Specimen Collection and Laboratory Diagnosis of Fungal Diseases

Vocabulary flashcards covering key terms and concepts from the notes on specimen collection, culture, and identification of fungal diseases.

Sterile collection method

Use sterile technique and instruments to obtain specimens from the infection site to avoid contamination.

Specimen from infection site

Collect from the actual site of infection to minimize normal flora contamination.

Adequate specimen quantity

Ensure the collected amount is sufficient for reliable culture and testing.

Accurate labeling with suspected diagnosis

Label the specimen accurately; including suspected diagnosis aids processing and interpretation.

Prompt delivery to the laboratory

Send specimens quickly to prevent overgrowth by contaminants and preserve organism viability.

Sputum

Respiratory tract specimen type for fungal culture and identification.

Induced sputum

Sputum obtained after induced coughing, used when spontaneous sputum is unavailable.

Bronchial washing

Bronchoscopic specimen collection for fungal analysis.

Tracheal aspirations

Tracheal secretions collected for mycological culture.

CSF filtration through 0.45-µm filter

Filter cerebrospinal fluid to concentrate organisms for culture or microscopy.

CSF centrifugation and sediment on agar

If CSF volume is small, centrifuge and plate sediment on several areas of agar.

CSF should never be refrigerated

CSF cultures should not be refrigerated; processing should occur promptly.

BACTEC automated blood culture systems

Automated systems used for detecting fungal/bacterial bloodstream infections.

Optimal fungal blood culture temperature

Incubate fungal cultures at 30°C for best recovery.

Incubation time for fungal cultures

Maintain cultures for up to 21 days before reporting negative.

Corneal scraping onto non-inhibitory media

Inoculate corneal scrapings directly onto media that do not inhibit fungi.

Vitreous humor sediment for smear/culture

Concentrate vitreous humor by centrifugation and use sediment for testing.

Olive oil disk for Malassezia furfur

An olive oil disk in the first quadrant aids isolation of Malassezia furfur on selective media.

Vaginal transport swabs

Use culture transport swabs to move vaginal samples to the lab.

Vaginal culture incubation for yeasts

Incubate vaginal cultures at 30°C for 7 days to detect yeasts.

24-hour urine unacceptable for culture

A 24-hour urine sample is not suitable for routine fungal culture.

Urine sediment culture by centrifugation

Centrifuge urine and culture the sediment to improve colony isolation.

Mincing tissue before culture

Mince tissue pieces prior to placing on culture media.

Bone marrow in a heparinized syringe

Collect bone marrow in a heparinized syringe for fungal culture.

Concentrate sterile fluids by centrifugation

Concentrate sterile body fluids before culturing; plate at least 1 mL.

Direct microscopic methods

Initial microscopic testing that should be confirmed by culture or antigen testing.

Wet mount

Direct observation of fungal elements in a saline preparation.

10% KOH preparation

KOH clears keratin to visualize fungal elements in skin, hair, or nails.

Lactophenol Cotton Blue (LPCB)

Stain that highlights fungal cell walls; lactic acid preserves structures, phenol kills organisms, blue stains chitin.

India Ink

Negative stain used to visualize cryptococcal capsule as a clear halo.

Germ Tube test

Presumptive identification of Candida albicans by germ tube formation in serum.

Calcofluor white stain

Fluorescent stain that binds to fungal cell wall chitin for rapid visualization.

Wood’s lamp

UV light that can cause infected hair/skin to fluoresce.

Huckert’s modification of Gram stain

Gram staining method where fungi often appear as small blue yeast forms.

Giemsa/Wright stain

Stains used to detect intracellular yeast forms in blood or tissues.

Periodic acid-Schiff (PAS) stain

Stains fungal hyphae and some yeasts red; highlights polysaccharides in cell walls.

Methenamine silver stain

Stains fungal cell walls black in tissue sections.

Mayer’s mucicarmine stain

Demonstrates mucoid capsule of Cryptococcus neoformans in tissue.

Hematoxylin and Eosin (H&E)

General tissue stain to evaluate hyaline and dematiaceous fungi in histology.

Papanicolaou stain

Cytology stain useful for demonstrating Cryptococcus neoformans capsule.

Fontana-Masson stain

Stains melanin or melanin-like substances in pigmented fungi.

Tease Mount

Rapid microscopy method to tease apart mycelium for observation; may disrupt spore arrangement.

Slide Culture

Accurate method to preserve fungal morphology on a slide; not suitable for all fungi.

Cellophane Tape Mount

Tape method to capture aerial hyphae for microscopic observation.

Carbohydrate Assimilation Test for Yeast

Identify yeast by their ability to assimilate specific carbohydrates.

Carbohydrate Fermentation Test

Identify yeast by fermentation of carbohydrates indicated by color change.

Rapid Urease Test for Yeast

Detect urease production; positive result changes color (pink/purple).

L-Dopa Ferric Citrate Test

Phenol oxidase test; positive black color indicates Cryptococcus neoformans.

Serologic tests (agglutination, precipitation, complement-fixation, IF, ELISA)

Antibody-based tests to aid fungal identification and diagnosis.

Cryptococcal antigen test (latex agglutination)

Detection of Cryptococcus polysaccharide antigen in CSF or serum.

Cross-reactivity issues in antibody tests

Antibody tests may react with related fungi, causing false positives or negatives.

Birdseed/Nigereed/Staib’s medium

Differential medium for Cryptococcus neoformans producing brown/black colonies due to phenol oxidase.

Cornmeal Agar

Medium used to promote C. albicans chlamydospore formation; enhanced by Tween-80.

Czapeck’s (Czapek) Agar

Medium for recovery and differentiation of Aspergillus species.

Cottonseed Medium

Medium used to induce mold-to-yeast conversion (Blastomyces) in some assays.

Rice Grain Medium

Medium used to differentiate dermatophytes; supports sporulation/ pigment production.

Potato Dextrose Agar (PDA)

General fungal culture medium that supports growth and sporulation of yeasts and molds.

Sabouraud Dextrose Agar (SDA)

General-purpose fungal culture medium; acidic to inhibit many bacteria.

SDA-CC (Mycobiotic/Mycosel)

SDA containing inhibitors (cycloheximide and/or chloramphenicol) to favor pathogenic fungi.

Brain-Heart Infusion (BHI) medium

Medium useful for isolation of pathogenic fungi from sterile specimens.

Dermatophyte Test Medium (DTM)

Selective medium with phenol red indicator; red color indicates dermatophyte growth.

Inhibitory Mold Agar

Medium that supports growth of cycloheximide-sensitive molds while inhibiting others.

Sabouraud-Brain-Heart Infusion Agar (SABIHA)

General-purpose medium useful for isolation of dimorphic fungi; blood enhances isolation.

Trichophyton Ågars 1-7

A set of media used for identification of Trichophyton dermatophyte species.

Yeast Fermentation Broth

Medium used to identify yeast by fermentation characteristics.

Yeast Nitrogen Base Agar

Medium used for carbohydrate assimilation/identification of yeast.

Topography (colony morphology)

Describes colony surface features such as flat, raised, rugose, or umbonate.

Umbonate

Colony elevated in the center; a topographic feature of fungal colonies.

Texture (colony)

Cowtony, woolly, velvety, silky, powdery, or granular textures observed on colonies.

Pigmentation (colony)

Color of the colony surface and reverse; important diagnostic trait.

Descriptive colony observation on reverse side

Topography is best seen on the reverse side of the colony.