Where is Streptococcus pneumoniae found?

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Streptococcus pneumoniae is found in the upper respiratory system of mammals as a part of the normal flora (2).

Host Interactions

When found in low densities, Streptococcus pneumoniae lives unnoticed in its host. However when found at larger densities, it causes pneumonia (1). Pneumonia is characterized by coughing, green-yellow phlegm, fever, and chest pain (1). Streptococcus pneumoniae causes Pneumonia by initiating a cytokine reaction in the lungs, which leads to the symptoms of Pneumonia. They are able to infect hosts due to various factors.

1.     The bacteria have long pili that enable it to attach to the epithelial tissue of the lungs and to resist being expelled by coughing (1).

2.     It contains a polysaccharide capsule that helps Streptococcus pneumoniae evade phagocytosis by immune cells (2).

Fun Fact: Streptococcus pneumoniae with a polysaccharide capsule are 100,000 times more virulent than strains without one! (1).

3.     Streptococcus pneumoniae contain five PBPs (penicillin binding proteins) that allow it to be penicillin resistant (2).

Phylogeny and Taxonomy

Bacteria-Firmicutes-Bacilli-Lactobacillales-Streptoccaceae-Streptococcus

References

(1) "Streptococcus pneumoniae." - MicrobeWiki. Ed. Kenyon College. Kenyon College, 29 Apr. 2011. Web. 21 Nov. 2014. <https://microbewiki.kenyon.edu/index.php/Streptococcus_pneumoniae>.

(2) Todar, Kenneth, PhD. "Streptococcus pneumoniae and Pneumococcal Pneumonia." Streptococcus pneumoniae and Pneumococcal Pneumonia. N.p., n.d. Web. 21 Nov. 2014. <http://textbookofbacteriology.net/S.pneumoniae.html>.