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PubMed1989

Molecular characterization of a cell wall-associated proteinase gene from Streptococcus lactis NCDO763.

Streptococcus lactis NCDO763 harbours a plasmid designated pLP763. The cells harbouring pLP763 are able to grow to a higher density in milk because of their proteinase-positive phenotype (Prt+). The 6.2 kb HindIII-PstI fragment from pLP763 was found to be responsible for the Prt+ phenotype. The DNA fragment contains an incomplete large open reading frame (ORF). Further sequence analysis downstream from the PstI site revealed that the ORF consists of 5706 bases. It was found that the deduced amino acid sequence consisting of 1902 amino acid residues was extremely similar to that of the Wg2 proteinase, a serine protease from Streptococcus cremoris, suggesting that both genes were derived from a common ancestral gene.

Amino Acid Sequence↗
PubMed1993

Positive transcriptional control of mry regulates virulence in the group A streptococcus.

Transcription of the antiphagocytic M protein in the group A streptococcus (Streptococcus pyogenes) is environmentally regulated in response to CO2 and requires Mry, a trans-acting positive regulatory protein. We have examined the role of Mry in environmental regulation by analysing the factors that regulate expression of the gene that encodes Mry (mry). By employing a strategy that utilizes integrational plasmids, it was found that expression of mry requires the participation of DNA sequences that extend 473 base pairs upstream of the Mry coding region. Transcription of mry, as analysed in S1 nuclease protection assays, is initiated from two separate promoters located within this extended regulatory region. Construction and analysis of transcriptional fusions between the mry promoters and a promoterless chloramphenicol acetyltransferase gene demonstrated that mry is autoregulated and environmentally regulated in response to the level of CO2. These data suggest a model for the regulation of virulence in S. pyogenes where positive transcriptional control of mry in response to environmental stimuli regulates the expression of the M protein.

Amino Acid Sequence↗
PubMed1993

Sucrose-derived exopolysaccharides of Streptococcus mutans V403 contribute to infectivity in endocarditis.

We used an isogenic mutant of Streptococcus mutans V403, which differs from the wild-type V403 in genes involved in glucan and fructan production, to examine the importance of these exopolysaccharides as factors affecting infectivity in endocarditis. Rats inoculated with V403 developed endocarditis more frequently than animals inoculated with the mutant strain which produced neither glucan nor fructan (58% versus 12%, P < 0.01). In phagocytosis assays, both strains were found to be associated with the human granulocytes but a greater number of live V403 than of mutant organisms could be recovered. Colony counts recovered from fibrin plates incubated with the mutant were lower than those incubated with V403. These experiments indicate that exopolysaccharides produced by Streptococcus mutans contribute to its infectivity in endocarditis.

Alleles↗
PubMed1994

The identification of rofA, a positive-acting regulatory component of prtF expression: use of an m gamma delta-based shuttle mutagenesis strategy in Streptococcus pyogenes.

Binding of the Gram-positive pathogenic bacterium Streptococcus pyogenes (group A streptococcus) to respiratory epithelium is mediated by the fibronectin-binding adhesin, protein F. Most strains of streptococci regulate the expression of protein F in response to oxygen levels and redox potential; however, JRS4 constitutively binds high levels of fibronectin under all environmental conditions. In this study, we have examined the regulation of protein F expression in JRS4 using a shuttle mutagenesis strategy novel to S. pyogenes. Cloned DNA representing the chromosomal loci adjacent to the gene which encodes protein F (prtF) was subjected to transposon mutagenesis in Escherichia coli using a derivative of transposon m gamma delta that was modified to contain a streptococcal antibiotic-resistance gene. mutagenized DNA was then returned to the streptococcal chromosome by allelic replacement. Analysis of the resulting fibronectin-binding phenotypes revealed that insertions in a region upstream of prtF abolished the constitutive phenotype. However, these mutants now demonstrated regulation in response to both oxygen levels and redox potential. Because these insertions define a locus responsible for the constitutive phenotype, it has been designated rofA (regulator of F). Chromosomal interruption studies using integrational plasmids together with complementation data from a previous study (VanHeyningen et al., 1993) suggested that rofA acts as a positive trans-acting regulator of prtF. Construction of prtF-lacZ fusions indicated that transcription of prtF is constitutive in JRS4 but is regulated in rofA mutants. Analysis of the DNA sequence defined by the rofA insertions revealed a 1495 bp open reading frame, whose predicted product (RofA) possessed both a putative helix-turn-helix motif and limited homology to two other transcriptional activators (Mry, PrgR) of Gram-positive surface proteins. Sequences homologous to rofA were found in regulated strains of S. pyogenes, which suggests that rofA may act as an activator of prtF in response to an unidentified environmental signal. We speculate that the allele reported here contains a mutation that renders it constitutively active.

Amino Acid Sequence↗
PubMed1995

The fimA locus of Streptococcus parasanguis encodes an ATP-binding membrane transport system.

The gene encoding fimA, a 36 kDa fimbrial adhesion of Streptococcus parasanguis FW213, is highly conserved in all four genetic groups of sanguis streptococci. FimA-like peptides were produced by all strains tested. The nucleotide sequence directly upstream of fimA contains two open reading frames, ORF5 and ORF1, whose deduced protein products are homologous to members of a superfamily of ATP-binding cassette membrane transport proteins, including both prokaryotic and eukaryotic uptake and export systems. The amino acid sequence of FimA contains the consensus prolipoprotein cleavage site (LxxC) common to the 'periplasmic' binding proteins of Gram-positive transport systems. The deduced product of ORF5 is a 28.6 kDa membrane-associated protein that has the consensus binding site for ATP (GxxGxGKS). It shares significant homology with AmiE of Streptococcus pneumoniae as well as with Escherichia coli proteins involved in iron(III) uptake. Allelic-replacement mutagenesis of ORF5 resulted in greatly increased resistance to aminopterin. These data demonstrate functionality with the amiE locus as well. The deduced product of ORF1 is an extremely hydrophobic integral membrane protein of 30.8 kDa with a pattern of six potential membrane-spanning regions, typical of a component of these types of transport system. The nucleotide sequence downstream of fimA, ORF3, encodes a 20 kDa protein having 78% identity with the 20 kDa protein encoded downstream of ssaB, a fimA homologue in S. sanguis 12. It also exhibits significant homology with bacterioferritin co-migratory protein (Bcp) of E. coli K-12. Allelic-replacement mutagenesis in the fimA locus of FW213 showed that (i) expression of fimA was initiated at a site far upstream of the fimA start codon, and (ii) expression of fimA was not linked to expression of ORF3. Northern blots probed with internal fragments of ORF5, ORF1, fimA or ORF3 hybridized to the same transcript of 3.3 kb, which suggested that these loci were transcribed as a polycistronic message. The ORF3 probe also hybridized to a 540 bp transcript consistent with the size of ORF3 alone and supportive of the mutagenesis data of non-linkage. Strains mutated in fimA continued to produce fimbriae, indicating that FimA was not the fimbrial structural subunit. Immunoelectron microscopy revealed FimA was localized at the tips of the fimbriae of FW213. This is the first study that demonstrates that an adhesin which binds a bacterial cell to a substrate is associated with an ATP-binding cassette.

ATP-Binding Cassette Transporters↗
PubMed1995

Role of the conserved C-repeat region of the M protein of Streptococcus pyogenes.

The surface-located M protein functions to protect Streptococcus pyogenes (the group A streptococcus) from phagocytosis by polymorphonuclear leukocytes. It has been suggested that this protection results from the ability of M protein to bind factor H, a serum protein that can inhibit the activation of complement. Among different serological variants of M protein, the C-repeat domain is highly conserved and is exposed on the bacterial surface. This domain has been implicated in binding to complement factor H and in M-protein-mediated adherence of streptococci to human keratinocytes in the cutaneous epithelium. In this study, we constructed an S. pyogenes mutant strain which expresses an M6 protein from which the entire C-repeat domain was deleted. As predicted, this mutant did not adhere well to human keratinocytes and was unable to bind to factor H. Unexpectedly, the mutant was able to survive and multiply in human blood. Therefore, while the binding of factor H and the facilitation of adherence to keratinocytes appear to involve recognition of the C-repeat domain, a region of the M-protein molecule distinct from the C-repeat domain confers upon S. pyogenes its ability to resist phagocytosis.

Alleles↗
PubMed2004

Defective cell wall synthesis in Streptococcus pneumoniae R6 depleted for the essential PcsB putative murein hydrolase or the VicR (YycF) response regulator.

PcsB is a protein of unknown function(s) that influences the cell morphology of several pathogenic species of streptococcus. PcsB contains a CHAP (cysteine, histidine-dependent amidohydrolase/peptidase) domain found in bacterial murein hydrolases; however, direct links between steps in cell wall biosynthesis and PcsB function(s) have not been demonstrated. We show here that pcsB is essential in the human respiratory pathogen, Streptococcus pneumoniae, that depletion of PcsB is bacteriostatic and that alanine substitutions in the conserved cysteine and histidine residues of the CHAP domain appear to be lethal. We stained wild-type parent and mutant bacteria deficient in expression of PcsB with fluorescent vancomycin and DAPI to determine patterns of cell wall synthesis and nucleoid segregation respectively. The wild-type parent strain exhibited ordered, simultaneous septal and equatorial cell wall synthesis. In contrast, reduced expression of PcsB resulted in formation of long chains of cells in which peptidoglycan synthesis occurred at nearly every division septum and cell equator. Severe depletion of PcsB led to abnormal, uncontrolled cell wall synthesis at misplaced septa and around large cells. Together, these physiological properties are consistent with a role for PcsB as a murein hydrolase that balances the extent of cell wall synthesis in S. pneumoniae. Finally, we show that the defects in morphology and cell wall synthesis that result from depletion of PcsB strongly resemble those caused by depletion of the essential VicRK two component regulatory system (TCS). This result and the essentiality of pcsB support the hypothesis that the essentiality of the VicRK TCS results from its positive regulation of PcsB expression.

Amino Acid Sequence↗
PubMed2004

CovS/CovR of group B streptococcus: a two-component global regulatory system involved in virulence.

In this study, we carried out a detailed structural and functional analysis of a Streptococcus agalactiae (GBS) two-component system which is orthologous to the CovS/CovR (CsrS/CsrR) regulatory system of Streptococcus pyogenes. In GBS, covR and covS are part of a seven gene operon transcribed from two promoters that are not regulated by CovR. A DeltacovSR mutant was found to display dramatic phenotypic changes such as increased haemolytic activity and reduced CAMP activity on blood agar. Adherence of the DeltacovSR mutant to epithelial cells was greatly increased and analysis by transmission electron microscopy revealed the presence at its surface of a fibrous extracellular matrix that might be involved in these intercellular interactions. However, the DeltacovSR mutant was unable to initiate growth in RPMI and its viability in human normal serum was greatly impaired. A major finding of this phenotypic analysis was that the CovS/CovR system is important for GBS virulence, as a 3 log increase of the LD(50) of the mutant strain was observed in the neonate rat sepsis model. The pleiotropic phenotype of the DeltacovSR mutant is in full agreement with the large number of genes controlled by CovS/CovR as seen by expression profiling analysis, many of which encode potentially secreted or cell surface-associated proteins: 76 genes are repressed whereas 63 were positively regulated. CovR was shown to bind directly to the regulatory regions of several of these genes and a consensus CovR recognition sequence was proposed using both DNase I footprinting and computational analyses.

Animals↗
PubMed2005

The PerR regulon in peroxide resistance and virulence of Streptococcus pyogenes.

Prior studies have shown that the catalase-deficient pathogen Streptococcus pyogenes (group A streptococcus) has a robust ability to resist oxidative stress that partially involves the transcriptional regulator PerR. However, the extent of the PerR regulon and the contribution of the members of this regulon to virulence are unknown. In this study, DNase I footprinting revealed that PerR binds specifically to a single site upstream of the promoter for the gene encoding alkyl hydroperoxide reductase (ahpC). However, analyses of transcript abundance revealed that while ahpC is regulated in response to growth phase, its regulation is independent of PerR. Instead, PerR regulates transcription of a divergent gene cluster that encodes a putative cold shock protein. The gene encoding the Dps-like peroxide resistance protein MrgA was repressed by PerR, consistent with the presence of a PerR binding site in its promoter. Phenotypic analyses of PerR-, AhpC- and MrgA- mutants revealed that while AhpC is not essential for resistance to challenge with hydrogen peroxide in vitro, AhpC does contribute to scavenging of endogenous hydrogen peroxide and is required for virulence in a murine model of infection. In contrast, a MrgA- mutant was hypersensitive to challenge with peroxide in vitro, but was fully virulent in all animal models tested. Finally, a PerR- mutant was hyper-resistant to peroxide, yet was highly attenuated for virulence in all murine models. These data demonstrate that while a mutant's capacity to resist peroxide stress did not directly correlate with its ability to cause disease, the appropriate regulation of the peroxide stress response is critical for virulence.

Animals↗
PubMed2005

The CovR response regulator of group A streptococcus (GAS) acts directly to repress its own promoter.

The CovR/S (CsrR/S) two component system is a global regulator of virulence gene expression in the group A streptococcus (GAS, Streptococcus pyogenes). The response regulator, CovR, regulates about 15% of the genes of GAS, including its own operon. Using in vitro DNA binding assays with purified CovR protein, we found that CovR binds a DNA fragment including the covR promoter (Pcov). DNaseI footprint analyses showed that phosphorylation of CovR enhanced and extended the protected regions. The proposed CovR consensus binding sequence (ATTARA) was present at most, but not all protected regions. The effect of replacing the two thymine residues in the consensus binding sequence (CB) with guanine residues was evaluated both in vitro and in vivo. Most, but not all, CB mutations reduced binding of CovR in vitro. Using a transcriptional reporter introduced in single copy into the GAS chromosome, we found that mutations at each CB completely or partially relieved CovR-mediated repression in vivo. This suggests that CovR regulation of Pcov is direct. Further support for this conclusion comes from use of an in vitro GAS transcription system in which CovR was sufficient to mediate repression of Pcov. This repression was enhanced by phosphorylation of the protein. In addition, we found that the CovR binding region overlapping the promoter was essential for wild type repression of Pcov both in vitro and in vivo, suggesting that promoter occlusion is a primary mechanism of Pcov repression by CovR.

Artificial Gene Fusion↗
PubMed2005

Binding of the Streptococcus gordonii surface glycoproteins GspB and Hsa to specific carbohydrate structures on platelet membrane glycoprotein Ibalpha.

GspB and Hsa are homologous serine-rich surface glycoproteins of Streptococcus gordonii strains M99 and Challis, respectively, that mediate the binding of these organisms to platelet membrane glycoprotein (GP) Ibalpha. Both GspB and Hsa consist of an N-terminal putative signal peptide, a short serine-rich region, a region (BR) that is rich in basic amino acids, a longer serine-rich region and a C-terminal cell wall anchoring domain. To further assess the mechanisms for GspB and Hsa binding, we investigated the binding of the BRs of GspB and Hsa (expressed as glutathione S-tranferase fusion proteins) to sialylated glycoproteins in vitro. Both fusion proteins showed significant levels of binding to sialylated moieties on fetuin and GPIbalpha. In contrast, the corresponding region of a GspB homologue of Streptococcus agalactiae, which is acidic rather than basic, showed no binding to either fetuin or GPIbalpha. As measured by surface plasmon resonance kinetic analysis, GspB- and Hsa-derived fusion proteins had high affinity for GPIbalpha, but with somewhat different dissociation constants. Dot blot analysis using a panel of synthesized oligosaccharides revealed that the BR of Hsa can bind both alpha(2-3) sialyllactosamine [NeuAcalpha(2-3)Galbeta(1-4)GlcNAc] and sialyl-T antigen [NeuAcalpha(2-3)Galbeta(1-3)GalNAc], whereas the BR of GspB only bound sialyl-T antigen. Moreover, far Western blotting using platelet membrane proteins revealed that GPIbalpha is the principal receptor for GspB and Hsa on human platelets. The combined results indicate that the BRs of GspB and Hsa are the binding domains of these adhesins. However, the subsets of carbohydrate structures on GPIbalpha recognized by the binding domains appear to be different between the two proteins.

Adhesins, Bacterial↗
PubMed2005

Ketolide resistance in Streptococcus pyogenes correlates with the degree of rRNA dimethylation by Erm.

Macrolide and ketolide antibiotics inhibit protein synthesis on the bacterial ribosome. Resistance to these antibiotics is conferred by dimethylation at 23S rRNA nucleotide A2058 within the ribosomal binding site. This form of resistance is encoded by erm dimethyltransferase genes, and is found in many pathogenic bacteria. Clinical isolates of Streptococcus pneumoniae with constitutive erm(B) and Streptococcus pyogenes with constitutive erm(A) subtype (TR) are resistant to macrolides, but remain susceptible to ketolides such as telithromycin. Paradoxically, some strains of S. pyogenes that possess an identical erm(B) gene are clinically resistant to ketolides as well as macrolides. Here we explore the molecular basis for the differences in these streptococcal strains using mass spectrometry to determine the methylation status of their rRNAs. We find a correlation between the levels of A2058-dimethylation and ketolide resistance, and dimethylation is greatest in S. pyogenes strains expressing erm(B). In constitutive erm strains that are ketolide-sensitive, appreciable proportions of the rRNA remain monomethylated. Incubation of these strains with subinhibitory amounts of the macrolide erythromycin increases the proportion of dimethylated A2058 (in a manner comparable with inducible erm strains) and reduces ketolide susceptibility. The designation 'constitutive' should thus be applied with some reservation for most streptococcal erm strains. One strain worthy of the constitutive designation is S. pyogenes isolate KuoR21, which has lost part of the regulatory region upstream of erm(B). In S. pyogenes KuoR21, nucleotide A2058 is fully dimethylated under all growth conditions, and this strain displays the highest resistance to telithromycin (MIC > 64 microg ml-1).

Amino Acid Sequence↗
PubMed1990

Low T- and B-cell reactivity is an apparently paradoxical request for murine immunoprotection against Streptococcus mutans. Murine protection can be achieved by immunization against a B-cell mitogen produced by these bacteria.

C57BL/6 mice thymectomized as adults or depleted of CD4+ cells were much less susceptible than intact conventional mice to the B-cell mitogenic and specific immunosuppressive effects of a protein designated as F5'EP-Sm secreted by Streptococcus mutans. These mice were also considerably more resistant to infection by these bacteria than intact individuals. The immunosuppressor effect of F5'EP-Sm was also abrogated, however, in conventional intact mice when immunized intraperitoneally against heat-inactivated F5'EP-Sm. On the other hand, resistance to bacterial infection could be achieved by immunization of conventional intact C57BL/6 mice against heat-inactivated F5'EP-Sm by intraperitoneal or intradermal routes even when the animals were infected 3 months after immunization and even when the immunization procedure did not include Freund's adjuvant, which was the case with the intradermal route. Interestingly, the protection against the bacterial infection was accompanied by only a minor increase in specific serum antibodies against F5'EP-Sm. These results are discussed in the context of adequate strategies for immunoprotection against Streptococcus mutans and other micro-organisms which are secretors of substances that share both B-cell mitogenic and immunosuppressive properties and which are thus able to suppress the immune response by overstimulation of the immune system of the host.

Animals↗
PubMed2005

High nasopharyngeal carriage of drug resistant Streptococcus pneumoniae and Haemophilus influenzae in North Indian schoolchildren.

OBJECTIVES: To determine the carriage rate of Streptococcus pneumoniae and Haemophilus influenzae in healthy Indian schoolchildren. The prevalence of antibiotic resistant strains in the community may be used to assess the trends of antibiotic resistance in invasive strains. Prevalence of resistance to various antimicrobial drugs among S. pneumoniae and H. influenzae was estimated. METHODS: Two thousand four hundred subjects, aged 5-10 years, were enrolled from 45 rural and 45 urban schools. A nasopharyngeal swab was collected from each child, after taking informed written consent. Swabs were processed to isolate S. pneumoniae and H. influenzae. All isolates were tested for resistance to chloramphenicol, erythromycin and co-trimoxazole. Streptococcus pneumoniae isolates were also tested against tetracycline and oxacillin while H. influenzae isolates were tested against ampicillin. RESULTS: Nasopharyngeal carriage of S. pneumoniae and H. influenzae was high in healthy schoolchildren. Stratified analysis showed that nasal carriage of pneumococci in urban children was significantly lower than in rural children [46.8% vs. 53.2%, P<0.001]. Carriage rates of H. influenzae in male and female populations were significantly different (47.8% vs. 52.3%, P<0.04). Penicillin resistance in S. pneumoniae was found low (3.3%), but 22.9% of H. influenzae isolates were ampicillin resistant. Resistance to co-trimoxazole was very high in both S. pneumoniae (81.8%) and H. influenzae (67.3%). CONCLUSION: There is high nasopharyngeal carriage of drug resistant S. pneumoniae and H. influenzae in schoolchildren of north India. Currently, in India, co-trimoxazole for 5 days is recommended for treatment of non-severe pneumonia and third generation cephalosporins are drug of choice for management of severe pneumococcal/H. influenzae diseases. We found high co-trimoxazole resistance and low penicillin resistance in pneumococcal isolates. This justifies empirical use of penicillin in management of invasive pneumococcal infections in India.

Carrier State↗
PubMed2004

Maternal colonisation with group B streptococcus and effectiveness of a culture-based protocol to prevent early-onset neonatal sepsis.

This study was conducted to find out the group B streptococcus colonisation of pregnant women in Kocaeli, Turkey. A culture plus individualised high-risk-based antibiotic prophylaxis was compared with high-risk-based approach alone. The screening of women was performed via vaginal and anal cultures for group B streptococcus (GBS). The maternal GBS colonisation rate was found to be 6.5%. All colonised women or preterm labours with unavailable culture results until delivery received prophylactic antibiotics. Neonatal colonisation rate and early-onset neonatal sepsis due to GBS was 1/200. The unscreened 900 women received prophylactic antibiotics due to a risk factor-based approach. The neonatal colonisation rate was 17/900 (p = 0.1), and the rate of early-onset neonatal sepsis was 3/900 (p = 0.6). A culture plus individualised high-risk-based antibiotic prophylaxis provided an insignificant change in neonatal colonisation and early-onset neonatal sepsis with GBS when compared with high-risk-based approach alone.

Adult↗
PubMed1989

Electrophoretic analysis of ureases in Streptococcus salivarius and in saliva.

Experimental conditions were established for the extraction, electrophoresis and detection of urease isoenzymes from Streptococcus salivarius. Thiol concentrations were critical and ureases from different strains varied in ease of dissociation. A characteristic pattern was obtained for 30 ureolytic S. salivarius strains isolated from; saliva (6), dental plaque (12), artificial dental plaque (6) and non-oral sources (6), and also for a ureolytic Streptococcus bovis from artificial plaque. One non-oral S. salivarius strain had ureases with slightly slower mobility. The electrophoretic pattern and mobility of ureases extracted from human mixed salivary bacteria were identical to those from S. salivarius except for an additional set of urease bands from unknown species of bacteria. There were no ureases from saliva matching those from Staphylococcus epidermidis--a contributor to ureolysis in artificial plaque. We conclude that there is considerable biochemical homogeneity among S. salivarius ureases and possibly other ureolytic streptococci. In saliva, urea is metabolized mainly by streptococcal ureases.

Dental Plaque↗
PubMed1991

Intracellular xylitol-phosphate hydrolysis and efflux of xylitol in Streptococcus sobrinus.

The parental strain Streptococcus sobrinus (Streptococcus mutans ATCC 27352), which is known to transport, phosphorylate and accumulate xylitol intracellularly as nonmetabolizable xylitol-phosphate (xylitol-sensitive (XS) strain) and its xylitol-resistant (XR) spontaneous mutant were used to further investigate the inhibitory action of xylitol on oral streptococci. Fructose-grown XR cells did not accumulate xylitol-phosphate, indicating that the inducible fructose PTS is incapable of transporting the pentitol. The intracellularly accumulated pentitol-phosphate by the XS cells did not prevent the subsequent uptake and degradation of glucose or fructose, despite a drop in the PEP pool and a 50% inhibition of the glucose but not the fructose catabolism. Intracellular dephosphorylation of the pentitol-phosphate and release of xylitol in the extracellular medium resulted in a rapid decrease of the intracellular level of this nonmetabolizable product. A Mg(++)- or Mn(++)-independent sugar-phosphate hydrolysing activity capable of splitting xylitol-phosphate was demonstrated in both XS and XR strains. Preincubation in the presence of N1-ethylmaleimide (NEM) and xylitol or NEM and fructose resulted in the subsequent inhibition of both xylitol uptake and efflux. The efflux kinetic at various temperatures is compatible with a facilitated diffusion by the phosphotransferase system EIIfru without, however, excluding the existence of an additional exit route, but it excludes a simple diffusion exit process. The results are consistent with the existence of a xylitol futile cycle contributing to the growth inhibition of S. sobrinus by the pentitol without excluding a toxic effect of xylitol-phosphate. Discrepancies in the literature on the action of xylitol on S. mutans could be explained in the light of the evidence presented.

Dental Plaque↗
PubMed1996

Immunochemical characterization of the carbohydrate antigens of serotype k and Lancefield group G "Streptococcus milleri".

Carbohydrate antigens of the serotype k/Lancefield group G "Streptococcus milleri" were extracted by autoclaving whole cells of the type k reference strain Streptococcus anginosus K214-2K. The type k and group G antigen molecules are separated from each other and partially purified by a DEAE-Sephadex A25 column chromatography followed by a Sephadex G-100 gel filtration. In the double diffusion and the immunoelectrophoresis, the type k and group G antigen preparations obtained yielded single bands with their homologous antisera respectively. The type k antigen preparation contained principally glycerol, rhamnose, ribitol, galactose and glucose in a molar ratio of 0.54:1.20:0.43:0.33:1.00. The quantitative precipitin inhibition test indicated that beta(1-6)glucosyl-glucose (gentiobiose) sequence played a major role in immunodeterminant structure. Thus, the type k antigen of "S. milleri" appears to be a new carbohydrate type antigen that is chemically different from any Ottens type antigen. In contrast, the group G antigen preparation contained high proportion of rhamnose in addition to glucose, N-acetylglucosamine and N-acetylgalactosamine in a molar ratio of 6.45:1.00:0.24:1.15, and the rhamnose residue was involved in the immunodominant epitope, being in good agreement with the previously proposed chemical structure of the group antigen.

Acetylgalactosamine↗