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Magnified 100x, this 1977 photograph depicted a Petri dish filled with heart infusion agar medium containing 5% defibrinated rabbit blood, referred to as a blood agar plate (BAP). A loop of diluted Streptococcus anginosus bacterial culture of was put into the melted agar (50oC), just before the blood was added to the melted agar. The agar was allowed to solidify, and then incubated at 35oC for 24-hours in a normal atmosphere. The culture grew subsurface colonies, one of which is seen here, surrounded by what is known as wide zone alpha hemolytic color changes, whereupon, the area immediately adjacent to the colony has some red blood cells (RBCs), but an area outside of that may be completely, or nearly completely, cleared of RBCs. Therefore, there is no reactive zones where complete RBC hemolysis had occurred, as is the case in beta-hemolytic reactions, hence the wide zone alpha terminology.
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Content Providers(s):CDC/ Richard R. Facklam, Ph.D.
Creation Date:1977
Photo Credit:
CDC Organization
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Copyright Restrictions:None - This image is in the public domain and thus free of any copyright restrictions. As a matter of courtesy we request that the content provider be credited and notified in any public or private usage of this image.