Streptococci

Question 1

properties and mechanism of Streptococcus pneumoniae

Answer 1

• gram +
• lancet shaped diplococci
• encapsulated
  
  • no virulence without capsule
• IgA protease
• Most OPtochin Sensitive (“MOPS”)

Question 2

what 4 things is Streptococcus pneumoniae the most common cause of?

Answer 2

• Meningitis
• Otitis media (in children)
• Pneumonia
• Sinusitis
  
  • “MOPS”

Question 3

what is pneumococcus often associated with?

Answer 3

• “rusty” sputum
• sepsis in patients with sickle cell disease and splenectomy

Question 4

properties of Viridans group streptococci

Answer 4

• gram +
• alpha hemolytic cocci

Question 5

Viridans group streptococci:

where are they normal? what do they cause?

Answer 5

• normal flora of the oropharynx
• cause dental caries (Streptococcus mutans and S. mitis)
• cause subacute bacterial endocarditis at damaged heart valves (S. sanguinis)
  
  • sanguinis=blood
    
    • think “ there is lots of blood in the heart (endocarditis)”
  • S. sanguinis makes dextrans–bind to fibrin platelet aggregates on damaged heart valves

Question 6

how to distinguish Viridans group streptococci from S. pneumoniae?

Answer 6

• Viridans group streptococci
  
  • resistant to optochin
• S. pneumoniae
  
  • alpha hemolytic, but optochin sensitive

Question 7

where do Viridans group streptococci live?

Answer 7

• in the mouth b/c they are not afraid of-the-chin (op-to-chin resistant)

Question 8

properties of Streptococcus pyogenes (group A streptococci)

Answer 8

• gram + cocci
• bacitracin sensitive
• beta hemolytic
• pyrrolidonyl arylamidase (PYR) +

Question 9

what does Group A strep cause?

Answer 9

• pyogenic
  
  • pharyngitis
  • cellulitis
  • impetigo
  • erysipelas
• toxigenic
  
  • scarlet fever
  • toxic shock like syndrome
  • necrotizing fasciitis
• immunologic
  
  • rheumatic fever
  • glomerulonephritis
    
    • “Pharyngitis can result in rheumatic ‘phever’ and glomerulonephritis”

Question 10

antibodies to M protein and S. pyogenes

Answer 10

• antibodies to M protein enhance host defenses against S. pyogenes but can give rise to rheumatic fever

Question 11

what will detect a recent S. pyogenes infection?

Answer 11

ASO titer

Question 12

what is the major criteria for acute rheumatic fever?

Answer 12

• “JONES”–think of the “O” as a heart
  
  • Joints–polyarthritis
  • heart–carditis
  • Nodules–subcutaneous
  • Erythema marginatum
  • Sydenham chorea

Question 13

what will usually procede glomerulonephritis brought on by group A stre?

Answer 13

impetigo

Question 14

Scarlet Fever

Answer 14

• can be caused by group A strep
• symptoms:
  
  • blanching
  • sandpaper like body rash
  • strawberry tongue
  • circumoral pallor
    
    • all occur in the setting of group A streptococcal pharyngitis (erythogenic toxin +)

Question 15

properties and mechanism of Streptococcus agalactiae (group B streptococci)

Answer 15

• gram + cocci
• bacitracin resistant
• beta hemolytic
• produces CAMP factor which enlarges area of hemolysis formed by S. aureus
• hippurate test +
• PYR -

Question 16

what does group B strep cause?

Answer 16

• pneumonia
• meningitis
• sepsis

Question 17

which population usually has Streptococcus agalactiae infections?

Answer 17

• group B strep is found mainly in Babies

Question 18

pregnancy and Streptoccus agalactiae

Answer 18

• screen pregnant women at 35-37 weeks of gestation
  
  • patients with a positive culture receive intrapartum penicillin prophylaxis

Question 19

properties of Streptococcus bovis

Answer 19

• gram + cocci
• colonizes the gut

Question 20

What does Streptococcus bovis cause?

Answer 20

• bacteremia
• subacute endocarditis
• is associated with colon cancer
  
  • “Bovis in the blood = cancer in the colon”