Fungi Classification (Superficial+Cutaneous) Flashcards
Is fungi successful at invading often
Humans have a high level of innate immunity to fungi and most of the infections they cause are mild and self-limiting
Body’s protection mechanisms against fungi
Fatty acid content of the skin pH of the skin, Mucosal surfaces and body fluids Epithelial turnover Normal flora Cilia of respiratory tract
Superificial mycoses (infection)
Infections limited to the outermost layers of the skin and hair
Tinea versicolor, Tinea nigra, Black piedra, White piedra
Tinea versicolor (Etiological agent+Symptoms)
Malassezia furfur
Hypopigmented macules
Tinea versicolor (Lab ID)
“spaghetti and meatballs” appearance of organism in skin scrapings (KOH wet mount) -> round yeast cells surrounded by angular mycelia
Wood light examination - golden-white fluorescence
PAS
SDA - yeast colonies
Tinea versicolour (Risk factors + Treatment)
Blood group O, Addison's disease, steroid therapy, IV (parenteral) therapy -systemic Grows where skin+oil accumulates Treatment: Selenium Sulfide Shampoos Ketoconazole 2% shampoo /oral Imidazoles Terbinafine, Itraconazole, Fluconazole
Tinea nigra (Transmission + Etiological agent)
Etiological agent
Exophiala werneckii
Infection via inoculation
Tinea nigra (Symptoms+lab ID)
Smooth, flat lesions affecting palms Lab ID Microscopically after treatment with 10% KOH -branching septate hyphae SDA Black, moist and shiny mycelium; grows until 15 days -Budding; blastospores seen prominent darkly-pigmented septa
Piedra
fungal infection of the hair
-presence of stony hard nodules along the hair shaft
piedraia hortae (Black piedra) Trichosporon beigelii (white piedra)
-scalp, beard and mustache
Piedra Pathogenesis
Black piedra
-affects only the hairs of the scalp where it invades beneath the cuticle, then expands and ruptures to spread around the hair shaft, forming dark brown and black nodules
Trichosporon beigelii (White peidra)
-light brown soft nodules on the beard or mustache
-less firmly attached than those of black piedra
Piedra (Lab ID)
P hortae
-Grows after 20 days
-Dark thick walled hyphae
T beigelli
-SDA; rapid growth
- Creamy, slimy growth -> wrinkled+darker
-Hyaline hyphae, blastoconidia, and arthospores are seen on Tween 80
Cutaneous mycoses
Refers to certain fungal infection of the skin caused by dermatophytes
-Hair, skin, nails
-Trichophyton, Microsporum, Epidermophyton
-> Keratin metabolizing filamentous fungi
Microsporum - infections on skin and hair (not nail)
Epidermophyton - infections on skin and nails (not hair)
Trichophyton - infections on skin, hair, and nails. .
Dermatophyte infection
- lesion with outer ring of an active infection with central healing in the ring.
Dermatophyte infection - severity
(1) strains/spp of fungus involved
(2) sensitivity of the host to pathogenic fungus.
More severe reactions occur when a dermatophyte crosses non-host lines (e.g., from an animal species to man).
Dermatophyte saprophytic to a parasitic lifestyle
Geophilic species - keratin-utilizing soil saprophytes (e.g., M. gypseum, T. ajelloi)
Zoophilic species - keratin-utilizing on hosts - living animals (e.g., M. canis, T. verrucosum)
Anthropophilic species - keratin-utilizing on hosts - humans (e.g., M. audounii, T. tonsurans)
Cutaneous mycosis classification
Based on area of infection Tinea capitis Tinea pedis Tinea corporis Tinea cruris Tinea barbae Tinea unguium Tinea favosa
Tinea capitis (Spp+ID)
- Scalp+hair
- Trichophyton and Microsporum
- Microsporum canis and Microsporum audouinii (children) -> Grey patch ringworm -> hair glows under lamp
- Trichophyton tonsurans and Trichophyton mentagrophytes - black dot ringworm
- > infected hair does not glow
Tinea capitis (Transmission+Pathogenesis)
- Can spread from animals/people
- scaly, erythematous lesions, topical and sometimes deep, ulcerative, kerion like eruptions
- Lesions cause thinning hair which falls leaving dark stumps (Black dot)
Tinea capitis (Treatment)
-Must treat hair follicle -> topical ineffective
Griseofulvin (children)
Imidazoles, terbinafine.
Steroids for inflamed lesions like Kerion
Tinea pedis
- feet, mostly toe webs and soles
- Ttrichophyton mentagrophytes, Trichophyton rubrum and Epidemophyton floccosum
- floors of pools, tight shoes, men affected more
Tinea pedis - Clinical varieties
Intertriginous type
- slow developing fissuring between the 4th and 5th toe and spreading to others.
Hyperhydrosis and itching is common.
Squamous or hyperkeratotic type
- the soles, sides of the feet and heels - well-defined, red or purplish scaly patches
-secondary bacterial infection common.
Acute vesiculo-pustullar-bullous type - groups of deep pruritic vesicles,vesiculopustules and bullae.
-in step, midsole and heel
Tinea pedis - Treatment
Alternate shoes, Absorbent powders, Change socks
Topicals and/or Systemics.
Topical: naftfine more effective than azoles.
Steroids if inflamed.
Systemic allylamines or azoles
Treat secondary bacterial infections.
Steroids for severe inflammation and ID.
Tinea corporis
-Ringworm of body - simple scaling to deep granuloma
-Persons/soil
-Males affected more
Trichophyton rubrum ,
Trichophyton tonsurans,
Trichophyton mentagrophytes,
Microsporum canis,
Microsporum. audouinii and
Microsporum gypseum.
Tinea corporis - Clinical manifestations
Anular type - lesion center is inactive, pink scaly, margin is active, raised and reddish
Hypertiform variety - small vesicular lesions studded together with many micropapules and vesicles.
Plaque form scaly red - plaques with pronounced vesiculation and crusting
Kerion type - also called Tinea profunda; deep granulomatous lesions
Tinea corporis (Treatment)
All forms of tinea corporis caused by T. rubrum, T. mentagrophytes, T. tonsurans, M. canis, and M. audouinii
are treatable with topical agent containing ketoconazole, miconazole
Tinea cruris
- groin, perineum and perianal region
- Epidermophyton floccosum and Trichophyton spp
- Transmission: public toilet seats, sex, laundry, feet fungus
- elevated, bilateral lesions
Tinea cruris (Treatment)
Ketaconazole, miconazole
Tinea barbae
- Trichophyton and Microsporum
- bearded area of the face and neck
- Superficial lesions
- cattle to man
Tinea barbae (Features)
- Brittle/lusterless hair
- Deep type of infection - deep follicular pustules, which result in abscess formation
Tinea unguium
- nails
- Trichophyton rubrum, Trichophyton mentagrophytes and Epidermophyton floccosum
- Transmission - soil
Tinea unguium (clinical feature)
- begin distally/at the lateral edge of the nail
- nail yellow/white/brown and pitted
- Toenail affect more
- Onchomycosis - infections of nail not caused by Dermatophytes e.g. Candiasis
Tinea unguium (treatment)
Debridement of infected area helps penetration / comfort. Mechanical Urea products (ex carmol)
Topical Treatment:
Can be effective for limited involvement and for prevention.
Agents
Mycocide Nail solution
Oral therapy
Effective. Relapse rate 15-20 % in one year.
Itraconazole 200 mg /day. 6 weeks/12 weeks
Tinea favosa
- chronic fungal infection caused by Trichophyton schoenleinii, Trichophyton violaceum or Microsporum gypseum
- scalp
- yellowish, cup-shaped crusts with “mousy” odor.
- starts off small and develops into cup shape
- Can lead to balding if untreated
Tinea favosa vs Tinea unguium
Tinea favosa of the nail is undistinguishable from other forms of tinea unguium.
General Lab ID
Spaghetti meatball appearance is classical for yeast
The most common pathogen for tinea capitus used to be microsporoum. It is now T. Tonsauran thus render wood’s light useless
Trichophyton schoenleinii
Trichophyton schoenleinii
Endothrix infection of hair
- large inverted cones of hyphae and arthroconidia at the base of the hair follicle
-branching hyphae throughout the length of the hair shaft.
No conidia (micro- or macro-)
Trichophyton violaceum
Trichophyton violaceum
Attacks hair, scalp, skin and nails.
Nail infections are persistent.
Endothrix (hair shaft infection)
-Rarely produces microconidia and macroconidia.
-Hyphae coarser in appearance than seen in other dermatophytes.
Chlamydoconidia are seen in culture
Microsporum audouinii
Microsporum audouinii
Usually devoid of conidia (macro- or microconidia).
Bizarre - shaped macrocondia:
-thick walled club or spindle shaped,
-multiseptate, with rough surface microconidia
-rare, terminal chlamydospores.
Septate hyphae with terminal chlamydoconidia, often pointed at the end
Specimen
Dermatophytes
Specimen: skin scrapings, nails, hair
Diagnostic characteristics: Septate hyphae/spherical yeast cells depending on etiological agent
Blastomyces dermatitidis
Specimen: Pus, sputum, skin sample
Diagnostic characteristics: Large Yeast cells
-dimorphic fungus with yeast cells in tissue.
Diagnosis of Dermatophytosis
Basic diagnostic techniques
KOH (skin-look for hyphae, culture nails, look for spores in hair w + w/o KOH)
-Growth inside hair shaft (endothrix)
-Growth inside and outside hair shaft (ectothrix)
Culture
Woods light(T.capitis)
Microsporum audouinii (Dermatophytes ID)
Usually devoid of conidia (macro/microconidia). Bizarre - shaped macrocondia: club or spindle shaped, multiseptate, with rough surface ---microconidia rare, terminal chlamydospores.
Microsporum canis
Thick walled, spindle shaped, large,
multiseptate rough walled macrocondia
with curved tip and knobby projections
— sparse microconidia: clavate (club-shaped),
smooth walled, and literally attached hyphae
Microsporum gypsum
Numerous, thick –walled, cigar -shaped
multiseptate macroconidia with spiny surface and rounded tips
—- sparse, clavate, smooth –walled micorconidia
Trichophyton
arthrospores in parallel rows inside the hair (endothrix type)
or in parallel rows outside the hair (ectothrix type)
and in chains of small arthrospores
or chains of large arthrospores
Trichophyton mentagrophytes
Microspores: arranged in small grape like clusters,
- -coiled, spiral hyphae may be observed
- –macrocondia: rare, thin walled, smooth and cigar shaped.
Trichophyton tonsurans
Microconidia: Abundant tear, club -, or balloon-shaped
Macrocondia: rare smooth walled, cylindrical.
Trichophyton rubrum
microconidia: Tear shaped bore laterally form long strands of hyphae
Macrocondition: rare, thin-walled, smooth, pencil –shaped.
Trichophyton verrucosum
Large-spored ectothrix.
chains of chlamydoconidia and antler-like hyphae.
small microconidia and occasionally macroconidia are produced.
Trichophyton schoenleinii
Endothrix infection of hair
-large inverted cones of hyphae and arthroconidia at the base of the hair follicle
and branching hyphae throughout the length of the hair shaft.
No conidia (micro- or macro-)
Trichophyton violaceum
Endothrix
Rarely produces microconidia and macroconidia.
Hyphae coarser in appearance than seen in other dermatophytes.
Chlamydoconidia in culture
Epidemophyton floccosum
Many club-shaped, smooth walled macroconidia with two to four cells in clusters
microcondia absent
Fungal Cultures
DTM (Dermatophyte Test Medium)
Yellow to red is (+).
Sabouraud’s Media
Molds
