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30 Cards in this Set
- Front
- Back
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How are Streptococcus species classified?
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According to Lancefield group or type of hemolysis.
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Describe the Lancefield group of Strep. pyogenes.
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Lancefield group A, beta hemolytic, bacitracin sensitive
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Streptococcus agalactiae; Lancefield.
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Lancefield group B, beta hemolytic
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Entero fecalis faecalis and Faecium, Lancefield
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Lancefield group D, alpha and beta hemolytic
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Strep. bovis, Lancefield.
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Lancefield group D, alpha hemolytic.
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What is the Lancefield group of Strep pneumoniae
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No Lancefield group, alpha hemolytic, bile soluble.
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What is the Lancefield of Viridins group Streptococci?
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No Lancefield group, alpha hemolytic, not bile soluble, not inhibited by optochin.
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What virulence factor causes beta hemolysis?
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Streptolysin O and S. Streptolysin O is inactivated by O2 and antistreptolysin O(ASO) antibodies are important in the diagnosis of rheumatic fever. Streptolysin S is Oxygen stable and is not immunogenic.
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S. pyogenes causes disease through what three broad pathogenic mechanisms?
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Pyogenic inflammation(pharyngitis and cellulitis), toxin mediated diseases(scarlet fever, toxic shock syndrome), immunologic diseases(rheumatic fever and glomerulonephritis).
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How does S. pyogenes pharyngitis usually present and why must it be treated with antibiotics?
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High fevers, pharyngeal erythema, swollen tonsils with exudates and tender cervical lymph nodes. It is treated with penicillin or a cephalosporin because untreated cases may result in rheumatic fever.
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How is Strep. impetigo different from Staph impetigo?
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Strep. impetigo manifests with vesicles, not bullae. Glomerulonephritis may develop secondary to untreated Strep. impetigo.
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What is Rheumatic fever?
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Immunologic disease caused by cross reactivity of S. pyogenes, M protein and antigens of joint and heart tissue. Clinically, it presents 2-3 weeks following S. pyogenes pharyngitid(Strep throat), and is seen with fever, polyarthritis, SQ nodules, chorea(rapid purposeless movements and carditis(murmur)
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What are the pathognomonic lesions of rheumatic heart disease?
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Aschoff bodies, which are foci of fibrinoid necrosis surrounded by lymphocytes and macrophages known as Anitschkow cells.
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How is rheumatic fever diagnosed?
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Using the modified Jones criteria(carditis, polyarthritis, SQ nodules, chorea, elevated C reactive protein.
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What is post streptococcal acute glomerulonephritis(AGN)?
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Immunologic disease cause by deposited antigen-antibody complexes onto the glomerular basement membrane. Hypertension, edema and smokey urine are symptoms and signs.
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Describe the immunofluorescence pattern of AGN glomerular basement membranes.
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Immune complexes form resulting in granular deposits. C3 is decreased.
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What is M protein?
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Antiphagocytic virulence factor S. pyogenes. Specific types of M protein are associated with pharyngitis/ acute rheumatic fever and cellulitis and glomerulonephritis.
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What toxins are associated with S. pyogenes?
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Erythrogenic toxin, exotoxins A and B, Streptolysin O and S.
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Which toxins act as superantigens. Which one is more associated with TSS?
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Erythrogenic and exotoxin A. Exotoxin A causes more cases of TSS.
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What is Scarlet fever?
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Erythrogenic toxin mediated disease that develops in association with infections of certain strains of S. pyogenes and is characterized by course, erythematous, blanching rash, a strawberry tongue, petecchial lesions in skin creases(Pastia's sign) and desquamation of theskin.
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What diseases are associated with Group B Streptococci or S. agalactiae?
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Sepsis and meningitis in neonates and UTIs, soft tissue and endocarditis infections in adults.
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What diseases are associated with Group D Enterococcus(E. faecalis and faecium)?
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UTIs, endocarditis and peritonitis.
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What diseases are associated with non-Enterococcus Group D Strep(S. bovis)?
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Endocarditis or bacteremia in the presence of colon cancer.
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What diseases do S. pneumoniae cause?
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Pneumonia, meningitis, otitis media, sepsis and sinusitis.
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How is S. pneumoniae described under the microscope?
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Gram+ lancet shaped diplococci.
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What are the important virulence factors for S. pneumoniae?
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Polysaccharide capsule, IgA protease, pneumolysin and lipotechoic acid.
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What is the clinical significance of the polysaccharide capsule?
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It is antiphagocytic, antibodies to the capsule are protective. Asplenic patients (associated with decreased opsonin antibody production) are more susceptible to S. pneumoniae infectionbs.
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What is the clinical significance of the IgA protease?
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IgA protease allows for infection of the respiratory tract leading to sinusitis and lobar pneumonia(rusty colored sputum).
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How is S. pneumoniae treated?
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Penicillin is the drug of choice, yet penicillin resistance is on the increase.
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Who should receive the S. pneumoniae vaccine?
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Older patients(>65yrs old), immunocompromised patients, asplenic patients and COPD patients.
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