پاورپوینت استرپتوکک جلسه چهارم (pptx) 32 اسلاید

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تعداد اسلاید: 32 اسلاید

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بنام خدا جلسه چهارم استرپتوکک انتروکک GENERAL DISCUSSION The streptococci are gram-positive cocci (0.5-1.0µm in diameter) which occur in pairs and chains of varying length. They are usually classified based on their hemolytic properties on blood agar and according to their serologic groups ( Lancefield grouping). The streptococci are usually isolated on Sheep Blood agar ( BAP) ( Tryptic soy agar with ( 5-10 ) % Sheep blood ). Hemolysis refers to is the lysis of the red blood cells in the agar surrounding bacterial colonies and is a result of bacterial enzymes called hemolysins. Reactions on blood agar are said to be beta, alpha, gamma, or double-zone: Beta hemolysis refers to a clear, colorless zone surrounding the colony, where a complete lysis of the red blood cells by the hemolysins has occurred. Alpha hemolysis appears as a zone of partial hemolysis surrounding the colony, often accompanied by a greenish or brown discoloration due to oxidation of hemoglobin to met-hemoglobin by hydrogen peroxide Gamma hemolysis refers to no hemolysis or discoloration of the agar surrounding the colony. Double-zone hemolysis refers to both a beta and an alpha zone of hemolysis surrounding the colony. Hemolysis on sheep blood agar: