Bailey & Scott's Diagnostic Microbiology: Laboratory Techniques in Mycology: Direct Examination-Microscopic Flashcards


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1

pages 799, 802-3

table 58.4, 58.5,

2

gram stain

differentially stains microorganisms based on cell wall structure to determine microscopic characteristics such as cell morphology and arrangements; cells that contain phospholipids have negatively charged membrane that attracts positively charged dyes; thick peptidoglycan layer traps CV-I complex; primary stain, mordant, and decolorizer followed by a secondary stain; QC: pos: Staph aureus (thick peptidoglycan), neg: E. coli (lack peptidoglycan)

3

chitin

contained in yeast which gives it the gram positive staining quality

4

acid-fast stain

used to stain cells that contain mycolic acid and other cellular structures that do not gram stain; Ziehl Neelsen (hot) or Kinyoun's (cold) methods; utilizes carbohfuchsin (primary) and methylene blue (secondary) with acid alcohol decolorizer; Mycobacterium (pos), E. coli (neg)

5

Ziehl Neelsen

uses heat/phenol to penetrate cell wall

6

Kinyoun's

uses more concetrated phenol (corrosive organic compound)

7

wet mount (lactophenol cotton blue or Aniline blue)

identifies organisms in liquid environment to visual natural structure and movement; preserves organisms sensitive to fixing or heating; lactic acid preserves the specimen; liquid and specimen placed on slide and cover-slipped; in house fungal isolate such as Aspergillus

8

potassium hydroxide (KOH) prep

fungal screening from hair, skin, and nails; KOH and specimen placed on slide with cover-slip; heat can accelerate clearing

9

calcofluor-white

screening for rapid identification of fungal elements in microscopic preparations; nonspecific fluorochrome that binds to cellulose and chitin and fluoresces under UV light or blue/white fluorescent filter; drop on slide, specimen, and coverslip; nonspecific stain; Candida albicans (pos), E. coli (neg)

10

Giemsa stain

visualize parasites or fungal elements in blood smear-used to identify, but not interpret fungal elements; dried smear fixed with methanol and stained; pH affects staining properties; regular smears used to check quality

11

Wright's stain

differentiate blood cells, parasites and fungal elements; eosin is acidic and binds to basic compounds or amino acids; methylene blue is basic aniline dye that binds to acidic molecules; one step simple stain with rinse and dry; freshly prepared blood smears used for QC

12

Periodic acid schiff stain

used to visualize fungal elements primarily in tissue samples; glycols are oxidized to aldehydes with periodic acid, Schiff's reagent (pararosaniline and sodium metabisulfate) releases pararosaniline adduct that stains glycol-containing cellular components; positive substances stain pink to red and nuclei are blue; Candida albicans (pos), E. coli (neg-little to no staining or blue)