BAP or SBA: An abbreviation for blood agar plate
or sheep blood agar. Blood agar contains mammalian blood (usually sheep,
rabbit or horse), typically at a concentration of 5-10%. Blood agar is
an enriched media used to isolate bacteria and to detect hemolytic
MacConkey: MacConkey agar is a selective medium
that inhibits the growth of Gram-positive bacteria due to the presence
of crystal violet and bile salts. Most Gram-negative bacteria grow well
on MacConkey. MacConkey agar also contains neutral red (a pH indicator)
and lactose (a disaccharide). Lactose fermenting bacteria or Lactose +
bacteria on MacConkey will appear as bright pink colonies. Non-lactose
fermenting bacteria will be colorless (or, if they have any color, will
be their natural color rather than pink).
albicans can exist as both yeast and mycelial (hyphal) forms. When
yeast cells are incubated with serum at 37 degrees C , tube-like appendages
(germ tubes) grow from the cell; these are the beginning hyphal forms as the
C albicans converts from yeast to mycelia.
Catalase test: The catalase
test is used to differentiate some bacterial species. The test is done
by placing a drop of hydrogen peroxide on a microscope slide. Using an
applicator stick, a small portion of a colony is then added to a drop of
hydrogen peroxide drop.
If bubbles or froth forms, the organism is
said to be catalase-positive.
Staphylococci and micrococci are catalase-positive
If no bubbles form, the organism is catalase-negative.
Streptococci and Enterococci are catalase-negative
Non-hemolytic (γ-hemolysis): If an organism
does not induce any hemolysis on a blood agar plate, it is said to
display gamma or no hemolysis. The agar under and around the colony is
Gram stain: The Gram stain, is a
laboratory staining technique that distinguishes between two groups of
bacteria that have differences in the structure of their cell walls.
Standard bacterial taxonomy makes a distinction between Gram-negative
bacteria, which stain red/pink and the Gram-positive bacteria, which
stain blue/purple. Different antimicrobial agents are directed
specifically at gram-positive bacteria and gram-negative bacteria.
Mucoid: Bacterial colonies that appear moist and
sticky (resembling mucus).
Urease: Urease is an enzyme that catalyzes the
hydrolysis of urea into carbon dioxide and ammonia. Urease is found in
certain bacteria and yeast. Cryptococcus is urease-positive and Candida