microbio final lab exam stains

gram stain primary stain

methylene blue

gram stain mordant

iodine

gram stain decolorizer

alcohol

gram stain counterstain

safranin

gram stain

Test Result Meaning

Example Pathogen (Genus species)

Gram+ = purple; Gram- = pink/red

Staphylococcus aureus, Escherichia coli

spore stain primary stain

malachite green

spore stain mordant

steam (heat)

spore stain decolorizer

water

spore stain counterstain

safranin

spore stain

Test Result Meaning

Example Pathogen (Genus species)

Spores = green; Vegetative cells = pink

Clostridium botulinum, Bacillus anthracis

simple stain primary stain

Methylene blue (or others)

simple stain

Test Result Meaning

Example Pathogen (Genus species)

All cells same color; shows shape/arrangement

General morphology; not species-specific

Negative Stain primary stain

Nigrosin or India ink

negative Stain

Test Result Meaning

Example Pathogen (Genus species)

Background stained; cells appear clear

Cryptococcus neoformans (fungus); for capsule view

Capsule Stain primary stain

Congo red or India ink

capsule stain Counterstain

Maneval’s stain (or crystal violet)

Capsule Stain

Test Result Meaning

Example Pathogen (Genus species)

Capsule = clear halo; background dark, cells stained

Klebsiella pneumoniae, Streptococcus pneumoniae

Acid-Fast Stain primary stain

Carbol fuchsin

Acid-Fast Stain mordant

steam (heat)

Acid-Fast Stain decolorizer

Acid-alcohol

Acid-Fast Stain counter stain

Methylene blue

Acid-Fast Stain

Test Result Meaning

Example Pathogen (Genus species)

Acid-fast = red/fuchsia; Non-acid-fast = blue/purple

Mycobacterium tuberculosis, Mycobacterium leprae