Superficial Mycoses
Mrs. Dalia kamal Eldien
Msc in Microbiology
Lecture NO (4)
Objectives
Definition of Mycosis
Classification of fungal infection according to the
tissue levels initially
Definition of Superficial mycoses the mode of
transmission
Causes of non-inflammatory Superficial mycoses
introduction
 Mycosis (plural: mycoses)is fungal infection of animals&
humans.
 Mycoses are classified according to the tissue levels initially
colonized to:1-Superficial mycoses
2-Cutaneous mycoses
3- Subcutaneous mycoses
4- Systemic mycoses due to primary pathogens
5- Systemic mycoses due to opportunistic pathogens
Superficial mycoses
 Defined as fungal infections of the skin and hair that invade
only the most superficial layers and cause little or no
inflammatory response.
 These fungi have ability to produce keratinase, which allows
them to metabolize and live on human keratin tissue like
skin, nail and hair.
 Are a major cause of morbidity in the world, particularly in
the tropics, where heat and humidity provide the ideal
conditions for the growth of fungi .
 Direct contact is sufficient to transmit the infection from a
contaminated surface or host to another.
PATHOGENICITY
 With superficial mycoses, fungi are confined to the
epidermis and annexes, and rarely invade the
dermis. In extremely rare cases, internal organs can
also be affected.
 There are two categories of infection:
 Non-inflammatory infection
 Inflammatory infections
NON-INFLAMMATORY INFECTIONS
Infection
Causative fungi
Malasseziosis
Malassezia species
Tinea nigra
Exophiala werneckii
Black piedra
Piedraia hortae
White piedra
Trichosporon species
Malasseziosis
 Also known as pityriasis or tinea versicolor
 Pityriasis versicolor is a common yeast infection of the skin,
in which flaky discoloured patches appear on the chest and
back.
 In people with dark skin tones, pigmentary changes such
as hypo pigmentation (loss of color) are common, while in
those with lighter skin color, hyper pigmentation (increase in
skin color) are more common.
 The term pityriasis is used to describe skin conditions in
which the scale appears similar to bran. The multiple colors
of pityriasis versicolor give rise to the second part of the
name versicolor.
pityriasis
Common species
• Tinea versicolor is caused by
 Malassezia globosa
 Malassezia restricta
 Malassezia furfur
Pathogenicity
 Pityriasis versicolor is not contagious.
 Pityriasis versicolor is a rash caused by a yeast-like germ
 Small numbers of this germ commonly live on the skin, and
do no harm. However, some people are prone to this germ
multiplying on their skin more than usual, which then leads to
a rash developing.
 Often the germ multiplies and causes the rash for no
apparent reason. In some cases, hot, sunny or humid
weather seems to trigger the germ to multiply on the skin.
 The rash usually starts as small pale patches, usually
appear on the chest, neck or upper arms. The rash
sometimes spreads to tummy (abdomen), thighs and
back.
 Pityriasis versicolor is usually asymptomatic, but in some
people it is mildly itchy.
 These fungi also cause folliculitis (inflammation of the hair
follicles)
 also cause seborrheic dermatitis and dandruff
Diagnosis –
Pityriasis versicolor is usually diagnosed clinically. However,
the following tests may be useful.
 Wood lamp (black light) examination— yellow-green
fluorescence may be observed in affected areas
 Specimen: skin scraping, skin biopsy
 Microscopy using potassium hydroxide (KOH)—appearance
of oval to round budding yeasts as well as short septate and
sometimes branching hyphae that resemble spaghetti and
meatballs are observed
 Fungal culture—this is usually reported to be negative, as it
is quite difficult to encourage the yeasts to grow in a lab.
 Skin biopsy—fungal elements may be seen within the outer
cells of the skin on histopathology.
Wood lamp examination
Septated Hyphae and yeast cell
Treatment
Mild pityriasis versicolor is treated with topical antifungal
agents.
 Propylene glycol solution
 Sodium thiosulphate solution
 Selenium sulfide
 Topical azole cream/shampoo (econazole, ketoconazole)
Tinea nigra
 Is a superficial fungal infection that causes dark brown to
black painless patches on the palms of the hands and the
soles of the feet
 The word Tinea means a fungal infection and Nigra means
black.
 Tinea nigra is overall an uncommon fungal infection when
compared to other tinea infections .
 Tinea nigra is more commonly seen in children and is more
likely in girls than boys. The conditions also tends to affect
lighter skinned individuals than darker skinned people.
 The infection is mostly acquired via direct inoculation of the
fungus onto the skin due to contact with soil, wood, and
decaying vegetation.
 Clinically, it is characterized by small unilateral, black
patches that appear on palmar skin or rarely on plantar
skin and the edges of fingers.
 Tinea nigra does not cause an itchy skin rash .
 Most patients are unaware of the fungal infection until
the characteristic brown to black rash develops.
 Tinea nigra is a superficial fungal infection caused by
one of the following fungi :
 Exophiala werneckii (Phaeoannellomyces werneckii)–
more common causative agent of tinea nigra.
 Stenella araguata
 Cladophialophora saturnica
Hand with Tinea nigra
Diagnosis
• The typical rash of tinea nigra may be sufficient to
make a diagnosis. Additional investigations will assist
in confirming the diagnosis and this includes :
 Clinical Material: Skin scrapings.
 Direct Microscopy: Skin scrapings should be
examined using 10% KOH and Parker ink or calcofluor
white mounts.
 Result 10% KOH showing pigmented brown to dark
olivaceous (dematiaceous) septate hyphal elements
and yeast cells
KOH smear showing irregular, branching,
septate dematiaceous hyphae
 Culture: Clinical specimens should be inoculated onto
primary isolation media, like Sabouraud's dextrose
agar.
 Colonial morphology:
 Exophiala werneckii grow slowly and mature within 21
days.
 From the front they are initially pale in color, moist,
shiny, and yeast-like. In time these colonies become
velvety, olive black, and are covered with a thin layer of
mycelium.
 From the reverse, the color is black.
 Microscopical exam by lactophenol cotton blue:
 Septate hyphae, yeast-like conidia, and
chlamydospores are observed.
 The yeast-like conidia are the initial structures
observed in the early phase of the colony
development.
 Septate, thick-walled, and brown hyphae are formed
as the colony ages
 Serology: Not required for diagnosis.
lactophenol stain is characterized by septated hyphae,
blastospore and arthrospore-typical of the
Phaeoannellomyces werneckii fungus
Black piedra
 Piedra, meaning stone in Spanish, is an asymptomatic
superficial fungal infection of the hair shaft, resulting in
the formation of nodules of different hardness on the
infected hair.
 Caused by the fungus piedraia hortae, which is more
common in tropical countries.
 The source of infection is unknown and person-toperson transmission has been suggested, but this is
not clear. Both sexes and people of all ages are equally
affected.
Clinical manifestations:
 Infections are usually localized to the scalp but may
also be seen on hairs of the beard, moustache and
pubic hair.
 Infected hairs generally have a number of hard
black nodules on the shaft.
 The most common complication is hair loss
Laboratory diagnosis:
 specimen: hairs with hard black nodules present on the
shaft.
 Direct Microscopy: Hairs should be examined using 10%
KOH or calcofluor white. Look for darkly pigmented nodules
that may partially or completely surround the hair shaft.
 Culture: Hair fragments should be implanted onto primary
isolation media, like Sabouraud's dextrose agar. Colonies of
Piedra hortae are small, folded, velvety dark, brown-black
and take about 2-3 weeks to appear.
 Microscopy:Septate hyphae, asci, and ascospores are
seen
 Serology: Not required for diagnosis.
Hair with Black Piedra
White piedra
 White piedra is a superficial cosmetic fungal infection
of the hair shaft.
 Infected hair develop soft greyish-white nodules along
the shaft.
 soft nodules composed of yeast cells and arthroconidia
that encompass hair shafts.
 Infections are usually localized to the axilla or scalp but
may also be seen on facial hairs and sometimes pubic
hair.
 Caused by the fungus Trichosporom beigelii.
Laboratory diagnosis:
 Specimen: hairs with white soft nodules present on the
shaft.
 Direct Microscopy: Hairs should be examined using 10%
KOH or calcofluor white mounts. Look for irregular, soft,
white or light brown nodules, 1.0-1.5 mm in length, firmly
adhering to the hairs.
 Culture: Hair fragments should be implanted onto primary
isolation media, like Sabouraud's dextrose agar. Colonies of
Trichosporon beigelii are white or yellowish to deep cream
colored, smooth, wrinkled, velvety, dull colonies with a
mycelial fringe.
 Serology: Not required for diagnosis.
(A) Culture on agar-Sabouraud showing a creamy, yellowish-white and
cerebriform yeast colony. (B) Direct mycological examination showing
a clear friable and soft nodule on the hair cuticle (10X), formed by
arthro-conidia and blastoconidia (C; 40X)
Colony of trichosporom beigelii