Medical Mycology

Medical Mycology

Introduction: Dr. Jawad Kadhum AL-Khafaji
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• Mycology is study of fungi. All Living things are classified into five kingdoms according to Whittaker (1969) . Monera, protista ,fungi, plantae and animalia. Bacteria belong to monera( prokaryote), protozoa are members of protista (eukaryote), fungi are belong to fungi kingdom(eukaryote), helminthes are classified in animalia kingdom.
• Bacteria ,Protozoa and yeast are unicellular , whereas molds and helminthes are complex multicellular organisms.

General properties of fungi :
1. Fungi are eukaryotic, larger than bacteria, and structurally more complex.
2. Fungi either unicellular(yeasts) or multicellular organisms(molds).
3. Most fungi are obligate aerobes, some are facultative anaerobe, but none is obligate anaerobe.
4. Natural habitat of most fungi is soil environment, except some yeasts such as : Candida and Malassezia are part of human normal flora.
5. Fungi have no organelles for locomotion (fungi non-motile).
6. Reproduction of fungi by spore formation.

Morphology of fungi :
Fungi can be grouped morphologically as either yeasts or molds.
1.Yeasts :
They grow as single cells(unicellular) and reproduce by budding. Their colonies on solid media resembling to colonies of bacteria.
2.Molds(filamentous fungi) grow as long multicellular filaments and reproduce by spores. Their colonies on solid media may be dry ,powdery with mycelia mass .
The basic structural units of molds are branching filaments termed (hyphae) that form intertwined mass called (mycelium). The hyphae may be divided by partitions ,termed septate, or aseptate





Fungal infections (Mycoses):
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Clinicians find value in classifying the fungi into five categories of mycoses:

• Superficial mycoses:
Tinea versicolor (pityriasis versicolor) :
It is caused by thermal dimorphic fungus, Malassezia species. The tinea is characterized by dry , scaling ,itching , depigmented maculae occur on skin ,usually of chest , neck , upper back ,arms, abdomen.
The fungus is part of normal flora and cause endogenous infection. The tinea is common with worldwide distribution , especially occur more frequently in hot and humid weather. The infection is higher prevalence in tropics, in immunocompromised patients such as patients who have undergone renal transplant , in patients with AIDS.
Treatment and prevention : the lesion is treated topically with selenium sulfide or with miconazole drug . Good hygiene is important in prevention.

• Cutaneous mycoses:(dermatophytoses)
Three genera of molds are cause dermatophytoses;
(i) Epidermophyton, infects the skin and nails , not hair
(ii) Microsporum , infects skin and hair ,not nails.
(iii) Trichophyton ; infects skin , hair , nails.
Tinea capitis(scalp infection) : is usaully caused by T. tonsurans and M. canis .It is characterized by dry , ring-like, scaly ,itchy, erythematous lesions on the scalp and may present as areas of alopecia(circular bald patches)due to broken hairs. The fungi grow around hair follicles lead to making it so fragile.
Tinea barbae (beard infection): is caused by T. verrucosum and characterized by inflammatory vesicopustular eruptions and areas of alopecia in beard and moustache area.
Tinea corporis( body infection) : is usually caused by T. rubrum , E. floccosum and characterized by circular patches with advancing red, scaling , pruritic lesions on smooth skin of the body.
Tinea pedis(athletes foot): is usually caused by T. rubrum , T. mentagrophytes, or E. floccosum and characterized by itchy ,peeling, erythematous, painful lesions between the toes.
The infection may be acquired by direct contact or through patient fomites such as hair comb. The incidence is higher in hot ,humid climates and under crowded living conditions, so dermatophytoses are located in warm, humid area of human body.
Treatment and prevention: infections are treated topically with Tolnaftate ,Terbinafine .Removal infected hair , use shampoo and the areas should be kept dry are very effective in prevent re-infection .