Lab Quiz: Lab 2 Flashcards
What is complex media?
Those that can not be chemically defined
They usually contain some type of biological fluid or component
What are examples of complex media?
Blood
Serum
Bile salts
Different enzymatic digests of protein
What is chemically defined media?
Those in which every component is chemically known and added at a defined concentration
What does differential media have added to it?
Some type of indicator or indicatory system
What are examples of differential media?
Blood for hemolysis detection
Specific carbohydrates and a pH indicating dye
What does selective media have added to it?
Some type of inhibitor to prevent the growth of certain organisms
What are examples of selective inhibitors?
Antibiotics High salt concentrations Bile salts Growth inhibiting dyes (crystal violet) Limiting nutrients
What is blood agar?
A universal complex differential medium used for the isolation and cultivation of pathogenic, and especially fastidious, microorganisms
What does blood agar support the growth of and detect?
Hemolysis by most medically important bacteria, yeasts, and fungi
What is trypticase soy agar?
A base medium to which 5% defibrillated sheep blood is added once the base medium is cooled to 50ºC
How much of the medium is in a standard 150 mm trypticase soy agar plate?
20 mL
What is colistin-nalidixic acid (CNA) agar?
Blood agar to which the antibiotics colistin and nalidixic acid have been added to preclude the growth of gram-negative organisms
What is colistin?
A peptide antibiotic
What is nalidixic acid?
A quinolone acid
What does CNA generally replace?
Phenyl Ethyl Alcohol (PEA)
What will grow on CNA agar?
Gram-positive organisms
What is MacConkey agar?
A moderately selective medium for the isolation and presumptive identification of enteric bacteria from feces and urine
What is MacConkey agar useful for?
Isolation and separation of swarming Proteus from other enteric organisms
Differentiating certain non-enteric gram-negative organisms in lab diagnosis
What do the peptones in MacConkey agar provide?
Nitrogenous nutrients and amino acids
What do coliform organisms, which ferment lactose develop into with MacConkey agar?
Red/pink colonies surrounded by a zone of precipitated bile
What do lactose nonfermenters develop into with MacConkey agar?
Colorless, transparent colonies
What do bile alts and crystal violet do in MacConkey agar?
Inhibit gram-positive and many gram-negative bacteria
What can grow on MacConkey agar?
Only certain types of gram-negative organisms
