Streptococcus oralis

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Streptococcus oralis. [1]


Higher order taxa:

Bacteria; Firmicutes; Bacilli; Lactobacillales; Streptococcaceae;


Streptococcus oralis

Description and significance

Streptococcus oralis is a commensal bacteria that belongs to the Mitis group, which contains the major human pathogen S. pneumoniae, and is found in the human oral cavity (2). S. oralis is a component of the normal human oral microbiota, and is capable of opportunistic pathogenicity. Like other related oral streptococci, it exhibits considerable phenotypic and genetic variation. (3) S. oralis is a gram positive, non-motile, α-haemolytic bacterium that form chains of cocci. Optimal conditions for survival of S. oralis are temperatures between 30 and 35 degrees Celsius. (3, 5)

Genome structure

The genome of S. oralis consists of a circular chromosome and is 1,958,690 bp in length, making it smaller than the S. mitits B6 and S. pneumoniae genomes. (2) The G+C content of the S. oralis is 41.14% and it has a coding percentage of 89.7. There are approximately 1,909 predicted protein coding sequences, with the average coding length of 921 bp, 61 tRNAs, 4 rRNAs loci, and 9 RNA coding genes. (2) S. oralis is most closely related to S. mitis and S. pneumoniae. They share over 99% 16S rRNA gene sequence identity even though DNA-DNA similarity for the entire chromosome is estimated at less than 60%.(4) Like the S. mitis B6 genome, the S. oralis genome shows a striking X alignment compared to "S. pneumoniae". (2) The main pneumococcal pathogenicity factors are missing in S. oralis, which is similar to the S. mitis B6 genome. The genome of S. oralis contains genetic islands and antibiotic resistance determinants that are representative of the genome of S. pneumoniae and other streptococcal species. (2)

Cell structure and metabolism

Streptococcus oralis is a gram positive, non-motile facultative anaerobe. S. oralis forms white clusters colonies on a Wilkins-Chalgren agar plate. (9)

Since S. oralis is a facultative anaerobe, it has expanded its metabolic capabilities. This makes it capable of growing in more adverse environments and allows it to utilize a greater range of nutrients. The main ways the organism gets energy is through the breakdown of glycoproteins. (9) Some strains of S. oralis can produce an IgA protease as well as neuraminidase, which renders them incapable of binding α-amylase. (3)


Once regarded as a minor opportunistic pathogen, S. oralis is now considered a significant pathogen that affects immunocompromised individuals and those with hematological malignancy (cancers that affect the blood). (1,4) In these individuals S. oralis is known to create such complications as bacterial endocarditis, adult respiratory distress syndrome and streptococcal shock. Penicillins were once a standard treatment for infections caused by S. oralis, however the emergence of antimicrobial resistance has rendered them less effective. (1) It exhibits antibiotic susceptibility results which are very close to the results of the other Mitis group member organisms. S. oralis is related to S. pneumoniae a common case of otitis media, septicemia, pneumonia, and meningitis in children that results in a significant mortality rate throughout the world. (4)

S. oralis is known to be one of the first bacteria to begin to form the plaque biofilm. Research shows that the S.oralis is able to interact with Porphyromonas gingivalis, which is considered to be one of the leading causes of periodontal disease. Periodontal disease is considered the most common disease affecting the human oral cavity. (8)

Interesting facts

S. oralis has only been reported to cause meningitis in cases where dental work was recently performed. However, in 2013 an 81- year old woman, who had no recent dental work performed was found to have bacterial meningitis after surgery. The woman was admitted for elective total knee replacement surgery, and before the surgery she was given spinal anesthesia. Early in the postoperative monitoring the patient presented with headache and nausea; after several more symptoms presented the patient was given a lumbar puncture and was diagnosed with bacterial meningitis. A culture of the cerebral spinal fluid grew gram positive staphylococci. Upon further tests the bacteria was found to be S. oralis, making this the first case of S. oralis causing bacterial meningitis from spinal anesthesia. (7)

S. oralis is also seeing use as a probiotic to help support a healthy oral cavity. The strain used as the probiotic is modified, and it helps to aid in restoring the mouth with good bacteria and helping to keep out bacteria that degenerate oral health. To do this, S. oralis colonizes sites around teeth such as the gums, and competes with other bacteria. (10)


1. Byers, H.L., E. Tarelli , K. A. Homer , and D. Beighton . "Isolation and characterisation of sialidase from a strain of Streptococcus oralis ." Joint Microbial Research Unit . 49. (2000): 235-244. Web. 16 Dec. 2013.

2. Reichmann , Peter, Michael Nuhn, et al. "Genome of Streptococcus oralis Strain Uo5." Journal of Microbiology . 193.11 (2011): 2888-2889. Web. 16 Dec. 2013.

3. Do, Thuy, Keith A. Jolley, et al. "Population structure of Streptococcus oralis ." Society of General Microbiology . 155.8 (2009): 2593-2602. Web. 16 Dec. 2013.

4. Whalan , Rachel H. , Simon G. P. Funnell , et al. "Distribution and Genetic Diversity of the ABC Transporter Lipoproteins PiuA and PiaA within Streptococcus pneumoniae and Related Streptococci ." Journal of Microbiology . 188.3 (2006): 1031-1038. Web. 16 Dec. 2013.

5. LeVan, Adriana , and Deena Jacob. Gram Stain: Gram-Positive Cocci . 2011. Photograph. American Society for Microbiology , College Park MD . Web. 16 Dec 2013.

6. Wilder , Jennifer, Michelle Ramanathan , et al. "Streptococcus oralis meningitis following spinal anaesthesia ." Association of Anesthetist of Great Britain and Ireland . 0092. (2013): n. page. Web. 16 Dec. 2013.

7. Streptococcus oralis Uo5. 2011. Photograph. Bacmap Genome Atlas , Bethesday MD. Web. 16 Dec 2013. <

8. Maeda, K. , H. Nagata, M. Kuboniwa, et al. "Identification and Characterization of Porphyromonas gingivalis Client Proteins That Bind to Streptococcus oralis Glyceraldehyde-3-Phosphate Dehydrogenase." Infection and Immunity . 81.3 (2013): 753-763. Web. 16 Dec. 2013.

9. Tilley , DO, M Arman , A Smolenski, et al. "Glycoprotein Ibα and FcγRIIa play key roles in platelet activation by the colonizing bacterium, Streptococcus oralis." Journal of Thrombosis and Haemostasis . 11.5 (2013): 941-950. Web. 16 Dec. 2013.

10. "How EvoraPro Oral Probiotics Aid Oral Heath ." Evroa Oral Probiotics . N.p., n. d. Web. 16 Dec. 2013.


Page written by Allison Wall and Stephen Taylor, students of Dr. Angela Hahn. Bemidji State University, Bemidji, MN.