mycology lecture for mbbs

1. Subcutaneous Mycoses

2. General characteristics
1. Fungal infections of dermis, subcutaneous
tissue, muscle, fasciae and bones.
2. Causative organisms reside in the soil and
in decaying or live vegetation and are of
low virulence.

3. General characteristics
3. Infections are almost always acquired
through traumatic lacerations or puncture
wounds. Therefore, common in
individuals who have frequent contact
with soil and vegetation and who wear
little protective clothing eg. farm
labourers, herds men, and wood cutters.
4. Not transmissible from human to human
under ordinary conditions.

4. Subcutaneous Mycoses
- Mycetoma
- Chromoblastomycosis
- Sporotrichosis
- Lobomycosis
- Rhinosporidioosis
- Phaehyphomycosis

5. Mycetoma
(Maduromycosis=Madura foot)
• Mycetoma is a chronic granulomatous infection
of the subcutaneous tissue, usually affects the
foot and rarely the other parts of the body.
• The disease was first described by Gill (1842)
from Madurai; South India & Carter (1860)
established the fungal origin of the disease. It is
commonly referred to as madura foot or
Maduromycosis. The name Madura foot comes
from the high prevalence of the disease in
Madurai.
• Seen mainly in the tropical countries. Common in
Tamil Naidu.

6. Pathogenesis of mycetoma
• The causative organism is believed to enter the
body through minor trauma.
• The disease begins as a sub-cutaneous swelling
usually of foot, which enlarges and burrows into
deeper tissues producing characteristic abscess.
The abscess bursts with the formation of chronic
multiple sinuses discharge, seropurulent fluid
containing granules. Colour & consistency of the
granule vary with the different causative agents.

7. • ‘3 S’ --- Swelling
Sinus formation
Sulphur granules

8. Aetiology of Mycetoma ( Cont-)
Causative agent Colour of grains
A. Eumycetoma (fungal)
Acremonium falciforme (hyaline) White-yellow
Madurella mycetomi Black
M. grisea Black
Pseudoallescheria boydii White-yellow
Exophiala jeanselmei Black
Phialaphora verrucosa (dematiceous fungus) Black
B. Actinomycetoma
Actinomyces (A. israelii, A. bovis) White-yellow
Actinomadura madurae White-yellow
A. pelletieri Red
Nocardia brasiliensis white
Streptomces somaliensis yellow

9. Lab Diagnosis
• Sample:--
1) Pus – Frank
2) In gauze piece: applied at the mouth of a sinus – collection of pus &
granules (Discharge)
• MICROSCOPY
1) Gross color of granules.
2) Crush granules between slides and coverslip, add KOH, and examine
If very thin filaments seen it is Actinomycotic mycetoma
If Thick broad hyphae seen with septae it is mycotic mycetoma

10. Lab Diagnosis
• Proper history
• Gross examination
• Clinical samples – grains
• Direct examination – KOH wet mount
• Culture: SDA with antibiotics
• Histopathology

11. X-ray, KOH Wet Prep & Grain

12. Excised mycetoma showing a draining sinus containing black
grains

13. Why we need to differentiate is for
treatment
• Actinomycotic mycetoma : responds to
antibiotics
• Eumycotic mycetoma : responds to antifungal >
severe invasive and may require amputation too.

14. Actinomycotic Mycetoma of left leg
Swelling, siuses and discharge of grains. Can be mycotic

15. Mycetoma
Mycetoma of the arm.

16. Mycetoma
Mycetoma of
the shoulder
and back.

17. • If untreated, bony involvement can be
extensive and devastating, leading to
complete bone destruction. Much later and
more rarely in the disease, lesions may affect
nerves and tendons.

18. Treatment
• Actinomycotic mycetoma usually respond well
to sulphonamides and antibiotics
• but mycotic mycetoma may require
amputation.

19. Chromomycosis
This is a slowly progressive granulomatous infection
that is caused by several soil fungi
- Fonsecaea pedrosoi
- Fonsacea compactum
- Phialophora verrucosa
- Cladosproium carrionii
- Rhinocladiella
when introduced into the skin through the trauma.
These fungi are collectively called Dematiaceous
fungi(Pigment producing), so named because their
conidia or hyphae are dark-coloured, either gray or
black.

20. Chromomycosis
• Wartlike lesion with
crusting abscesses extend
along the lymphatics.
• The disease occurs mainly
in the tropics and is found
on bare feet and legs.
• In the clinical laboratory,
dark brown, round fungal
cell (Copper pennies,
sclerotic bodies)are seen in
leukocytes or giant cells.
• The disease is treated with
oral flucytosine or
thiabendazole, plus local
surgery.
Chromoblastomycosis,
hyperkeratotic lesions

21. Chromoycosis
Chromoblastomycosis, hyperkeratotic lesions

22. Sclerotic bodies (Copper pennies)

23. Sporotrichosis schenckii
• A thermo dimorphic fungus. Yeast at 37°C & mould
at room temperature.
i. Sporotrichosis is a nodular, ulcerating disease of
skin and subcutaneous tissue.
ii. It usually affects the hands or the forearm.
iii. The fungus gains access through thorn pricks or
some injuries. It is more common in gardeners'
(rose gardeners) & farmers.
i. The fungus spread through lymphatics up to
regional lymph nodes & rarely beyond that.
ii. The disease is world wide, though more common in
USA.

24. Laboratory diagnosis of
Sporothrix schenckii
• Diagnosis is made by culture
• S. schenckii occurs in the yeast phase & cultures at
370C, and in mycelial phase in cultures at 220C-250C
(dimorphic fungus).
• Yeast phase appears as cigar- shaped cells & mould
form contains carrying flower like clusters of small
conidia borne on delicate sterigmata.
• The fungus produces progressive disease in
rats on I/P.

25. 433
Lymphocutaneous sporotrichosis showing typical elevated
subcutaneous nodules developing along the regional lymphatics of the forearm

26. Lymphocutaneous sporotrichosis showing more advanced, ulcerating lesions developing
along the lymph system of the forearm.

27. Fixed cutaneous verrucous-type
sporotrichosis of the wrist and hand,
looking remarkably similar to
chromoblastomycosis

28. 438
Section from a fixed cutaneous lesion on the face of a child with sporotrichosis showing round Periodic Acid-
Schiff (PAS) positive yeast-like cells, one with an elongated bud. Sporothrix schenckii is a dimorphic fungus
and this is the typical parasitic or yeast-like form seen in tissue

29. 439
Sporothrix schenckii on Sabouraud's dextrose agar grown at 25oC colonies are moist and glabrous,
with a wrinkled and folded surface. Pigmentation may vary from white to cream to black

30. 44
Microscopic morphology of the saprophytic
or mycelial form of Sporothrix schenckii
when grown on Sabouraud's dextrose agar
at 25oC.
Microscopic morphology of the yeast form of
Sporothrix schenckii when grown on brain
heart infusion agar containing blood and
incubated at 370C. Note budding yeast cells.

31. Lobomycosis
• Lobomycosis is a
chronic skin infection
• It hasn’t been
successfully isolated.
• It has been reported
from few countries of
South America.
• Cause subcutaneous
lesions with a
tendency to form
keloids.

32. Lobomycosis (GMS)

33. Rhinosporidiasis
• Rhinosporidiosis is a chronic granulomatous
disease characterised by formation of friable
polyps, usually confined to nose, mouth or
eyes & rarely seen on other mucous
membranes.
• Causative agent is Rhinosporidium seeberi.
• More than 80% cases are seen in India & Sri
Lanka.

34. Rhinosporidium seeberi
• The fungus can not be cultivated.
• Diagnosis depends on the
demonstration of sporangia.
• Tissue section stained with H & E
stain show large numbers of
endospores within the sporangia
embeded in a connective tissue &
capilaries.
• *The sporangium (10-200μm)
contains thousands of endospores
(6-7μm in diameter). These spores
when released develop into new
sporangia.
Rhinosporidiosis, GIANT
sprorangium, 350um