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PubMed1985

Immunochemical properties and intracellular localization of two molecular forms of arginine aminopeptidase in Streptococcus mitis ATCC 9811.

Streptococcus mitis contains two multiple forms of arginine aminopeptidase (I and II) which differ from each other with respect to their content, immunochemical properties and cellular localization. Immunological analyses by Ouchterlony double immunodiffusion and immunoprecipitation showed an antigenic difference between each form by the use of antisera specific for each enzyme. The amounts of enzymes I and II within the cell were estimated to be 230 +/- 4.3 and 646 +/- 20 ng/mg protein (+/- S.D.), respectively, using a standard curve of purified enzyme in a single radial immunodiffusion assay. When intact cells were treated with the cell wall lytic enzyme, N-acetylmuramidase, though both enzymes were solubilized, a time lag was observed for the solubilization of enzyme II. Enzyme I was detected only in the cell wall fraction and showed no detectable associated with the membrane. Although most of the enzyme II activity was recovered in the cell wall fraction, a slight amount (7.5%) of the total activity was also found in the membrane fraction.

Aminopeptidases↗
PubMed2001

[A study on the pathogenesis of Streptococcus mitis exotoxin].

OBJECTIVE: To study the isolation, purification and pathogenesis of Streptococcus mitis pyrogenic exotoxin causing toxic shock syndrome. METHODS: Streptococcus mitis isolated from patients' throat were shaking cultivated. After being centrifuged, the supernatant fluid of the culture was precipitated with 20%, 40%, 60%, 80% (NH(4))(2)SO(4) respectively and the fast protein liquid chromatography(FPLC) was used for the final step of purification. Rabbits receiving subcutaneous injection with respective purified proteins were monitored daily for fever. The ability of the purified proteins to enhance the susceptibility of the rabbits to lethal Escherichia coli endotoxin shock is recorded, when the endotoxin was injected intravenously 4 hours after administration of 10 microg Streptococcus mitis exotoxin. RESULTS: Only the protein precipitated by 20% (NH(4))(2)SO(4) (molecular weight is 34,000) from culture supernatant fluid was pyrogenic for rabbits (average temperature increase near 1 degrees C), and it can also cause the proliferation of rabbit splenocytes (mitogenicity). All the animals receiving subcutaneous injection of exotoxin containing purified proteins precipitated with higher concentrations of (NH(4))(2)SO(4) died within 16 approximately 29 hours after intravenous injection of the Escherichia coli endotoxin, demonstrating the enhanced susceptibility of the animals to lethal endotoxin shock. The control rabbits displayed none of these effects. CONCLUSION: Streptococcus mitis exotoxin is a novel streptococcal pyrogenic exotoxin.

Animals↗
PubMed2006

Fulminant septicaemia caused by multi-drug-resistant Streptococcus mitis following unrelated cord blood transplantation.

Streptococcus mitis (a common and usually harmless bacterium found in the nose, mouth and throat) can have an unusually high level of resistance to beta-lactam antibiotics. We report a patient who developed fatal Streptococcus mitis septicaemia following unrelated cord blood transplantation. Administration of vancomycin to patients with recurrent fever during allogeneic stem cell transplantation might be indicated.

Child↗
PubMed1983

Ion interactions in the aggregation of Streptococcus mitis.

Spontaneous aggregation of Streptococcus mitis ATCC 903 was highly dependent on various electrolytes such as sodium chloride, sodium phosphate or potassium phosphate with an optimum at 10 mM concentration. No aggregation was obtained in distilled water. Addition of a number of mono- or divalent ions to bacteria incubated in 10 mM phosphate or tris-maleate buffers resulted in an inhibition of aggregation. A 50% inhibition of aggregation was obtained at low concentrations of calcium, magnesium, sulphate and carbonate ions. Other mono- and divalent ions tested were needed in significantly higher concentrations in order to obtain the same inhibition. Aggregation inhibition by calcium or magnesium salts was reversed by chelation with EDTA. Washing bacteria previously treated with magnesium or calcium salts resulted in a complete recovery of aggregating ability. Spontaneously aggregated cells were completely dissociated at 10 mM magnesium sulphate or 100 mM sodium chloride. The results indicate that electrostatic interactions are of major importance for aggregation of S. mitis ATCC 903 whereas hydrophobic interaction plays a minor role.

Calcium↗
PubMed1984

Induction of aggregation in Streptococcus mitis by certain ions.

Streptococcus mitis ATCC 903 aggregated when suspended in salt solutions containing the ions zinc, aluminium, lanthanum and cerium. This aggregation was very rapid as compared to spontaneous aggregation occurring in this strain. It was not inhibited by alkaline pH. Washed bacteria treated previously with zinc sulphate recovered and retained their ability to aggregate spontaneously at a slow rate. No such effect was observed with lanthanum-induced aggregation. The aggregates caused by lanthanum chloride were stable in sodium chloride up to 5 M concentrations. Magnesium sulphate dissociated these aggregates at 250 mM. Aggregation induced by zinc sulphate was less stable in these salts. The spontaneously aggregated cells were dissociated completely at 10 mM magnesium sulphate or 100 mM sodium chloride. Bacteria which had lost their ability to aggregate, owing to trypsin or beta-galactosidase treatment, were re-aggregated after addition of zinc, lanthanum or aluminium ions. Galactosamine inhibited the spontaneous aggregation and aggregation induced by zinc but not the aggregation induced by lanthanum or aluminium ions. In conclusion, the results provide a molecular model of induced and spontaneous aggregations where the two phenomena are qualitatively different.

Aluminum↗
PubMed1986

Streptococcus mitis endocarditis. Report of 17 cases.

Seventeen patients with Streptococcus mitis endocarditis were treated at a municipal hospital over a three-year period. Thirteen patients were intravenous drug addicts. Streptococcus mitis has a predilection for right-sided endocarditis in intravenous drug addicts and left-sided endocarditis in non-drug addicts. Streptococcus mitis is highly susceptible to therapy with penicillin G potassium (minimal inhibitory concentration less than or equal to 0.1 mg/L of penicillin in all of these 17 cases), and four to six weeks of therapy is safe and effective.

Adult↗
PubMed2003

Genomic organization and molecular characterization of SM1, a temperate bacteriophage of Streptococcus mitis.

The direct binding of Streptococcus mitis to human platelets is mediated in part by two proteins (PblA and PblB) encoded by a lysogenic bacteriophage (SM1). Since SM1 is the first prophage of S. mitis that has been identified and because of the possible role of these phage-encoded proteins in virulence, we sought to characterize SM1 in greater detail. Sequencing of the SM1 genome revealed that it consisted of 34,692 bp, with an overall G+C content of 39 mol%. Fifty-six genes encoding proteins of 40 or more amino acids were identified. The genes of SM1 appear to be arranged in a modular, life cycle-specific organization. BLAST analysis also revealed that the proteins of SM1 have homologies to proteins from a wide variety of lambdoid phages. Bioinformatic analyses, in addition to N-terminal sequencing of the proteins, led to the assignment of possible functions to a number of proteins, including the integrase, the terminase, and two major structural proteins. Examination of the phage structural components indicates that the phage head may assemble using stable multimers of the major capsid protein, in a process similar to that of phage r1t. These findings indicate that SM1 may be part of a discrete subfamily of the Siphoviridae that includes at least phages r1t of Lactococcus lactis and SF370.3 of Streptococcus pyogenes.

Base Composition↗
PubMed1992

Physico-chemical and structural properties of the surfaces of Peptostreptococcus micros and Streptococcus mitis as compared to those of mutans streptococci, Streptococcus sanguis and Streptococcus salivarius.

The surface properties of nine Streptococcus mitis and four Peptostreptococcus micros strains from the oral cavity were examined and compared with a large group of oral streptococci. Zeta potential and contact angle measurements were employed to determine physico-chemical cell surface properties. In addition, elemental surface concentration ratios were obtained via X-ray photoelectron spectroscopy, and surface structures were examined with transmission electron microscopy. The S. mitis and P. micros strains were found to have higher isoelectric points, higher hydrophobicities and higher N/C surface concentration ratios than some other oral streptococci. The combined data suggest that both species possess large amounts of surface protein. All the S. mitis strains displayed abundant surface fibrils in negative staining, but the P. micros strains were devoid of surface appendages indicating that surface protein is present in different forms in the two species. The surfaces of S. mitis and P. micros type strains differed significantly from the other strains examined.

Bacterial Adhesion↗
PubMed2006

Identification of a secreted cholesterol-dependent cytolysin (mitilysin) from Streptococcus mitis.

We have detected a cholesterol-dependent cytolysin, which we have named mitilysin, in a small number of Streptococcus mitis isolates. We have sequenced the mitilysin gene from seven isolates of S. mitis. Comparisons with the pneumococcal pneumolysin gene show 15 amino acid substitutions. S. mitis appear to release mitilysin extracellularly. Certain alleles of mitilysin are not recognized by a monoclonal antibody raised to the related toxin pneumolysin. Based on enzyme-linked immunosorbent assay and neutralization assay results, one isolate of S. mitis may produce a further hemolytic toxin in addition to mitilysin. As genetic exchange is known to occur between S. mitis and Streptococcus pneumoniae, this finding may have implications for the development of vaccines or therapies for pneumococcal disease that are based on pneumolysin.

Amino Acid Sequence↗
PubMed1997

Endogenous endophthalmitis caused by Streptococcus mitis.

PURPOSE: To report endogenous endophthalmitis caused by Streptococcus mitis. METHODS: A 3-year-old girl was hospitalized for possible retinoblastoma after she suddenly developed a red and sensitive left eye. After administration of anesthesia, we examined the patient and obtained samples of aqueous, vitreous, and blood for culture. RESULTS: Blood and vitreous cultures grew S mitis. Intravenous and intravitreal injections of antibiotics were used to treat the infection. CONCLUSIONS: Streptococcus mitis should be considered a cause of endogenous endophthalmitis.

Administration, Topical↗
PubMed1993

Streptococcus mitis septicemia in leukemia patients; clinical features and outcome.

The frequency of streptococcal infections has been reported to be increasing. To determine the significance of such infections complicating treatment of leukemia, we studied the incidence and clinical features of Streptococcus mitis septicemia among 51 leukemia patients in our department. During 166 consecutive treatment courses for leukemia, eight episodes of Streptococcus mitis septicemia were observed in 35 septicemic patients. In seven out of eight episodes (88%), severe mucositis developed after aggressive chemotherapy, suggesting that oral mucosa might be the site of entry for Streptococcus mitis. The isolates were sensitive to imipenam/cilastatin and cefuzonam, and were relatively resistant to amikacin. Although none of the patients died of Streptococcus mitis septicemia, life-threatening adult respiratory distress syndrome (ARDS) developed in two independent treatment courses. We should thus be aware of the risk of ARDS in patients with Streptococcus mitis septicemia.

Adolescent↗
PubMed1998

Cellular heterogeneity in non-immune IgG-binding in a strain of Streptococcus mitis.

Electron microscopy revealed that Streptococcus mitis ATCC 903 bound gold probes conjugated with goat IgG by non-immune mechanisms. Only a few of the cells and the cell wall fragments could bind IgG, in contrast to Staphylococcus aureus and Streptococcus group G which showed a more homogeneous binding to nearly all cells or cell wall fragments.

Cell Wall↗
PubMed1983

Hydrogen peroxide-mediated antagonism against serratia marcescens by Streptococcus mitis.

The alpha-hemolytic Streptococcus mitis strain no. 17-1, isolated from the oral cavity of an healthy female adult, antagonized the growth of all 24 test strains of Serratia marcescens examined; furthermore, this strain inhibited the growth of various strains of Staphylococcus aureus, S. epidermidis, Streptococcus pyogenes, S. agalactiae, S. pneumoniae, Haemophilus influenzae, Listeria monocytogenes, and Corynebacterium diphtheriae. However, strans of Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, and Pseudomonas aeruginosa proved refractory. The mechanism of microbial antagonism was due to production and release of hydrogen peroxide under aerobic atmospheric conditions, which was neutralized through incorporation of bovine liver catalase into the solid assay medium.

Adult↗
PubMed1994

Lung abscess due to Streptococcus mitis: case report and review.

Streptococcus mitis is a bacterium traditionally regarded as a normal commensal of the oropharynx, skin, and intestinal and genital tracts. To our knowledge, we describe the first case of bilateral lung abscesses caused by S. mitis in an immunocompetent host. The abscesses were successfully treated with clindamycin and gentamicin. Our case illustrates that S. mitis should be considered a cause of pulmonary abscesses.

Clindamycin↗
PubMed1987

Metal ion inactivation and chelator stimulation of Streptococcus mitis arginine aminopeptidase.

Activation of Streptococcus mitis (ATTC 9811) arginine aminopeptidase resulted in removal of the metal(s) from the enzyme molecule, and the action of the heavy metal ion in the inactivation process was shown to involve formation of a chelate complex between the enzyme molecule and metal or oxidation of functional group(s) on the enzyme surface. The enzyme also underwent activation by bovine serum albumin, amino acids, phosphate, and citric acid, which are probable physiological chelators.

Aminopeptidases↗
PubMed1994

Measurement of long-range2 13C-1H coupling constants of 95% uniformly 13C-labeled polysaccharide from Streptococcus mitis J22.

The coaggregation of Streptococcus mitis strain J22 in the early stages of dental plaque formation has been shown to result from interaction of cell wall polysaccharides with lectins on the surface of other oral bacterial species. This bacterium was grown in a medium containing 13C as the sole carbon source. We have isolated the lectin receptor polysaccharide from this strain with full enrichment in 13C and have determined a number of two-bond and three-bond 13C-1H coupling constants from measurements of the offsets in two-dimensional homonuclear nmr spectra [exclusive correlated spectroscopy (E-COSY) method]. A scheme for reliable extraction of these coupling constants from homonuclear Hartmann-Hahn and nuclear Overhauser effect spectroscopy spectra is tested in model compounds. We interpret the three-bond coupling across the glycosidic linkage in terms of dihedral angles in order to provide conformational information to supplement molecular modeling and nuclear Overhauser effect data. We show that the E-COSY method works well even for coupling constants smaller than the nmr line width and that a number of the 3JCH across the glycosidic linkage are in the range of 1-2 Hz, which is much smaller than many previously reported values.

Carbohydrate Conformation↗
PubMed1983

Penicillin therapy of experimental endocarditis induced by tolerant Streptococcus sanguis and nontolerant Streptococcus mitis.

The response of tolerant Streptococcus sanguis and nontolerant Streptococcus mitis infections to penicillin therapy was compared in the rabbit model of endocarditis. The minimal inhibitory and bactericidal concentrations of penicillin were 0.1 and 0.1 mug/ml, respectively, for S. mitis and 0.05 and 6.2 mug/ml, respectively, for S. sanguis. Time-kill studies done in vitro with penicillin concentrations of 2 and 20 mug/ml demonstrated minimal killing of the tolerant strain, with a 3 log difference in survival between the two strains after 24 and 48 h. Both strains produced endocarditis with comparable bacterial densities on the valvular vegetations. Rabbits were treated with procaine penicillin G in two dosage regimens, 80,000 or 5,000 U/kg given every 8 h. There was no difference between bacterial densities in valvular vegetations removed from rabbits infected with either strain after 2, 4, or 6 days of treatment with the high-dose regimen (serum penicillin concentration at 0.5 h, 9.4 mug/ml), despite the fact that serum bactericidal activity against the tolerant strain at 0.5 h was minimal. With the low-dose penicillin regimen (serum concentration at 0.5 h, 2.5 mug/ml), therapy was significantly less effective in the tolerant group only after 6 days of treatment. Similar results were obtained when penicillin was administered in low and high doses to prevent infection. In this animal model of infection, penicillin tolerance was associated with a diminished response to penicillin therapy only when the dose was severely restricted. In the high-dose regimen, there was no difference in the response to penicillin therapy between animals infected with either strain, despite the presence of only minimal serum bactericidal activity in the rabbits infected with the tolerant strain.

Animals↗
PubMed1993

Chromosomally mediated high-level gentamicin resistance in Streptococcus mitis.

Four blood culture isolates of Streptococcus mitis were found to be resistant to penicillin (MIC, 16 to 32 micrograms/ml) and gentamicin (MIC, 128 or 1,000 micrograms/ml), and the two antibiotics demonstrated a lack of in vitro synergy. As shown by polymerase chain reaction assays, the structural gene known to encode high-level gentamicin resistance in Enterococcus faecalis, Enterococcus faecium, and Streptococcus agalactiae was also present in all four S. mitis strains. Attempts to isolate plasmids were unsuccessful, but an oligonucleotide probe derived from the gentamicin resistance gene hybridized to distinct restriction fragments of genomic DNA, suggesting that the resistance genes in these strains are integrated into the bacterial chromosome.

Chromosomes, Bacterial↗