Brief description of common Dermatophytosis

1. Mycology
Aman Ullah
B.Sc. MLT
M. Phil Microbiology
Master in Health Research
Certificate in Health Professional Education

2. STRUCTURE & GROWTH
• Fungi are eukaryotic organisms
• Two fungal cell structures are important medically:
• The fungal cell wall consists primarily of chitin
• The fungal cell wall contains other polysaccharides as
well, the most important of which is -glucan, a long
polymer of D-glucose
• it is the site of action of the antifungal drug
• The fungal cell membrane contains ergosterol, also site
of action of antifungal drug

3. STRUCTURE & GROWTH
• There are two types of fungi: yeasts and molds
• Yeasts grow as single cells that reproduce by asexual budding
• Molds grow as long filaments (hyphae) and form a mat
(mycelium)
• Some hyphae form transverse walls (septate hyphae), whereas
others do not (nonseptate hyphae)
• Several medically important fungi are thermally dimorphic, i.e.,
they form different structures at different temperatures
• They exist as molds in the environment at ambient
temperature and as yeasts (or other structures) in human
tissues at body temperature

4. STRUCTURE & GROWTH
• Most fungi are obligate aerobes; some are
facultative anaerobes; but none are obligate
anaerobes
• The natural habitat of most fungi is
environment
• An important exception is Candida albicans,
which is part of the normal human flora

5. FUNGAL TOXINS & ALLERGIES
• In addition to mycotic infections, there are two
other kinds of fungal disease:
• Mycotoxicoses, caused by ingested toxins, and
• Allergies to fungal spores
• The best-known mycotoxicosis occurs after eating
Amanita mushroom
• Allergies to fungal spores, particularly those of
Aspergillus, are manifested primarily by an
asthmatic reaction, eosinophilia

6. Mycosis
• Infection caused by fungi is called mycosis
• Medical mycoses can be divided into four
categories:
• Cutaneous
• Subcutaneous
• Systemic
• Opportunistic

7. CUTANEOUS MYCOSES
• Also called dermatophytoses
• These common diseases are caused by a
group of related fungi, the dermatophytes
• Dermatophytes fall into three genera, each
with many species:
• Trichophyton
• Epidermophyton
• Microsporum

8. CUTANEOUS MYCOSES
Transmission
• Transmission from human to human or animal to
human is by infected skin scales on inanimate objects
• Only the pathogenic fungi are capable of human-to-
human spread
Pathology
• A defining characteristic of the dermatophytes is their
ability to use keratin as a source of nutrition
• This ability allows them to infect ker-atinized tissues
and structures, such as skin, hair, and nails

9. CUTANEOUS MYCOSES
Clinical significance
• Dermatophytoses are characterized by itching,
scaling skin patches that can become inflamed
• Specific diseases are usually identified
according to affected tissue (for example,
scalp, pubic area, or feet)
• But a given disease can be caused by any one
of several organisms, and some organisms can
cause more than one disease

10. CUTANEOUS MYCOSES
• Tinea pedis (“athlete’s foot”):The infected tissue is initially
between the toes but can spread to the nails, which become yellow
and brittle
• Tinea corporis (“ringworm”): Although any site on the body can be
affected, lesions most often occur on nonhairy areas of the trunk
• Tinea capitis (“scalp ringworm”):Disease manifestations range from
small, scaling patches, to involvement of the entire scalp with
extensive hair loss
• Tinea cruris (“jock itch”):Disease manifestations are similar to
ringworm, except that lesions occur in the moist groin area, where
they can spread from the upper thighs to the genitals
• Tinea unguium (onychomycosis): Nails thicken and become
discolored and brittle

11. Tinea pedis Tinea corporis Tinea capitis
Tinea cruris Tinea unguium

12. Candidiasis (candidosis)
• Candidiasis is caused by the yeast Candida albicans and other Candida
species, which are normal body flora found in the skin, mouth, vagina,
and intestines
• Infections occur when competing bacterial flora are eliminated, for
example, by antibacterial antibiotics, allowing the yeast to overgrow
• Candida infections have various manifestations, depending on the site
and the degree of immunoincompetence of the patient
• For example, oral candidiasis (thrush) presents as raised, white plaques
• on the oral mucosa, tongue, or gums
• The plaques can become confluent and ulcerated and spread to the
throat
• Vaginal candidiasis presents as itching and burning pain of the vulva
and vagina, accompanied by a white discharge
• Systemic candidiasis is a potentially life-threatening infection that
occurs in immunocopromised patient
• Systemic candidiasis may involve the gastrointestinal (GI) tract, kidneys,
liver, and spleen.