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
What are the 2 alpha-haemolytic streptococci?
S. pneumoniae & viridans streptococci
How to identify S. pneumoniae on culture?
Grows as ‘draughtsman’ colonies
How is ARF diagnosed?
Revised JONES criteria
How to differentiate S. pneumoniae from viridans streptococcus?
S. pnuemoniae is optochin susceptible
Treatment for S. pyogenes infection?
Clindamycin
IVIG
What are the 3 bacteria that cause post-influenza pneumonia?
S. pyogenes
S. aureus
S. pneumoniae
Name 2 Group D streps
S. bovis
Enterococci
Where are Group D streps usually found?
GIT
What is S. bovis associated with?
Endocarditis
Colon cancer
What infections do enterococci cause?
Endocarditis
UTI
Biliary infections
What are the 2 main risk factors for S. pneumoniae infection?
Age - young & old
Spleen (lol)
People with no spleen are predisposed to infections by the 3 capsulated bacteria
