Question
Lacto Phenol Cotton Blue mount (LPCB mount)
Answer
Lacto Phenol Cotton Blue (LPCB) mount is the standard, simple wet-mount preparation used in the mycology laboratory for the microscopic examination of fungal elements (hyphae, spores, conidia) — both directly from clinical specimens and, more commonly, from fungal cultures for identification purposes.
Composition and function of each component:
- Lactic acid — acts as a preservative and clearing agent, dehydrating and preserving the fungal structures, preventing distortion/collapse during examination.
- Phenol — kills the fungal elements (rendering the preparation non-infectious/safe for handling and microscopy) and also has a mild clearing effect.
- Cotton (aniline) blue dye — stains the chitinous fungal cell wall components, providing colour contrast that makes hyphae, conidiophores, and spores clearly visible under the microscope against an otherwise unstained background.
- Glycerol (in some formulations) — prevents the preparation from drying out too quickly, extending its usability.
Procedure: a small drop of LPCB mounting fluid is placed on a clean glass slide; a small portion of the fungal colony (teased/scraped with a sterile needle) is placed into the drop and gently teased apart to spread the fungal elements; a coverslip is placed on top (avoiding air bubbles); the preparation is then examined under the light microscope (low and high power) for characteristic fungal morphology.
Clinical significance: allows visualization of key diagnostic features — septate vs. non-septate/broad hyphae, hyphal branching angle, and the characteristic shape/arrangement of conidiophores and conidia (macroconidia, microconidia) — essential for presumptive/definitive identification of moulds and dermatophytes in a routine diagnostic mycology laboratory; simple, rapid, and low-cost, making it a first-line technique widely used alongside culture for fungal identification.