Streptococci

Definition

Streptococci are a genus of Gram-positive bacteria that form chains or pairs and are known for causing various infections in humans. They are classified based on their hemolytic properties and carbohydrate antigens on their cell walls.

5 Must Know Facts For Your Next Test

1. Streptococci are divided into groups A, B, C, D, and G based on the Lancefield classification system.
2. Group A Streptococcus (GAS) is responsible for diseases such as strep throat, scarlet fever, and rheumatic fever.
3. Streptococcus pneumoniae is a significant cause of bacterial pneumonia and meningitis.
4. The identification of streptococci in the laboratory often involves hemolysis patterns on blood agar plates: alpha (partial), beta (complete), or gamma (none).
5. Agglutination assays can be used to identify specific streptococcal species by detecting unique carbohydrate antigens.

Review Questions

• What are the different hemolytic patterns observed in Streptococci on blood agar plates?
• Name three diseases caused by Group A Streptococcus (GAS).
• How does the Lancefield classification system categorize Streptococci?

Related terms

Hemolysis:

The breakdown of red blood cells which can be partial, complete, or absent when identifying bacteria.

Lancefield Classification: A system of categorizing streptococci based on carbohydrate antigens present on their cell walls.

Agglutination Assay: A diagnostic test that involves the clumping of particles to detect specific antigens or antibodies.