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Micro - Streptococci


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What are the bacterial characteristics of S. pyogenes? What are its growth characteristics in culture?
*G+ cocci
*sensitive to bacitracin (A disk)
One of the Strep species can cause 3 different skin or fascia infections. What is the agent and what are the infections?
*S. pyogenes (GAS)
*necrotizing fasciitis
What is the most common manifestation of S. pyogenes in infected children? What are the symptoms?
*strep throat
*pharyngitis, tonsillar exudate, fever
*may or may not include scarlett fever rash
Antibiotic therapy of strep throat is generally indicated, even in mild cases, to prevent post-infection sequelae. What are these sequelae and how are they caused?
*AGN and rheumatic fever
*the body generates antibodies that are cross-reactive to the bacterial M-protein and cardiac and renal epitopes
Name 3 endogenous (i.e. NOT exotoxins) virulence factors associated with S. pyogenes. How does each contricute to pathogenesis?
*M-protein: antiphagocytic, adhesin
*hyaluronic capsule: antiphagocytic
*F protein: binds fibronectin
What's the function of Streptolysin O and and C5a peptidase in S. pyogenes?
*streptolysin O: direct tissue damage
*C5a peptidase: destroys complement
What are the 3 Spe exotoxins? What does each do?
*Spe A & C: superAgs; associated with scarlett fever and STSS
*Spe B: protease associated with necrotizing fasciitis
What is the recommended treatment for S. pyogenes? What drug is this bug resistant to?
*treat with PCN
*resistant to macrolides
What are the bacterial and growth characteristics of S. veridans? Where is it normally found?
*G+ coccus
*normal flora of oral cavity
What serious condition is S. veridans associated with? How does this happen? What can be done to prevent it?
*subacute bacterial endocarditis
*bacteria enter bloodstream through a break in gingival mucosa and attach to pre-existing defect on myocardium or valve
*biofilm growth is difficult to tx.
*antibiotic prophylaxis before dental tx for pts with pre-existing heart problems
What are the bacterial and culture growth characteristics of S. pneumoniae?
*G+ diplococci
*sensitive to optochin (P disk)
What are four disease states attributable to S. pneumoniae?
1.bacterial pneumonia
2.otitis media
3.pneumococcal meningitis
How is S. pneumoniae spread?
*p-p via aerosolized droplets
What predisposes a person to infection with S. pneumoniae?
Viral infection
What are 3 virulence factors of S. pneumoniae? What does each do?
1.Capsule - antiphagocytic
2.Peptidoglycan - proinflammatory
3.Pneumolysin - lyses RBC
How can S. pneumoniae be prevented?
Two vaccines:
*adult: polysaccharide against 23 strains
*peds: conjugate against 7 strains
What are the bacterial and culture growth characteristics of Enterococcus? Where can it normally be found?
*G+ cocci
*able to grow in harsh conditions including bile
*normal flora of GI and GU tracts
Enterococcus presents most often as a community-acquired infection.
False: Enterococcus is a major nosocomial infection and rarely presents as being community-acquired.
What are 3 disease states caused by enterococcus?
1.Subacute bacterial endocarditis
2.UTI, esp. catheter-related
What is the recommended treatment for Group D streptococcus? What kinds of resistance problems are associated with this organism?
*synergistic PCN + aminoglycoside
*multi-rx resistance, esp. VRE
What are the bacterial and culture growth characteristics of GBS?
*G+ coccus
What are three disease states associated with GBS?
*neonatal sepsis and meningitis
*post partum sepsis
*asymptomatic carrier
What 3 patient populations are most at risk for infection with GBS?
*pregnant women
What are 2 virulence factors associated with GBS?
*anti-phagocytic capsule
*C5a peptidase
Name 3 difficulties in creating a vaccine for S. pyogenes.
1.Antigenic variation of M protein
2.Cross-reactivity of M protein
3.Many M protein serotypes

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