Mycology, which is the study of fungi, is an important topic in microbiology. Fungal infections are becoming increasingly common, making mycology a highly relevant topic for the NEET PG exam.
Moreover, fungal infections can often mimic bacterial or viral infections, which makes it all the more essential to have a strong understanding of mycology in order to avoid misdiagnosis.
Let’s learn more about this important NExT/NEET PG exam topic of microbiology through this blog.
Morphological Classification
Yeast - Cryptococcus neoformans
Yeast like - Candida (Yeast, yeast like hyphae, pseudo hyphae)
Molds - Aspergillus, Rhizopus
Dimorphic Fungus
Mold– 25° C
Yeast - 37° C
Dimorphic Fungal Disease
Histoplasmosis
Sporotrichosis
Blastomycosis
Coccidioidomycosis
Paracoccidioidomycosis
Penicilliosis
Types Of Spores
Sexual Spores
Zygospores
Ascospores
Basidiospores
Asexual Spores
Arthroconidia
Blastomyces
Chlamydospores
Based On Location
Superficial Mycosis
Tinea versicolor
Tinea nigra
Dermatophytes
Subcutaneous Mycosis
Mycetoma
Rhinosporidiosis
Chromoblastomycosis
Sporotrichosis
Systemic Mycosis / Deep Mycosis
HSBCP2 (All dimorphic fungal diseases)
Candida
Cryptococcus
Lab Diagnosis
Culture Media
SDA (Sabouraud’s dextrose agar) → Universal fungal culture media
pH = 5.4 – 5.6
Fungal Stains
Negative staining (Eg: Cryptococcus) capsule
Indian ink stain
Mucicarmine stain
Nigrosin
GMS (Gomori Methenamine Silver)
Eg: Pneumocystis Carinii (Green colour)
LPCB (Lactophenol Cotton Blue)
H&E (Haematoxylin + Eosin)
Calcofluor white – Fungal Fluorescent stain
Important Information
Wet mount with 10% KOH - to see fungal elements
Tinea
T. Versicolor (Pityriasis Versicolor)
Caused by Malassezia furfur / M. globosa
Spaghetti & meatball appearance
Fried egg colonies (lipophilic fungus) on SDA
Golden yellow fluorescence
T. Nigra
Exophiala werneckii
Piedra (Hair nodules)
White
Trichosporon beigelii
Black
Piedra Hortae
Dermatophytes
Skin
Hair
Nails
Trichophyton
?
?
?
Microsporum
?
?
x
Epidermophyton
?
x
?
Lab Diagnosis
Culture growth on SDA + LPCB
Macroconidia
Microconidia
Trichophyton
Pencil shaped
Numerous
Microsporum
Spindle shaped
Less
Epidermophyton
Club / boat shaped
Absent microconidia
T. Capitis
Favus
T. Schoenleinii(Trichophyton)
Kerion
Painful boggy swelling
T. Mentagrophytes, T. Verrucosum
T. Cruris
Dhobi itch or jock itch
T. Pedis
Athlete’s foot
MYCETOMA (Madura foot)
Triad
Sinus
Swelling
Granules (Discharging)
Actinomycetoma
Eumycetoma
Numerous sinus & swelling
Colour of granules – Yellow / white except in – Actinomadurae pelletieri where they have red granules
Responds to antibiotic
Single sinus & swelling
Black -Madurella mycetomatis
White – Acremonium, Pseudallescheria boydii
Amputation
Rhinosporidiosis
Caused by Rhinosporidiumseeberi
Aquatic protist – protozoa
B/ L nasal polyp
On Polyp biopsy
Spherule
Within spherule there are endospores
Non cultured on SDA
Treatment – Surgical removal
Chromoblastomycosis
Colourful fungus
Dematiaceous fungus
Eg
Alternaria
Bipolaris
Curvularia
Phialophora
Cladosporium
Exophiala werneckii
Thorn prick / wood worker → Verrucous lesion
On tissue biopsy + H & E staining
Medlar bodies
Brown coloured sclerotic bodies
Copper penny / muriform appearance
Sporotrichosis
Sporothrix schenckii
Rose gardener’s disease
Lymphocutaneous spread
Increased incidence in and around valentine’s day
Dimorphic
Mold-Flower like sporulation
Yeast- Cigar shaped yeast cell (Narrow based budding)
Asteroid yeast cell
Histoplasmosis
Darling’s Disease
Mimics TB (when involves lungs)
Histoplasma capsulatum
Aerosols - Pulmonary involvement
Blood
Visceral involvement
Mold - Tuberculate macroconidia
Yeast - Narrow based budding
Blastomycosis
North American’s disease / Gil Christ disease
Yeast cell → Figure of ‘8’ appearance or broad-based budding yeast cell
Smooth mucoid creamy colonies (SDA cannot differentiate Cryptococcus and Candida)
Phenyl oxidase enzyme in Cryptococcus – responsible for melanin production
On Niger seed agar – Brown black colonies are seen
Latex card agglutination Test for Cryptococcal Antigen
PCR for C. Neoformans
Capsulated organism (Polysaccharide) - Indian ink staining (negative stain)
Polysaccharide capsule → Virulence factor
Treatment
DOC Cryptococcal meningitis - Lysosomal amphotericin B (LAMB)+ Flucytosine
Zygomycetes
Seen in Terminally ill patients
Rhizopus
Absidia
Mucor
Rhinocerebral Zygomycosis is a fulminant disease
Lab Diagnosis
Tissue biopsy - H & E stain
Aseptate hyphae
Obtuse angled
Biopsy material on SDA
Culture growth + LPCB
Rhizopus
Different Zygomycetes
Absidia – Inter nodal rhizoids arrangement
Mucor - No rhizoids
Mucormycosis
Mucormycosis is commonly seen in
DM
Frequent blood transfusion
Chronic dialysis
Aspergillosis
Common in DM, Immunodeficient
A. Fumigatus
Leads to allergic bronchopulmonary aspergillosis
Associated with aspergilloma (Fungal balls)
Oculomycosis
Otomycosis
On SDA Greenish colour colonies in SDA
A. Niger
Blackish crust from ear
On SDA - Black coloured colonies
A. Flavus
produces aflatoxin which leads to hepato cellular Carcinoma
Lab Diagnosis: On Tissue Biopsy + H & E Staining
Septate hyphae
Dichotomous branching
Mostly Angle 45º
Important Information
Ergotoxicosis
Claviceps purpurea seed along with edibles.
St. Anthony’s fire or St. Vitus dance
To learn more about this topic for NEET PG/NExT exam preparations, download the PrepLadder app and find high-quality and relevant NEET PG study material.
PrepLadder Medical
Get access to all the essential resources required to ace your medical exam Preparation. Stay updated with the latest news and developments in the medical exam, improve your Medical Exam preparation, and turn your dreams into a reality!