Direct Microscopy Staining

10% - 20% KOH

acts as a strong clearing agent that dissolves background keratin, cellular debris, mucus, and host cellular material, leaving chitinous fungal cell walls intact.

Potassium Hydroxide (KOH) Preparation

A drop of KOH is added to scrapings (skin, hair, nails) or thick specimens, covered, and gently warmed (not boiled) to accelerate digestion.

Potassium Hydroxide (KOH) Preparation

Rapid detection of fungal elements in dermatophytoses, cutaneous candidiasis, and tissue scrapings.

Calcofluor White Stain

A fluorochrome dye that binds specifically to beta-(1,3) and beta-(1,4) polysaccharides (chitin and cellulose) in the fungal cell wall.

Calcofluor White Stain

Requires a fluorescence microscope (UV wavelength 300-410nm). Fungi exhibit a bright apple-green or blue-white fluorescence against a dark background.

Calcofluor White Stain

Significantly increases detection sensitivity over standard KOH, particularly in samples with low fungal loads (e.g., skin scrapings, sputum, bronchoalveolar lavage, CSF). Can be combined directly with KOH.

Lactophenol Cotton Blue (LPCB)

Standard wet mount stain used primarily for identifying isolated fungal colonies from culture media (not recommended for direct clinical specimens containing high host tissue density).

LPCB Component: Phenol

Kills living fungal structures.

LPCB Component: Lactic Acid

Preserves fungal morphology and cell wall architecture.

LPCB Component: Cotton Blue (Aniline Blue)

Stains chitin and cell wall structures deep blue.

LPCB Component: Glycerol

Maintains moisture and prevents evaporation.

India Ink / Nigrosin (Negative Staining)

Fine carbon particles are excluded by the large, gelatinous polysaccharide capsule of encapsulated fungi.

India Ink / Nigrosin

Fungal cells appear as distinct, clear halos surrounding round, budding yeast cells against a dark, opaque background.

India Ink / Nigrosin

Used on CSF sediment for rapid screening of Cryptococcus neoformans.

budding

Leukocytes, erythrocytes, and myelin droplets can mimic encapsulated yeast; presence of ___ distinguishes true fungal cells. (Replaced in high-volume settings by Cryptococcal antigen latex agglutination/lateral flow assays due to higher sensitivity).

Gram Stain

Fungi take up crystal violet and resist decolorization, rendering them gram-positive (deep purple)

large, dark purple oval structures (2-8 µm) + budding or pseudohyphae

Gram Stain: Yeast cells (e.g., Candida, Cryptococcus) appear as

Gram Stain

Routine detection of yeasts in blood cultures, urine, body fluids, and mucosal swabs.

mold hyphae

In Gram stain, it stain irregularly or weakly gram-positive