تويت
Streptococcus pyogenes : Group A , B hemolytic streptococcus Group of bacteria gram positive cocci .Characteristics
Habitat
Transmission
Pathogenesis
Diseases
Laboratory Identification
- Gr + Ve cocci in chain .
- Non Sporing , Non Motile Cocci .
- Some strains produce a hyaluronic acid capsule .
- Facultative anaerobic .
- Growth is optimal on enriched-blood agar media.
- inhibited if the medium contain high conc.of glucose.
- the basic structural cell wall is peptidoglycan.
Habitat
- Commensal in the throat or skin .
Transmission
- Direct contact
- Airborne route
Pathogenesis
- M Protein = Antiphagocytosis ” Major Virulence Factor “
- T protein= unknown function.
- capsule=Antiphagocytosis.
- Hemolysins = lyse RBCs.
- Erythrogenic toxins = cause fever & rash in scarlet fever
- Streptokinase = lyses Blood clot .
- DNAse = hydrolyses DNA .
- NADase = Kills Leucocytes .
Diseases
- Pharyngitis , Tonsilitist , Otitist media .
- Erysipelae & lampotigo .
- Scarlet Fever .
- Rheumatic Fever .(ASO confirming test)
- Endocarditis .
Laboratory Identification
- White small colonies on blood agar .
- Colonies surrounded by Beta Hemolysis.
- Catalase –Ve
- Bacitracin Sensitive
- PYR +Ve.