This 1977 photograph (no magnification) depicted a Petri dish filled with trypticase soy agar medium containing 5% defibrinated sheep's blood, i.e., blood agar plate (BAP) that had been inoculated by streaking and stabbing the surface of the BAP with a non-hemolytic group A Streptococcus pyogenes (GAS) bacteria. The BAP was then incubated in a carbon dioxide enriched atmosphere at 35oC for 24 hours, and grew bacterial surface colonies with no characteristic color changes surrounding each colony, or in the stabbed areas. Under examination, no red blood cells in the blood agar medium had been altered, or "hemolyzed", indicating that these bacteria were indeed non-hemolytic in nature.Infection with non-hemolytic GAS can result in a range of symptoms identical to that of typical beta-hemolytic GAS:- No illness- Mild illness (strep throat or a skin infection such as impetigo)- Severe illness (necrotizing faciitis, streptococcal toxic shock syndrome)
CDC/ Richard R. Facklam, Ph.D.
December 4, 2012
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