Identification of tinea
Study note
Microsporum, epidermophyton, Trichophyton
Scytalidium hyalinum
Scytalidium has typical colony – fluffy white, If yes,
look for arthrospore
Arthrospore
Other Tinea should have - Aleurispore
A single terminal spore develops at the end of the conidiophores. It gets separated, and the conidiophore retains a scar.
No other spore develops there. The next spore develops from a branch below it. The detached spore has a large flat base.
Now we will look at these -
Colour of the colony – white, cream, brown, purple tinge
Consistency – granular, suede
Edge – glabrous
Back – brown, red, white, yellow, orange
Back- sharply defined or not sharply defined
Microscopy – Macroconidia mostly, or sparse
Macroconidia – smooth/rough surface, beak present/absent
Microconidia – shape – small, large, circular, ovoid, club-shaped,
Microconidia – broad base, narrow base
Hyphae – look for spiral hyphae
A. Look for macroconidia
Conidia is a spore produced asexually by various fungi at the tip of a specialised hypha. If they are large, they are called macroconidia.
Macroconidia
Microconidia
If it is present - is the outer surface rough? If yes, think Microsporum
Rough macroconidia
Smooth macroconidia
B. Look for a terminal beak in the macroconidia
No terminal beak
M gypseum/fulvum
Terminal beak
M canis/equinum –
if macroconidia large (>6 cell)= canis;
if small equinum
C. If smooth macroconidia (usually less abundant) present - Look at colony
Epidermophyton floccosum
Khaki brown to greenish yellow colony
Ideally like this
Colony may look like this in young culture.
Causes - tinea pedis, tinea cruris, tinea corporis and onychomycosis
Treatment – Itraconazole, terbinafine
Trichophyton terrestre
White cream or clear yellow colony, (even pink!)
Usually contaminant, clinically not relevant
Trichophyton rubrum
Colony has some purple colour
May not show typical feature
Trichophyton rubrum granular form. Look for macro and microconidia.
May cause tinea capitis, corporis or pedis
D. If mainly microconidia are visible
E. Look for spiral hyphae
No spiral hyphae
Spiral hyphae present
Microsporum persicolor
Trichophyton mentagrophytes
Trichophyton interdigitale
F. If spiral hyphae are present, look at microconidia structure and colony
Microsporum persicolor
Widebased microconidia +/-branches
Urease +
T mentagrophytes
Narrow base microconidia, colony has a granular appearance
Urease +, hair perforation test
(T rubrum – urease neg mostly)
T interdigitale
Narrow based round shaped microconidia. Suede like colony, reverse may be cream or if brown – not sharply defined
G. If no spiral hyphae present – look at the edge of the colony. Is there a yellow glabrous fringe edge?
No
T interdigitale,
T rubrum,
T interdigitale downy,
T rubrum granuler,
T tonsurans,
T erinacei
Yes
T soudanese,
T equinum,
Tinterdigitale noduler or
T erinacei
H. If the glabrous edge is present – look at the back of the colony and check how long it is been incubating
Fast growing. reverse dark brown
T equinum
Fast growing. reverse dark orange
T interdigitale nodular
Fast growing, reverse bright yellow
T erinacei
Slow growing (>1 week)
T soudanese
I. If no glabrous edge – look at the back of the colony, colony colour and microconidia
Bright yellow back = T erinacei
Back red, cream or brown = Trichophyton interdigitale, T rubrum, tonsurans
J. for group 2 - Look at microconidia and colony
Trichophyton interdigitale
Microconidia small, round.
Back of the colony may be brown/cream but not sharply defined.
Trichophyton rubrum
Microconidia small, club shaped
Back – dark red/brown, sharply defined white edge, urase neg at 1 week
Trichophyton interdigitale downey
Microconidia small, club shaped
Back – reverse may be cream or if brown – not sharply defined
Trichophyton rubrum granular
Large microconidia, ovoid/club shaped
Colony – some red/purple colour
Trichophyton tonsurans
