Streptococcus salivarius

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Streptococcus salivarius
A colony of Streptococcus salivarius on blood agar

A colony of Streptococcus salivarius on blood agar

Systematics
Class : Bacilli
Order : Lactobacillales
Family : Streptococcaceae
Genre : Streptococcus
Type : Streptococcus salivarius
Scientific name
Streptococcus salivarius
Andrewes & Horder 1906

Streptococcus salivarius is a bacterium found in the normalhuman oral flora . It is usually harmless to humans, but it cancause illnessif the immune system is weak.

features

The cells of Streptococcus salivarius are morphologically cocci-shaped and have a diameter of 0.8 - 1 μm . They form typical cell chains of different lengths: from diplococci , i.e. consisting of only two cells, to chains of over 30 cells. There are no flagella . The bacterium reacts positively to the Gram test .

Streptococcus salivarius reacts with soluble sugar molecules on agar containing sucrose . This is a chain form made from fructose , the levan . The enzyme levansaccharase , which belongs to the hexosyltransferases and which can form larger, mucous (mucoid) colonies, is used for this purpose.

Some strains also produce dextrans , a form of insoluble chains made from glucose. The production of glucans and fructans is an important characteristic of various oral streptococci, i.e. those living in the mouth of humans . In addition to S. salivarius , this includes z. B. Streptococcus mutans , Streptococcus sanguis and Streptococcus oralis .

The majority of the strains of Streptococcus salivarius are non-hemolytic on blood agar ; that is, they do not produce toxins that destroy red blood cells ( erythrocytes ) ( hemolysis ). However, α-hemolytic and β-hemolytic culture strains also occasionally occur . The former form a greenish halo around the colonies, it is also referred to as "greening". These species deprive red blood cells e.g. B. potassium , but the erythrocytes are not completely dissolved. In the β-hemolytic types, the blood cells are now completely dissolved. The non-hemolytic types are also referred to as "y-hemolytic". Nevertheless, Streptococcus salivarius belongs to the Viridans group , in which many bacteria exhibit greening hemolysis. This group, which is phylogenetically not precisely defined, consists of human commensals , which make up a large part of the oral flora.

In many types of streptococci, a certain polysaccharide is expressed in the cell wall , which acts as an antigen , the so-called C-polysaccharide. Depending on the structure of the polysaccharide, the species are divided into so-called Lancefield groups . Streptococcus salivarius falls into the K, L or M group depending on the culture strain.

metabolism

The metabolic pathway of Streptococcus salivarius is fermentation . It is the homofermentative anaerobic lactic acid fermentation . Only a single fermentation product, lactic acid , occurs here. For most of the strains, the end product is the L-isomer of lactic acid.

It tolerates the presence of oxygen (aerotolerant). It depends on carbohydrates for nutrition . Like all lactic acid bacteria, it needs vitamins to grow; thus it is also auxotrophic . Esculin and starch are split ( hydrolyzed ). Urea is hydrolyzed by some culture strains. Arginine and hippuric acid are not hydrolyzed. The Voges-Proskauer test (VP) is positive for the majority of the strains, they produce acetoin . The catalase test is negative. Mannitol and sorbitol are not fermented.

Chemotaxonomic Features

The proportion of guanine and cytosine within the DNA (the so-called GC content ) of Streptococcus salivarius is 39-42 mol percent . Two different types of the macromolecule murein , which is involved in the structure of the cell wall of bacteria, were found in Streptococcus salivarius : the Lys-Ala 2-3 type and the Lys-Thr-Gly type.

Systematics

Streptococcus salivarius is a member of the Streptococcaceae family of the Firmicutes .

The streptococci are phylogenetically divided into 6 groups: Anginosus, Bovis, Mitis, Mutans, Pyogenes and Salivarius groups. In addition to Streptococcus salivarius , the latter also include S. alactolyticus , S. hyointestinalis , S. infantarius , S. thermophilus and S. vestibularis . Within medical microbiology, the species is assigned to the group of Viridans streptococci , which is a non-phylogenetic classification. As a subspecies of Streptococcus salivarius , it used to be called Streptococcus salivarius subsp. thermophilus nor the bacterium Streptococcus thermophilus .

Pathogenicity

Streptococcus salivarius is part of the natural oral flora of humans. It colonizes the mouth and throat just two days after birth . However, as an opportunistic pathogen , this germ can sometimes cause diseases. The bacteria can, for. B. if they enter the bloodstream through oral micro-lesions , trigger sepsis in people with a lack of certain immune cells ( neutropenia ) . The species was u. a. Associated with endocarditis and meningitis . S. salivarius has been shown to cause tooth decay in rats , but is believed to pose a low risk of tooth decay in humans. Even in severely immunocompromised patients, the bacterium can cause disease, such as B. in connection with carcinoma .

Individual evidence

  1. ^ A b c Paul Vos, George Garrity, Dorothy Jones, Noel R. Krieg, Wolfgang Ludwig, Fred A. Rainey, Karl-Heinz Schleifer, William B. Whitman: Bergey's Manual of Systematic Bacteriology: Volume 3: The Firmicutes . Springer, 2009, ISBN 978-0-387-95041-9 .
  2. ↑ a b c Alexander Steinbüchel: Microbiological internship . Springer Verlag, Heidelberg 2003, ISBN 3-540-44383-5
  3. ↑ a b Fritz H. Kayser et al .: Medical Microbiology. Pocket textbook medical microbiology. 12th revised and expanded edition. Thieme, 2010. ISBN 978-3-13-444812-2
  4. ^ Alan Coykendall: Classification and Identification of the Viridans Streptococci . In: Clinical Microbiology Reviews July 1989, pp. 315-328. doi: 10.1128 / CMR.2.3.315
  5. ↑ a b Brian JBWood: The Lactic Acid Bacteria in Health & Disease . Volume 1. Springer, 1992 ISBN 978-1-4615-3522-5 .
  6. ↑ Anica Meinelt: Molecular methods for the detection of the oral-probiotic strain Streptococcus salivarius ssp. salivarius K12 and application in vitro and in vivo Aachen University of Technology, dissertation
  7. ↑ a b Beate Houben: In-vitro study on the effectiveness of the bacteriocins of Streptococcus salivarius for the inhibition of Streptococcus pyogenes Technical University Aachen, dissertation
  8. ^ S. Svane: Acute phlegmonous jejunitis and viridans streptococcal peritonitis associated with bronchial carcinoma. In: Scandinavian Journal of Infectious Diseases (2000) 32: pp. 421 - 422. doi: 10.1080 / 003655400750045033
  9. ↑ JF Legier: Streptococcus salivarius meningitis and colonic carcinoma In: Southern Medical Journal (1991) 84: pp. 1058-1059. doi: 10.1097 / 00007611-199108000-00031
  10. ↑ Sakamoto, H., Naito, H., Ohta, Y., Tanakna, R., Maeda, N., Sasaki, J., Nord, CE: Isolation of bacteria from cervical lymph nodes in patients with oral cancer. In: Archives of Oral Biology (1991) 44: pp. 789-793

literature

  • Fritz H. Kayser among others: Medical microbiology. Pocket textbook medical microbiology. 12th revised and expanded edition. Thieme, 2010. ISBN 978-3-13-444812-2
  • Brian JBWood: The Lactic Acid Bacteria in Health & Disease . Volume 1. Springer, 1992 ISBN 978-1-4615-3522-5
  • Paul Vos, George Garrity, Dorothy Jones, Noel R. Krieg, Wolfgang Ludwig, Fred A. Rainey, Karl-Heinz Schleifer, William B. Whitman: Bergey's Manual of Systematic Bacteriology: Volume 3: The Firmicutes , Springer 2009. ISBN 978- 0-387-95041-9

Web links

Commons : Streptococcus salivarius  - Collection of images, videos and audio files
  • ScienceDirect - Collection of articles on Streptococcus salivarius in ScienceDirect