Quiz 9/23 – Microbiology

Enriched - not selective and can be used to grow a wide variety of microbial types
Differential Medium - permits growth of several types of microbes that show differing reactions

Enriched - not selective and can be used to grow a wide variety of microbial types

Selective - growth is restricted to a particular group or type of microbe
Differential Medium - Permits growth of several types of microbes that show differing reactions

Selective - growth is restricted to a particular group or type of microbe
Differential Medium - Permits growth of several types of microbes that show differing reactions

used to grow organisms that are highly fastidious, which are the hardest to grow

used to grow one type of bacteria but inhibit the growth of another. Media are "enriched"

used to grow many species of bacteria but can distinguish between species of bacteria based upon one or more biochemical characteristics. Media are "enriched"

5% Sheep Red Blood Cells

Same ingredients as blood agar except RBC's are lysed due to heat (gives chocolate color)

Can distinguish between bacterial species based upon the organisms ability to hemolyze RBC's

Clear zone around colony, Complete destruction of RBC (ex. Staphylococcus aureus, Streptococcus pyogenes)

Green zone around colony, Bacteria produce hydrogen peroxide that result in oxidation of hemoglobin to produce methemoglobin (ex. Streptococcus pneumoniae)

no hemolysis

Used to grow highly fastidious organisms - lysing RBC's by heating releases essential nutrients for organisms to grow (ex. Hemophilus influenzae, Neisseria meningitidis and Neisseria Gonorrhoeae)

Used to grow one type of microbe but suppress the growth of other microbes. Is type of Chocolate agar that has 4 different anti-microbials added to allow the selective growth of fastidious organisms but prevent the growth of other organisms

Vancomycin - kills most gram-positive organisms
Colistin - kills most gram-negative organisms (except neisseria)
Nystatin - kills most fungi
SXT - inhibits gram-negative organisms, especially swarming proteus
(only genus will grow are Neisseria)

used to identify gram negative lactose fermenting bacteria - both selective and differential
Metabolism of sugars (lactose) yield acid by-products such as pyruvic acid that lowers pH, this turns colonies pink, if not fermented stays colorless

Selective agent - crystal violet, allows the growth of gram - negative bacilli but prevents the growth of gram - positive cocci
Differential Agent - neutral red, changes from red to yellow between 6.8 to 8

used to grow gram-positive cocci (opposite of ManConkey)

Selective medium: colistin and nalidixic acid added to prevent the growth of gram-negative bacilli
Differential medium: contains red blood cells to identify types of hemolysis

used to grow bacteria that require low oxygen atmosphere (ex; clostridium perfingens, clostridium tetani)

selective component - low pH 5.6, fungi loves it bacteria hates it
Use - allows growth of fungi, prevents growth of bacteria