Microlab Techniques

Question 1

Sensitivity

Answer 1

positive when organism is there

true positive

Question 2

Specificity

Answer 2

negative when organism is not there

true negative

Question 3

What can happen when you have low levels of pathogens?

Answer 3

sensitivity can increase (positive when actually there)

specificity can decrease (might test negative when organism is actually there)

Question 4

positive predictive value

Answer 4

probability that test-positives truly have the disease

high sensitivity

Question 5

negative predictive value

Answer 5

probability that test-negatives don’t have the disease

high specificity

Question 6

McClung Egg Yolk Agar

Answer 6

selectively differentiate different clostridium species

Question 7

CNA blood agar

Answer 7

allows you to isolate gram positive species

can differentiate gram positives based on hemolytic pattern

Question 8

Steps of gram staining

Answer 8

crystal violet, iodine, alcohol decolor, safranin counterstain

Question 9

Why do you need to add safranin at end of gram staining?

Answer 9

need to turn the gram negative bacteria pink since they will not hold crystal violet

Question 10

MALDI-TOF

Answer 10

measures the relative abundance of protein masses

need a culture to test from

Question 11

What does PCR allow you to see?

Answer 11

different strain types

Question 12

16S amplicon

Answer 12

can use as a marker gene when you cannot culture microbe

use for bacteria

Question 13

18S amplicon

Answer 13

can use as a marker gene when you cannot culture microbe

use for fungi and eukaryotes

Question 14

amplicon vs. shotgun metagenomics

Answer 14

amplicon can only give genus not species

metagenomic can give us more information but requires more DNA and is more expensive