08-Streptococcus_and_Enterococcus_v1-_3

08-Streptococcus_and_Enterococcus_v1-_3 - Streptococcus and...

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Streptococcus and Enterococcus Dr. John R. Warren Department of Pathology Northwestern University Feinberg School of Medicine June 2007
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Taxonomy of Streptococcus and Enterococcus Enterococcal group D Streptococcus (previously Streptococcus faecalis and Streptococcus faecium ) currently classified in the genus Enterococcus Group D Streptococcus consists of a single pathogen Streptococcus bovis
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Taxonomy of Streptococcus and Enterococcus Nutritionally-variant (pyridoxal- dependent) Streptococcus (NVS) currently classified in the genera Abiotrophia (A . defectiva ) and Granulicatella ( G . adiacens and G . elegans )
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Hemolytic Reactions on Sheep Blood Agar Tryptic (trypticase) soy agar base with 5% sheep blood widely used for the determination of hemolytic reactions of Streptococcus and Enterococcus . The base medium contains soybean and casein peptides as a carbon and nitrogen source, and sheep blood provides hemin (X factor) for growth of fastidious organisms.
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Hemolytic Reactions on Sheep Blood Agar Absence of carbohydrate prevents fermentative acids that inhibit hemolysis. Sheep blood contains NADase that inactivates NAD released by red cells, thus preventing growth of the β - hemolytic organisms Haemophilus haemolyticus and H . parahaemolyticus that require exogenous NAD.
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Hemolytic Reactions on Blood Agar (Sheep, Horse, Rabbit) 2200 β -hemolysis Complete clearing of blood agar due to lysis of red cells by oxygen-stable and oxygen-labile hemolysin 2200 α -hemolysis Greening of blood agar due to partial lysis of red cells 2200 γ -hemolysis Absence of hemolysis
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Streptococcal β -Hemolysins Oxygen-labile streptolysin (Streptolysin O) 1 Oxygen-stable streptolysin (Streptolysin S) 1 Activity of streptolysin O expressed in deep stabs of inoculum into anaerobic portions of sheep blood agar
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Broad Groups of Streptococcus 2200 β -hemolytic groups A, C, and G streptococci form large (>0.5 mm) or small (<0.5 mm) colonies on sheep blood agar. Large colony formers are pyogenic streptococci including Streptococcus pyogenes (group A)
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Broad Groups of Streptococcus Small colony formers of β -hemolytic streptococci with group A, C, or G antigens differ genetically from the pyogenic streptococci and are placed in the anginosus group of Streptococcus All β -hemolytic group B streptococci are Streptococcus agalactiae
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Broad Groups of Streptococcus Non- β hemolytic streptococci show either green hemolysis ( α -hemolysis) or no hemolysis on sheep blood agar. A useful definition of viridans streptococci is organisms that demonstrate α -hemolysis or no hemolysis.
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Broad Groups of Streptococcus Viridans streptococci are grouped into Streptococcus pneumoniae , S . bovis , the anginosus group of Streptococcus , and other. Other groups of viridans streptococci (mitis, mutans, and salivarius) consist of endocarditis-producing strains, invasive strains in neutropenia, saprophytes, and contaminants.
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Major Enterococcus Species Enterococcus faecalis constitutes ~90% of clinically significant enterococcal isolates, E . faecium ~10%.
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