Microbiology Exam #1 Lab Info Flashcards
describe the steps of a gram stain?
- flood slide with crystal violet for 60sec, then wash it off with water
- flood slide with gram’s iodine for 20sec, then wash it off
- decolorize carefully/indirectly
- flood slide with gram’s safranin for 60sec
- rinse off slide and dry with bibulous/blotting paper
which cell type remains purple in gram stain?
gram positive - crystal violet
which cell type is red in gram stain?
gram negative - safranin
gram positive or negative?
positive
gram postive or negative?
positive
gram positive or negative?
negative
what does a catalase test test for?
only organisms with a catalase enzyme (ex: Staphylococcus) will have a positive reaction when hydrogen peroxide added to sample
what does a positive catalase test look like?
bubbling once hydrogen peroxide added
what does a negative catalase test look like?
NO bubbling when hydrogen peroxide added
describe alpha hemolysis
partial, greenish halo around bacterial colonies
result of hydrogen peroxide produced by bacteria acting on hemoglobin to make methemoglobin
describe beta hemolysis
aka complete hemolysis
complete lysis of RBC in media around bacterial colonies and is result of hemolysin enzyme produced by specific bacterial species
describe gamma hemolysis
NOT hemolysis at all
absence of hemolysis surrounding non-hemolytic colonies
ID the types of hemolysis indicated by the arrows
- beta hemolysis
- alpha hemolysis
- gamma hemolysis
what is the most common organism isolated from cases of pyoderma in dogs/cats?
Staphylococcus pseudintermedius
Biopsies are the sample of choice for diagnosing bacterial dermatitis in what type of skin lesions?
Papules
When operating normally, our bacteriology course laboratory is conducted under which of the following biosafety levels?
BSL-1
Which organisms may be found as part of the healthy skin microbiota?
a) Commensal organisms
b) Opportunistic organisms
c) Pathogenic organisms
Which of the following forms of hemolysis is best described as a partial, greenish halo around bacterial colonies?
alpha
The differential qualities of TSA+5% sheep blood agar allow it to discriminate bacteria that are what?
Hemolytic vs. non-hemolytic
what type of microscope is useful for seeing internal details on unstained, living organism?
phase-contrast microscope
what microscope type is used to generate highly magnified 3D image of bacteria?
scanning electron microscope
Native or exotic agents that may be aerosolized and cause serious disease in humans, like Mycobacterium tuberculosis, are handled under which biosafety level?
BSL-3
What factors are thought to affect the skin microbiota?
breed, diet, medications
Which of the following best describes the TSA+5% sheep blood agar plates used in lab?
differential media
Which of the following forms of hemolysis is best described as the complete lysis of red blood cells in the media around bacterial colonies?
beta
which of the following stains highlights gram positive organisms?
crystal violet
which of the following stains highlights gram negative organisms?
gram’s safranin
Which of the following microscopes is the most commonly used in clinical medicine, and is the sort we use in our bacteriology laboratory?
bright field microscope
which microscope is useful for visualizing extremely small or thin bacterial, like Borrelia?
dark field microscope
At what biosafety level do most diagnostic laboratories operate at?
BSL-2
What biosafety level would be required to handle Ebola virus?
BSL-4
what biochemical tests is looking for an enzyme not commonly present in members of the family Enterobacteriaceae?
oxidase test
what test can help to quickly discriminate Gram-negative organisms from Gram- positive ones?
KOH test
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?
catalase test
what test is looking for an enzyme which converts fibrinogen to fibrin?
coagulase test
ID hemolysis type
beta
ID hemolysis type
alpha
