Streptococcus pyogenes (Group A streptococci)
Streptococcus pyogenes on Columbia agar with 5% sheep blood. Cultivation 24 hours, in an aerobic atmosphere enriched with 5% carbon dioxide. Colonies are surroundend by a wide zone of beta-hemolysis.
Positive PYR test is useful for preliminary identification of isolated strains (together with the negative catalase test). Identification can be confirmed by the latex agglutination test.
S. pyogenes is the cause of many important human diseases, ranging from mild superficial skin infections to life-threatening systemic diseases. Infections typically begin in the throat or skin. Examples of mild S. pyogenes infections include pharyngitis ("strep throat") and localized skin infection (impetigo). Erysipelas and cellulitis are characterized by multiplication and lateral spread of S. pyogenes in deep layers of the skin. S. pyogenes invasion and multiplication in the fascia can lead to necrotizing fasciitis, a potentially life-threatening condition requiring surgical treatment. Infections due to certain strains of S. pyogenes can be associated with the release of bacterial toxins. Throat infections associated with release of certain toxins lead to scarlet fever. Other toxigenic S. pyogenes infections may lead to streptococcal toxic shock syndrome, which can be life-threatening.
Streptococcus pyogenes can also cause disease in the form of postinfectious "nonpyogenic" (not associated with local bacterial multiplication and pus formation) syndromes. These autoimmune-mediated complications follow a small percentage of infections and include rheumatic fever and acute postinfectious glomerulonephritis. Both conditions appear several weeks following the initial streptococcal infection. Rheumatic fever is characterised by inflammation of the joints and/or heart following an episode of streptococcal pharyngitis. Acute glomerulonephritis, inflammation of the renal glomerulus, can follow streptococcal pharyngitis or skin infection.
Streptococcus pyogenes basic characteristics
- GRAM-POSITIVE COCCI
- CATALASE: NEGATIVE
- OXIDASE: NEGATIVE
- FACULTATIVELY ANAEROBIC
Identification of Streptococcus pyogenes
- The catalase test (negative)
- The PYR test (positive)
- Lancefield's group A antigen presence(e.g., latex agglutination)
Antibiotic treatment of Streptococcus pyogenes infections
Other beta-lactam antibiotics, e.g.:
Streptococcus pyogenes colonies on agar cultivation media
Streptococcus pyogenes identification
Streptococcus pyogenes Gram stain
- Streptococcus sp.
- Streptococcus pyogenes
- Virulence factors
- Group A streptococcal infection
- M protein (Streptococcus)
CENTERS FOR DISEASE CONTROL AND PREVENTION (CDC)