Saturday, 19 October 2013

Trichophyton terrestre

Trichphyton terrestre (Fungus/Mould)

Trichphyton terrestre is a cosmopolitan (found everywhere), geophilic (soil loving) fungus.
It may also be recovered as a saprobe (living on dead organic matter) on the fur of small animals, presumably picked up from soils.

Trichophyton terrestre fails to grow once 35ºC to 37ºC is reached
As it fails to grow at human body temperature, there have been no reports of human infection by this fungus, nor has it been implicated in animal infections.
T.terrestre may occasionally be encountered as a laboratory contaminant.
Correct identification is important so as to not confuse it with pathogenic dermatophytes.

Macroscopic Morphology:
  • Trichophyton terrestre exhibits moderate growth at 25ºC, maturing in about 8 days.
  • Colonies expanded in diameter rather slowly.
  • Colonies were off-white to light in colour.
  • Reverse appeared yellowish to ochraceous, or even slightly reddish in colour.
  • Texture was felty to powdery
The isolate presented here developed a pale to golden yellow exudate on prolonged incubation which was not reported in other sources.

 Trichophyton terrestre on SAB, 15 days incubation at 30˚C

Trichophyton terrestre on SAB,  25 days incubation at 30˚C

Microscopic Morphology:
  • Trichphyton terrestre produces hyaline (clear, non-pigmented), septate hyphae.
  • Microconidia (4 – 7 µm by 1 -5 µm) are tear-drop to slightly club-shaped.
  • They are borne directly from the vegetative hyphae or are found on pedicles (stalk).
  • Macroconidia (4 – 5 µm by 8 – 50 µm) have smooth, thin walls and usually contain between 2 to 6 cells or divisions internally.
  • Macroconidia are cylindrical (parallel sides) or slightly clavate (club) shaped.
There may not be an obvious distinction between what may be called micro or macro conidia.  (ie. The two are not clearly differentiated.)
Free micro (& macro conidia) exhibit a truncate base or basal scar at what was their point of attachment.

Trichophyton terrestre - Adhesive tape preparation, 250X, LPCB (Nikon)

Trichophyton terrestre - Branching with development of Macro & Micro Conidia.
 LPCB 400X (DMD-108)

Trichophyton terrestre -as above
 LPCB 400X (DMD-108)

 Trichophyton terrestre - free macro & micro conidia
400+10X, LPCB (DMD-108)

Trichophyton terrestre - Conidia stain darker with the LPCB than the hyphae usually do
1000X, LPCB (DMD-108)

Trichophyton terrestre - Here again, the conidia at the tips of the hyphae (conidiophore) can be seen as staining a darker blue than the hyphae themselves.  Measurements shown (inset) are for the conidia and hyphe.  I regret that I didn't just measure the length of the conidia alone.
1000X, LPCB (DMD-108)

Trichophyton terrestre -extensive branching at near right angles.
1000X, LPCB (DMD-108)

Trichophyton terrestre -more of the same.  Darker blue conidia are seen at the end of the hyphae, branching at near right angles.
1000X, LPCB (DMD-108)

Trichophyton terrestre - divisions can be seen in some of the developing conidia (macroconidium)
1000X, LPCB (DMD-108)

Trichophyton terrestre -conidia staining a darker blue with the LPCB stain.  Divisions can be seen in the conidia.  The one on the lower left of the photo clearly has two.
1000X, LPCB (DMD-108)

Trichophyton terrestre -free macroconidium (4 septations or 5 compartments)
1000X, LPCB Nikon (appears larger due to cropping of photo)

Physiological Characteristics:
  • Hair perforation test is POSITIVE
  • Urease is POSITIVE
  • BCPCG Media reaction is POSITIVE
  • No growth at 35ºC to 37ºC
Trichophyton Agars:
Good growth on all Trichophyton agars.  No special growth requirements are required for growth.
Caution: on early growth, the fungus may somewhat resemble a Chrysosporium species.  Chrysosporium’s conidia generally do not exceed two cells in length.

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