Strep Pharyngitis

Question 1

When is it appropriate to begin strep treatment w/out test?

Answer 1

• Positive for 3/4 centor criteria
• 5-15yo
• Previous case of GAS infection or recent contact with strep throat

Question 2

Bacteria responsible for GAS infection?

Answer 2

Streptococcus pyogenes

Question 3

Classification of GAS?

Answer 3

Gram positive, cocci, arranged in chains, beta-hemolytic

Question 4

Distinguishing features of GAS?

Answer 4

• B-hemolytic: streptolysins O (anaerobic only) and S form pores in blood cells
• Catalase negative (unlike staph “staff” that has a cat)
• Lancefield group A antigen (surface antigen carb.)

Question 5

Adhesion molecules of GAS?

Answer 5

• M-protein (anti-phagocytotic, amino-terminal on EC side)

- Lipoteichoic acid (LTA) and Protein F

Question 6

Anti-phagocytosis components of GAS?

Answer 6

• M-proteins (binds to serum factor H sequestering it -> decrease in complement component C3b deposition on GAS surface)
• C5a peptidase inactivates C5a (blocking chemotaxis of neutrophils to site)

Question 7

Pathophysiological components of GAS?

Answer 7

• Streptolysins O and S (“cell murderers”)
• Exotoxins (super-antigens) -> T-lymphocytes, cytokines (TNF, IL-1b, IL-2, IL-6) release -> febrile response
• Nucleases A-D (pus formation)

Question 8

What other important diseases can GAS cause?

Answer 8

• Impetigo, Pyoderma, Necrotizing Fasciitis (skin)
• Strep pharyngitis
• Rheumatic fever, Glomerulonephritis
• Scarlet fever
• Toxic shock syndrome

Question 9

What are the other groups of Streptococci?

Answer 9

• Group B strep (stretococcus agalactidae)
• Viridans Group strep (many species)
• Group D strep (several species)
• Streptococcus pneumonia (penicillin resistant)

Question 10

Epidemiology for strep pharyngitis?

Answer 10

• 5-15yo
• Winter/early Spring
• Schools, military camps, crowded areas, poor hygeine (underdeveloped areas)
• Exposure to others with known GAS infection

Question 11

Sensitivity (for diagnostic tests):

Answer 11

TP/(TP+FN)

• High SeNsitivity, when Negative, rules OUT disease (SN-N-OUT)
• Used for low prevalence diseases
• When you want to know if you don’t have disease (e.g. HIV)

Question 12

Specificity (for diagnostic tests):

Answer 12

TN/(TN+FP)

• Highly SPecific, when Positive, rules IN disease (SP-P-IN)
• Used to rule in disease (e.g. RADT for strep)

Question 13

Positive Prediction Value (PPV) (for diagnostic tests):

Answer 13

TP/Total P

-Probability that the pt with a positive test result has the disease

Question 14

Negative Prediction Value (NPV) (for diagnostic tests):

Answer 14

TN/Total N

-Probability that pt with negative test result actually doesn’t have the disease

Question 15

Treatment for Strep Pharyngitis?

Answer 15

• Penicillin
• Or Cephalosporin for penicillin-allergic pts
• Fluids, Analgesics for pain reduction

Question 16

Common post-strep pharyngitis complications?

Answer 16

• Acute Rheumatic Fever and Glomerulonephritis (PSGN more common after impetigo than pharyngitis)
• Both related to auto-immune processes (heart and kidney respectively)

Question 17

Symptoms of Rheumatic Fever?

Answer 17

(JoNES criteria)

JOINTS - polyarthritis, CARDITIS - murmurs, NODULES, ERYTHEMA marginatum, SYNDENHAM’s chorea (uncontrolled movements)

Question 18

Common Sx of PSGN?

Answer 18

• Smoky/cola-colored urine! (hematuria, proteinuria)

- Malaise, fever

Question 19

What are the Centor Criteria?

Answer 19

• Recent fever >101F
• Tonsillar exudate
• Lack of cough
• Anterior cervical lymphadenopathy