Selective/Differential Media Quiz

MacConkey Agar

isolating and differentiating ENTERIC organisms based on ability to ferment lactose Neutral red dye for pH. Use dye and bile salts to inhibit growth of gram +

Phenol Red Broth

pH = phenol red. Metabolize sugar = yellow Has Durham tube that shows if sugar metabolized in generation of gas, will have small bubble

Hektoen Enteric-Agar (HEA)

Differentiate b/w Salmonella and Shigella from other gram negative enteric orgs. Will turn dark green Bile salts & 2 dyes restrict growth of gram + Lactose, sucrose, and salicin provide carbs. Those producing acid will turn pink to orange

Phenyl Ethyl Alcohol Agar (PEA)

Gram positive because phenyl ethyl interferes w/ gram negative DNA synthesis. Isolate Staphylococcus species from mixed culture

Mannitol Salt Agar (MSA)

Isolate Staphylococcus species and differentiate b/w pathogenic species (ie: S. aureus) contains sugar-alc mannitol, Phenol Red (pH) and NaCl concentration red but will turn pink (high pH) or yellow (low pH)

Examples of what selective media selects for

-ability to utilize sugars for energy/carbon -fermentation of different sugars -Ability to alter pH -Ability to tolerate toxic substances (ie: dyes, salts)

Triple Sugar Iron

agar slant to differentiate gram negative enterics whether or not they reduce sulfur & ferment carbs. 3 sugars, sulfur, pH indicator Ferment sugars? = yellow. Looking for sulfur reduction and gas production

Differential media definition

allows to identify particular genera or species of bacteria based on growth properties and metabolic capcity. Allows growth of more than one type of microorganism Contains substrate and chemical indicator

Eosin Methylene Blue-Agar (EMB)

coliform bacteria from fecal samples -non-endospore forming gram - rods capable of fermenting lactose and producing both acid and gas. Dyes inhibit growth of gram + and allows for gram - to grow (strong vs. weak fermenters) - strong = darker green

Selective media definition

designed to inhibit growth of some microorganisms while allowing growth of others

Blood agar

for fastidious bacteria that can secrete hemolysins For gram + cocci beta hemolysis = complete hemolysis (clear halo) alpha-hemolysis = green-yellow gamma-hemolysis = no lysis