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PubMed1975

Streptococcus salivarius, Streptococcus sanguis and Streptococcus "mitis" as indicators of contamination of root canal cultures.

Small samples were taken from the first drop of saliva entering an operation field for root canal treatment isolated by rubber dam, which was intentionally leaky. The samples were primarly cultured in TAS- and BLH-medium and on MS-agar aerobically. The culture media were inoculated directly and via transport medium (VMG III). The cultures were analysed for Strep. salivarius, Strep. sanguis and/or Strep. "mitis" after subculture on MS-agar as soon as visible growth had appeared in the broth media and again after a further 2 days. The following observations were made: 1. Strep. salivarius was almost regularly found in either or both of TAS- and BLH-medium at primary culture of the samples contaminated with saliva. The result was the same whether these broth media were inoculated directly or via VMG III. 2. Strep. salivarius was always found in mixed cultures and was nearly always accompanied by Strep. sanguis and/or Strep. "mitis". 3. Strep. salivarius as well as Strep. sanguis survived two days after visible growth significantly more oftern in BLH-medium than in TAS-medium. The findings lend support to the hypothesis based on clinical studies that when present in root canal cultures Strep. salivarius is ascribable to contamination with saliva.

Adolescent↗
PubMed1991

[2 newborn infants with septicemia caused by multiresistant Streptococcus mitis].

Multiresistant viridans streptococci had not yet been encountered in the Netherlands. In the spring of 1990 we isolated multiresistant S. mitis from blood of two Dutch neonates (minimal inhibitory concentration of penicillin 64 mg/l). In both patients septicaemia developed while they were being treated with beta-lactam antibiotics. Although viridans streptococci usually are extremely sensitive to penicillin and other beta-lactams, the possibility of development of (multi-)resistance in these microorganisms during antibiotic treatment should be kept in mind.

Drug Resistance, Microbial↗
PubMed1998

Streptococcus mitis with unusually high level resistance to beta-lactam antibiotics.

Penicillin-resistant oral streptococci constitute the genetic reservoir for beta-lactam resistance in S. pneumoniae. Here we report the isolation of clinical strains of S. mitis with unusually high MIC values for beta-lactam antibiotics; resistance to benzylpenicillin was 64 microg/ml and to cefotaxime 128 microg/ml. Among the beta-lactam compounds tested, only the carbapenems imipenem and meropenem showed MICs below 32 microg/ml. Both S. mitis strains were resistant to tetracycline and were highly resistant to aminoglycosides. Pulse field mapping of chromosomal DNA revealed identical patterns in both strains, indicating clonal identity of the two isolates. Using chromosomal S. mitis DNA, the laboratory strain S. pneumoniae R6 could be transformed in four successive steps to cefotaxime and benzylpenicillin resistance of 64 microg/ml. The results exemplify the importance of commensal streptococci for the development of cefotaxime resistance in S. pneumoniae.

Anti-Bacterial Agents↗
PubMed1980

Phosphoenolpyruvate-dependent glucose phosphotransferase activity in Streptococcus mitis ATCC 903.

A constitutive phosphoenolpyruvate (PEP)-dependent glucose phosphotransferase system was found in decryptified cells of Strep. mitis. The system displayed saturation kinetics and the apparent Km value for the non-fermentable analogue 2-deoxyglucose (2DG) was 0.4 mM. Sodium fluoride inhibited the activity when 2-phosphoglycerate was used as the energy source instead of PEP. Intact cells accumulated 2DG and also a derivative that behaved chromatographically like 2DG-6-phosphate. PEP-dependent glucose phosphotransferase activity was also demonstrated in freshly collected plaque.

Adult↗
PubMed1989

[Frequency and severity of systemic infections caused by Streptococcus mitis and sanguis II in neutropenic children].

We have retrospectively evaluated 24 sepsis episodes caused by viridans streptococci in 23 neutropenic children during a 21 months period at the Pediatric Hematology Unit of St. Louis Hospital. The underlying malignancies included acute lymphoblastic leukemia, acute non lymphoblastic leukemia, aplastic anemia and solid tumor. In 17 children neutropenia, defined as a neutrophil count of less than 500 per cubic millimeter, was caused by cytotoxic chemotherapy. For 6 other children neutropenia was consequential to pretransplant treatment regimen for autologous bone marrow transplantation including cytotoxic chemotherapy and total body irradiation. All patients had a silicone rubber atrial catheter. In 9 patients sepsis was associated only with fever for less than 48 hours. In 5 other children fever was prolonged more than 72 hours in spite of specific antimicrobial therapy. No other organism was isolated. In 10 patients, however, the infectious syndrome was severe and the features included cardiac failure (7 patients), pneumonia (7 patients) resembling adult respiratory distress syndrome, encephalopathy (3 patients) without meningitis and proteinuria, 7 of these patients needed a management in a pediatric intensive care unit and 2 died in spite of adapted antibiotics. Streptococci were isolated in blood cultures in 23 children.

Adolescent↗
PubMed1996

Dynamics of uniformly 13C-enriched cell wall polysaccharide of Streptococcus mitis J22 studied by 13C relaxation rates.

We have studied the dynamics of the motion of a complex polysaccharide having seven sugar residues in the repeating subunit and which is a receptor for lectin interaction in the coaggregation of oral bacteria. Measurements of the longitudinal and the rotating frame relaxation rates and the heteronuclear nuclear Overhauser effects were carried out on a uniformly 13C-enriched sample using pulse sequences chosen to minimize the effects 13C-13C coupling and cross relaxation. T1 and T1 rho measurements both showed single exponential decay for the anomeric carbon atom resonances of the polysaccharide. The results show the polymer to be highly flexible with a hinge at the (1-->6)-linked galactofuranoside residue. Since there is no generally accepted scheme for interpreting polysaccharide dynamics, several different methods of data analysis were used including a reduced spectral density function method as well as several different methods in which a series of isotropically decaying rotational correlation functions are assumed. The different analyses all show that there are differing amounts of internal motion in the different residues of the polysaccharide. One possible interpretation of the data, which uses an extended version of the model-free treatment, indicates that picosecond motion is exhibited to a similar degree by all the residues in addition to a slower motion on the nanosecond time scale whose amplitude is greatest in the hinge region around the (1-->6)-linked galactofuranoside residue in the polysaccharide.

Carbohydrate Sequence↗
PubMed1996

Molecular modeling of the flexible cell wall polysaccharide of Streptococcus mitis J22 on the basis of heteronuclear NMR coupling constants.

A method for constructing conformational models of flexible complex polysaccharides on the basis of NMR data and molecular modeling is described and is applied to a polysaccharide which is a lectin-binding receptor important in coaggregation of oral bacteria. The method involves uniform biosynthetic enrichment of the polysaccharide with 13C which allows accurate measurements of heteronuclear coupling constants from a three-dimensional coupled HMQC-NOESY spectrum. The improved resolution of the 3D spectrum also provides a large number of accurate values of NOE cross peak volumes in a decoupled HMQC-NOESY spectrum. While it was not possible to construct a model for the flexible polysaccharide directly from the NOE data, a model was successfully built from the coupling constant data. Possible values of glycosidic dihedral angles were extracted from the 3JCH data to build models which were evaluated by molecular modeling calculations. A simple average over a linear combination of low-energy conformations was selected which matched the experimental 3JCH data within experimental error. Simulation of the NOE data for this same combination of conformers gave excellent agreement with experimental NOESY data. Molecular dynamics trajectories both with and without coupling constant constraints do not represent the experimental NOE and 3JCH data as well as the linear combination model. While the polysaccharide has some flexibility in the antigenic site, the lectin-binding site, which contains a furanoside with (1-->6)-linkages, provides a more flexible hinge in the polysaccharide.

Carbohydrate Conformation↗