INTRODUCTION TO MEDICAL MYCOLOGY
Some fungi are of medical importance having the ability to incite morbidity and possibly death.
Mycosis(pl mycoses) is a disease in animals and man incited by fungi. Some of the fungi express
dimorphism, having both filamentous and yeast like phases. Also some can produce mycotoxins and
allergens. The production of sexual organs is rare among fungi inciting mycoses. They are important as
agent of established or opportunistic infections . Opportunistic infections include cryptococcosis and
candidiasis in the HIV -AIDS (and other infections)-infected individuals. Other fungi associated with
immunosuppression include Aspergillus , Rhizopus and, Rhizomucor .
Mycoses can be divided into
1. Superficial . These are also called dermatophytoses. The causal agents are called dermatophytic fungi,
causingTinea infections
Generally, fungal invaders of the skin are Tinea capitis(Microsporum audouinii, Trichophyton
mentagrophytes, )Tinea corporis( M. audouinii, , M gypseum) Tinea nigra( Cladosporium werneckii),
white piedra(Trichophyton beigelli), otomycosis(Aspergillus spp, Mucor spp, Rhizopus spp). The
dermatophytes belong to the division ascomycota, class euromycetes, and order onygenales and family
anthromodermatiaceae. They are associated with the general disease called Tinea which invade
keratinized human and animal tissues like the scalp, nails, and hairs. They can be grouped into
Tinea pedis—athletes foot affecting the feet
Tinea faciei—face
Tinea barbae---facial hair
Tinea cruris---the groin
Tinea corporis arms and legs
Tinea unguim fingernails and toe nails
Tinea capitis--- scalp ringworm
The Dermatophytic fungi are classified based on vegetative and reproductive morphology
Summary of the groups is described below
1 Yeast-like forms, including Candida(inciting thrush, vaginitis), Torulopsis( causing meningitis) and
Blastomyces(causing blastomycosis), Candida albicans(moniliasis), Coccidioides
immitis(coccidioidomycosis),Histoplasma capulatum(histoplasmosis),Cryptococcus
neoformans(cryptococcosis)
2 Filamentous forms. This comprises of Microsporum canis (in dogs and cats), Microsporum audouinii,
in humans(in children). Both cause Tinea capitis
Others are Trichophyton rubrum, T mentagrophytes , T violaceum and T tonsurans causing barbers itch.
More than 70% of all dermatophytoses are incited by Trichophyton rubrum
Epidermophyton flocossum causes the mycosis of hand, foot and groin
The 3 dermatophytes are distinct from each other in the following ways
1. Trichophyton -Microconidia always present, may or may not have macroconidia. When present, it
is thin walled and cigar shaped. Lesions can be as elevated plaques, scaly reddish with pustules
on the fringes. The lesions can form concentric rings on face, hand and neck. Most times, hairs
are excluded(Fig 7.1)are.
, a
Fig.1 Trichophyton a) microconidium
b)macroconidium
2 Microsporum spp----Microconidia are present and rough walled, sometimes with microconidia.
The macroconidia are multiseptate and spindle shaped.(Fig 7.2)
Fig 2 Microsporum sp
Lesions are not raised, but reddish and darker at the border, forming concentric rings that appear
to heal from the centre. It’s found on hand face, and skin.
3 Epidermophyton spp—This has no microconidia(Fig 7.3). Macroconidia are large, multicellular
and thin walled. The macroconidia are generally associated with short range dispersal and energy
reservoir to facilitate invasion of new site. The conidia are most times, egg shaped, at times,
clavate with smooth wall. They are generally located between toes and fingers.
Some fungi are of medical importance having the ability to incite morbidity and possibly death.
Mycosis(pl mycoses) is a disease in animals and man incited by fungi. Some of the fungi express
dimorphism, having both filamentous and yeast like phases. Also some can produce mycotoxins and
allergens. The production of sexual organs is rare among fungi inciting mycoses. They are important as
agent of established or opportunistic infections . Opportunistic infections include cryptococcosis and
candidiasis in the HIV -AIDS (and other infections)-infected individuals. Other fungi associated with
immunosuppression include Aspergillus , Rhizopus and, Rhizomucor .
Mycoses can be divided into
1. Superficial . These are also called dermatophytoses. The causal agents are called dermatophytic fungi,
causingTinea infections
Generally, fungal invaders of the skin are Tinea capitis(Microsporum audouinii, Trichophyton
mentagrophytes, )Tinea corporis( M. audouinii, , M gypseum) Tinea nigra( Cladosporium werneckii),
white piedra(Trichophyton beigelli), otomycosis(Aspergillus spp, Mucor spp, Rhizopus spp). The
dermatophytes belong to the division ascomycota, class euromycetes, and order onygenales and family
anthromodermatiaceae. They are associated with the general disease called Tinea which invade
keratinized human and animal tissues like the scalp, nails, and hairs. They can be grouped into
Tinea pedis—athletes foot affecting the feet
Tinea faciei—face
Tinea barbae---facial hair
Tinea cruris---the groin
Tinea corporis arms and legs
Tinea unguim fingernails and toe nails
Tinea capitis--- scalp ringworm
The Dermatophytic fungi are classified based on vegetative and reproductive morphology
Summary of the groups is described below
1 Yeast-like forms, including Candida(inciting thrush, vaginitis), Torulopsis( causing meningitis) and
Blastomyces(causing blastomycosis), Candida albicans(moniliasis), Coccidioides
immitis(coccidioidomycosis),Histoplasma capulatum(histoplasmosis),Cryptococcus
neoformans(cryptococcosis)
2 Filamentous forms. This comprises of Microsporum canis (in dogs and cats), Microsporum audouinii,
in humans(in children). Both cause Tinea capitis
Others are Trichophyton rubrum, T mentagrophytes , T violaceum and T tonsurans causing barbers itch.
More than 70% of all dermatophytoses are incited by Trichophyton rubrum
Epidermophyton flocossum causes the mycosis of hand, foot and groin
The 3 dermatophytes are distinct from each other in the following ways
1. Trichophyton -Microconidia always present, may or may not have macroconidia. When present, it
is thin walled and cigar shaped. Lesions can be as elevated plaques, scaly reddish with pustules
on the fringes. The lesions can form concentric rings on face, hand and neck. Most times, hairs
are excluded(Fig 7.1)are.
, a
Fig.1 Trichophyton a) microconidium
b)macroconidium
2 Microsporum spp----Microconidia are present and rough walled, sometimes with microconidia.
The macroconidia are multiseptate and spindle shaped.(Fig 7.2)
Fig 2 Microsporum sp
Lesions are not raised, but reddish and darker at the border, forming concentric rings that appear
to heal from the centre. It’s found on hand face, and skin.
3 Epidermophyton spp—This has no microconidia(Fig 7.3). Macroconidia are large, multicellular
and thin walled. The macroconidia are generally associated with short range dispersal and energy
reservoir to facilitate invasion of new site. The conidia are most times, egg shaped, at times,
clavate with smooth wall. They are generally located between toes and fingers.
