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

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pages 799, 802-3

table 58.4, 58.5,


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)



contained in yeast which gives it the gram positive staining quality


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)


Ziehl Neelsen

uses heat/phenol to penetrate cell wall



uses more concetrated phenol (corrosive organic compound)


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


potassium hydroxide (KOH) prep

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



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)


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


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


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)