Microlab1 Document Flashcards
What type of color would you expect to see in alpha-hemolytic bacteria on blood agar?
Greening
What is nosocomial infection?
infection that begins in the hospital
What are the most common bacteria in throat/mouth?
Viridans streptococci, neisseria species, and staphylococcus epidermis
What is the most common, clinically important bacteria on skin?
staphylococcus epidermis
What are some major bacterium of the nose/nares?
Staphylococcus epidermis and Stapylococcus aureus.
What is the Gram stain?
a stain using crystal violet dye and iodine mordant to fix it. They dye-iodine complex is easily washed away from G- cells but more slowly from G+.
G- cells must then be colored with safranin (red) to make them visible.
G+ cells will appear blue/purple
What are blood agar plates (BAP) useful for?
They are differential, based on hemolysis type.
Alpha - partial lysis (green from reduced heme) around colonies
Beta - complete lysis (clear) around colonies
Non-hemolytic - no change around colonies
What are mannitol salt agars useful for?
They are both Selective and Differential.
Selective for Staphylococci because high salt inhibits most others.
Differential for S aureus because of the pH indicator phenol red, which turns yellow when acidic (S. aureus produces acid = yellow)
S. aureus - yellow
S. epidermis - no change
What is eosin methylene blue (EMB) agar useful for?
It is both selective and differential. Selective for G- bacilli because it contains dyes that inhibit G+. Differential because contains lactose. Black/purple = lactose fermentor uncolored = nonfermentor (proteus) metallic black/purple = E. coli Brown/black/mucoid = Klebsiella
What type of bacteria produces a metalic black/purple color on EMB agar?
E. Coli
What type of bacteria produces a brown/black mucoid product on EMB?
Klebsiella
What type of test would be most useful for determining if a bacterium is S. aureus? What indications would you look for?
Mannitol Salt agar. Yellow color due to acid production
What is sodium chloride broth useful for?
It is selective.
Inhibits growth of most things except Enterococci. (streptococci)
What are coagulase tests useful for?
differentiate staph aureus from other staph.
coag+ = staph aureus
Coag- = other staph species
What is the tube coagulase test good for?
If there is a clot -> staph aureus
