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30 Cards in this Set

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