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PubMed2006

Skl, a novel choline-binding N-acetylmuramoyl-L-alanine amidase of Streptococcus mitis SK137 containing a CHAP domain.

The skl gene from Streptococcus mitis SK137 encodes a peptidoglycan hydrolase (Skl) that has been purified and biochemically characterized. Analysis of the degradation products obtained by digestion of pneumococcal cell walls with Skl revealed that this enzyme is an N-acetylmuramoyl-L-alanine amidase (EC 3.5.1.28), showing optimum activity at 30 degrees C and at a pH of 6.5. Skl is a unique member of the choline-binding family of proteins since it contains a cysteine, histidine-dependent amidohydrolases/peptidases (CHAP) domain. The CHAP domain of Skl showed homology to lysins of unknown especificity from a variety of streptococcal prophages. Skl represents the first characterized member of a new subfamily of CHAP-containing choline-binding proteins.

Amino Acid Sequence↗
PubMed1981

Mixed culture studies of Streptococcus mitis and oral enterococci.

Strains of Streptococcus mitis and oral enterococci were grown in mixed culture in 0.5% peptone, 1.0% peptone and 1.0% peptone supplemented with 0.5% glucose. In all three media the enterococci inhibited the S. mitis strains. The inhibition was strongest in the glucose supplemented broths, probably due to pH toxicity. Inhibition in the unsupplemented broths was not similarly caused, but no other inhibitory factors could be isolated from these culture.

Culture Media↗
PubMed1985

[Neonatal meningitis caused by Streptococcus mitis].

We report on a female newborn, 37 weeks of gestational age, who - after normal pregnancy and delivery - fell ill with a neonatal meningitis caused by streptococcus mitis. Until now this bacillus has been thought to be apathogen. The disease was cured completely by Penicillin therapy. The infection of a healthy newborn caused by streptococcus mitis, a streptococcus viridans, has not been described before.

Bacteriological Techniques↗
PubMed1964

METABOLISM OF INTRACELLULAR POLYSACCHARIDE BY STREPTOCOCCUS MITIS AND ITS RELATION TO INDUCIBLE ENZYME FORMATION.

Gibbons, R. J. (Forsyth Dental Center, Boston Mass.). Metabolism of intracellular polysaccharide by Streptococcus mitis and its relation to inducible enzyme formation. J. Bacteriol. 87:1512-1520. 1964.-The synthesis and catabolism of an intracellular iodine staining polysaccharide produced from glucose by Streptococcus mitis was investigated. Approximately 15% of the total glucose metabolized by buffered suspensions of S. mitis was assimilated. Over 90% of the assimilated glucose was converted into a polysaccharide of the glycogen-amylopectin type. Use of uniformly labeled C(14)-glucose provided a convenient method for determining polysaccharide accumulation in this organism. Glucose assimilation occurred at a rate of over 80 mug of glucose per hr per 100 mug of starting dry cell weight. Prolonged assimilation produced cells containing over 50% polysaccharide on a dry weight basis. Accumulated polysaccharide was catabolized at the same rate when the organism was suspended in buffer, sugar-free broth, or sugar-free broth containing thiomethyl galactoside. Metabolic intermediates produced from polysaccharide catabolism did not markedly repress inducible enzyme synthesis. The last glucose molecules incorporated into polysaccharide were among the first molecules to be removed during catabolism. Catabolism of polysaccharide provides S. mitis with energy in a utilizable form, for cells containing polysaccharide increased in beta-galactosidase activity when induced with thiomethyl galactoside in the absence of an exogenous energy source. Cells devoid of polysaccharide, and a polysaccharide-negative variant of S. mitis did not increase in beta-galactosidase activity when induced in a similar manner. It appears that the intracellular polysaccharide is the sole substrate for the endogenous metabolism of S. mitis.

Carbohydrate Metabolism↗
PubMed1966

Metabolism of the reserve polysaccharide of Streptococcus mitis: Properties of a transglucosylase.

1. A transglucosylase has been separated from cell extracts of Streptococcus mitis, and has been partially purified by chromatography on DEAE-cellulose. 2. The transglucosylase was present in the six strains of Streptococcus mitis that were examined, and the activity of the enzyme was the same whether the cells had grown on glucose or on maltose. Four of the strains could store intracellular iodophilic polysaccharide when grown on high concentrations of glucose or maltose (1%), but none of the strains stored polysaccharide during growth on 0.1% glucose. The activity of transglucosylase in cell extracts was the same whether or not the cells had stored polysaccharide. 3. The transglucosylase degrades amylose in the presence of a suitable acceptor, transferring one or more glucosyl residues from the non-reducing end of the donor to the non-reducing end of the acceptor. With [(14)C]glucose as acceptor the maltodextrins produced were labelled in the reducing glucose unit only. 4. The enzyme can synthesize higher maltodextrins from maltose and maltotriose. Maltotetraose is disproportionated to give products of sufficient chain length to give a stain with iodine. 5. The action pattern of S. mitis during the degradation of synthetic amylose was shown to be intermediate between the single-chain and multi-chain mechanism.

Journal Article↗
PubMed1986

Preparation of a sialic acid-binding protein from Streptococcus mitis KS32AR.

A recent report has identified a lectin on the surfaces of several strains of Streptococcus mitis and Streptococcus sanguis with specificity for an N-acetylneuraminic acid alpha 2,3-galactose-beta 1,3-N-acetylgalactosamine sequence (P.A. Murray, M.J. Levine, L.A. Tabak, and M.S. Reddy, Biochem. Biophys. Res. Commun. 106:390-396, 1982). In the present study, purification and characterization of this sialic acid-binding protein (SABP) was begun. A clinical isolate of S. mitis was grown to mid stationary phase in synthetic FMC medium and then extracted with lithium 3,5-diiodosalicylate. Lyophilized extract was subjected to gel filtration on a Sephadex G-200 column, giving four protein peaks (A to D). Peak B, shown by hemagglutination assay to contain SABP, was next subjected to affinity chromatography on a Sepharose-4B matrix coupled to fetuin glycopeptides. After an extensive washing, peak B materials bound to the affinity matrix were eluted with buffered N-acetylneuraminic acid. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis with 2-mercaptoethanol on 7.5% gels of affinity-purified materials revealed components of 96, 70, and 65 kilodaltons (kDa). Without reducing agent, only the 65-kDa band and materials which did not penetrate the gel were visualized, suggesting that the 96- and 70-kDa components were disulfide linked. The chemical cross-linking agent, disuccinimidyl suberate, was used to demonstrate specific interactions between the SABP preparation and [14C]fetuin glycopeptides. After cross-linking, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography revealed the 96- and 70-kDa components, indicating that the SABP is at least bivalent. These findings support our previous suggestion that human salivary glycoproteins facilitate clearance of selected oral streptococci via specific interactions between sialic acid-containing oligosaccharides and a carbohydrate-binding protein on the bacterial cell surface.

Adhesiveness↗
PubMed1987

Multiply resistant Streptococcus mitis isolated from conjunctival exudate of newborns.

Streptococcus mitis resistant to most of the commonly used antimicrobial agents but sensitive to cefotaxime, clindamycin, vancomycin and rifampicin was isolated from conjunctival exudate of newborns. The isolate had group C streptococcal antigen, was beta-haemolytic on horse but alpha-haemolytic on sheep blood agar plates and might therefore be misidentified as beta-haemolytic group C streptococci.

Conjunctiva↗
PubMed1978

Interactions between Neisseria sicca and viridin B, a bacteriocin produced by Streptococcus mitis.

Viridin B, a bacteriocin produced by Streptococcus mitis (mitior), is bactericidal to Neisseria sicca. Oxygen consumption by actively growing N. sicca cultures ceased immediately upon exposure to viridin B. Adenosine triphosphate production was slightly enhanced within 1 h of exposure to the bacteriocin but was subsequently repressed. The uptake and incorporation of glucose was prevented in the presence of viridin B. The bacteriocin also blocked uptake of an amino acid mixture in chloramphenicol-pretreated cells. Pretreatment or concomitant treatment with a variety of antibiotics known to inhibit specific synthetic pathways did not alter the inhibition of macromolecular synthesis produced by the bacteriocin. Although viridin B blocks protein and nucleic acid syntheses, no degradation of such macromolecules was observed. The inhibitory effects of viridin B on macromolecular synthesis and on viability required the presence of sufficient nutrients to allow active metabolism of N. sicca. The bacteriocin did not inhibit viability or macromolecular synthesis in anaerobically incubated N. sicca. Thus, active, oxidative metabolism by N. sicca cells is essential for viridin B action. A model for viridin B action is proposed.

Adenosine Triphosphate↗
PubMed2004

rpoB mutations in Streptococcus mitis clinical isolates resistant to rifampin.

Activity of rifampin against 129 Streptococcus mitis isolates obtained from patients with hematologic cancer was investigated. One hundred twenty-five strains were susceptible to rifampin, and 4 were resistant (MIC = 32 to 64 microg/ml). Resistance to rifampin was related to mutations in the rpoB gene: His(526)Asn in three strains and His(526)Asp in one strain.

Antibiotics, Antitubercular↗
PubMed2000

Streptococcus mitis septicaemia and hepatitis.

The case of an otherwise well 9-y-old boy with fever, papular rash, jaundice and impaired liver function is presented. Streptococcus mitis sensitive to penicillin grew in blood culture. The boy had an excellent outcome. The clinical spectrum of viridans streptococci may be wider than currently anticipated, and Streptococcus mitis may cause septicaemia and hepatitis in immunocompetent individuals.

Acute Disease↗
PubMed2000

Genetic relationships between clinical isolates of Streptococcus pneumoniae, Streptococcus oralis, and Streptococcus mitis: characterization of "Atypical" pneumococci and organisms allied to S. mitis harboring S. pneumoniae virulence factor-encoding genes.

The oral streptococcal group (mitis phylogenetic group) currently consists of nine recognized species, although the group has been traditionally difficult to classify, with frequent changes in nomenclature over the years. The pneumococcus (Streptococcus pneumoniae), an important human pathogen, is traditionally distinguished from the most closely related oral streptococcal species Streptococcus mitis and Streptococcus oralis on the basis of three differentiating characteristics: optochin susceptibility, bile solubility, and agglutination with antipneumococcal polysaccharide capsule antibodies. However, there are many reports in the literature of pneumococci lacking one or more of these defining characteristics. Sometimes called "atypical" pneumococci, these isolates can be the source of considerable confusion in the clinical laboratory. Little is known to date about the genetic relationships of such organisms with classical S. pneumoniae isolates. Here we describe these relationships based on sequence analysis of housekeeping genes in comparison with previously characterized isolates of S. pneumoniae, S. mitis, and S. oralis. While most pneumococci were found to represent a closely related group these studies identified a subgroup of atypical pneumococcal isolates (bile insoluble and/or "acapsular") distinct from, though most closely related to, the "typical" pneumococcal isolates. However, a large proportion of isolates, found to be atypical on the basis of capsule reaction alone, did group with typical pneumococci, suggesting that they have either lost capsule production or represent as-yet-unrecognized capsular types. In contrast to typical S. pneumoniae, isolates phenotypically identified as S. mitis and S. oralis, which included isolates previously characterized in taxonomic studies, were genetically diverse. While most of the S. oralis isolates did fall into a well-separated group, S. mitis isolates did not cluster into a well-separated group. During the course of these studies we also identified a number of potentially important pathogenic isolates, which were frequently associated with respiratory disease, that phenotypically and genetically are most closely related to S. mitis but which harbor genes encoding the virulence determinants pneumolysin and autolysin classically associated with S. pneumoniae.

Bacterial Proteins↗
PubMed1999

Molecular characterization of multidrug resistance in Streptococcus mitis.

Antimicrobial resistance was characterized for 14 strains of Streptococcus mitis. HinfI restriction fragment length mapping of gyrA PCR amplicons from three ciprofloxacin-resistant isolates correlated with mutations associated with such resistance in other organisms. By using PCR, seven erythromycin-resistant strains were found to possess either the mef or ermB gene. Hybridization revealed tet(M) in seven tetracycline-resistant isolates.

Drug Resistance, Microbial↗
PubMed2002

Apparent failure of endocarditis prophylaxis caused by penicillin-resistant Streptococcus mitis.

Antibiotic resistance among viridans streptococci has increased with Streptococcus mitis being more resistant than other viridans species. In a case presented in this report, it is possible that antibiotic resistance contributed to an apparent failure of endocarditis prophylaxis. The patient had undergone periodontal surgery on 2 separate occasions and in both instances was administered 2 g of amoxicillin orally 1 hour before each procedure. He subsequently developed a subacute illness and had multiple blood cultures drawn that grew S. mitis with a minimum inhibitory concentration of 1.0 microg/mL for penicillin. Transesophageal echocardiogram provided further evidence of infective endocarditis with vegetations seen on the anterior leaflet of the mitral valve. Combination therapy with high-dose intravenous aqueous crystalline penicillin G and gentamicin sulfate for 4 weeks was curative. Clindamycin, rather than amoxicillin, has since been used as dental prophylaxis for subsequent procedures.

Aged↗
PubMed1988

Comparison between the adhesion to solid substrata of Streptococcus mitis and that of polystyrene particles.

The adhesion of Streptococcus mitis to solid substrata from phosphate suspensions with various ionic strengths was studied and compared with the adhesion of polystyrene particles. At all ionic strengths, the interfacial free energy of adhesion governed the relative number of bacteria or polystyrene particles adhering at equilibrium, except that in a low-ionic-strength buffer, adhesion occurred less frequently because of increased electrostatic repulsion. Large differences between bacterial and polystyrene particle adhesion were observed, as indicated by the ratio of bacteria to polystyrene particles adhering, which decreased from 30 to 4 with a change from low to high ionic strength.

Adhesiveness↗
PubMed1981

Spontaneous aggregation of streptococcus mitis ATCC 903.

Glucose or sucrose grown cells of Streptococcus mitis ATCC 903 bind spontaneously to the surface of each other producing visible microbial aggregates upon incubation in 10 mM phosphate, citrate-phosphate or tris-maleate buffers. Aggregation was delayed and proceeded at a slower rate when bacteria grown in a culture medium with a low carbohydrate/nitrogen ratio were used. Growth in this culture medium resulted in carbohydrate limitation. The aggregation was highly reproducible and was unaffected by pH in the range of 4.4-7.0 but was decreased at pH 8.0 and completely inhibited at pH 9.0. No inhibition of the reaction was observed when a series of simple and complex carbohydrates were added. There was no significant difference in the rate of aggregation at 20, 30 and 37 degrees C. Aggregation occurred at a demonstrable rate of 0 degrees. Chloramphenicol did not inhibit aggregation. Since inhibition of aggregation was obtained by treatment of bacteria with trypsin or heat it appears that protein of glycoprotein components on the bacterial surface were involved in the reaction.

Bacteriological Techniques↗
PubMed2006

Physiological and serological variation in Streptococcus mitis biovar 1 from the human oral cavity during the first year of life.

OBJECTIVE: The purpose of the study was to explore the physiological and antigenic diversity of a large number of Streptococcus mitis biovar 1 isolates in order to begin to determine whether these properties contribute to species persistence. DESIGN: S. mitis biovar 1 was collected from four infants from birth to the first year of age. At each of eight to nine visits, 60 isolates each were obtained from the cheeks, tongue and incisors (once erupted) yielding 4440 in total. These were tested for production of neuraminidase, beta1-N-acetylglucosaminidase, beta1-N-acetylgalactosaminidase, IgA1 protease and amylase-binding. Antigenic diversity was examined by ELISA and Western immunoblotting using antisera raised against S. mitis biovar 1 NCTC 12261(T) and SK145. RESULTS: Three thousand three hundred and thirty (75%) of the isolates were identified as S. mitis biovar 1 and 3144 (94.4%) could be divided into four large phenotypic groups based on glycosidase production. Fifty-four percent of the isolates produced IgA1 protease, but production was disproportionate among the phenotypes. Between one-third and one-half of the strains of each phenotype bound salivary alpha-amylase. Antisera against strains NCTC 12261(T) and SK145 displayed different patterns of reactivity with randomly selected representatives of the four phenotypes. CONCLUSIONS: S. mitis biovar 1 is physiologically and antigenically diverse, properties which could aid strains in avoiding host immunity and promote re-colonization of a habitat or transfer to a new habitat.

Antigens, Bacterial↗
PubMed1994

The cell wall polysaccharide of Streptococcus gordonii 38: structure and immunochemical comparison with the receptor polysaccharides of Streptococcus oralis 34 and Streptococcus mitis J22.

As part of our ongoing investigations involving lectin-mediated adhesion among oral bacteria, the receptor polysaccharide from Streptococcus gordonii 38 was isolated and characterized. Carbohydrate analysis of the hydrolysed S. gordonii 38 polysaccharide by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) showed galactose (Gal) (2 mol), N-acetylgalactosamine (GalNAc) (1 mol), rhamnose (Rha) (2 mol), glucose (Glc) (1 mol) and galactosamine-6-phosphate (1 mol). Mild acid hydrolysis of the polysaccharide yielded a heptasaccharide repeating unit. The structure of the heptasaccharide repeating unit was determined by high-resolution NMR spectroscopy which includes various homonuclear (DQF-COSY, TQF-COSY, NOESY and HOHAHA) and heteronuclear experiments (HMQC), including linkage assignments by 1H-13C long-range correlation (HMBC). Complete 1H and 13C NMR assignments for the intact polysaccharide yielded the covalent structure of a heptasaccharide repeating unit: [Formula: see text] The structure of the strain 38 polysaccharide is closely related to those of Streptococcus mitis J22 and Streptococcus oralis 34. Thus, the difference between the strain 38 and J22 heptasaccharides was at their reducing ends, with GaLNAc beta-(1-->3)-Gal in the former and Gal beta-(1-->3)-GalNAc in the latter, while the difference between the 38 heptasaccharide and 34 hexasaccharide was at the non-reducing ends, where a rhamnose branch occurred in the former but not the latter structure. When compared by their quantitative precipitin curves with rabbit antibodies against each streptococcal strain, the strain 38 polysaccharide reacted more like the polysaccharide of strain J22 than that of strain 34. In contrast, each strain was recognized by the Gal- and GalNAc-reactive lectins of Actinomyces spp., but only strains 38 and 34 were recognized by GalNAc-sensitive lectins of other streptococci. These findings strongly support the hypothesis that the immunogenic features of these polysaccharides are distinct from those detected by lectin binding.

Animals↗