A. DESCRIPTION Gram positive diplococci, also called pneumococci. Lancet-shaped or arranged in chains Polysaccharide capsule. Positive in the Quellung Reaction for specific capsular polysaccharide.

1. Most of the organism's energy is obtained from fermentation of glucose. Production of lactic acid is growth-limiting.
2. Catalase negative and peroxidase negative.
3. Autolysis: Older cultures of S. pneumoniae produce autolytic enzymes which cause partial destruction of the cell wall.
4. Lysis of S. pneumoniae is greatly enhanced by the addition of bile or sodium deoxycholate to a broth culture (bile solubility test) .
5. Optochin inhibition on blood agar is the primary diagnostic test for S. pneumoniae. Optochin is a surface active agent that specifically interacts with the cell membrane of S. pneumoniae to produce cell lysis. It is not used as an antibiotic for humans.
6. The development of alpha-hemolysis on blood agar is another characteristic of S. pneumoniae.

1. Capsular polysaccharide. Elicits mainly a B cell response. The capsule is also anti-phagocytic.
2. C substance, or group-specific carbohydrate. Common to all pneumococci may be involved in the organism's virulence.
3. M Protein. Contained in the somatic portion of the bacterial cell; characteristic for each type of Strep. Does not play a role in virulence and is not anti-phagocytic.

1. Pneumolysin. Causes red blood cell lysis.
2. Hyaluronidase. Digests extracellular matrix.
3. DNAse. Degrades DNA.
4. Proteinases. Degrades protein.

E. DISEASE

1. Type 1-8 pneumococci are responsible for about 75% of the reported adult cases and nearly half of all fatalities (usually bacterial pneumonia). Usually carriers are adults (pharyngeal).
2. In children, types 6, 14, 19 and 23 are more common.
3. S. pneumoniae is most infectious during the course of other infections. Initial infection will spreads to the lobes of the lungs during mucous-producing viral infections.
4. Symptoms include sudden onset of fever and chills and sharp pleural pain
5. Pathological Process
   Infection causes an outpouring of fibrinous fluid into the alveoli. Portions of the lung may become consolidated. Exudate carries bacteria away from infected foci. Complications include inflammation of the sinuses and inner ear.

F. TREATMENT

1. Penicillin is the DRUG OF CHOICE (DOC: this term will be used commonly throughout the bacteriology section).
2. New penicillin G-resistant pneumococci have been reported in the U.S. and elsewhere. These are a severe management problem in meningitis, (limited access of alternative antibiotics to the central nervous system).
3. Erythromycin is the secondary DOC.
4. Vaccines: A multivalent vaccine consisting of 23 types of S. pneumoniae capsules is available. Recommended for infants and the elderly who are at risk of exposure to the organism; also immunosuppressed or debilitated patients.

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Created by Mary T. Johnson, Ph.D. Copyright 1997-2001, Indiana University School of Medicine Last modified January 5, 2003