Pneumococcal Infection

by Michael_Koger

Pneumococcal disease is a common illness which may be life-threatening to many groups of people.

Human infection with Streptococcus pneumoniae is well-known across the globe, and in the United States it is responsible for 400,000 hospitalizations every year. Death from it occurs mostly in developing countries. Worldwide, it kills more than a half million children less than the age of five each year [1, 2, 3].

Though penicillin has long been an effective agent to treat this type of pneumonia, there have been problems with antimicrobial resistance which make it difficult to manage. The microbe is a Gram-positive, lancet-shaped, facultative anaerobic bacterium which occurs mostly in pairs; however, it may also appear singly or in chains [1, 2, 3].

The microscopic appearance of pairs is why microbiologists have referred to it as Diplococcus pneumoniae several decades ago as “diplo” implies occurrences of “two.”

Invasive Pneumococcal Disease

Nevertheless, it tends to reside in the human respiratory tract and may lead to pneumonia, otitis media, meningitis, and bacteremia.  Situations other than pneumonia may lead to a life-threatening invasive illness as well.  In fact, meningitis from this microorganism is the most severe form of pneumococcal infection in poor countries [1, 2, 3]. 

Moreover, in the United States, Streptococcus pneumoniae infection is the leading cause of bacterial meningitis in small children less than five years of age [3].

A quarter of patients who have pneumococcal pneumonia subsequently develop bacteremia.  This is when the infection spreads to the bloodstream, and it therefore constitutes invasive pneumococcal disease.  Similarly, spread of the microorganism to the cerebrospinal fluid is a form of that as well.  These situations require aggressive medical therapy as the clients who have them tend to be particularly at risk before it even reaches that point [1, 2, 3].

Risk Factors

Though the list of medical conditions which predispose to the occurrence of invasive pneumococcal disease is quite extensive, it is well-known that individuals with immune system compromise are at risk for it.  The same is true for elderly clients who are at least 65 years of age, and infants too have a predisposition as their immune systems have not yet fully developed [1, 3].

Additionally, people with chronic conditions of the heart, liver, kidney, or lung will be at risk for this infection.  Smokers comprise another group who require a high index of suspicion.  The absence of a spleen dramatically increases the risk as well [1, 2, 3].


Pneumococcal disease has long been an occurrence in hospitals and clinics.  However, drug resistance and the emergence of other issues such as immune system compromise have made it a complex scenario to manage.


  1. Pallotta, A. and Rehm, S.  (2016).  Navigating pneumococcal vaccination in adults. Cleveland Clinic Journal of Medicine, 83, 427-433.
  2. World Health Organization.  (2016).  Immunization coverage.  Fact Sheet.  Retrieved July 4, 2016.
  3. Centers for Disease Control.  (2015).  Pneumococcal disease.  Retrieved July 4, 2016.
  4. The photo is a micrograph of Streptococcus pneumoniae from a blood culture.  Reprinted with permission from Centers for Disease Control/Dr. Mike Miller.


The information contained in this article is for educational purposes only and should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is concerned about his or her health should contact their physician for advice.


Updated: 07/09/2016, Michael_Koger
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