MYCOLOGY PART 2: Diagnosis and Laboratory Examinations

1. KOH prep ( potassium hydroxide solution)

2. Calcofluor white stain

3. Fungal Culture

Tests for superficial infection (3)

1. Susceptibility Testing

2.Antigen Testing

3. Antibody Testing

4. Molecular test for DNA and RNA

Tests for Systemic infection:

TEST FOR SUPERFICIAL INFECTION

Skin scrapings,

hair or nail clippings,

tissue,

vaginal swab,

body fluids,

sputum

SAMPLE: (6) for

SUPERFICIAL INFECTION

KOH prep ( potassium hydroxide solution)

Description: Reveals yeast cells and fungal hyphae (branching filaments)

Use: Primary screening tool, detects fungi but does not tell what specific fungus is present

Time of result: Rapid

Calcofluor white stain

Description: Stain binds to fungal elements in a sample and fluoresces ( glows) under UV light.

Use: Detects fungi but does not tell what specific fungus is present

Time of result: Rapid

Fungal Culture

Description: Sample is placed on or into a culture media and incubated to grow.

Use: Primary tool to diagnose a fungal infections, grows fungi for identification and susceptibility test

Time of result: Weeks

Sabouraud dextrose agar

Fungal cultures grow in

Tests for Systemic infection:

Susceptibility testing

Sample of fungus isolated in culture

Sample: (1)

Description: Follow up to fungal culture, when a pathogenic culture has been identified, this is done to know the best medication against the fungi

Use: Guide treatment

Time of result: Days to weeks after culture

Antigen Testing

Blood, urine, CSF and body fluids

Sample: (3)

Description: Detects proteins associated with a specific fungus

DUse: Diagnose infection by specific fungus

Time of result: Days; rapid test are available for some fungi ( Cryptococcus, Histoplasma spp.)

Antibody Testing

Blood, urine, CSF (Cerebrospinal Fluid) and body fluids

Sample: (3)

Description: Detects immune response to a specific fungus

Use: Diagnose current or recent infection by specific fungus; monitor treatment

Time of result: Days to weeks

Molecular test for DNA and RNA

Sx of fungus isolated in culture, blood, CSF and body fluids

Sample:

Description: Detects genetic material from specific fungus

Use: Detects some fungi, not widely available, some in research setting only

Time of result: Days to weeks

Treatment of Fungal infection:

Terbinafine

Conversion of

Squalene->Squalene epoxide

Azole

Conversion of

Ergosterol->Lanosterol

Echinocandins

Acts on B-glucan synthesis

Flucytosine

Acts on DNA, RNA Synthesis

Ampothericin B

Polyene macrolide:

MOA: Forms pores in fungal membranes (which contain ergosterol) but not in mammalian (cholesterol containing) membranes

Ampothericin B

Effect: Loss of intracellular contents through pores is fungicidal ; broad spectrum of action

1.) Localized and systemic candidemia;

2.) Cryptococcus;

3.) Histoplasma;

4.) Blastomyces;

5.) Coccidioides;

6.) Aspergillus

Clinical Application: Ampothericin B (6)

Oral form is not absorbed,

IV for systemic use

Infusion reaction,

Renal impairment

Ampothericin B

Kinetics: (2)

Toxicity: (2)

Flucytosine

Pyrimidine Analog:

MOA: interferes with the DNA and RNA synthesis selectively in fungi

Flucytosine

Effects: Synergistic effect with amphotericin; systemic toxicity in the host DNA and RNA effects

Cryptococcus and

Chromoblastomycosis infection

Clinical applications: Flucytosine (2)

Oral, renally excreted

Myelosuppression

Flucytosine

•Kinetics: (2)

•Toxicity: (1)

Ketoconazole

Azoles:

MOA: Block fungal P450 enzymes and interfere with ergosterol synthesis

Effects: Poorly selective, interferes with P450 mammalian function

Broad spectrum but toxicity restricts use to topical therapy

Clinical Application: ketoconazole (1)

Oral, topical

Interferes with steroid hormone synthesis and Phase I drug metabolism

ketoconazole

Kinetics: (2)

Toxicity: (1)

Itraconazole

Azole:

MOA: Block fungal P450 enzymes and interfere with ergosterol synthesis

Effects: Much more selective than ketoconazole

Broad spectrum:

Candida,

Cryptococcus,

blastomycosis,

coccidiodomycosis,

histoplasmosis

Clinical Application: Itraconazole (5)

Oral and IV, 1-2 days, poor CNS penetration

Low toxicity

Itraconazole

Kinetics: (1)

Toxicity: (1)

Fluconazole,

voriconazole,

posaconazole,

isavuconazole:

Same actions: (4) Itraconazole

Fluconazole

has excellent CNS penetration, used in fungal meningitis

Caspofungin

Echinocandins:

MOA: Blocks beta glucan synthase

Effects: Prevents synthesis of fungal cell wall

Clinical Application: Fungicidal Candida spp. Also used in aspergillosis

Kinetics: IV only, 11-15 hour duration

Toxicity: Minor Gl effects, flushing

Interaction: Increase cyclosporine level (avoid combination)

Micafungin

anidulatungin

___ increases levels of nifedipine, cyclosporine, sirolimus;

___ is relatively tree of this interaction

Terbinafine

Allylamine:

MOA: Inhibits epoxidation of squalene in fungi, increased levels are toxic to fungi

Effects: Reduces ergosterol, prevents synthesis of fungal cell membrane

Clinical Application: mucocutaneous infections

Kinetics: Oral, duration: days,

Toxicity: Gl upset, headache, hepatotoxicity