6 Streptococci Flashcards
How do micro-organisms cause disease?
Exposure > Adherence > Invasion > Multiplication > Dissemination
List features os streptococci
Gram positive
Cocci
Strings
What are the three haemolysis groups?
Alpha - Partial Haemolysis
Beta - Full hamolysis
Gamma - no haemolysis
What colour does alpha haemolysis go?
Green
What haemolysis group is S.pneumoniae in?
Alpha
What haemolysis group is S.pyogenes?
Beta
Name a bacteria in the gamma heamolysis group?
Enterococcus faecalis
What is lancefield grouping?
Classification of beta haemolytic streptococci based on the antigens in the cell wall
What bacteria are group A?
Streptococcus pyogenes
Group B?
Streptococcus Agalactiae
List the virulence factors for streptococcus pyogenes
Hyaluronic Capsule M proteins Adhesins Streptolysins DNAses Hyaluronidase Streptokinase
Why is the capsule a virulence factor?
Inhibits phagocytosis
Invisibility cloak, poor immunogenic surface, not recognised as foreign due to tissue hyaluronate
What is an M protein?
Inhibits the activation of the alternative complement pathway on bacterial cell surface
What do streptolysins do?
Lysis of erythrocytes, neutrophils and platelets
What age group is streptococcal pharyngitis seen in?
5-15 year olds
What causes streptococcal pharungitis?
S.pyogenes
What is the treatment for Streptococcal pharyngitis?
No antibiotics, little effect but disrupts the development of antibodies to M proteins
What doe suppurative mean?
production of pus
What complication of setreptoccoal pharyngitis can lead to high fever, sepsis and jaundice
Scarlet fever
What complication of streptoccal pharyngitis leads to inflammation of the heart, joints and CNS?
Acute rheumatic fever
List some skin infections caused by streptococcus pyogenes?
Impetigo
Erysipelas
Cellulitis
Necrotising fasciitis
