Alpha-hemolytic
Alpha-hemolytic
The term Alpha-hemolytic (pronounced: al-fa he-mo-lit-ik) refers to a type of bacteria that, when grown on blood agar, produces a greenish discoloration around the colonies due to partial hemolysis of red blood cells. This is in contrast to beta-hemolytic bacteria, which completely lyse red blood cells, and gamma-hemolytic bacteria, which do not cause hemolysis.
Etymology
The term "Alpha-hemolytic" is derived from the Greek words "alpha" (α), the first letter of the Greek alphabet, and "hemolysis" (from haima "blood" + lysis "a loosening").
Types of Alpha-hemolytic bacteria
There are several types of alpha-hemolytic bacteria, including:
- Streptococcus pneumoniae: This is the most common cause of bacterial pneumonia and meningitis in adults, and of sepsis in those aged over 65 years.
- Streptococcus viridans: This group of bacteria are a common cause of subacute bacterial endocarditis.
- Streptococcus mitis: This bacterium is part of the normal flora of the mouth and upper respiratory tract, but can cause disease in immunocompromised individuals.
Clinical significance
Alpha-hemolytic bacteria are important in medical microbiology as they are often involved in human infections. For example, Streptococcus pneumoniae is a leading cause of pneumonia, meningitis, and otitis media (middle ear infection) in children.
See also
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