microbio labs 13-16

hemolysins

bacterial exotoxins that destroy hemoglobin, resulting in the release of iron for the bacteria to use

beta hemolysis

complete destruction of hemoglobin resulting in translucent agar

alpha hemolysis

partial destruction of hemoglobin (medium remains opaque) resulting in a color change in sheep blood agar to green (streptococcus, enterococcus)

gamma hemolysis

non-hemolysis (staphylococcus, streptococcus, and enterococcus)

Bile Esculin Test

bile inhibits the growth of gram positive bacteria. if the bacteria can grow in and hydrolyzes esculin, a brown/black precipitate forms (enterococcus and streptococcus)

coagulase

an enzyme in bacteria that allows them to form clots and coat themselves with the fibrin in blood, making it highly resistant to phagocytosis

what is a selective ingredient

an inhibitory ingredient that is used to test whether a bacterium can it

what is a differential ingredient

an ingredient that is used to test a bacterium that can tolerate an inhibitory ingredient to determine the presence or absence of a physiological trait

mannitol salt agar (MSA)

used to test for growth in 7.5% NaCl and mannitol fermentation using a fermentable sugar and phenol red, which turns yellow in acidic pH

blood agar

used to test for bacterium's ability to hemolyze RBCs

Streptolysin O

a type of hemolysin produced by streptococci that cannot grow in oxygen

Streptolysin S

a type of hemolysin produced by streptococci that can grow in oxygen but grows best in anaerobic

PYR test

determines presence of PYR enzyme (red = positive, no color change/yellow/orange = negative)

CAMP test

differentiates between catalase- gram+ cocci

zone of inhibition

area around an antibiotic placed on a bacterial lawn of a hemolysis test where the antibiotic inhibited the growth of bacteria

eosin methylene blue (EMB) agar

detects graam negative bacteria and lactose fermenters (purple/pink or green for e. coli)

MacConkey (MAC) agar

detects gram negative bacteria and lactose fermenters (pink)