Laboratory Procedures for Fungal Culture and Isolation

A comprehensive set of flashcards covering key terms and concepts related to fungal culture and isolation procedures.

Core Objective

Isolate and identify pathogenic fungi.

Identification Methods

Methods used to identify fungi include culture characteristics, microscopy, morphology, biochemical tests, and MALDI-TOF.

Culture Characteristics

Observations made based on fungi growth on media.

Biochemical Tests

Tests conducted to understand the metabolic characteristics of fungi.

MALDI-TOF

rapid molecular ID

Safety Precautions

handle systemic fungi as biohazards, follow strict lab safety

Coccidioides

A type of systemic fungus airborne quickly

Specimen Collection Rules

collecting samples from active infection sites.

Proper Labeling

Essential details include the time, date, and patient ID.

Temperature for Fungi

Most fungi grow at 25-30*C, while dermatophytes should not be refrigerated.

Hair Collection

Pluck hair and include the root for fungal culture.

Skin Collection

Alcohol clean the skin and scrape the lesion for samples.

Nail Collection

Scrape nails for samples, which are often hard to culture.

Sputum Collection

deep sample, not saliva.

Urine Collection

First morning urine sample is best then centrifuge and use the sediment for testing.

Genital Specimen

normal flora complicates interpretations

Blood Collection

Use Myco vials to detect CO₂ production from fungi.

Sterile Fluids

Collect large volumes and centrifuge for sediment.

Stool Collection

Stool samples are not accepted due to normal flora.

Tissue Collection

Specimens should be minced, not grind.

Sabouraud Dextrose Agar (Sabdex)

Most important medium for fungal culture, inhibits bacteria.

Brain Heart Infusion (BHI)

enriched medium for dimorphic fungi.

Mycobiotic Agar (Mycosel)

Selective for dermatophytes that contains inhibitors.

Chloramphenicol

Antibiotic that inhibit bacterial growth.

Cycloheximide

Inhibitor that affects certain fungi, Always use backup media due to its inhibitory effects.

Inhibitory Mold Agar (IMA)

Contains chloramphenicol and supports pathogenic fungi while inhibiting bacteria

Cornmeal Agar

Used to observe fungal morphology but not for growth.

Birdseed Agar

Specifically for Cryptococcus, produces brown colonies.

Incubation Temperature

Molds 25-30*C, Yeast 35-37*C dimorphic fungi

Growth Rates

Yeasts grow in 1–5 days, dermatophytes in about 1 week, dimorphic >2 weeks, and hold all for 4-6 weeks

KOH Prep

Dissolves keratin to reveal fungi in skin, hair, nails. A first-line direct exam.

Calcofluor White

A stain that binds chitin and fluoresces under a microscope.

India Ink

Used to detect Cryptococcus capsules, shows a halo effect.

Lactophenol Cotton Blue (LPCB)

Not for diagnosis, used mostly for teaching and morphology.

GMS Stain

Tissue stain for fungal to detect Pneumocystis fungi.

Dermatophytes Temperature Preference

Dermatophytes do not tolerate cold well.

Birdseed Agar Function

Used specifically for identifying Cryptococcus.

Biochemical Identification

Utilizing metabolic tests to further identify fungi.

Pathogenic Fungi

Fungi capable of causing disease in humans.

Chitin Detection

Calcofluor White specifically binds to chitin in fungi.

Contamination Prevention

Seal culture plates properly to prevent drying and contamination.

Cryptococcus Identification Techniques

Using India ink and Birdseed agar for effective identification.

KOH and India ink

serve important roles in direct examination.

Fungal Identification Techniques

Include cultural, morphological, and biochemical assessments.

Dermatophyte Growth Characteristics

Specific requirements and rates for dermatophyte growth.

Multi-Method Identification

Employing a combination of techniques for fungal identification.