Streptococci Flashcards
Are streptococci gram positive or negative?
Gram-positive
Are streptococci catalase positive or negative?
Catalase-negative
What is another name for Grp A BHS?
S. pyogenes
What are the 4 virulence factors for S. pyogenes?
- M proteins
- Erythrogenic toxins - scarlett fever
- Streptolysin - causes cell death & tissue damage
- Hyaluronidase - breaks down components in soft tissue
What are the common acute presentations of an S. pyogenes infection?
- Pharyngitis
- Post-influenza pneumonia
- Skin & soft tissue infections (e.g. cellulitis, erysipelas, impetigo)
What are the non-suppurative post-infectious sequelae caused by a S. pyogenes infection?
- Acute glomerulonephritis
- Acute rheumatic fever which can cause damage to heart valves
What prophylactic antibiotics should be prescribed when a patient presents with pharyngitis in order to prevent ARF?
Oral penicillins/cephalosporins
How is S. pyogenes toxic shock syndrome caused?
Exotoxins act as superantigen, causing nonspecific cross-linking of MHC class II which results in polyclonal T-cell activation, releasing a cytokine storm and inducing Systemic Inflammatory Response Syndrome (SIRS)
How is S. pyogenes infection diagnosed?
Gram stain & culture on wound swab
What is another name for Grp B BHS?
S. agalactiae
What is S. agalactiae commonly associated with?
No. 1 cause of neonatal sepsis & meningitis and sepsis in people with co-morbidities
How is S. agalactiae acquired in SEA?
Consumption of raw freshwater fish
What are the 3 common invasive infections associated with S. pneumoniae?
Pneumonia, meningitis, bacteremia/septicemia
What are the common non-invasive infections associated with S. pneumoniae?
URTI, sinusitis/otitis/conjunctivitis
What pneumococcal vaccine should be given to young children and why?
Conjugated vaccine (PCV) should be given to young children as it elicits a T-cell dependent response with memory
