Streptococcus mitis: Difference between revisions

From MicrobeWiki, the student-edited microbiology resource
No edit summary
 
(26 intermediate revisions by 3 users not shown)
Line 1: Line 1:
{{Curated}}
{{Biorealm Genus}}
{{Biorealm Genus}}


Line 12: Line 13:
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''
|}
|}
''Streptococcus mitis''
''Streptococcus mitis''


==Description and significance==
==Description and significance==
Describe the appearance, habitat, etc. of the organism, and why it is important enough to have its genome sequenced. Describe how and where it was isolated.
''Streptococcus mitis'' are commensal bacteria that colonize hard surfaces in the oral cavity such as dental hard tissues as well as mucous membranes and are part of the oral flora. They are usually arranged in short chains in the shape of cocci (10). These Gram-positive bacteria are not usually pathogenic but commonly cause bacterial endocarditis, which is the inflammation of an inner layer of the heart. ''S. mitis'' are alpha hemolytic, meaning it can break down red blood cells. ''S. mitis'' are not motile, do not form spores and lack group-specific antigens (2). ''S. mitis'' live optimally at temperatures between 30 and 35 degrees Celsius, making them mesophiles. They are facultative anaerobes, which is a bacterium that makes ATP by aerobic respiration if oxygen is present but is also capable of switching to fermentation in the absence of oxygen (7).
Include a picture or two (with sources) if you can find them.


==Genome structure==
==Genome structure==
Describe the size and content of the genome. How many chromosomes?  Circular or linear?  Other interesting features?  What is known about its sequence?
The genome of ''S. mitis'' has been sequenced and consists of a circular chromosome with about two million bp that varies with different strains. Its GC and AT content are respectively 40.4% and 59.1%. There are a total of 2222 genes of which 2149 are protein coding genes (3).
Does it have any plasmids?  Are they important to the organism's lifestyle?
 
The genes encoding the lipoproteins Pb1A and Pb1B in ''S. mitis'' are clustered close to the genes that are very similar to the streptococcal phages r1t, 01205 and Dp-1. This implies that Pb1A and Pb1B might be located within a prophage (4). To test this possibility, mitomycin C and UV light were used because both can induce the lytic cycle of many phages. Cultures of ''S. mitis'' were exposed to this and a significant increase expression of Pb1A and Pb1B were detected by Western blot analysis. Phage particles were visible in the cultures of ''S. mitis'', which was named SM1. This phage had a DNA genome of about 35 kb. All these experiments concluded that Pb1A and Pb1B are encoded by a lysogenic bacteriophage (4).


==Cell structure and metabolism==
==Cell structure and metabolism==
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
4.1 Cell Structure
 
As demonstrated by electron microscopy, ''S. mitis'' strains usually carry sparsely distributed, long fibrils, and their cell surfaces are often regarded as being soft.  The electrophoretic softness and fixed negative charge density of -1.2 to -4.3×106 Cm-3 in the polyelectrolyte layer of ''S.  mitis'' strains, were determined by the soft particle analysis using measured electrophoretic mobilities (5).
 
There is a very high frequency of occurrence of extracellular surface structures on ''S. mitis'' strains and a variety of appendages with different lengths up to several microns have been found (5). Between different strains, the density of appendages on cell surfaces can vary significantly (5).
 
''S. mitis'' is characterized by its C-polysaccharide cell wall and a teichoic acid-like polysaccharide. The teichoic acid-like polysaccharide contains a heptasaccharide phosphate repeating unit that neither consists of ribitol nor glycerol phosphate as normally seen in teichoic acids (6). The C-polysaccharide of S. mitis contains, in each repeating unit, two residues of phosphocholine and both galactosamine residues (6).
 
4.2 Metabolism
 
''S. mitis'' is a facilitated anaerobe which makes its metabolism very versatile. The utilization and synthesis of intracellular glycogen and its catabolism to lactate has been detected in ''S. mitis''. The glycogen-like polysaccharide functions as the only source of utilizable energy in ''S. mitis'' (7).
 
When an exogenous energy source is absent, the break down of polysaccharide provides ''S. mitis'' with energy in a utilizable form, for cells that have polysaccharide increased in β-galactosidase activity when induced with thiomethyl galactoside (8). When induced in a similar manner, cells that lack polysaccharide, and a polysaccharide-negative variant of ''S. mitis'' did not increase in β-galactosidase activity. The only substrate for the endogenous metabolism of ''S. mitis'' is intracellular polysaccharide (8).


==Ecology==
==Ecology==
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
''S. mitis'' is a part of the normal mammal flora. They usually inhabit the mouth, throat, and nasopharynx. Certain strains of ''S. mitis'' have the ability to produce IgIA1 protease and bind salivary alpha-amylase, which are two properties that are determinants for streptococcus viridans, which are a large group of generally non-pathogenic, commensal, streptococcal bacteria. Some ''S. mitis'' that produce neuraminidase tend to colonize mucosal surfaces, although the production of this enzyme is not required for successful colonization (9). However, neither immunoglobulin A1 protease activity nor the ability to bind α-amylase from saliva was a preferential characteristic of persistent genotypes. The major origin of new clones occupied by ''S. mitis'' can be found in the respiratory tract (9).


==Pathology==
==Pathology==
How does this organism cause disease?  Human, animal, plant hosts?  Virulence factors, as well as patient symptoms.
''S. mitis'' is usually an etiologic agent in odontogenic infection and endocarditis and only in some cases have been acknowledged as respiratory pathogens. The most common host is humans. The major interaction in the pathogenesis of infective endocarditis is the direct binding of bacteria to platelets (10). ''S. mitis'' is a commensal organism that is closely related to the pathogen ''Streptococcus pneumoniae'', the causative agent of otitis, pneumonia, sepsis and meningitis. Homologous recombination between these species has been observed and the transfer of genetic determinants from ''S. mitis'' to ''S. pneumoniae'' contributes to penicillin resistance in the pathogen (10).
 
Numerous phages are known to carry determinants that increase virulence to the bacterial host.
These factors have been predominantly secreted toxins, such as the streptococcal erythrogenic toxin, staphylococcal enterotoxin A, diphtheria toxin, and cholera toxin (10). Other phage-encoded virulence determinants include extracellular enzymes such as staphylokinase and streptococcal hyaluronidase, enzymes that alter the antigenic properties of the host strain, and outer membrane proteins that increases serum resistance (10). It is likely that Pb1A and Pb1B bind platelets directly, although the mechanism by which PblA and PblB mediate platelet binding by ''S. mitis'' has not been illustrated. Thus, the encoding of PblA and PblB by lysogenic SM1 may represent a class of phage-mediated virulence determinants (10).


==Application to Biotechnology==
==Application to Biotechnology==
Does this organism produce any useful compounds or enzymes?  What are they and how are they used?
In a small number of ''S. mitis'' isolates, a cholesterol-dependent cytolysin named mitilysin has been detected. The mitilysin gene was sequenced from seven isolates of ''S. mitis''. Comparisons with the pneumococcal pneumolysin gene show 15 amino acid substitutions (11). ''S. mitis'' appear to release mitilysin extracellularly. Based on enzyme-linked immunosorbent assay and neutralization assay results, one isolate of ''S. mitis'' may produce a hemolytic toxin in addition to mitilysin (11). 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 and its properties (11).


==Current Research==
==Current Research==


Enter summaries of the most recent research here--at least three required
Ready (et al) analyzed genes coding for antibiotic resistance that can be found on the same genetic elements as the mercury (Hg) resistance genes. They used dental techniques which used restorative materials that may promote Hg resistance as well as antibiotic resistance (12). Using an in vitro biofilm model to grow dental plaques on amalgam substrata and enamel, they observed the number and proportion of Hg-resistant bacteria over time. Of the 42 Hg-resistant bacteria isolated, 98% were streptococci, with ''S. mitis'' predominating. Seventy-one percent of the Hg-resistant isolates were also resistant to a variety of antibiotics; tetracycline being encountered most frequently (12). The results of this study “indicate that placement of amalgam restorations may play a role in promoting the levels of Hg- and antibiotic-resistant bacteria present in the oral cavity” and ways to prevent bacteria from becoming antibiotic-resistant by analyzing the genes (12).
 
Oliveira (et al.) investigated the capability of lectin from ''Talisia esculenta'' (TEL), which is a tree found in Brazil, and a protein from ''Labramia bojeri'' seeds (Labramin) to inhibit adherence of microbes and employ antimicrobial effects. “The minimum inhibitory and bactericidal concentrations of these proteins were determined using 5 species of bacteria: ''Streptococcus mutans'' UA159, ''Streptococcus sobrinus'' 6715, ''Streptococcus sanguinis'' ATCC10556, ''S. mitis'' ATCC903 and ''Streptococcus oralis'' PB182” (13). An adherence assay was performed using these 5 bacterial species. Labramin showed inhibitory effects on the adherence of ''S. mutans'' and ''S. sobrinus''. These results indicate that “Labramin is potentially useful as a biofilm-inhibiting drug” (13).
 
Ip (et al) examined unique strains of pneumococcus and atypical sequence variations within the “quinolone resistance-determining regions (QRDRs) of the gyrase and topoisomerase genes in comparison with the ''Streptococcus pneumoniae'' R6 strain” (14). Using multilocus sequence typing (MLST) analysis on sequences of the six loci “distinguished the ‘atypical’ strains from pneumococci and these strains clustered closely with ''S. mitis''” (14). All these strains have one to three gyrA, gyrB, parC, and parE genes whose “QRDR sequences clustered with those of ''S. pneumoniae'', providing evidence of horizontal transfer of the QRDRs of the gyrase and topoisomerase genes from pneumococci into viridans streptococci” (14). These genes also possess fluoroquinolone resistance to viridans streptococci. The fluoroquinolone resistance agents of 32 characterized ''S. mitis'' and ''Streptococcus oralis'' strains from patients were analyzed. The recombination events and de novo mutations play a significant role in the development of fluoroquinolone resistance in bacteria and how to prevent it (14).


==References==
==References==
[Sample reference] [http://ijs.sgmjournals.org/cgi/reprint/50/2/489 Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "''Palaeococcus ferrophilus'' gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". ''International Journal of Systematic and Evolutionary Microbiology''. 2000. Volume 50. p. 489-500.]


Edited by student of [mailto:ralarsen@ucsd.edu Rachel Larsen]
1. Bischoff, J., Domrachev, M., Federhen, S., Hotton, C., Leipe, D., Soussov, V., Sternberg, R., Turner, S. [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=246201&lvl=3&lin=f&keep=1&srchmode=1&unlock  NCBI taxonomy database] Accessed Aug. 26, 2007
 
2. [http://www.ncbi.nlm.nih.gov/sites/entrez?Db=genomeprj&cmd=ShowDetailView&TermToSearch=173 Entrez Genome Project]
Accessed: Aug 23, 2007
 
3. TIGR CMR Genome Database, [http://www.gem.re.kr/tigr-scripts/CMR2/DNA_mol_info.spl?suborg=Streptococcus+mitis+NCTC+12261&subid=46644 DNA Fact Table]
Accessed: Aug 26, 2007
 
4. Whalan RH, Funnell SG, Bowler LD, Hudson MJ, Robinson A, Dowson CG. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1347328 Distribution and genetic diversity of the ABC transporter lipoproteins PiuA and PiaA within Streptococcus pneumoniae and related streptococci.] J Bacteriol. Feb 2006. Volume 188, No.3. p. 1031-1038.
 
5. Rodríguez, V., Busscher, H., Van der Mei, W., and H. [http://dissertations.ub.rug.nl/FILES/faculties/medicine/2004/v.vadillo.rodriguez/c2.pdf Softness of the bacterial cell wall of Streptococcus mitis as probed by micro-electrophoresis.] Electrophoresis. 2002. Volume 23. p. 2007-2011.
6. Bergstrom, N., Jansson, P.E., Kilian, M., Skov Sorensen, U.B. [http://grande.nal.usda.gov/ibids/index.php?mode2=detail&origin=ibids_references&therow=575537 Structures of two cell wall-associated polysaccharides of a Streptococcus mitis biovar 1 strain. A unique teichoic acid-like polysaccharide and the group O antigen which is a C-polysaccharide in common with pneumococci.] Eur-J-Biochem. Dec. 2000. Volume 267, No. 24. p. 7147-57.
 
7. Houte, J.V., Jansen, H.M. [http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=250433&blobtype=pdf Role of Glycogen in Survival of Streptococcus mitis.] Journal of Bacteriology. Mar. 1970. Volume 101, No. 3. p. 1083-1085.
 
8. Gibbons, R. J. (Forsyth Dental Center, Boston Mass.). [http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=277233&blobtype=pdf
Metabolism of Intracellular Polysaccharide by Streptococcus mitis and its Relation to Inducible Enzyme Formation.] J. Bacteriol. 1964. Volume 87. p. 1512–1520.
 
9. Kirchherr, J.L., Bowden, G.H., Richmond, D.A., Sheridan, M.J., Wirth, K.A., Cole, M.F. [http://www.ingentaconnect.com/content/tandf/smic/2005/00000017/00000003/art00002;jsessionid=81tigtj2h242.alice?format=print Distribution of Streptococcus mitis biovar 1 phenotypes on shedding and non-shedding oral surfaces of human infants during the first year of life.] Microbial Ecology in Health and Disease. Sept. 2005. Volume 17, Issue 3. p. 138 – 145.
 
10. Bensing, B.A., Rubens, C.E., Sullam, P.M. [http://iai.asm.org/cgi/reprint/69/10/6186.pdf Genetic Loci of Streptococcus mitis That Mediate Binding to Human Platelets.] Infect Immun. Mar. 2001. Volume 69, No. 3. p. 1373–1380.
 
11. Jefferies, J., Nieminen, L., Kirkham, L., Johnston, C., Smith, A., and Mitchell, T.J. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1797409 Identification of a Secreted Cholesterol-Dependent Cytolysin (Mitilysin) from Streptococcus mitis.] J Bacteriol. Jan. 2007. Volume 189, No. 2. p. 627–632.
 
12. Ready, D., Pratten, J., Mordan, N., Watts, E., Wilson, M. [http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=17459664&ordinalpos=6&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum The effect of amalgam exposure on mercury- and antibiotic-resistant bacteria.] Int J Antimicrob Agents. Jul. 2007.; Volume 30, No. 1. p. 34-39.
13. Oliveira, M.R., Napimoga, M.H., Cogo, K., Gonçalves, R.B., Macedo, M.L., Freire, M.G., Groppo, F.C. [http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=17634727&ordinalpos=9&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum Inhibition of bacterial adherence to saliva-coated through plant lectins.] J Oral Sci. Jun. 2007. Volume 49, No. 2. p. 141-145.
 
14. Ip, M., Chau, S.S., Chi, F., Tang, J., Chan, P.K. [http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=17548487&ordinalpos=3&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum Fluoroquinolone resistance in atypical pneumococci and oral streptococci: evidence of horizontal gene transfer of fluoroquinolone resistance determinants from Streptococcus pneumoniae.] Antimicrob Agents Chemother. Aug. 2007. Volume 51, No. 8. p. 2690-700. 
 
 
Edited by Nancy Le student of [mailto:ralarsen@ucsd.edu Rachel Larsen]
 
Edited by KLB

Latest revision as of 20:27, 29 April 2011

This is a curated page. Report corrections to Microbewiki.

A Microbial Biorealm page on the genus Streptococcus mitis

Classification

Higher order taxa

Bacteria; Firmicutes; Bacilli; Lactobacillales; Streptococcaceae;

Species

NCBI: Taxonomy

Streptococcus mitis

Description and significance

Streptococcus mitis are commensal bacteria that colonize hard surfaces in the oral cavity such as dental hard tissues as well as mucous membranes and are part of the oral flora. They are usually arranged in short chains in the shape of cocci (10). These Gram-positive bacteria are not usually pathogenic but commonly cause bacterial endocarditis, which is the inflammation of an inner layer of the heart. S. mitis are alpha hemolytic, meaning it can break down red blood cells. S. mitis are not motile, do not form spores and lack group-specific antigens (2). S. mitis live optimally at temperatures between 30 and 35 degrees Celsius, making them mesophiles. They are facultative anaerobes, which is a bacterium that makes ATP by aerobic respiration if oxygen is present but is also capable of switching to fermentation in the absence of oxygen (7).

Genome structure

The genome of S. mitis has been sequenced and consists of a circular chromosome with about two million bp that varies with different strains. Its GC and AT content are respectively 40.4% and 59.1%. There are a total of 2222 genes of which 2149 are protein coding genes (3).

The genes encoding the lipoproteins Pb1A and Pb1B in S. mitis are clustered close to the genes that are very similar to the streptococcal phages r1t, 01205 and Dp-1. This implies that Pb1A and Pb1B might be located within a prophage (4). To test this possibility, mitomycin C and UV light were used because both can induce the lytic cycle of many phages. Cultures of S. mitis were exposed to this and a significant increase expression of Pb1A and Pb1B were detected by Western blot analysis. Phage particles were visible in the cultures of S. mitis, which was named SM1. This phage had a DNA genome of about 35 kb. All these experiments concluded that Pb1A and Pb1B are encoded by a lysogenic bacteriophage (4).

Cell structure and metabolism

4.1 Cell Structure

As demonstrated by electron microscopy, S. mitis strains usually carry sparsely distributed, long fibrils, and their cell surfaces are often regarded as being soft. The electrophoretic softness and fixed negative charge density of -1.2 to -4.3×106 Cm-3 in the polyelectrolyte layer of S. mitis strains, were determined by the soft particle analysis using measured electrophoretic mobilities (5).

There is a very high frequency of occurrence of extracellular surface structures on S. mitis strains and a variety of appendages with different lengths up to several microns have been found (5). Between different strains, the density of appendages on cell surfaces can vary significantly (5).

S. mitis is characterized by its C-polysaccharide cell wall and a teichoic acid-like polysaccharide. The teichoic acid-like polysaccharide contains a heptasaccharide phosphate repeating unit that neither consists of ribitol nor glycerol phosphate as normally seen in teichoic acids (6). The C-polysaccharide of S. mitis contains, in each repeating unit, two residues of phosphocholine and both galactosamine residues (6).

4.2 Metabolism

S. mitis is a facilitated anaerobe which makes its metabolism very versatile. The utilization and synthesis of intracellular glycogen and its catabolism to lactate has been detected in S. mitis. The glycogen-like polysaccharide functions as the only source of utilizable energy in S. mitis (7).

When an exogenous energy source is absent, the break down of polysaccharide provides S. mitis with energy in a utilizable form, for cells that have polysaccharide increased in β-galactosidase activity when induced with thiomethyl galactoside (8). When induced in a similar manner, cells that lack polysaccharide, and a polysaccharide-negative variant of S. mitis did not increase in β-galactosidase activity. The only substrate for the endogenous metabolism of S. mitis is intracellular polysaccharide (8).

Ecology

S. mitis is a part of the normal mammal flora. They usually inhabit the mouth, throat, and nasopharynx. Certain strains of S. mitis have the ability to produce IgIA1 protease and bind salivary alpha-amylase, which are two properties that are determinants for streptococcus viridans, which are a large group of generally non-pathogenic, commensal, streptococcal bacteria. Some S. mitis that produce neuraminidase tend to colonize mucosal surfaces, although the production of this enzyme is not required for successful colonization (9). However, neither immunoglobulin A1 protease activity nor the ability to bind α-amylase from saliva was a preferential characteristic of persistent genotypes. The major origin of new clones occupied by S. mitis can be found in the respiratory tract (9).

Pathology

S. mitis is usually an etiologic agent in odontogenic infection and endocarditis and only in some cases have been acknowledged as respiratory pathogens. The most common host is humans. The major interaction in the pathogenesis of infective endocarditis is the direct binding of bacteria to platelets (10). S. mitis is a commensal organism that is closely related to the pathogen Streptococcus pneumoniae, the causative agent of otitis, pneumonia, sepsis and meningitis. Homologous recombination between these species has been observed and the transfer of genetic determinants from S. mitis to S. pneumoniae contributes to penicillin resistance in the pathogen (10).

Numerous phages are known to carry determinants that increase virulence to the bacterial host. These factors have been predominantly secreted toxins, such as the streptococcal erythrogenic toxin, staphylococcal enterotoxin A, diphtheria toxin, and cholera toxin (10). Other phage-encoded virulence determinants include extracellular enzymes such as staphylokinase and streptococcal hyaluronidase, enzymes that alter the antigenic properties of the host strain, and outer membrane proteins that increases serum resistance (10). It is likely that Pb1A and Pb1B bind platelets directly, although the mechanism by which PblA and PblB mediate platelet binding by S. mitis has not been illustrated. Thus, the encoding of PblA and PblB by lysogenic SM1 may represent a class of phage-mediated virulence determinants (10).

Application to Biotechnology

In a small number of S. mitis isolates, a cholesterol-dependent cytolysin named mitilysin has been detected. The mitilysin gene was sequenced from seven isolates of S. mitis. Comparisons with the pneumococcal pneumolysin gene show 15 amino acid substitutions (11). S. mitis appear to release mitilysin extracellularly. Based on enzyme-linked immunosorbent assay and neutralization assay results, one isolate of S. mitis may produce a hemolytic toxin in addition to mitilysin (11). 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 and its properties (11).

Current Research

Ready (et al) analyzed genes coding for antibiotic resistance that can be found on the same genetic elements as the mercury (Hg) resistance genes. They used dental techniques which used restorative materials that may promote Hg resistance as well as antibiotic resistance (12). Using an in vitro biofilm model to grow dental plaques on amalgam substrata and enamel, they observed the number and proportion of Hg-resistant bacteria over time. Of the 42 Hg-resistant bacteria isolated, 98% were streptococci, with S. mitis predominating. Seventy-one percent of the Hg-resistant isolates were also resistant to a variety of antibiotics; tetracycline being encountered most frequently (12). The results of this study “indicate that placement of amalgam restorations may play a role in promoting the levels of Hg- and antibiotic-resistant bacteria present in the oral cavity” and ways to prevent bacteria from becoming antibiotic-resistant by analyzing the genes (12).

Oliveira (et al.) investigated the capability of lectin from Talisia esculenta (TEL), which is a tree found in Brazil, and a protein from Labramia bojeri seeds (Labramin) to inhibit adherence of microbes and employ antimicrobial effects. “The minimum inhibitory and bactericidal concentrations of these proteins were determined using 5 species of bacteria: Streptococcus mutans UA159, Streptococcus sobrinus 6715, Streptococcus sanguinis ATCC10556, S. mitis ATCC903 and Streptococcus oralis PB182” (13). An adherence assay was performed using these 5 bacterial species. Labramin showed inhibitory effects on the adherence of S. mutans and S. sobrinus. These results indicate that “Labramin is potentially useful as a biofilm-inhibiting drug” (13).

Ip (et al) examined unique strains of pneumococcus and atypical sequence variations within the “quinolone resistance-determining regions (QRDRs) of the gyrase and topoisomerase genes in comparison with the Streptococcus pneumoniae R6 strain” (14). Using multilocus sequence typing (MLST) analysis on sequences of the six loci “distinguished the ‘atypical’ strains from pneumococci and these strains clustered closely with S. mitis” (14). All these strains have one to three gyrA, gyrB, parC, and parE genes whose “QRDR sequences clustered with those of S. pneumoniae, providing evidence of horizontal transfer of the QRDRs of the gyrase and topoisomerase genes from pneumococci into viridans streptococci” (14). These genes also possess fluoroquinolone resistance to viridans streptococci. The fluoroquinolone resistance agents of 32 characterized S. mitis and Streptococcus oralis strains from patients were analyzed. The recombination events and de novo mutations play a significant role in the development of fluoroquinolone resistance in bacteria and how to prevent it (14).

References

1. Bischoff, J., Domrachev, M., Federhen, S., Hotton, C., Leipe, D., Soussov, V., Sternberg, R., Turner, S. NCBI taxonomy database Accessed Aug. 26, 2007

2. Entrez Genome Project Accessed: Aug 23, 2007

3. TIGR CMR Genome Database, DNA Fact Table Accessed: Aug 26, 2007

4. Whalan RH, Funnell SG, Bowler LD, Hudson MJ, Robinson A, Dowson CG. Distribution and genetic diversity of the ABC transporter lipoproteins PiuA and PiaA within Streptococcus pneumoniae and related streptococci. J Bacteriol. Feb 2006. Volume 188, No.3. p. 1031-1038.

5. Rodríguez, V., Busscher, H., Van der Mei, W., and H. Softness of the bacterial cell wall of Streptococcus mitis as probed by micro-electrophoresis. Electrophoresis. 2002. Volume 23. p. 2007-2011.

6. Bergstrom, N., Jansson, P.E., Kilian, M., Skov Sorensen, U.B. Structures of two cell wall-associated polysaccharides of a Streptococcus mitis biovar 1 strain. A unique teichoic acid-like polysaccharide and the group O antigen which is a C-polysaccharide in common with pneumococci. Eur-J-Biochem. Dec. 2000. Volume 267, No. 24. p. 7147-57.

7. Houte, J.V., Jansen, H.M. Role of Glycogen in Survival of Streptococcus mitis. Journal of Bacteriology. Mar. 1970. Volume 101, No. 3. p. 1083-1085.

8. Gibbons, R. J. (Forsyth Dental Center, Boston Mass.). [http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=277233&blobtype=pdf Metabolism of Intracellular Polysaccharide by Streptococcus mitis and its Relation to Inducible Enzyme Formation.] J. Bacteriol. 1964. Volume 87. p. 1512–1520.

9. Kirchherr, J.L., Bowden, G.H., Richmond, D.A., Sheridan, M.J., Wirth, K.A., Cole, M.F. Distribution of Streptococcus mitis biovar 1 phenotypes on shedding and non-shedding oral surfaces of human infants during the first year of life. Microbial Ecology in Health and Disease. Sept. 2005. Volume 17, Issue 3. p. 138 – 145.

10. Bensing, B.A., Rubens, C.E., Sullam, P.M. Genetic Loci of Streptococcus mitis That Mediate Binding to Human Platelets. Infect Immun. Mar. 2001. Volume 69, No. 3. p. 1373–1380.

11. Jefferies, J., Nieminen, L., Kirkham, L., Johnston, C., Smith, A., and Mitchell, T.J. Identification of a Secreted Cholesterol-Dependent Cytolysin (Mitilysin) from Streptococcus mitis. J Bacteriol. Jan. 2007. Volume 189, No. 2. p. 627–632.

12. Ready, D., Pratten, J., Mordan, N., Watts, E., Wilson, M. The effect of amalgam exposure on mercury- and antibiotic-resistant bacteria. Int J Antimicrob Agents. Jul. 2007.; Volume 30, No. 1. p. 34-39.

13. Oliveira, M.R., Napimoga, M.H., Cogo, K., Gonçalves, R.B., Macedo, M.L., Freire, M.G., Groppo, F.C. Inhibition of bacterial adherence to saliva-coated through plant lectins. J Oral Sci. Jun. 2007. Volume 49, No. 2. p. 141-145.

14. Ip, M., Chau, S.S., Chi, F., Tang, J., Chan, P.K. Fluoroquinolone resistance in atypical pneumococci and oral streptococci: evidence of horizontal gene transfer of fluoroquinolone resistance determinants from Streptococcus pneumoniae. Antimicrob Agents Chemother. Aug. 2007. Volume 51, No. 8. p. 2690-700.


Edited by Nancy Le student of Rachel Larsen

Edited by KLB