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Biology of FUNgi

Lecture 21The Ugly - localized disease-causing

fungi

Flashback - fungitoxins

Toxins you should know about

The deadly

Group I: Amatoxin and phyllotoxin (cyclicpeptides) containing species.Group II: Orellanin (cyclic peptides) containingspecies.Group III: Gyromitrin (monomethyl hydrazine -MMH) containing species.

GalerinaautumnalisAmanita phalloides

Cortinarius alboviolaceous

Gyromitra esculenta

Gyromitracaroliniana

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Flashback - fungitoxinsToxins you should know about

Silly heads

Group IV: Muscarine containing species.

Group V: Ibotenic acid and muscimol(mycoatropines) containing species.

Group VI: Psilocin and psilocybin (indolederivatives) containing species.

Tummy aches

Many of the above

Group VII: Mixed bag of GI-irritants

Amanita muscaria

Amanita pantherinaAmanita muscaria

Psilocybe cubensisPsilocybecyanescens

Last time...

• Inhaled fungitoxins - Stachybotrys.

• Allergens - various indoor fungi.

• Ingested fungitoxins - aflatoxin,trichothecenes

• Poisonous mushrooms.

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Fungus of the day -Ajellomyces capsulatus

Taxonomy: Phylum (subphylum) Ascomycota Order - Onygenales (Cleistothecial) Family - Onygenaceae

Ajellomyces capsulatus is better known for itsanamorph – Histoplasma capsulatum.

A. capsulatus is the causal agent ofhistoplasmosis.

Dimorphic fungus, which is filamentous on solidsubstrates and unicellular in liquid substrates.

Temperature has an impact on the growth formas well.

Histoplasma capsulatum macro-and microconidia.

Histoplasma capsulatumunicellular yeast growth.

Fungus of the day -Ajellomyces capsulatus

Histoplasma capsulatum infection ispulmonary, but systemic infections mayinvolve cutanous symptoms.

Pulmonary infection is often a result ofinhalation of spores.

Fungus is soil-borne but inhalation risk isgreater if you are exposed to bird and/or batdroppings.

The pulmonary infection can result in systemicinfection as Histoplasma spores aredisseminated through the bloodstream.

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Fungus of the day -Ajellomyces capsulatus

Histoplasma capsulatum infection is often benignand asymptomatic.

Pulmonary symptoms include dry cough, chestpains, fever and fatigue. The chronic infection issimilar to tuberculosis with bloody cough.

Symptoms may vary widely. Systemic(throughout the body) infection symptomsinclude enlarged liver and spleen, mouth andgastrointestinal sores, possibly also death.

Necrotic lesions in the lung x-ray andbiopsy. Lesions indicate individualHistoplasma colonies.

LesionHistoplasma colonies

Lesion

Although initially pulmonary, systemic histoplasmosisinvolves lesions in almost every possible organ in thebody and includes cutanous infections.

Fortunately, 95% of the cases are benign andsubclinical.

The 5% become chronic infecting cutaneous tissuesand/or lungs and may rapidly turn into fatal systemicinfections.

Cutanoushistoplasmosis lesions

Pulmonary histoplasmosis

Fungus of the day -Ajellomyces capsulatus

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Fungus of the day -Ajellomyces capsulatus

How common is histoplasmosis?

Almost 90% of the people living in theMississippi, Missouri and Kansas River valleyshave a chronic pulmonary Histoplasmainfection.

This equals 40,000,000 americans testingpositive for histoplasmosis.

These are mainly benign infections, causingonly lesions in the lungs and no acutesymptoms.

Histoplasma distribution based on thehome of nearly 300,000 navy recruits.

Histoplasma capsulatum, conidialstage of the etiologic agent.

Histoplasmosis was brought to the spotlights when Bob Dylan contractedpulmonary histoplasmosis, which thenturned systemic.

In benign cases, no treatment is necessary.Rest is recommended.

Acute, severe cases, like Dylan’s, requireextended treatments with systemicfungicides.

Bob Dylan introducedhistoplasmosis to the greateraudiences.

Fungus of the day -Ajellomyces capsulatus

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Topics of the day...

• Localized mycoses of the skin

– Superficial

– Cutanous

– Subcutanous

The Ugly - disease-causing fungi

• Fungal diseases may not be particularlydiverse, but they are ubiquitous.

• In addition to true disease-causing fungi,there is a whole number of common indoorand outdoor fungi which are opportunisticcolonizers of immunocompromized patientsor organ transplant recipients.

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The Ugly - disease-causing fungi

• For convenience and clarity we will dividethe fungal diseases into five differentgroups:– 1) Superficial mycoses

– 2) True dermatophytoses

– 3) Subcutanous mycoses

– 4) True systemic mycoses

– And, 5) opportunistic fungal infections.

The Ugly - superficial mycoses

Primarily cause just cosmetic effects.

Otomycosis - symptoms include itching anddeposits of epithelial debris (+masses ofbacteria and fungi) on ears.

Piedra - fungal infection of hair.

Black piedra: The piedra symptoms includesmall stony nodules on hair.

Black piedra appears exclusive to scalp, i.e.,not in the pubic hair or beard.

Piedraia hortai - black piedra onhair and in pure culture

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The Ugly - superficial mycoses

White piedra: Like black piedra, smallstony nodules on hair.

As opposed to black piedra, white piedraappears exclusive to the hair of beard andmustache.

Both piedras occur world-wide.

The fungi can easily be brought into pureculture from colonized hair. Convenient!

Trichosporon beigelii - white piedra onhair and in pure culture

The Ugly - dermatophytoses

Infection of keratinous tissues (nail, skin) invarious parts of the body.

The diseases are known as tineas: Tinea capitis(head), Tinea manuum (hand), Tinea pedis(foot), Tinea corporis (body).

The common name for tineas is ringworm.

Various anamorphic species: e.g. Microsporum,Trichophyton.

Microsporum audoninii - colony andphragmosporic conidia

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The Ugly - dermatophytoses

Microsporum spp: Anamorphic genus with anumber of species infecting animals andhumans. Microsporum spp. can be found inany part of the body: scalp, beard (or face),or body.

Microsporum may be among the mostcommon soil isolated keratin-utilizing fungi.

Tinea capitis, the ring worm. Fungalcolonies form concentric rings from theinfection point outwards.

The Ugly - dermatophytoses

Trichophyton spp: Another anamorphicgenus with a number of species infectingskin, hair and nails of especially feet andtoes. Infection may result in a variety ofsymptoms including lumpy colonies in theinfected areas.

Like Microsporum, Trichophyton is oftenisolated from soil. Trichophyton, too, can bebaited with keratinized tissues from soil

Trichophyton tonsurans - a causal agentof many tineas.

Tinea pedis caused by Trichophyton sp.

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The Ugly - subcutanous mycoses

Subcutanous infections are most commonlyassociated with traumatic implantation intothe skin.

Usually the infection remains localized orslowly spread from the site of implantation.

Some of these infections may spread throughthe lymphatic channels to other parts of thebody (e.g. Sporothrix; Ophiostomatales).

True systemic infections most frequentlyenter the body through the pulmonary route.

Typical mode of entry for thesubcutanous mycoses.

Systemic Exophiala infection in animmonocompromized child.

The Ugly - subcutanous mycoses

Mycetoma: Mycetoma is a chronic granularinfection of, most often, feet. The disease is bestcharacterized warty outgrowths enlargement,deformity and bone destruction.

Several etiological agents may be involved, bothfungal and actinomycetous. Depending on theetiological agent the granule color may be blackor white.

Mycetoma of the foot. Lumps areusually clusters of fungalsclerotia (resting structures), thegranules.

Cross section of tissue containing blackgranules

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The Ugly - subcutanous mycoses

To provide a few examples of fungi causingmycetomas and to gain appreciation for theirdiversity, Acremonium sp., Fusarium sp.and Pseudallescheria sp. produce whitegranules.

Fusarium sp. conidiophore.

Pseudallescheria boydii cleistothecium White sclerotia inmycetomatous foot tissue

The Ugly - subcutanous mycoses

Others produce black granules.

Examples of those include Curvularia sp.,Exophiala sp. and Leptosphaeria sp. Curvularia verruculosa conidiophore.

Black sclerotia inmycetomatous foot tissue

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The Ugly - subcutanous mycoses

Chromoblastomycosis: Fairly commonsubcutanous fungal infection.

Chromoblastomycoses are typically localized,chronic skin and subcutaneous tissueinfections.

These differ from mycetomas by more oftenproducing ulcerating warty or tumor-likelesions.

Fungal cells inchromoblastomycoticlesion tissue.

Chromoblastomycosis on foot,note the ulcerating lesions.

The Ugly - subcutanous mycoses

Chromoblastomycosis: Like mycetomas,chromoblastomycoses mainly infect thelower extremities but may also occur in faceor neck area.

Chromoblastomycosis on foot, note theulcerating lesions.

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The Ugly - subcutanous mycoses

Chromoblastomycosis: There are five mainetiological agents for chromoblastomycosis:Fonsacea pedrosi, F. compacta, Phialophoraverrucosa, Cladosporium carrionii,Rhinocladiella aquaspersa.

All these have global distribution and are fairlycommon

These are dematiaceous (dark colored, melaninpigments in the cell wall) and occur commonly insoil.

They are introduced, typically to subcutaneousinfections, by splinters or skin abrasion.

Fonsacea pedrosi melanized,anamorphic causal agent ofchromoblastomycosis

Phialophora verrucosa also amelanized anamorph

The Ugly - subcutanous mycoses

Sporotrichosis: Sporotrichosis is manifested asnodular lesions and ulcers in the lymphaticsystem, skin, or as subcutanous tissues.

Sporotrichosis may also involve primarypulmonary infection.

Although mostly known to occur as localizedlesions following a trauma in hands arms orlegs, disseminated infection may involve alsobones, joints and central nervous system.

The dissemination occurs through bloodstream.

Sporotrichosis primary lesionafter trauma.

Sporotrichosis nodularlesions

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The Ugly - subcutanous mycoses

Sporotrichosis: The etiological agent Sporothrixschenkii, an anamorph of a perithecial ascomycete(member of Ophiostomatales).

Sporothrix schenkii commonly occurs in soil, woodor vegetation.

It can be injected through wounds from infectedsplinters, or the can be conidia inhaled causing asubcutanous infection in the lungs.

Sporothrix schenkii cultureand conidia.

Summary

• Fungal infections of skin

– Superficial infections (Piedras)

– Cutanous infections (Tineas)

– Subcutanous infections (Sporotrichosis,Mycetomas, and Chromoblastomycoses)