Gram Positive Strep

Question 1

Group A beta-hemolytic strep

(Streptococcus pyogenes)

Physiological Features

Answer 1

• Catalase negative
• Classified by the presence of an A antigen
• Beta-hemolytic (completely lyse)
• Pyo- “pus producing”

Question 2

Group A beta-hemolytic strep

(Streptococcus pyogenes)

Clinical Correlation

Answer 2

1. Cause
   
   • Classic strep throat
   • Streptococcal pharyngitis
   • Scarlet fever
   • rheumatic fever
   • post-streptococcal glomerulonephritis
2. Symptoms:
   
   • erythematous
   • edematous tonsils and pharynx
   • purulent tonsilar exudate
   • fever
   • cervical lymphadenopathy
3. Screened via Rapid Strep Test (RADT): rapid antigen detection test
4. Treated effectively with penicillin

Question 3

Group B beta- hemolytic streptococci

(Streptococcus agalactiae)

Physiological Features

Answer 3

• Catalase negative
• Classified by the presence of a B antigen
• Beta-hemolytic (completely lyse)

Question 4

Group B beta- hemolytic streptococci

(Streptococcus agalactiae)

Clinical correlation

Answer 4

1. 25% of women carry vaginally
2. May be passed to baby during vaginal delivery
3. Cause
   
   • neonatal meningitis
   • pneumonia
   • sepsis
4. Pregnant women screened at 35-37 weeks

Question 5

Group D Strep

Enterococci, Streptococcus bovis

Physiological Features

Answer 5

• Catalase negative
• Classified by the presence of an D antigen
• Alpha or non-hemolytic

Question 6

Group D Strep

Enterococci

Clinical Correlation

Answer 6

Enterococci (normal bowel flora)

1. Cause:
   
   • UTI’s
   • biliary tract infections
   • bacteremia
   • endocarditis
2. Hospitalized patients especially at risk
3. Highly resistant to antibiotics

Non-enterococci: also live in GI and linked with colon cancer

Question 7

Streptococcus pneumoniae

Physiological Features

Answer 7

• ​Diplococci
• Catalase negative
• Polysaccharide capsule prevent antibody binding

Question 8

Streptococcus pneumoniae

Clinical correlation

Answer 8

1. Cause
   
   • Adults: pneumonia and meningitis
   • Children: Otitis
2. High antibiotic resistance

Question 9

Viridans

Physiological Features

Answer 9

• Most are alpha-hemolytic (partially lyse) or non-hemolytic

Question 10

Viridans

Clinical correlation

Answer 10

1. Cause:
   
   • Dental infections (dental caries) - Streptococcus mutans
   • Endocarditis
   • Abscesses
2. Found:
   
   • oropharynx and colon
   • dental plaque
   • tongue
   • saliva