Streptococcus pneumoniae


by Christina Jackson

Disease/Etiological Agent:

Streptococcus pneumoniae (Pneumococcus)


Usually transmitted directly or by droplet mechanisms from up to 6 feet away from an infected human coughing or sneezing.  Sometimes S. pneumoniae is transmitted through the nasopharynx of an individual.


Humans are the only reservoirs because it is a human pathogen.

General Characteristics of MO:

S. pneumoniae are gram positive cocci usually in pairs (diplococci) or sometimes in chains.  They are alpha hemolytic, non-motile, and are fermentative aerotolerant anaerobes (1). S. pneumoniae is also fastidious, catalase negative, and optochin sensitive(1 and 3).

Key Tests for Identification:

S. pneumoniae is usually identified by performing an Optochin sensitivity test, but can be identified by a bile solubility test, an inulin fermentation test, urine test, or a complete blood count.  (1 and 5)

Signs and Symptoms of Disease:

Once an individual is infected, a 1 to 3 day period of incubation begins.  After incubation the infected individual will begin to acquire symptoms such as a high fever, chills, cough, sore throat, chest pains, body aches, fatigue, rapid breathing, and maybe even nausea/vomiting.  (10 and 11).

Historical Information:

In 1881 S. pneumoniae was discovered by Leo Escolar and was isolated/grown by Louis Pasteur and George Sternberg.  In 1884 Albert Fraenkle performed a gram stain where it was found to be diplococcal.  In 1902 Neufeld discovered swelling of the capsular which lead to serotyping.  The type-specific antibody development in S. pneumoniae was shown by Lister in 1913.  In 1944 transformation experiments were performed by McCarty.  Lastly in 1997 Joseph Dillard and Janet Yother cloned common capsule DNA regions. (9).

Virulence Factors:

One virulence factor is a polysaccharide capsule that releases pneumococci from the host by preventing phagocytosis.  Another virulence factor is pnuemolysin which inhibits many things such as antibody synthesis and lymphocyte proliferation.  Inflammation is caused from the virulence factor of cell wall components, which are thought to be the main cause of symptoms.  There is also autolysin (enzyme) which is a virulence factor that releases the cell wall products. (13).


Those who are infected with S. pneumoniae should stay inside away from others since it is a contagious infection from direct or droplet contact.  S. pneumoniae is usually treated with antibiotics and sometimes with penicillin depending on the severity.

Prevention/Vaccine info, New Trials?:

Two current vaccines, a pneumococcal vaccination a 23-valent capsular polysaccharide vaccine and a heptavalent protein-polysaccharide conjugate vaccine (PCV7) that was recommended in July 2000 for children.  (4)

Local Cases or Outbreaks:

In the United States 175,000 individuals were hospitalized.  In Texas there were 294 cases in Harris County, 187 cases in Dallas County, 135 cases in Bexar County, 162 cases in Tarrant County, and 129 cases in Travis County. (12)

Global Cases or Outbreaks:

Worldwide 14.5 million cases were reported causing 735,000 deaths.  Each year about 2 million children under the age of 2 die.  (12)


1.      Todar, Kenneth.  “Streptococcus pneumoniae”  2011.  Todar’s Online Textbook of Bacteriology.  May 6, 2011.

2.      Streptococcus pneumoniae Disease” September 3, 2008.  Centers for Disease Control and Prevention.  May 6, 2011.

3.      Tuomanen, Elaine.  “Microbiology and Pathogenesis of Streptococcus pneumoniae” July 12, 2010.  UpToDate.  May 6, 2011.

4.      Streptococcus pneumoniae”.  National Center for Preparedness, Detection, and Control of Infectious Diseases. May 6, 2011.

5.      Streptococcus pneumoniae”.  The Physician’s Guide to Laboratory Test Selection and Interpretation.  May 6, 2011.

6.      Fox, Alvin.  “Bacteriology - Chapter Thirteen Streptococcus pneumoniae and Staphylococci” October 12, 2010.  Microbiology and Immunology On-line; University of South Carolina School of Medicine.  May 6, 2011.

7.      “Pneumococcal Disease (Streptococcus pneumoniae)” October 2002.  New York City Department of Health and Mental Hygiene.  May 6, 2011.

8.      Weber, David; Rutala, William.  “Streptococcus pneumoniae Infections: Microbiology, Epidemiology, Treatment, and Prevention” April 17, 2003.  Medscape Education.  May 6, 2011.

9.      “Timeline” May 9, 2011.,or.r_gc.r_pw.&fp=c47720ba43ce4197

10.  Schueler, Stephen.  “Streptococcus pneumoniae Symptoms” January 5, 2011.  Freemd.  May 6, 2011.

11.  Streptococcus pneumoniae” December 2, 2005.  The Medical Symptoms Database.  May 6, 2011.

12.  Kelly, Caroline.  “Pneumococcal Disease”.  May 9, 2011.

13.  Velasco, Alonsod “Streptococcus pneumoniae: Virulence Factors, Pathogenesis, and Vaccines” December 1995.  American Society for Microbiology.  May 9, 2011.