Streptococcus pneumoniae

Morphology :

• Gram positive, commonly arranged in diplococcic (although it named "streptococcus")
  
• Lancet-shaped, 0.5 – 1.25 µm in diameter
  
• Anaerobe bacteria
  
• The older its age, it becomes more gram negative & lyses easily
  

s. pneumonia, taken from http://wishart.biology.ualberta.ca/BacMap/includes/species/Streptococcus_pneumoniae.png

Culture :

• Alpha-hemolytic on blood agar
  
• Growth is enhanced by 5- 10 % CO₂
  
• Culture is created by sputum cultured on blood agar & incubated in CO2 or a candle jar
  
• Optochin sensitive
  

Pathogenesis:

Epithelium if nasopharynx is the primary site of colonization for S. pneumonia. When it's being aspirated and move to the lungs, it will attach to the type II pneumocytes in lungs. Then, cell walls of growing bacteria bind to epithelia, endothelia, & leukocytes. It's eliciting the production og IL-1, the separation of endothelial cells, & the accumulation of serous exudates. Pneumococci then may gain access to the systemic circulation via the pulmonary capillaries or the cervical lymphatics. The activated endothelium expresses tissue factor, PAF. Neutrophils are recruited, activation of complement, etc amplifies the recruitment of leukocytes. When bacteria begin to die, they release pneumolysin & cell wall components which stimulate further inflammation.

S. pneumoniae is a normal inhabitant of the human respiratory tract.

S. pneumonia may cause:

    * lobar type pneumonia

    * paranasal sinusitis

    * otitis media

    * meningitis

    * osteomyelitis

    * septic arthritis

    * endocarditis

    * peritonitis

    * cellulitis

    * brain abscesses

Treatment:

Penicillin remains the drug of choice!
In patients with mild to moderate disease who are candidates or oral therapy :

• Penicillin V
  
• Amoxicillin
  
• Ampicillin
  
• Erythromycin
  
• Clindamycin
  
• First or second generation of Cephalosporin
  

If the patient appears toxic, has moderate to severe respiratory distress, or if empyema is present, gives parenteral therapy of penicillin G (per IV) or

• Cefuroxime IV
  
• Cefotaxime Iv
  
• Ceftriaxone IV
  
• Ampicillin IV
  
• Clindamycin IV
  
• Chloramphenicol IV
  

Note: parenteral therapy should be continued or 48-72 hours after abatement of fever. Oral antimicrobial should be administered to complete a total 7 – 10 days therapy.

Prevention:

23-valent pneumococcal vaccine

 

Taken from :     Jawet'z Medical Microbiology

        Kendig's Pediatrics

        Todar's Online Textbook of Bacteriology