AgP fibroblasts were incubated ≤ 6 d with high molecular weight non-dialyzable material (NDM) (derived from cranberry juice (1-500 μg/mL) or lipopolysaccharide (1 μg/mL) ± NDM. Membrane damage and viability were assessed by enzyme activity released into cell supernatants and activity of a mitochondrial enzyme, respectively. Secreted IL-6 and MMP-3 were measured by ELISA. NF-κB p65 was measured via binding to an oligonucleotide containing the NF-κB consensus site. Data were analyzed using analysis of variance and Scheffe's F procedure for post hoc comparisons.

RESULTS

Short-term exposure to NDM, or lipopolysaccharide ± NDM caused no membrane damage. NDM (≤ 100 μg/mL) or lipopolysaccharide ± NDM had no effect on viability ≤ 7 d exposure. NDM (50 μg/mL) inhibited lipopolysaccharide-stimulated p65 (P ≤ 0.003) and constitutive or lipopolysaccharide-stimulated MMP-3 (P ≤ 0.02). NDM increased AgP fibroblast constitutive or lipopolysaccharide-stimulated IL-6 (P ≤ 0.0001), but inhibited normal human gingival fibroblast IL-6 (P ≤ 0.01).

CONCLUSION

Lack of toxicity of low NDM concentrations, and its inhibition of NF-κB and MMP-3, suggest that cranberry components may regulate AgP fibroblast inflammatory responses. Distinct effects of NDM on AgP and gingival fibroblast production of IL-6 (which can have both positive and negative effects on bone metabolism) may reflect phenotypic differences in IL-6 regulation in the two cell types.

Inhibition of neutrophil and monocyte defensive functions by nicotine

To learn more about the effects of smokeless tobacco on the defensive functions of neutrophils, we studied the influence of nicotine on these cells in vitro, looking at their bactericidal activity against oral pathogens, and at their ability to produce microbicidal reactive oxygen species (oxygen radicals). Exposure of human blood neutrophils to nicotine (0.01% to 0.1%) inhibited their ability to kill Actinomyces naeslundii, Actinobacillus actinomycetemcomitans, and Fusobacterium nucleatum. Although these concentrations of nicotine are high, such concentrations are relevant to phagocytes in the gingival sulcus, because smokeless tobacco contains 0.5% to 3.5% nicotine by dry weight. Nicotine had no such inhibitory effect when the killing assay was performed in an anaerobic environment, implying that nicotine preferentially affected oxygen-dependent killing mechanisms. To further investigate the effects of nicotine on production of oxygen radicals, neutrophils were primed with lipopolysaccharide and triggered with f-met-leu-phe or phorbol ester in the presence of nicotine. Nicotine inhibited production of superoxide anion (measured by reduction of cytochrome c) and hydrogen peroxide (measured by oxidation of phenol red). Nicotine inhibition of superoxide production was reversible by washing away the nicotine. By observing that nicotine inhibited the reduction of cytochrome c by reagent potassium superoxide, we determined that nicotine directly absorbed superoxide. In addition, by examining nicotine inhibition of the uptake of oxygen by neutrophils, we determined that nicotine also interfered with the production of oxygen radicals by these cells. Nicotine also inhibited production of superoxide and interleukin-1 beta by monocytes. Nicotine did not affect the viability of neutrophils and monocytes, as determined by their ability to exclude trypan blue dye. Inhibition of the aerobic antimicrobial functions of neutrophils and monocytes by nicotine may alter the microbial ecology of the oral cavity, and this might be one mechanism by which nicotine compromises the oral health of users of tobacco products.

Attachment of Fusobacterium nucleatum to fibronectin immobilized on gingival epithelial cells or glass coverslips

To learn more about colonization of the oral epithelium by Fusobacterium nucleatum and the role of fibronectin in mediating adhesion of this microorganism, we studied attachment of this bacterium to cultured gingival epithelial cells that were coated with exogenous, purified plasma fibronectin. The three strains of F. nucleatum studied adhered in large numbers to epithelial cells that had been coated with fibronectin, compared with buffer-coated control cells. Bacterial adherence was also enhanced when epithelial cells were coated with whole human saliva. However, cells coated with saliva depleted of fibronectin did not facilitate adhesion of bacteria. Bacterial adhesion was restored when purified fibronectin was added back. We also tested adherence of bacteria to coverslips coated with fibronectin, saliva, and saliva depleted of fibronectin. The bacteria adhered to coverslips coated with fibronectin or whole human saliva, but did not adhere to coverslips coated with fibronectin-depleted saliva. Bacterial adhesion to coverslips was restored upon addition of purified fibronectin to the fibronectin-depleted saliva. Bacterial attachment to fibronectin-coated coverslips was found to be temperature-dependent, with maximal adhesion observed at 37 degrees C. Pre-treatment of F. nucleatum with soluble fibronectin inhibited attachment of the bacteria by 92%, whereas pre-treatment with bovine serum albumin had no effect. Pre-treatment of bacteria with laminin or type IV collagen caused moderate inhibition of attachment by 60% and 50%, respectively. Treatment of fibronectin-coated coverslips with Fab fragments of anti-fibronectin IgG blocked the attachment of F. nucleatum by 93%. Fab fragments of the other antisera tested had no inhibitory effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Corrected formula for estimating peripheral blood flow by impedance plethysmography

In this paper, the limitations of the conventional formula for the computation of peripheral blood flow from impedance plethysmograms are highlighted, and a correction to the formula is suggested. A conductivity cell experiment is described to show the dependence of the value of the blood flow index (BFI), obtained from the conventional formula, on the mean resistivity of the cell. It is also shown that the value of the corrected BFI is independent of the mean resistivity. Anomalies observed in the amplitude of systolic waves in impedance plethysmograms of patients with oedema are explained.

Glycerol-induced unraveling of the tight helical conformation of Escherichia coli type 1 fimbriae

Glycerol was found to unravel the helical conformation of Escherichia coli type 1 fimbriae without appreciable depolymerization. The linearized fimbrial polymers have a diameter of 2 nm, react strongly with a monoclonal antibody directed at an inaccessible epitope on native fimbriae, and display greater mannose-binding activity and trypsin sensitivity than native fimbriae. Removal of glycerol by dialysis results in spontaneous reassembly of the linear polymers into structures morphologically, antigenically, and functionally indistinguishable from native fimbriae.

Isolation and characterization of a 180-kiloDalton salivary glycoprotein which mediates the attachment of Actinomyces naeslundii to human buccal epithelial cells

The adherence of Actinomyces naeslundii to human buccal mucosa is mediated by specific interactions between the bacterial cell surface fimbriae and complementary beta-linked galactoside receptors on the epithelial cell surface. The buccal mucosa and the bacteria that colonize its surface are constantly bathed in saliva. Several salivary components are thought to play an important role in modulating adhesive interactions between oral bacteria and the buccal epithelium. We have observed that pretreatment of isolated buccal epithelial cells (BEC) with human parotid saliva increased the attachment of three different strains of A. naeslundii. By employing affinity chromatography, ion-exchange and high-pressure liquid chromatographic techniques we have isolated a 180 kDa A. naeslundii-binding salivary glycoprotein (An-SPG). This salivary glycoprotein was capable of mediating separate but specific binding interactions with A. naeslundii and BEC. Pretreatment of BEC with increasing amounts of An-SGP resulted in a corresponding increase in the attachment of A. naeslundii. The adherence of A. naeslundii to An-SGP-coated BEC is sensitive to the same inhibitors previously shown to block adherence of A. naeslundii to uncoated BEC, namely lactose- and galactosyl-binding lectins. When a solubilized extract of freshly isolated and washed BEC was reacted on a Western blot with antibodies to An-SGP, a prominent 180 kDa immunoreactive band was detected. Furthermore, the immunoreactive component was demonstrated on the BEC surface when assayed by immunofluorescence using An-SGP-specific antibodies, suggesting that An-SGP or a protein structurally and immunologically identical to the isolated glycoprotein is present on BEC.

Diagnosis of peripheral arterial occlusive diseases using impedance plethysmography

Impedance plethysmographic observations have been compared with arteriographic findings in 216 patients with peripheral arterial occlusive diseases. Impedance plethysmographic diagnosis in these patients was obtained by Parulkar's method without apriori knowledge of arteriographic diagnosis. But for minor discrepancy in the anatomical location of the block in few patients, impedance plethysmographic observations correlated very well with arteriographic findings. Impedance plethysmographic diagnosis was found to be correct in 312, wrong in 53, false negative in 8 limbs respectively, yielding a sensitivity of 97.5% and specificity of 98.1% of this technique.

Impedance plethysmography: basic principles

Impedance Plethysmography technique has been discussed with explanation of two compartment model and parallel conductor theory for the estimation of peripheral blood flow and stroke volume. Various methods for signal enhancement to facilitate computation of blood flow are briefly described. Source of error in the estimation of peripheral blood flow is identified and the correction has been suggested.

Technical aspects of impedance plethysmography

This paper describes the basic methods for measurement of body impedance, electrodes and their configuration, and the measuring instrument with its limitations. A microcomputer assisted impedance plethysmograph system, developed at BARC and different lead configurations for impedance plethysmographic investigation are also described. Typical impedance plethysmographic waveforms recorded from a normal subject and measurement of their amplitude and various time intervals are illustrated.

Interaction of a 60-kilodalton D-mannose-containing salivary glycoprotein with type 1 fimbriae of Escherichia coli

A 60-kilodalton glycoprotein previously isolated and purified from human saliva (J. B. Babu, E. H. Beachey, D. L. Hasty, and W. A. Simpson, Infect. Immun. 51: 405-413, 1986) was found to interact with type 1 fimbriae and prevent adhesion of type 1 fimbriated Escherichia coli to animal cells in a D-mannose-sensitive manner. Purified salivary glycoprotein agglutinated type 1 fimbriated E. coli and, at subagglutinating concentrations, blocked the ability of type 1 fimbriated E. coli to attach to human buccal epithelial cells or agglutinate guinea pig erythrocytes. Both interactions were inhibited by alpha-methyl-D-mannoside but not by alpha-methyl-D-glucoside. Complexing of the glycoprotein to type 1 fimbriae was demonstrated by molecular sieve chromatography and modified Western blots. When mixed with type 1 fimbriae, the radiolabeled salivary glycoprotein coeluted with type 1 fimbriae from a column of Sepharose 4B. When blotted from a sodium dodecyl sulfate gel to nitrocellulose sheets, the glycoprotein interacted directly with type 1 fimbriae applied to the blots. Both of the latter interactions also were blocked by alpha-methyl-D-mannoside but not by alpha-methyl-D-glucoside. Chemical modification of the glycoprotein with sodium metaperiodate abolished its ability to interact with isolated type 1 fimbriae or type 1 fimbriated E. coli. These results suggest that the carbohydrate moiety of the 60-kilodalton glycoprotein serves as a receptor for type 1 fimbriae in the oral cavity, and we postulate that the interaction may cause agglutination and early removal of E. coli, thereby preventing colonization by these organisms of oropharyngeal mucosae and dental tissues.

Interaction of salivary fibronectin with oral streptococci

Immunoreactive Fibronectin (Fn) has been demonstrated in stimulated human parotid saliva by western blot analysis and also found to be a component of the artificial tooth pellicles derived from hydroxyapatite (HA) beads coated with parotid saliva. Saliva depleted of gelatin-binding components showed a significantly lower degree of reactivity with anti-Fn antibodies than did the control saliva when tested by and enzyme-linked immunosorbent assay (ELISA). Depletion of gelatin-binding components from saliva was also found to affect the degree of saliva-mediated aggregation of four of the seven oral streptococci tested [Streptococcus mutans strains GS-5 and OMZ 176, S. sobrinus, and S. rattus]. Similarly, the adherence of the same four micro-organisms to the artificial tooth pellicles (derived form saliva which had previously been depleted of gelatin-binding component) was significantly inhibited (37-53%) when compared with the control saliva-coated HA beads. Pre-treatment of streptococci with 100 micrograms of soluble Fn also caused a 34-57% inhibition of adherence of the same oral streptococci to saliva-treated HA beads. Quantitation of Fn in human parotid saliva showed that the amounts of immunoreactive Fn varied form 2 to 6 micrograms/mL of parotid saliva. Furthermore, the Fn from parotid saliva was found to be adsorbed onto the bacterial surfaces, as demonstrated by immunofluorescence and ELISA. The presence of Fn in parotid saliva and its ability to bind to HA beads (artificial pellicles), in conjunction with the ability of soluble Fn to inhibit the adherence of streptococcal strains to the artificial tooth pellicles, suggest that the microbial ecology of the oral cavity may, in part, be influenced by the interactions mediated by salivary fibronectin.

Inhibition of the interaction of Streptococcus sanguis with hexadecane droplets by 55- and 60-kilodalton hydrophobic proteins of human saliva

The effect of salivary secretions on the hydrophobicity of Streptococcus sanguis was investigated. Pretreatment of the bacteria with paraffin-stimulated whole saliva resulted in a 79% inhibition of adhesion to hexadecane droplets. Column chromatography on Sepharose 4B and sodium dodecyl sulfate gel electrophoretic analysis indicated that the inhibitory activity of saliva resided in a fraction containing material of approximately 60,000 molecular weight. The active components, which we have termed the hydrophobic components (HC), bind to octyl-Sepharose beads. Pretreatment of S. sanguis with HC resulted in a dose-dependent inhibition of the streptococcus-hexadecane interaction that reached a maximum of 85%. Furthermore, HC effectively blocked the ability of S. sanguis to adhere to hydroxyapatite beads coated with either whole saliva or HC. Sodium dodecyl sulfate-polyacrylamide gel analysis indicated that HC eluted from octyl-Sepharose consisted primarily of two proteins (60 kDa and 55 kilodaltons) which could be resolved by high-pressure liquid chromatography. Both of these proteins were able to inhibit the binding of S. sanguis to hexadecane in a dose-dependent manner; however, the 60-kilodalton molecule was slightly more effective in this assay. Amino acid analysis of these proteins showed that both proteins contained a high percentage of nonpolar amino acids. These findings suggest that certain components of saliva influence the interaction of S. sanguis with hydrophobic surfaces.

Isolation and characterization of a 60-kilodalton salivary glycoprotein with agglutinating activity against strains of Streptococcus mutans

A bacterial agglutinin specific for strains of Streptococcus mutans was isolated from human saliva. Physiochemical analyses showed the agglutinin to be a glycoprotein with a molecular weight of 60,000. The agglutinin aggregated four of the eight strains of Streptococcus mutans tested but did not aggregate the strains of Streptococcus salivarius, Streptococcus sanguis, and Streptococcus mitis tested. Chemical modification of carbohydrate moieties of the agglutinin with sodium metaperiodate had no effect on aggregation, whereas modification of the polypeptide portion with trypsin abolished aggregating activity. A set of five murine hybridoma antibodies was employed to further analyze the agglutinin. Two carbohydrate-specific antibodies, directed against D-mannose and N-acetylgalactosamine moieties, respectively, failed to block agglutinin- or whole saliva-mediated aggregation of S. mutans cells. In contrast, two antibodies directed against pronase-sensitive antigenic sites blocked both agglutinin- and saliva-mediated aggregation of S. mutans cells. Western blot analysis with the agglutinin-specific hybridoma antibodies demonstrated the agglutinin in whole saliva and in artificial tooth pellicles formed on hydroxyapatite beads incubated with saliva. These results suggest that a 60-kilodalton glycoprotein of human saliva is a bacterial agglutinin with specificity for certain strains of S. mutans. They further suggest that aggregation is mediated by polypeptide rather than carbohydrate determinants of the glycoprotein.

Protection against Escherichia coli-induced urinary tract infections with hybridoma antibodies directed against type 1 fimbriae or complementary D-mannose receptors

Hybridoma antibodies directed against quaternary structural epitopes of the type 1 fimbrial adhesin of Escherichia coli or against D-mannose, the sugar determinant in the complementary host cell receptor, prevented the attachment of mannose-sensitive E. coli to various eucaryotic cells. Passive intraperitoneal administration of the fimbria-specific or D-mannose-specific antibodies protected mice against retrograde colonization with mannose-sensitive E. coli instilled into their urinary bladders. Monoclonal antibodies directed against fimbrial subunits rather than quaternary structural epitopes or against N-acetylgalactosamine rather than D-mannose residues lacked protective activity. These studies provide evidence that bacterial colonization can be blocked or interrupted by antibodies directed against either the adhesin or the complementary host cell receptor of pathogenic microorganisms.

New type of oxygenase involved in the metabolism of propane and isobutane

Nocardia paraffinicum (Rhodococcus rhodochrous), a hydrocarbon-degrading microorganism, was used in a study of propane and isobutane metabolism. The bacterium was able to utilize propane or isobutane as a sole source of carbon, and oxygen was found to be essential for its metabolism. Gas chromatographic analysis showed that n-propanol was the major compound recovered from the metabolism of propane by resting cells, although trace amounts of isopropanol and acetone were detected. When a mixture of propane and isobutane was used, drastic inhibition (72 to 88%) of hydrocarbon utilization by resting cells occurred. The ratio of hydrocarbon to oxygen consumed was found to be approximately 2:1 during the metabolism of propane or isobutane by resting cells when these substrates were provided individually to the organism. Gas chromatographic-mass spectrometric analysis of products formed from O(2) confirmed that the initial oxidative step in the metabolism of these substrates involved molecular oxygen. The proportion of the alcohol containing O was the same as that of O(2) in the gas mixture. Only a negligible amount of O was detected in the alcohol when H(2)O was incorporated into the system. The observed 2:1 ratio of hydrocarbon to oxygen consumption suggests that the oxygenase in N. paraffinicum, unlike the conventional mono- or dioxygenases, requires two hydrocarbon-binding sites for each of the oxygen-binding sites and is therefore an intermolecular dioxygenase. The newly described oxygenase, which catalyzes the reaction of two molecules of propane with one molecule of oxygen to yield two molecules of a C(3) alcohol, is proposed as the initial oxidation step of the hydrocarbon substrate.

Interaction of human plasma fibronectin with cariogenic and non-cariogenic oral streptococci

The interaction of purified human plasma fibronectin (Fn) with bacteria was studied with a variety of oral streptococci. Each of the strains of Streptococcus mutans, Streptococcus salivarius, Streptococcus sanguis, and Streptococcus mitis tested was aggregated by Fn to various degrees, depending on the concentration of Fn added to the test mixtures. Binding assays performed with radiolabeled Fn and various strains of streptococci demonstrated various capabilities to bind Fn, and the amount of Fn bound by each strain was paralleled by its Fn-induced aggregation, with S. mutans 6715 giving the highest values in both assays. Because of the avid binding of Fn by certain strains of potentially cariogenic streptococci, we investigated the possibility that Fn may be present in human saliva and may be adsorbed from saliva onto artificial tooth pellicles. Immunoreactive Fn was detected in paraffin-stimulated whole saliva by enzyme-linked immunosorbent assays of saliva adsorbed onto gelatin-coated cuvettes and by immunoelectroblots (Western blots) of salivary components separated on sodium dodecyl sulfate-polyacrylamide slab gels. Furthermore, immunoreactive Fn was found to be present in artificial tooth pellicles formed by incubating hydroxyapatite beads with whole human saliva. These results demonstrate that certain strains of oral streptococci bind to and are aggregated by Fn. The presence of Fn in artificial tooth pellicles suggests that this macromolecule may play a role in the attachment of potentially cariogenic and other oral streptococci to dental tissues.

Use of CB hamsters in the study of Treponema pertenue

The CB/Ss LAK strain of inbred hamster was used as a model for studies of infection with Treponema pertenue and of acquired resistance to it. When infected, this strain developed cutaneous lesions which lasted for six to seven months, even in the presence of peak titres of antitreponemal antibody. The rate of appearance and resolution of these lesions varied with the size of the inoculum. The infected hamsters' inguinal lymph nodes increased significantly in weight and teemed with treponemes for several weeks. Animals infected for eight or 10 weeks obtained quick resolution of their lesions by treatment with penicillin and were thereafter resistant to reinfection.

Evaluation of ten anaerobic blood culture media

Selection of an anaerobic blood culture based upon clinical findings that have compared the isolation rates of bacteremic agents from different blood culture media. No agreement has been reached as to which of the commercially available blood culture media is optimal for detection of bacteremia. The purpose of this study was to determine the rates of recovery of anaerobic microorganisms from various anaerobic blood culture media. The blood culture media were inoculated with a small inoculum of microorganisms in the presence or absence of an erythrocyte-serum mixture. The results demonstrated that the type of medium and the erythrocyte-serum mixture influenced the ability of blood culture media to support the growth of microorganisms. The majority of the media failed to support the growth of 87% or more of the microorganisms within four days after inoculation. Pre-reduced brain-heart infusion broth supported the growth of a larger proportion of microorganisms than the other types of blood culture media.

Recovery of Haemophilus influenzae from twenty-three blood culture media

Haemophilus influenzae is an important agent of bacteremia and has fastidious growth requirements. The purpose of this investigation was to determine the ability of commercial blood culture media to support the growth of this fastidious microorganism. Twenty-three types of blood culture media were inoculated with individual suspensions of eight strains of H. influenzae in the presence or absence of an erythrocyte-serum mixture. The rates of recovery of the H. influenzae strains from the various types of blood culture media were compared. The results demonstrated that the type of medium, the manufacturer, the erythrocyte-serum mixture, and the strain of H. influenzae influenced the recovery rates of H. influenzae. Optimal recovery of the strains of H. influenzae was obtained from brain heart infustion blood culture medium (GIBCO). Trypic soy broth (GIBCO) and supplemental peptone of Becton, Dickinson and Co. also were found to be superior to the remaining types of media tested for the recovery of H. influenzae.

Evaluation of twenty-three blood culture media

Several investigators have evaluated clinically a variety of commercially available blood culture media. No agreement has been reached as to which of these media is optimal for detection of bacteremia. The purpose of this study was to determine the rate of recovery of microorganisms from various blood culture media. A total of 23 blood culture media were inoculated with 7 to 15 microorganisms per bottle in the presence or absence of an erythrocyte-serum mixture. The results demonstrated that blood culture media differed in their ability to support the growth of microorganisms. At 4 days after inoculation, only 10 of the 23 blood culture media supported the growth of 91% (10 of the 11) or more of the test microorganisms. The recovery rate of microorganisms depended not only upon the type of medium but also upon the manufacturer of the type of blood culture medium. The addition of an erythrocyte-serum mixture to the blood culture media did not influence the difference in the recovery rate of microorganisms among media and the same type of medium prepared by different manufacturers. The majority (15 of the 23) of the blood culture media supplemented with the erythrocyte-serum mixture failed to support the growth of 91% or more of the test microorganisms at 4 days after inoculation. These results have demonstrated that blood culture media need to be improved. Better quality control measures should also be implemented to evaluate commercial blood culture media.

Passive transfer of resistance to frambesial infection in hamsters

The immune mechanism by which hamsters acquire resistance to infection with Treponema pertenue, the causative agent of frambesia, or yaws, has not been elucidated. Serum or cells (spleen or lymph node) obtained from hamsters resistant to frambesial infection were transferred to normal syngenic recipients, who are subsequently infected with T. pertenue. The following parameters were used to measure the ability of immune serum of cells to confer resistance on recipient hamsters to frambesial infection: inhibition of the development of cutaneous lesions, decreased weight, and number of treponemes in the inguinal lymph nodes. This investigation demonstrated that immune serum conferred protection on recipient hamsters infected with T. pertenue. Discontinuation of the administration of immune serum (18 days after frambesial infection) did not result in the development of cutaneous lesions. Since the inguinal lymph nodes contained a sizeable number of treponemes (2.6 X 10(5)), immune serum failed to prevent frambesial infection. Recipients of immune spleen or lymph node cells initially developed frambesial lesions 9 days after infection. The frambesial lesions began to resolve 12 to 14 days after infection and by day 21 had completely regressed. These results illustrated that humoral factors and cells are involved in resistance of the hamster to frambesial infection.