Microbiology Exam #1 Lab Info

Question 1

describe the steps of a gram stain?

Answer 1

1. flood slide with crystal violet for 60sec, then wash it off with water
2. flood slide with gram’s iodine for 20sec, then wash it off
3. decolorize carefully/indirectly
4. flood slide with gram’s safranin for 60sec
5. rinse off slide and dry with bibulous/blotting paper

Question 2

which cell type remains purple in gram stain?

Answer 2

gram positive - crystal violet

Question 3

which cell type is red in gram stain?

Answer 3

gram negative - safranin

Question 4

gram positive or negative?

Answer 4

positive

Question 5

gram postive or negative?

Answer 5

positive

Question 6

gram positive or negative?

Answer 6

negative

Question 7

what does a catalase test test for?

Answer 7

only organisms with a catalase enzyme (ex: Staphylococcus) will have a positive reaction when hydrogen peroxide added to sample

Question 8

what does a positive catalase test look like?

Answer 8

bubbling once hydrogen peroxide added

Question 9

what does a negative catalase test look like?

Answer 9

NO bubbling when hydrogen peroxide added

Question 10

describe alpha hemolysis

Answer 10

partial, greenish halo around bacterial colonies
result of hydrogen peroxide produced by bacteria acting on hemoglobin to make methemoglobin

Question 11

describe beta hemolysis

Answer 11

aka complete hemolysis
complete lysis of RBC in media around bacterial colonies and is result of hemolysin enzyme produced by specific bacterial species

Question 12

describe gamma hemolysis

Answer 12

NOT hemolysis at all
absence of hemolysis surrounding non-hemolytic colonies

Question 13

ID the types of hemolysis indicated by the arrows

Answer 13

1. beta hemolysis
2. alpha hemolysis
3. gamma hemolysis

Question 14

what is the most common organism isolated from cases of pyoderma in dogs/cats?

Answer 14

Staphylococcus pseudintermedius

Question 15

Biopsies are the sample of choice for diagnosing bacterial dermatitis in what type of skin lesions?

Answer 15

Papules

Question 16

When operating normally, our bacteriology course laboratory is conducted under which of the following biosafety levels?

Answer 16

BSL-1

Question 17

Which organisms may be found as part of the healthy skin microbiota?

Answer 17

a) Commensal organisms
b) Opportunistic organisms
c) Pathogenic organisms

Question 18

Which of the following forms of hemolysis is best described as a partial, greenish halo around bacterial colonies?

Answer 18

alpha

Question 19

The differential qualities of TSA+5% sheep blood agar allow it to discriminate bacteria that are what?

Answer 19

Hemolytic vs. non-hemolytic

Question 20

what type of microscope is useful for seeing internal details on unstained, living organism?

Answer 20

phase-contrast microscope

Question 21

what microscope type is used to generate highly magnified 3D image of bacteria?

Answer 21

scanning electron microscope

Question 22

Native or exotic agents that may be aerosolized and cause serious disease in humans, like Mycobacterium tuberculosis, are handled under which biosafety level?

Answer 22

BSL-3

Question 23

What factors are thought to affect the skin microbiota?

Answer 23

breed, diet, medications

Question 24

Which of the following best describes the TSA+5% sheep blood agar plates used in lab?

Answer 24

differential media

Question 25

Which of the following forms of hemolysis is best described as the complete lysis of red blood cells in the media around bacterial colonies?

Answer 25

beta

Question 26

which of the following stains highlights gram positive organisms?

Answer 26

crystal violet

Question 27

which of the following stains highlights gram negative organisms?

Answer 27

gram's safranin

Question 28

Which of the following microscopes is the most commonly used in clinical medicine, and is the sort we use in our bacteriology laboratory?

Answer 28

bright field microscope

Question 29

which microscope is useful for visualizing extremely small or thin bacterial, like Borrelia?

Answer 29

dark field microscope

Question 30

At what biosafety level do most diagnostic laboratories operate at?

Answer 30

BSL-2

Question 31

What biosafety level would be required to handle Ebola virus?

Answer 31

BSL-4

Question 32

what biochemical tests is looking for an enzyme not commonly present in members of the family Enterobacteriaceae?

Answer 32

oxidase test

Question 33

what test can help to quickly discriminate Gram-negative organisms from Gram- positive ones?

Answer 33

KOH test

Question 34

what biochemical tests is looking for an enzyme which can reduce hydrogen peroxide to water and oxygen, with the appearance of bubbling in a positive test?

Answer 34

catalase test

Question 35

what test is looking for an enzyme which converts fibrinogen to fibrin?

Answer 35

coagulase test

Question 36

ID hemolysis type

Answer 36

beta

Question 37

ID hemolysis type

Answer 37

alpha