Common Fungal Infections PDF

Common Fungal infections Hasan H. Alfahemi Assistant Professor of Medical Microbiology Faculty of Medicine Department of Medical Microbiology Al-Baha University Cutaneous Mycoses • Also called dermatophytoses • Common diseases caused by a group of related fungi • Dermatophytes:- Microsporum – 3...

Common Fungal infections Hasan H. Alfahemi Assistant Professor of Medical Microbiology Faculty of Medicine Department of Medical Microbiology Al-Baha University Cutaneous Mycoses • Also called dermatophytoses • Common diseases caused by a group of related fungi • Dermatophytes:- Microsporum – 3 genera:- Trichophyton Epidermophyton Pathology • Defining characteristic of dermatophytes:– Ability to use keratin source of nutrition. – allows infection of keratinized tissues & structures:• Skin • Hair • Nails. Pathology • Some specificity of genera in infection site – All 3 genera attack skin – Microsporum not infect nails – Epidermophyton not infect hair – None invade underlying non-keratinized tissue. Epidemiology • The causative organisms of dermatophycoses are often distingushed according to their natural habitats. • Anthropophilic ( Residing on human skin). • Zoophilic ( Residing on the skin of domestic and farm animals). • Geophilic (Residing in the soil). • Most human infections are by anthrophilic and zoophilic organisms. • Transmission from human to human or animal to human is by infected skin scales. Tinea pedis (athlete's foot): Most often :Ø Trichophyton rubrum Ø Trichophyton mentagrophytes ØEpidermophyton floccosum. ØInfected tissue:ØInitially between toes ØCan spread to nails:ØBecome yellow & breakable. ØSkin fissures can lead to:Ø 2ndary bacterial infections, Ø consequent lymph node inflammation. Tinea corporis (ringworm): • Organisms most often isolated:– Epidermophyton floccosum. – Trichophyton – Microsporum. – Lesions appear as:- • advancing annular rings • with scaly centers • periphery of the ring which is the site of active fungal growth • Usually inflamed and vesiculated. – Any site on body can be affected – lesions most often on non-hairy areas of trunk. Tinea capitis (scalp ringworm): • Several species of:– Trichophyton – Microsporum – Predominant infecting species depending on the geographical location of the patient. – In USA predominant infecting specie is Trichophyton tonsurans. • Disease manifestations range:– Small scaling patches – Involvement of entire scalp – With extensive hair loss Tinea capitis (scalp ringworm) üHair shafts invaded by Microsporum hyphae üManifests by green fluorescence in long-wave ultraviolet light (Wood lamp). Tinea cruris (jock itch) • • • • Causative organisms:E. floccosum T. rubrum. Disease manifestations – similar to ringworm – Except lesions in moist groin area – Where they can spread from upper thighs to genitals. Tinea unguium (onychomycosis): • causative organism most often:– T. rubrum. • Nails:– thickened – Discolored – brittle. • Treatment must continue 34 months until all infected portions of nail grow out and are trimmed off Subcutaneous Mycoses • It is fungal infection of dermis, subcutaneous tissue, and bone. • Causative organisms often reside in the soil and decaying or live vegetation. Epidemiology of Subcutaneous Mycoses • Subcutaneous fungal infections are almost always acquired through traumatic lacerations or puncture wounds. • Sporotrichosis, for example, is often acquired from the prick of a thorn. • As expected, these infections are more common in individuals who have frequent contact with soil and vegetation and wear little protective clothing. • The subcutaneous mycoses are not transmissible from human to human under ordinary conditions. VAGINAL CANDIDIASIS Oral candidiasis • Oral candidiasis, also known as oral thrush is candidiasis that occurs in the mouth. • It is is a mycosis (yeast/fungal infection) of Candida species on the mucous membrane of the mouth. Laboratory diagnosis • Sample: scraping of:– scaly skin – affected nails – affected hair • Wet preparation of sample with 10-20% poattasium hydroxide • Direct examination under light microscope Laboratory diagnosis • • • • Isolation in a culture. KOH mount. Serology Molecular techniques: DNA hybridization, PCR. Treatment • Removal of infected skin • Followed by topical of antifungal:– Miconazole – Clotrimazole • Infections of hair and nails:– systemic (oral) therapy. • Terbinafine drug of choice for onychomycosis (fungal infection of the fingernails or toenails that causes discoloration, thickening, and separation from the nail bed). !"#"$"%&" • Harvey RA et al. Lippincott’s Illustrated Reviews: Microbiology Third Edition, 2013, Chapter 20, Page 203-206