Streptococci

All streptococci are Catalase -ve. Beta hemolytic streptococci have two imp antigens which are C carbohydrate and M protein. Important streptococci include S. pyogenes and S. pneumoniae.

Streptococcus. pyogenes

1. common cause of Throat infections ( pharyngitis , cellulitis)
2. cause toxic shock ( through production of exotoxin)
3. cause immune mediated post stretococcal pathogenesis which could lead to Rheumatic Fever or Acute glomerulonephritis.

Labs:

1. Beta hemolytic. (group A beta hemolytic)
2. Bacitracin sensitive
3. Throat swab contaning bacterial antigens (Agglutination of colored latex particles occures)

S. Pneumoniae

1. most common cause of community aquired pneumonia ( Typical pneumonia )
2. Also cause otitis media, sinusitis and meningitis

Labs:

1. Sputum is red or brown rusty color
2. Colonies are alpha hemolytic and are bile soluble.
3. quellung reaction test
4. lancet shaped, gram positive diplococci