Chapter 4: Streptococci
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- How can you differentiate streptococci from staphylococci?
- Catalase test: staph is positive
- What do alpha, beta, and gamma hemolytic refer to?
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Groups of streptococci, based on their ability to hemolyze RBCs
alpha = partial
beta = complete
gamma = none -
Group A beta hemolytic strep:
- aka?
- Cause which diseases? -
- Strep pyogenes
- Strep throat, scarlet fever, rheumatic fever, post-streptococcal glomerulonephritis, streptococcal skin infections, streptococcal toxic shock syndrome - How would you treat skin infections such as folliculitis, cellulites, and impetigo? Why?
- Penicillinase resistant penicillin like dicloxacillin, because it covers both group A beta-hemolytic streptococci and Staph aureus, both of which can cause these skin infections
- What is scarlet fever and how is it caused?
- Certain beta-hemolytic group A streptococci produce pyrogenic/erythrogenic toxin, causing fever and a scarlet-red rash (sparing the face)
- What is rheumatic fever?
- Now rare, follows untreated beta-hemolytic group A streptococcal pharyngitis. Antibody mediated; manifests with fever, myocarditis, arthritis, chorea, subQ nodules, and an erythema marginatum rash. (Think of the John Travolta “Rheumatic Fever†picture).
- What is acute post-strep glomerulonephritis?
- Antibody-mediated disease occurring about one week after infection of either the pharynx or skin by nephritogenic strains of beta-hemolytic Group A strep
- What are the Group B beta-hemolytic streptococci?
- Think Group B “Baby.†Neonates can acquire these bugs during delivery, which can cause meningitis, pneumonia, and sepsis.
- What are the three most common pathogens associated with meningitis in infants < 3 months?
- E choli, Listeria, and Group B strep
- What are the Viridans Group streptococci? What infections do they cause?
- Heterogenous group of mostly alpha hemolytic streptococci. Normal GI flora. Think of ‘verde.’ Flora can bind to teeth… dental procedures can send these organisms into the blood stream. Cause: dental infections (cavities), subacute bacterial endocarditis, and abscesses
- What could cause subacute bacterial endocarditis? Acute infective endocarditis? What are the clinical manifestations of each?
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Viridans streptococci – low-grade fevers, fatigue, anemia, and heart murmur secondary to valve destruction.
Staphylococcal infection – abrupt onset of shaking chills, high spiking fevers, and rapid valve destruction. - What are enterococci? Are now resistant to⬦?
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Gram positive alpha/gamma hemolytic streptococci. Normal bowel flora.
Resistant to ampicillin and vancomycin - Strep bovis infection has been shown to be associated with⬦?
- Colon cancer
- What is strep pneumo? Shape, virulence factor, lab tests?
- Most common cause of adult pneumonia and bacterial meningitis. Most common cause of otitis media in children. Diplococci. Polysaccharide capsule. Quellung reaction and optochin sensitivity.
- Which drugs are useful against strep pneumo with intermediate level resitance?
- High dose penicillin and cephalosporins.