Microbiology Lab

Question 1

selective media

Answer 1

inhibits the growth of one type of bacterium while permitting the growth of another, facilitating isolation of a pathogen from a clinical sample

Question 2

differential media

Answer 2

does not inhibit one bacterium over another; but rather is designed such that different types of bacteria display different characteristics

Question 3

Sheep blood agar

Answer 3

differential based on the ability to produce enzymes, hemolysins, which can lyse the red blood cells

Question 4

saebouraud dextrose agar

Answer 4

selective based on pH of 5.6 and a higher concentration of dextrose than most bacteria prefer; used for fungi

Question 5

mannitol salt agar

Answer 5

selective for staphylococcus ; differential among staphylococci based on the ability to ferment mannitol from red (negative) to yellow (positive)

Question 6

macconkey

Answer 6

selective for gram negative bacteria because crystal violet and bile salts inhibit gram +, differential between lactose fermenters (turns red) and non-fermenters

Question 7

triple sugar iron (TSI)

Answer 7

tests for sugar fermentation, sulfur reduction, and gas production

Question 8

motility-indole ornithine decarboxylase (MIO)

Answer 8

test for presence of tryptophan