Microbiology-Lab Test 1 Flashcards

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Define and/or describe the following terms:
a. Hanging drop slide:
b. Basic Dye

a. Concavity slide, petroleum jelly, drop of specimen (used to observe live non-pathogenic bacteria and their motility.
b. Catatonic. positively charged, and dyes the cell, does not dye the background.


List three specific advantages of the negative stain.

a. Easy, simple, fast
b. nigrosin dye needed
c. Do not need to heat fix


Define and/or describe the following terms:
a. magnification
b. Iris Diaphragm
c. Course adjustment
d. Immersion oil

a. Object appear larger
b. opens and closes light source, light or dark
c. Moves stage up and down rapidly
d. Used with 100x to improve resolution of slide.


List the reagents used in the Gram Stain, in order of use, and describe the purpose of each reagent.

Reagent: a. crystal violet Purpose: primary stain
Reagent: b. Iodine Purpose: mordant/fixer
Reagent: c. 95% alcohol Purpose: decolorizer
Reagent: d. safranine Purpose: counterstain


Identify the medical importance of the following stains:
a. capsule stain
b. acid-fast stain:
c. metachromatic granule stain

a. used to diagnose bronchitis and pneumaneia
b. used to diagnose leprosy and tuberculosis
c. used to diagnose diphtheria


Define and/or describe the following terms:
a. hanging drop slide
b. ocular lens
c. parfocal
d. negative stain

a. concave slide and cover slip, drop liquid to be studied, petroleum jelly is used to seal the cover slide to allow prolonged observation, reduced light is used to observe transparent organisms to avoid excessive heat buildup.
b. eye piece, small lens, end of microscope tube magnifies 10x
c. ability to focus and switch from scanning to lens to the oil immersion lens
d. a form of observation of living bacteria using nigrosin dye.


Describe the medical importance of the following stain:
a. acid-fast

a. member of mycobacterium (tuberculosis, leprosy or Hansen's disease)
and nocardia (pulmonary nocardiosis and lumpy jaw)contain large amount of waxy substance (mycolic acids) resist staining, pathogenic to man and animals, purpose of acid-fast distinguish between pathogenic and non-pathogenic. detects: mycobacterium tuberculosis-tuberculosis/leprosy


Describe the medical importance of the following stain:
b. endospore

b. characteristics of bacillus and clostridia, both are large gram positive, soil inhabiting rods, both pathogenic and non-pathogenic species, staining allows observation of the location of the endospore within the cytoplasm. detects: clostridium tetani-tenus, bacillus anthracis- anthrax.


Describe the medical importance of the following stain:
c. metachromatic

c. some bacteria accumulate large quantities of inorganic phosphate granules as a metabolic by-product. metachromatic granules in club-shaped pleomorphic bacteria obtained from patients with severe pharyngitis, may indicate the presence of Corynebacterium diphtheriae which can cause diphtheria.


List four aseptic techniques that should be used when working with bacterial cultures.

a. incinerate loop/needle before and after collecting a sample.
b. sterilize lips of culture tubes by flaming or holding close to the incinerator before and after use.
c. always hold culture tubes caps in your hand to avoid misplacing them.
d. always hold culture tubes at an angle to avoid airborne contamination.


Contrast a basic dye with an acidic dye:
a. basic dye

a. the cation (+) is the chromophore, is used for positive or direct staining and the specimen is stained while the background remains clear, basic dyes are most common, they include crystal violet, methylene blue, malachite green, & safranine.


Contrast a basic dye with an acidic dye:
b. acidic dye

b. the anion (-) is the chromophore in an acidic dye, dyes are not attracted to most types of bacteria because of the negative ions are repelled by the negatively charged bacterial surface, so the stain colors the only the background.