[2S] UNIT 6 Laboratory Diagnosis of Common Fungal Diseases Flashcards
Selective media for fungal culture
Saboraud Dextrose Agar (SDA)
Primarily used for isolation of Dermatophytes, yeasts and various other pathogenic and non-pathogenic fungi
Saboraud Dextrose Agar (SDA)
Example of fungus for SDA
Penicillium globrum
Sporothrix schenkii
SDA Components
Peptone & Dextrose
SDA
Source of amino acids and nitrogenous
compounds
Peptone
SDA
Source of carbon and energy
Dextrose (glucose)
SDA pH & temp
5.6 at 25C
French Physician that first formulated SDA
Dr Raymond Jacques Adrien Sabouraud
Frequently used microbial growth media for cultivation of molds, yeasts and other fungi
POTATO DEXTROSE AGAR (PDA)
Fungus for PDA
Aspergillus flavus
Penicillium chrysogenum
General-purpose medium for yeasts and molds
POTATO DEXTROSE AGAR (PDA)
Carbohydrate source: support luxuriant growth of fungi and bacteria
Potato infusion and dextrose
Encourage mold sporulation and pigment production
Potato infusion and dextrose
Supplemented with selective agents to inhibit growth of bacteria
POTATO DEXTROSE AGAR (PDA)
2 Selective agents which inhibit the growth of bacteria in PDA
o Acids : tartaric acid
o Antibiotics : chloramphenicol or chlortetracycline
Highly nutritious base that meets growth requirements
o Bacteria, yeast, molds
BRAIN HEART INFUSION (BHI) AGAR
General purpose medium
BHI & PDA AGAR
Isolation, cultivation, and maintenance of fastidious and non-fastidious organisms
BRAIN HEART INFUSION (BHI) AGAR
Selective formulation containing chloramphenicol and cycloheximide
BRAIN HEART INFUSION (BHI) AGAR
Allow pathogenic fungi while inhibiting a wide range of bacteria and saprophytic fungi
BHI: Chloramphenicol & Cycloheximide
____ (Water Agar) – contains agar
o Solidifying agent and purified deionized water
1.5%
Recommended for enumeration, cultivation and observation of sporulation of some fungi
Water Agar
General appearance : granular to wooly/cottony
MICROSPORUM SPP.
Color : Varies from yellow, white and brown
- Certain strains : excuse a cream color
MICROSPORUM SPP.
ID CONIDIA & SPECIE
Hyaline, multi-septate, with thick rough cell walls, and are clavate, fusiform or spindle- shaped
Microsporum spp. Macroconidia
MICROSPORUM SPP. ID CONIDIA & SPECIE
Absent or rarely found
Microsporum audoinii Macroconidia
MICROSPORUM SPP.
have a longer appearance than Microsporum canis
MICROSPORUM AUDOINII
MICROSPORUM SPP.
Chlamydospores : Most cultures are sterile or produce only the thick-walled chlamydospores (Chlamydoconidium)
MICROSPORUM AUDOINII
ID CONIDIA & SPECIE
Single-cell, hyaline, smooth- walled, and are predominantly clavate in shape
Microsporum spp. Microconidia
MICROSPORUM SPP. CONFIRMATORY TEST
Salmon Pink to Pinkish Brown
Microsporum audoinii
MICROSPORUM SPP. ID CONIDIA & SPECIE
Pyriform to clavate
Microsporum audoinii & Microsporum canis Microconidia
MICROSPORUM SPP. CONFIRMATORY TEST
No growth on rice grains
Microsporum audoinii
MICROSPORUM SPP. CONFIRMATORY TEST
Reverse Pigmentation on Potato Dextrose Agar (PDA) - Salmon Pink to Pinkish Brown
Microsporum audoinii
MICROSPORUM SPP. CONFIRMATORY TEST
Demonstrates rapid pH change to alkaline (purple coloration)
BCP Milk Solids Glucose Agar on Microsporum audoinii
MICROSPORUM SPP. CONFIRMATORY TEST
Hair Perforation Test Negative
Microsporum audoinii
MICROSPORUM SPP. CONFIRMATORY TEST
Reverse Pigmentation on PDA - Bright Yellow
Microsporum canis
MICROSPORUM SPP. ID CONIDIA & SPECIE
Spindle shaped (5-15 cells), verrucose, thick-walled and have terminal knobs
MICROSPORUM CANIS MACROCONIDIA
MICROSPORUM SPP. CONFIRMATORY TEST
Good growth on rice grains
Microsporum canis
MICROSPORUM SPP. CONFIRMATORY TEST
Positive Hair Perforation Test
Microsporum canis
MICROSPORUM SPP.
No macroconidia and microconidia
Microsporum ferrugineum
MICROSPORUM SPP.
“bamboo” hyphae
Microsporum ferrugineum
MICROSPORUM SPP.
Visualization : confirms this species and the other specific colonial features of the Microsporum genus
Microsporum ferrugineum
Epidermophyton that is clinically significant affecting humans
Epidermophyton floccosum
Colonial characteristics on Culture Medium: Older cultures : white pleomorphic tufts of mycelium
EPIDERMOPHYTON
Colonial characteristics on Culture Medium: Greenish-brown with a suede-like surface, raised and folded in the center, with a flat periphery merged fringe of growth
EPIDERMOPHYTON
Colonial characteristics on Culture Medium: A deep yellowish-brown reverse pigment
EPIDERMOPHYTON
- Microscopic features
o Smooth, thin-walled macroconidia: often produced in clusters growing directly from the hyphae
EPIDERMOPHYTON
- Microscopic features
o Numerous chlamydospores are formed in older
o Microconidia : absent
EPIDERMOPHYTON
TRICHOSPORON SPP.
- Colonial characteristics :
o White to cream-coloured, powdery, suede-like to farinose with radial furrows and irregular folds
Trichosporon asahii
TRICHOSPORON SPP.
- Microscopic Morphology
o Budding cells and lateral conidia are absent
o Arthroconidia : barrel-shaped
Trichosporon asahii
TRICHOSPORON SPP.
- Laboratory Diagnosis
o Species assimilates L-arabinose but not melibiose
o Growth at 37C
Trichosporon asahii
TRICHOSPORON SPP.
Most common species from invasive infections
Trichosporon asahii
TRICHOSPORON SPP.
*Colonial characteristics :
o Restricted, white, finely cerebriform with a granular covering, without marginal zone, often cracking the media
Trichosporon inkin
TRICHOSPORON SPP.
Laboratory Diagnosis
o Species assimilates myo-inositol but not melibiose and is tolerant to 0.01% (variable tolerance to 0.1%) cycloheximide
o Growth at 37C
Trichosporon inkin
TRICHOSPORON SPP.
Microscopic Morphology
o Budding cells and lateral conidia are absent
o Arthroconidia : long and cylindrical
Trichosporon inkin