11 Streptococcus, Pharyngitis, EBV Flashcards
Describe the gram stain of Streptococci
Gram positive cocci (purple)
Classification of Streptococci
α (partial) haemolysis: green appearance
Viridans streptococci
β (complete) haemolysis: shiny capsules
Streptococcus pyogenes
Non-haemolytic: Enterococcus faecalis
Virulence factors of Streptococcus pyogenes
M protein: Resistance to phagocytosis by inhibiting activation of alternative complement pathway on bacterial cell surface
How is Lancefield grouping used to classify Streptococci
20 groups
Based on the presence of polysaccharide antigens in the bacterial cell wall
How did Sherman classify streptococci
- Pyogenic
- Viridans
- Enterococcal
- Lactic
Main infection of Streptococcus pyogenes
Streptococcal pharyngitis/strep throat
Symptoms of Streptococcus pyogenes
Sore throat
Fever
Headache
Tonsillopharyngeal exudates
Complications of Streptococcus Pharyngitis
Scarlet fever
Abscesses in the head and neck region
Peritonsillar abscess
Retropharayngeal abscess
Mastoiditis, sinusitis
Meningitis
What causes scarlet fever as a complication of streptococcal pharyngitis
Infection with streptococcal pyrogenic exotoxin strain of S.pyogenes
What are the two post-streptococcal pharyngitis’ complications
Acute rheumatic fever:
-inflammation of heart, joints
-rheumatogenic M types
-Mechanism; auto-immune
Acute post-streptococcal glomerulonephritis:
-inflammation of renal glomerulus
-m type specific
What are the two post-streptococcal pharyngitis’ complications
Acute rheumatic fever:
-inflammation of heart, joints
-rheumatogenic M types
-Mechanism; auto-immune
Acute post-streptococcal glomerulonephritis:
-inflammation of renal glomerulus
-m type specific
Streptococcus pyogenes skin infection
Impetigo
Erysipelas
Cellulitis
Necrotising fasciitis
Describe Streptococcal toxic shock syndrome
Entry of group A strep into deeper tissues and bloodstream
Deep tissue infection with Strep pyogenes
＋Bacteraemia
＋Vascular collapse
＋Organ failure
Monocyte cytokines induced in Streptococcal toxic shock syndrome
TNFα
IL-2
IL-6
Lymphokines induced in Streptococcal toxic shock syndrome
TNF-β
IL-2
IFN-γ
