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sheep red blood cells
to identify the colonial appearance of staphylococci through pigment and hemolytic activity
7.5% salt
added in mannitol salt agar, creates a high concentration of salt/ hypertonic environment that inhibits gram-positive cocci
mannitol
an indicator to differentiate S. aureus strains from S. epidermidis growing on it
phenol red
a pH indicator, detects acid, will turn red/pink in high pH and yellow in low pH
list 4 ways S. aureus can be distinguished from S. epidermidis
hemolysis
pigment and colony size
mannitol fermentation
salt tolerance
how is the production of coagulase related to virulence
causes inappropriate clotting
gram stain appearance of staphylococci
purple, grape like clusters
why is it important to not remove any media when doing a catalase test from organisms growing on a blood agar plate?
blood will also fizz on it
why is the catalase test used?
differentiate Streptococcus pyogenes and Staphylococcus aureus
alpha hemolysis
incomplete breakdown of RBCs, oxidizes iron, makes green color
beta hemolysis
complete destruction of RBCs, appears yellow/clear/transparent
gamma hemolysis
no breakdown, no appearance change
what type of hemolysis is demonstrated by normal throat flora?
alpha, beta, and gamma
what type of hemolysis is displayed by streptococci that are most pathogenic for humans?
beta
test that differentiates normal throat streptococci from Group A streptococci?
hemolysis and bacitracin sensitivity
gram stain morphology of streptococci
gram-positive, cocci in chains