Superficial Mycosis

1. Dr. Arun Kumar Parthasarathy Ph.D
Dept. of Microbiology
D.Y Patil Medical College, Kolhapur
Superficial Mycosis

2. Fungal infection in human can be classified
according to the tissues involved
• Superficial Mycosis
• Subcutaneous mycosis
• Systemic mycosis
• Opportunistic mycosis
Fungal infection in humans are broadly classified
into two types depending on the tissue affected
1.Superficial and
2.Deep mycosis

4. Superficial Mycosis
Surface Infections
•Fungi live exclusively on the
dead layers of the skin and its
appendages
•They have no contact with
living tissue and no elict
inflammatory response
•Only changes produced are
cosmetic effects
•Example:- Tinea (Pityriasis
versicolor), Tinea nigra and
pidra
Cutaneous infection
•Infection generally confined
to the cornified layer of the
skin and appendages
•Various inflammatory and
allergic responses are induced
in the host by the presence of
fungus and by their metabolic
products
•Dermatophytosis caused by a
group of fungi called the
Dermatophytes

5. Superficial Mycosis
Pityriasis versicolor (Tinea versicolor):-
Chronic, usually asymptomatic involvement of the stratum
corneum
Distribution:-
• Worldwide distribution
• More prevalent in tropics
• Occurs mainly in young adults
Causative agent:-
• Malassezia furfur (formerly Pityrosporum orbiculare)
Lipophilic, yeast –like fungus

6. Clinical features:-
Characteristic discrete or confluent
macular areas of discolorisation or
depigmentation occur on the skin of the
chest, abdomen, upper limbs and back.
The fungus may be demonstrated on
normal skin and the disease may be
considered an opportunistic infection.
Diagnosis:-
Examination of skin scrapings shows
an abundant of yeast like cells and short,
branched filaments.
The fungus can grown on Sabouraud
dextrose agar covered with layer of olive oil.

7. Tinea nigra
Localized infection of stratum corneum,
particularly of the palms, producing black or
brownish macular lesions
Distribution:- Mainly occurs in Tropics
Causative agent:-
1. Exophiala werneckii (formerly Cladosporium
wernickii, Hortea wernickii)
2. Exophiala castellanii
Diagnosis:-
Skin scraping show brownish, branched,
septate hyphae and budding cells.
Colonies on Sabouraud dextrose agar
are grey or black in color.

8. Piedra
Fungal infection of hair
Characterized by the presence of firm, irregular nodules
along the hair shaft,
These nodules composed of fungal elements cemented
together on the hair
2 varieties of Piedra are recognized
1. Black piedra- Piedraia hortae
2. White piedra – Trichospora beigelii

9. Cutaneous Mycoses
(Dermatophytoses)
Dermatophytoses (commonly called tinea or ringworm) refers to
infection of keratinized structures (Hair, Nail and Skin).
Caused by group of Ketaniophilic fungi called Dermatophytes
Infection may be acute or chronic
Chronic course with episodes of remission and exacerbation
Characteristics of Dermatophytes:-
• Hyaline filamentous fungi that digest keratin by enzymatic but
unable to invade living tissue
• Variety of pathological changes occur in the infected host
because of fungi and their metabolic products
• Resist to chlorhexidine
• Classified into 3 groups depending on their usual habitat.

10. Genera of Dermatophytes
3 genera of Dermatophytes
1. Microsporum (16) -M. gypseum, M.canis, M.nanum
2. Trichophyton (24)– T.rubrum, T.mentagrophytes,
T.verrucosum
3. Epidermatophyton (1) - E. floccosum
About 40 species of Dermatophytes are known to
cause infections in humans and animals

11. Clinical aspects of Dermatophytosis
More common in males than females
Clinical classification is according to the anatomical site involved
1. Tinea barbae (barber’s itch)- involves the bearded area of the
face and neck
2. Tinea corporis (Tinea glabrosa)- ringworm of smooth or non-
hairy skin of the body
3. Tinea imbricata- special type of T.corporis found in tropics,
characteristics extensive concentric rings of papulosquamous
scaly patches
4. Tinea capitis- ringworm of scalp, favus and Kerion are variants
5. Tinea cruris (jock itch)- involves the groin and perineum
6. Tinea pedis (athlete’s foot)- ringworm of the foot
7. Tinea manuum- involves the hand
8. Tinea unguium- involves the nails

13. Dermatophytoses-Causative agent
Sr.No Disease Common causative agents
1 Tinea capitis Microsporum species
Trichophyton species
2 Favus Microsporum gypseum
Trichophyton schoenleinii
Trichophyton violaceum
3 Tinea barbae Trichophyton rubrum
Trichophyton mentagrophytes
Trichophyton verrucosum
4 Tinea imbricata Trichophyton concentricum
5 Tinea corporis Trichophyton rubrum and other Dermatophytes
6 Tinea cruris Epidermatophyton floccosum
Trichophyton rubrum
7 Tinea pedis Epidermatophyton floccosum
Trichophyton rubrum

14. Clinical features:-
Lesion in the skin tend to be circular, dry,
erythymatous, scaly and itchy
Lesions of the hair include Kerion, scarring and
alopecia
Favus:- A chronic type of ringworm in which dense
crusts (Scutula) develop in the hair follicles, leading
to alopecia and scarring
Kerion:- sever boggy lesions with marked
inflammatory reaction that sometimes develops in
scalp due to Dermatophytes
• Nails infected by Dermatophytes are deformed,
friable and discolored and there is accumulation of
debris under the nails.
• In lesions Dermatophytes appear as hyphae and
arthrospores

15. Pathogenicity
Dermatophytes grow only on the keratinized
layer of the skin and its appendages
Do not ordinarily penetrate living tissue
Mechanisms of pathogenesis are unclear
Fungal products may responsible for inciting
local inflammation
Hypersensitivity of fungal infection may play a
vital role and may be responsible for sterile
vesicular lesions
The reaction may follow oral antifungal therapy
and confused with an allergic drug reaction
Called dermatophytids (or id reactions)
Hypersensitivity can be demonstrated by skin
testing with fungus antigen trichophytin

16. Laboratory diagnosis
Specimens:-
Scraping of skin and nail
Short length of plucked hair from scalp
Scraping are taken from the edges of ringworm
lesions
Direct Microscopy examination:-
• 10-20% KOH wet mount preparation
• Suspected Tinea capitis, fungal elements
looked by exposure to UV light (wood’s lamp
examination). Infected hair will fluorescent
• 2 types of hair infection may be
distinguished in wet mounts
• Ectothrix- arthrospores are seen as a
sheath surrounding the hair
• Endothrix- arthrospores are inside the
hair shaft

18. Culture:-
Sabouraud glucose neopeptone agar containing Chloramphenicol
Sabouraud dextrose agar containing Chloramphenicol and
Cycloheximide
Dermatophytes Test Medium (DTM)
Cycloheximide –Inhibits the saprophyte molds,
Gentamicin- and Chlortetracycline- Inhibit the bacteria
Phenol Red- indicator changes yellow to red within 14 days when
the medium is alkaline as a result of dermatophytes.
Temp:- 25-30 ºC upto 21 days

19. Colony Character
Trichophyton:- Colonies may be powdery, velvety or waxy
with pigmentation characteristic of different species.
Macroconidia- usually rare, elongated and blunt ends,
smooth, thin walls & Variable in shape (Cylindrical, fusiform or
clavate), vary in number of septa (2-8) and in size (20-50 X 4-6
µm). They are arranged in singly or in clusters
Microconidia- abundant , arranged in clusters along the hyphae
on conidiophores
Hyphae:- Special type of hyphae ,
Spiral hyphae
Racquet hyphae
Favic chandeliers

20. Microsporum:- colonies are velvety, cottony or powdery with
white to brown pigmentation
Macroconidia- Numerous, typically thick walled and rough
(varying from minutely to strongly roughened)
Varying in shape (fusiform to obovate)
No. of septa :- 3-15 and size:- 5-100 X 3-8 µm
Microconidia- Scarce, pyriform or clavate, usually arranged in
singly along the sides of the hyphae.

21. Epidermatophyton:- colonies are powdery and greenish
yellow
Microconidia- Absent
Macroconidia- club shaped, 2-6 septa,
Size:- 20-40 X 6-8 µm in size
Thin and slightly thick walled and are singly or clusters

22. Trichophyton mentagrophytes White to tan, cottony or powdery pigment variable
Trichophyton rubrum Velvety, red pigment on reverse
Trichophyton violaceum Very slow growing , waxy, violet or purple pigment
Microsporum canis Cottony, orange pigment on reverse
Microsporum audouinii Velvety, brownish slow growing
Microsporum gypseum Powdery buff colored
Epidermatophyton floccosum Yellowish green, powdery
Colony Character

23. Trichophyton
mentagrophytes
Clusters of microconidia, cigar
shaped macroconidia with
terminal rat-tail filaments
Trichophyton
rubrum
Few, long , pencil shaped
macroconidia
Trichophyton
violaceum
Hyphal swelling,
chlamydospores, favic chandelier,
disorted hyphae, conidia rare.
Identification

24. Microsporum canis Abundant thick walled spindle
shaped macroconidia with upto
15 septa
Microsporum
audouinii
Thick walled chlamydospores,
conidia rare and irregular
Microsporum
gypseum
Abundant thin walled
macroconidia with 4-6 septa
Epidermatophyton
floccosum
Club shaped macroconidia in
clusters
Identification

25. Cellophane tape mount

26. Hair Perforation test
Useful in differentiating Trichophyton rubrum from T.mentagrophytes
To observe hair perforation, short (5-10mm)strands of human hair
placed in a Petri dish with 20 ml of autoclaved distilled water
2 or 3 drops of 10% sterilized yeast extract are added to the petri dish
Hair strands are inoculated with small fragments of test fungus grown
of SDA
Incubate at 25-30C and the hair stands are removed and observed
microscopically at weekly intervals upto 1 month
T.rubrum- surface erosin of hair shafts in this test
T.Mentragrophytes – wedge shaped perforation perpendicular to hair
shaft

27. Urease test
Useful for distinguishing isolate of T.mentagrophytes from T.rubrum
Urease splits urea in Christensen's medium, producing ammonia,
which raises the pH and causes a color from amber to pink (Phenol
red)
T.mentagrophytes- produces bright pink color (positive)
T.rubrum- No color change (Negative)