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PubMed1989

Effect of neuraminidase on the adherence to salivary pellicle of Streptococcus sanguis and Streptococcus mitis.

Neuraminidase-sensitive adherence to experimental salivary pellicles was studied using eight strains of Streptococcus sanguis and five strains of Streptococcus mitis. Approximately 60% of the strains of each species showed significantly lower adherence to neuraminidase-treated versus untreated saliva-coated hydroxyapatite. In addition, the adherence of several of these streptococcal strains to saliva-coated hydroxyapatite and neuraminidase-treated saliva-coated hydroxyapatite was inhibited using galactose and N-acetyl-D-galactosamine. Results from these studies suggested that several salivary receptors mediate adherence of these species.

Acetylgalactosamine↗

PubMed1992

Purification and characterization of an aminopeptidase from Streptococcus mitis ATCC 903.

An aminopeptidase isolated from the cytoplasmic fraction of a cell extract of Streptococcus mitis ATCC 903 was purified 330-fold by ion-exchange chromatography, gel filtration, and hydroxyapatite chromatography. The partially purified enzyme had a broad substrate specificity. Twelve aminoacyl-beta-naphthylamide substrates were hydrolyzed and also several di-, tri-, tetra-, and pentapeptides and bradykinin. The enzyme hydrolyzed arginine-beta-naphthylamide at the highest rate. Optimal conditions for activity were at pH 7.0-7.2 and at 37-40 degrees C. The molecular weight of the enzyme was estimated to be 93,000. The enzyme was activated by Co2+ ions. Hg2+ inhibited the activity completely. SDS, EDTA, urea, and pCMB also inhibited activity. Inhibition by EDTA could be completely reversed by dialysis and addition of Co2+ ions. Reducing agents, sodium fluoride, and PMSF had no effect on the activity of the enzyme. The isoelectric point of the enzyme was at pH 4.3. High substrate concentrations inhibited activity. Substrate inhibition increased in the presence of high concentrations of Co2+ ions.

Amino Acid Sequence↗

PubMed1996

Induction of lymphocytes cytotoxic to oral epithelial cells by Streptococcus mitis superantigen.

The preparation of a superantigenic fraction F-2 from the culture supernatant of Streptococcus mitis 108, a fresh isolate from human tooth surfaces, was reported previously. Now, to determine the possible pathogenic role of the superantigen in oral mucosal diseases, we examined the cytotoxic effects of human peripheral blood T-cells activated with F-2 on human oral epithelial cells. T-cells activated with F-2 were cytotoxic to the human squamous carcinoma HO-1-N-1 cells derived from the oral mucosa, similar to those activated with Staphylococcus aureus enterotoxin B (SEB). This cytotoxic effect was increased in a dose-dependent manner by the addition of the respective stimulant, F-2 or SEB, to the cytotoxic assay system. F-2 endowed mainly CD8+ T-cells with cytotoxic activity. Pretreatment with human interferon gamma increased the sensitivity of the HO-1-N-1 cells to the cytotoxic effects of F-2-activated T-cells. The F-2-activated T-cells were also cytotoxic to human keratinocytes derived from gingiva. There was no correlation between the degree of cytotoxicity and the levels of tumor necrosis factor alpha in co-cultures of F-2-activated T-cells and HO-1-N-1 cells. A double-chamber plate experiment revealed no cytotoxic effects when the F-2-activated T-cells were separated from the HO-1-N-1 cells. Supernatants of the co-cultures of target and effector cells were not cytotoxic to HO-1-N-1 cells. These findings suggest that the cytotoxic effects of the F-2-activated T-cells on HO-1-N-1 cells were mediated not by soluble factors but by the direct interaction between the activated T-cells and the target cells. The cytotoxicity of the F-2-activated T-cells against HO-1-N-1 cells was markedly inhibited by monoclonal antibodies (MAbs) against CD11a and CD54, but was only slightly inhibited by MAbs against human leukocyte antigen (HLA)-DR and CD2. Thus, the interaction between lymphocyte-function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1) was crucial for the F-2-dependent T-cell-mediated cytotoxicity against oral epithelial cells, while HLA-DR and CD2 molecules are not necessarily involved in the cytotoxicity observed.

Antigens, Bacterial↗

PubMed1994

Pre-emptive administration of corticosteroids prevents the development of ARDS associated with Streptococcus mitis bacteremia following chemotherapy with high-dose cytarabine.

Adult respiratory distress syndrome (ARDS) complicating Streptococcus mitis bacteremia is a major cause of mortality in patients undergoing therapy for leukemia. In order to try to prevent the development of ARDS in 11 patients with S. mitis bacteremia following chemotherapy including cytarabine, high doses of corticosteroids were administered pre-emptively. None of these patients developed ARDS. In a historical control group of 21 comparable patients who had not been given corticosteroids, the incidence of ARDS was high (38%), with a death rate of 14%. Preemptive administration of high-dose corticosteroids appeared to be highly effective in suppressing the mechanisms that induce ARDS in patients with S. mitis bacteremia after cytarabine treatment. The results suggest that ARDS complicating S. mitis bacteremia is not merely a microbiological problem but may, at least in part, represent an immunologically mediated phenomenon.

Adolescent↗

PubMed1990

Inhibitory effect of human plasma and saliva on co-aggregation between Bacteroides gingivalis and Streptococcus mitis.

The effect of human plasma and saliva on co-aggregation between Bacteroides gingivalis and Streptococcus mitis was studied by means of a turbidimetric assay. The co-aggregation activity was obtained from the maximum slope of the absorbance vs. time curve. Its dependence on pH, temperature, and ionic strength was examined, and the number of Bacteroides cells in relation to the number of Streptococcus cells resulting in optimal co-aggregation was established. Co-aggregation inhibition experiments showed that the co-aggregation activity was inhibited by l-arginine and l-lysine, although the activity was unaffected by the sugars tested. Human plasma and saliva were able to inhibit the co-aggregation in a dose-dependent reaction. Plasma exhibited the most potent inhibitory activity in these fluids. Fibrinogen was the most potent inhibitor of the plasma-derived proteins tested. These data suggest the possibility that the oral fluids may modulate the attachment of B. gingivalis to Gram-positive bacteria in periodontal pockets.

Adult↗

PubMed1968

Metabolism of the reserve polysaccharide of Streptococcus mitis. Some properties of a pullulanase.

1. A pullulanase has been separated from cell extracts of Streptococcus mitis. The enzyme was freed from transglucosylase by fractionation with ammonium sulphate. 2. Pullulanase was produced in the absence of inducers, and addition of glucose or maltose to the broth did not increase the yield of enzyme. 3. The pullulanase acted rapidly on alpha-(1-->6)-bonds in substrates having the structure alpha-maltodextrinyl-(1-->6)-maltodextrin, but had no action on isomaltose, 6-alpha-glucosylmaltodextrins or 6-alpha-maltodextrinylglucoses. 4. 6-alpha-Maltotriosylmaltodextrins were hydrolysed over 10 times faster than 6-alpha-maltosylmaltodextrins. 5. The branch linkages of amylopectin phosphorylase limit dextrin, glycogen phosphorylase limit dextrin and glycogen beta-amylase limit dextrin were hydrolysed. The action of pullulanase on amylopectin and glycogen was accompanied by a rise in the iodine stain of 50% and 30% respectively. 6. A reversal of pullulanase action occurred on incubation with high concentrations of maltotriose. Condensation of maltosyl units to form a branched tetrasaccharide occurred less readily. 7. S. mitis pullulanase was rapidly inactivated at temperatures higher than 40 degrees , and the enzyme did not recover activity on storage at room temperature.

Chemical Precipitation↗

PubMed2025

TrkA of Streptococcus mitis CCUG31611 binds cyclic di-adenosine monophosphate and is required for growth in low potassium conditions.

Cyclic di-adenosine monophosphate (c-di-AMP) is a bacterial second messenger regulating many physiological processes in bacteria. In the oral commensal species Streptococcus mitis, c-di-AMP is involved in regulating metabolism, growth, colony morphology, chain length, biofilm formation and DNA stress tolerance. However, no c-di-AMP-regulated effector proteins have yet been characterized in S. mitis. In this study, we first show that a ΔcdaA mutant, unable to produce c-di-AMP, grows slowly under low environmental potassium conditions. Growth of the cdaA mutant was not restored by reintroducing cdaA in the original locus (KBcdaA). Whole-genome sequencing of multiple KBcdaA isolates revealed secondary mutations in a putative potassium transporter. The mutations were predicted to result in the truncation of the protein or the alteration of a conserved glycine residue essential for selective potassium uptake, disrupting protein function. A Δpde2 mutant overproducing c-di-AMP survived poorly under high environmental sodium concentrations. We then characterized the potassium transporter regulator protein TrkA. Biochemical analyses of the purified recombinant TrkA protein revealed that it specifically binds c-di-AMP with high affinity in vitro. Using deletion mutants of trkA, we demonstrate that TrkA is essential for growth under low environmental potassium conditions. Ultra-high-performance liquid chromatography coupled to tandem mass spectrometry revealed lower c-di-AMP concentration in the ΔtrkA mutant compared to the WT. This was not due to transcriptional regulation of the expression of the c-di-AMP turnover proteins CdaA, Pde1 or Pde2. C-di-AMP production is not affected by the extracellular potassium concentrations under the conditions tested. We also demonstrate a potential role of TrkA in UV stress tolerance but do not characterize the mechanism in this study.

Potassium↗

PubMed2004

Susceptibility testing of Streptococcus mitis group isolates.

BACKGROUND & OBJECTIVES: Suppurative oral and maxillofacial infections are usually mixed infections due to aerobic and anaerobic bacteria, most frequently by oral streptococci and antimicrobial treatment is necessary for such infections. The aim of this study was to investigate the antimicrobial susceptibility of Streptococcus mitis group strains isolated from Romanian patients with different oral and maxillofacial infections. METHODS: Eighty-five isolates belonging to S. mitis group isolated from pus samples were identified at species level by the Rapid ID 32 STREP system. The E test was used to determine the susceptibilities of the isolates to penicillin, ampicillin, cefotaxime, erythromycin, clindamycin, chloramphenicol and tetracycline. RESULTS: Of the 151 samples studied, 85 isolates belonged to S. mitis group. The minimum inhibitory concentration (MIC) values (mg/l) ranged from 0.016-0.75 for penicillin, 0.016-2 for ampicillin, 0.016- 1 for cefotaxime, 0.016-4 for erythromycin, 0.016-0.047 for clindamycin, 0.5-4 for chloramphenicol and 0.047-256 for tetracycline. INTERPRETATION & CONCLUSION: The low susceptibility and the resistance to some commonly used antibiotics found in this study indicated a need for a careful surveillance of the susceptibility pattern of oral streptococci isolates of clinical significance. Clindamycin and chloramphenicol might be suitable alternative agents in treatment of oral and maxillofacial infections involving penicillin-resistant bacteria and in case of patients with hypersensitivity to beta-lactam antibiotics.

Anti-Bacterial Agents↗

PubMed1993

Evolution of penicillin resistance in Streptococcus pneumoniae; the role of Streptococcus mitis in the formation of a low affinity PBP2B in S. pneumoniae.

Penicillin-resistant strains of Streptococcus pneumoniae possess forms of penicillin-binding proteins (PBPs) that have a low affinity for penicillin compared to those from penicillin-sensitive strains. PBP genes from penicillin-resistant isolates are very variable and have a mosaic structure composed of blocks of nucleotides that are similar to those found in PBP genes from penicillin-sensitive isolates and blocks that differ by up to 21%. These chromosomally encoded mosaic genes have presumably arisen following transformation and homologous recombination with PBP genes from a number of closely related species. This study shows that PBP2B genes from many penicillin-resistant isolates of S. pneumoniae contain blocks of nucleotides originating from Streptococcus mitis. In several instances it would appear that this material alone is sufficient to produce a low affinity PBP2B. In other examples PBP2B genes possess blocks of nucleotides from S. mitis and at least one additional unidentified species. Mosaic structure was also found in the PBP2B genes of penicillin-sensitive isolates of S. mitis or S. pneumoniae. These mosaics did not confer penicillin resistance but nevertheless reveal something of the extent to which localized recombination occurs in these naturally transformable streptococci.

Amino Acid Sequence↗

PubMed1995

Immunopathological activities of extracellular products of Streptococcus mitis, particularly a superantigenic fraction.

Previously, we prepared extracellular products, fractions F-1 and F-2 of Streptococcus mitis 108, an isolate from the tooth surface of an infant, and showed that F-1 exhibited inflammatory cytokine-inducing activities. In the present study, we present evidence that fraction F-2 induced human T-cell proliferation in the presence of irradiated human peripheral blood mononuclear cells and selectively activated T cells bearing V beta 2 and V beta 5.1 in the T-cell receptor. F-1, on the other hand, stimulated human gingival fibroblasts to support the T-cell proliferation in the same way as human gamma interferon or Prevotella intermedia lipopolysaccharide (LPS). Fraction F-1 also primed gingival fibroblasts to support the production of interleukin-2 and gamma interferon by the T cells upon stimulation with F-2. Human gingival fibroblasts stimulated with fraction F-1, like those stimulated by P. intermedia LPS and human gamma interferon, exhibited human leukocyte antigen (HLA)-DR mRNA expression and cell surface HLA-DR molecules as detected by enzyme-linked immunosorbent assay. An anti-HLA-DR monoclonal antibody inhibited T-cell proliferation in response to F-2, probably through inactivating the accessory function of HLA-DR-bearing fibroblasts. T cells activated with F-2 in the presence of irradiated peripheral blood mononuclear cells exhibited definite cytotoxic effects against fibroblasts and squamous carcinoma cells originating from human oral tissues. These findings are strongly suggestive of an association of extracellular products of viridans streptococci with pathogenesis of oral mucosal diseases, particularly those disorders in gingiva which are accompanied by heavy infiltration of T cells.

Antibodies, Monoclonal↗

PubMed1996

Detection by physico-chemical techniques of an amphiphilic surface component on Streptococcus mitis strains involved in non-electrostatic binding to surfaces.

Indications for the presence of an amphiphilic molecule in Streptococcus mitis strains cultured on TY-agar were obtained from infrared absorption spectra, especially from the shape of the CH2/CH3 absorption bands around 2900 cm-1, which were absent when strains were grown on blood agar. It was the aim of this study to determine for S. mitis strains grown on different growth media whether the amphiphile is located intracellularly or on the cell surface by measuring zeta potentials, elemental surface compositions and adhesion to hexadecane of differently grown cells. There was no significant effect of the presence of the amphiphile on the zeta potentials of the S. mitis strains, but adhesion to hexadecane was increased by the presence of the amphiphile when the pH of the suspension was such that electrostatic interactions between the organisms and the hexadecane could be neglected. Furthermore, lower N/C surface concentration ratios were found for organisms possessing the amphiphilic molecule. Consequently, it was concluded that the amphiphilic molecule is located on the cell surface, and that it is involved in the non-electrostatic binding of S. mitis cells to surfaces.

Agar↗

PubMed1997

Purification and partial characterization of a novel human platelet aggregation factor in the extracellular products of Streptococcus mitis, strain Nm-65.

A human blood platelet aggregation factor was purified from the extracellular products (ECP) of Streptococcus mitis, strain Nm-65 by sequential chromatography on DEAE-Sepharose CL-6B, hydroxyapatite and Superdex 75 columns. The purified factor (S. mitis-derived human platelet aggregation factor, Sm-hPAF) gave a single band with a molecular weight of 66 kDa on SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Sm-hPAF showed a peak absorption at 278 nm and an isoelectric point of around 8.5. Chemical analyses revealed that Sm-hPAF contained no sugars and that its first 15 amino-terminal amino acid residues were H-DEQGNRPVETENIAR. Platelet aggregation activity of Sm-hPAF was abolished by heating at 45 degrees C for 10 min. Platelet aggregation by Sm-hPAF was accompanied by a release of prostaglandin E2 (PGE2) in a dose-dependent manner. The platelet aggregation was not inhibited by either prostaglandin E1 (PGE1) or Gly-Arg-Gly-Asp-Ser (GRGDS), that inhibit the platelet aggregation induced by collagen. Twenty (77%) platelet rich-plasma (PRP) specimens derived from 26 healthy volunteers were aggregated by Sm-hPAF, but the remaining 6 (23%) were not reactive. A preliminary study suggested the presence of an inhibitory factor against Sm-hPAF in the plasma from a non-reactive donor.

Adult↗

PubMed2003

Beta-lactam resistance in Streptococcus mitis isolated from saliva of healthy subjects.

The purpose of this study was to examine the percentage of Beta-lactam-resistant streptococcal carriers in healthy adults, and to investigate the relationships among minimum inhibitory concentrations (MICs) of Beta-lactams, alterations in the penicillin-binding protein genes ( pbp genes), and the affinity of penicillin-binding proteins (PBPs) for ampicillin (ABPC) in Streptococcus mitis. We also compared numbers of surviving bacteria at various ABPC concentrations in both ABPC-susceptible and -resistant S. mitis strains. The percentages of subjects carrying ABPC- and cefaclor (CCL)-resistant streptococci were 52% (27 of 52 subjects) and 100%, respectively. S. mitis, including both antibiotic-susceptible and -resistant strains, were classified into five groups according to the pbp gene mutations that resulted in alterations of the deduced amino-acid sequence in the homology boxes of PBPs. All ABPC-resistant strains showed alterations in PBP1A, 2X, and 2B, while no or only PBP2X alterations were detected in the susceptible strains. These results suggest that the accumulation of pbp gene mutations is strongly related to the MIC of ABPC for S. mitis. In the resistant strains, the affinity of PBPs for ABPC was reduced in comparison with that in the susceptible strains, and the bactericidal effect of ABPC was also reduced. Therefore, we should be aware of conditions such as infective endocarditis that are caused by Beta-lactam-nonsusceptible streptococci in the normal oral flora.

Adult↗

PubMed2004

Relations between macroscopic and microscopic adhesion of Streptococcus mitis strains to surfaces.

Application of physico-chemical models to describe bacterial adhesion to surfaces has hitherto only been partly successful due to the structural and chemical heterogeneities of bacterial surfaces, which remain largely unaccounted for in macroscopic physico-chemical characterizations of the cell surfaces. In this study, the authors attempted to correlate microscopic adhesion of a collection of nine Streptococcus mitis strains to the negatively charged, hydrophilic silicon nitride tip of an atomic force microscope (AFM) with macroscopic adhesion of the strains to a negatively charged, hydrophilic glass in a parallel-plate flow chamber. The repulsive force probed by AFM upon approach of the tip to a bacterial cell surface ranged from 1.7 to 7.7 nN depending on the strain considered and was found to correspond to an activation barrier, governing initial, macroscopic adhesion of the organisms to the glass surface. Moreover, maximum distances at which attractive forces were probed by the AFM upon retraction of the tip (120 to 1186 nm) were related to the area blocked by an adhering bacterium, i.e. the distance kept between adhering bacteria. Bacterial desorption could not be related to adhesive forces as probed by the AFM, possibly due to the distinct nature of the desorption process occurring in the parallel-plate flow chamber and the forced detachment in AFM.

Bacterial Adhesion↗

PubMed2001

All detectable high-molecular-mass penicillin-binding proteins are modified in a high-level beta-lactam-resistant clinical isolate of Streptococcus mitis.

All detectable high-molecular-mass penicillin-binding proteins (HMM PBPs) are altered in a clinical isolate of Streptococcus mitis for which the beta-lactam MICs are increased from those previously reported in our region (cefotaxime MIC, 64 microg/ml). These proteins were hardly detected at concentrations that saturate all PBPs in clinical isolates and showed, after densitometric analysis, 50-fold-lower radiotracer binding. Resistance was related to mosaic structure in all HMM PBP-coding genes, where critical region replacement was complemented not only by substitutions already reported for the closely related Streptococcus pneumoniae but also by other specific replacements that are presumably close to the active-site serine. Mosaic structure was also presumed in a pbp1a-sensitive strain used for comparison, confirming that these structures do not unambiguously imply, by themselves, detectable critical changes in the kinetic properties of these proteins.

Amino Acid Substitution↗

PubMed1983

Purification and some properties of neuraminidase isolated from the culture medium of oral bacterium Streptococcus mitis ATCC 9811.

Neuraminidase acting on the salivary bacterial agglutinating factor was isolated and purified from the culture medium of Streptococcus mitis ATCC 9811. The molecular weight and the isoelectric point of the enzyme were determined to be 42,000 and a pH of 4.6, respectively. The enzyme showed high activity against human glycoprotein substrates, especially the salivary bacterial agglutinating factor.

Electrophoresis, Polyacrylamide Gel↗

PubMed2001

Population dynamics of Streptococcus mitis in its natural habitat.

The purpose of this study was to examine the genetic structure of the typical commensal Streptococcus mitis biovar 1 in its natural habitat in the human oral cavity and pharynx and to investigate the role that selected microbial properties and host, spatial, and temporal factors play in determining the structure of the bacterial population. Consecutive samples were collected from buccal and pharyngeal mucosal surfaces of two infants, their four parents, and two elderly individuals over a period of approximately 1 year. A total of 751 isolates identified as S. mitis biovar 1 were typed by restriction endonuclease analysis (REA) and representative clones were typed by multilocus enzyme electrophoresis (MLEE). The genetic diversity of the S. mitis biovar 1 isolates collected from single infant hosts over a period of 9 to 10 months was found to be between 0.69 and 0.76, which is considerably higher than that previously observed for intestinal populations of Escherichia coli. The study provides evidence of the existence of both transient and persistent clones in adult individuals. In the two infants, however, none of 42 demonstrated clones were detected on more than a single occasion. Statistical calculations showed that the ability to persist was not distributed at random in the S. mitis biovar 1 population. However, neither immunoglobulin A1 protease activity nor the ability to bind alpha-amylase from saliva was a preferential characteristic of persistent genotypes. In contrast to current concepts of climax ecosystems, the species niche in the habitat appears to be maintained predominantly by a succession of clones rather than by stable strains. Several lines of evidence suggest that the major origin of "new" clones is the many other habitats in the respiratory tract that are occupied by this species.

Adult↗

PubMed1978

Substances that interfere with action of viridin B, a Streptococcus mitis bacteriocin.

Several body fluids and various substances were examined for their effects on the action of viridin B, a Streptococcus mitis bacteriocin. Heme has been shown previously to interfere with viridin B action. In the present study, peroxidase and catalase, but not superoxide dismutase, interfered with the bacteriocin. Sulfhydryl-containing compounds had no effect. Trypsin, protease, and amylase exhibited interfering capacities. Of various body fluids tested, serum, saliva, and leukocyte lysate interfered with viridin B. The activity in leukocyte lysate was probably due to myeloperoxidase. Salivary activity was likely due to both peroxidase and amylase. Interfering activity in serum was neither complement dependent nor antibody mediated and was probably due to a combination of enzymatic activities. Temporal studies with these agents suggested more than one mechanism of interference with viridin B.

Amylases↗