Streptococcus Pneumoniae

WHAT IS IT?

Streptococcus pneumoniae (often called “strep pneumo”) is a lancet-shaped, gram-positive diplococci bacteria.

Gram stain of strep pneumo (source)
Gram stain of Streptococcus pneumoniae (source)
CULTURE CHARACTERISTICS

Alpha hemolytic: form green area of hemolysis on blood agar (due to incomplete/partial hemolysis)

Alpha, beta, and gamma hemolytic strains of bacteria on a blood agar plate (source).
Alpha, beta, and gamma hemolytic strains of bacteria on a blood agar plate (source).

Optochin sensitive: bacteria will not grow in the presence of optochin.

Catalase negative: bubbles will not be observed when hydrogen peroxide is added to a colony of the bacteria.

MOLECULAR CHARACTERISTICS

Encapsulated: this bacteria is not thought to be virulent without its capsule. The Quellung reaction can detect the presence of the polysaccharide antigen.

IgA protease: this bacterium releases this enzyme that cleaves the IgA immunoglobulin. Helps colonize respiratory mucosa.

TRANSMISSION

Infections can be community acquired

CONDITIONS CAUSED

CNS: meningitis (this pathogen is the most common cause of meningitis)

HEENT: Otitis media, sinusitis (most common cause of these both), conjunctivitis

Respiratory:  lobar pneumonia (most common cause), bronchopneumonia

TREATMENT

Penicillin G, V are commonly used as first line treatments for infection with this pathogen. Cephalasporins can also be used.

Chloramphenicol is a bacteriostatic antibiotic that blocks peptidyltransferase at 50S ribosomal subunit.

Telithromycin is a macrolide that has improved activity against S. pneumoniae 

Antimetabolites—Trimethoprim/Sulfamethoxazole can also be used to treat infection with this pathogen.

VACCINE

Two types of vaccinations are available for this microbe. 

1.) 23 varient pneumococcal polisaccaride vaccine (PPSv23, Pneumovax):

  • Recommended for all adults > 65
  • Not immunogenic for children < 2 years of age
  • Covers more variants
  • Antibody levels decide over 5 years
  • Unconjugated vaccine 

2.) 13 varient pneumococcal conjugate vaccine (PCV13, Prevnar)

  • Polysaccharide antigen conjugated to a nontoxic diphtheria protein: boosts immune response through T cell recruitment. 
  • Covers less variants. 
OTHER HY FACTS

Transformation (uptake of environmental DNA) is common with this bacteria.

Associated with (as far as the step exam is concerned):

  • Rusty sputum
  • Sepsis in sickle cell disease
  • Splenectomy (which predisposes to infection with this pathogen, and other capsulated bacteria).
  • Decreased B-cells are associated with infection with this pathogen.

Influenza patients are at risk for super-infection from this pathogen.

Multiple myeloma patients are at increased risk of infection with S. pneumoniae 

Cystic fibrosis patients are predisposed to getting pneumonia from this pathogen.

ARCHIVE OF STANDARDIZED EXAM QUESTIONS 

This archive compiles standardized exam questions that relate to this topic.

 

Page Updated: 05.17.2016