Fungi Classification (Subcutaneous) Flashcards
Subcutaneous
- initially involve the deeper layers of the dermis, subcutaneous tissue or bone
- Mostly chronic
- Extends to epidermis; not systemic
- Lesions
- Transmission: skin trauma; humans are accidental hosts
- Treatment: Difficult; surgery often used
Subcutaneous mycoses
Sporotrichosis Maduromycosis Phaeohyphomycosis Chromoblastomycosis Rhinosporidiosis
Sporotrichosis (rose gardener’s disease)
Sporothrix schenckii- dimorphic fungus -Chronic -Soil, wood, plants -Inoculation/ inhalation/ handling contaminated dressing (not person to person)
Types of sporotrichosis
Fixed cutaneous sporotrichosis
Lymphocutaneous sporotrichosis
Fixed cutaneous sporotrichosis
- Primary lesions at implantation site
- Start off painless then become large ulcerate
- Fluid discharged
- Localized lesions; no spread to lymphatic channels
Lymphocutaneous sporotrichosis
- Primary lesions at implantation site
- Secondary lesions along lymphatic channels
- Painless nodules -> small ulcerate
- Dissemination rare; pulmonary infection if occurs
Specimen - Sporotrichosis
Specimen: unopened subcutaneous nodules / open draining lesions
Direct examination - Sporotrichosis
Reveals yeast cells (unicellular reproduced by budding)
Blood agar and sabouraud’s glucose agar slants
Antibiotic media
Animal inoculation
Colonies
Small, white -> Moist, wrinkled
Colours variable
-Cream to black
-Pigment changes when transferred to new media
Sporotrichosis - Hyphal vs Yeast form
Hyphal form
(2µ in width), branching, septate hyphae bear conidia laterally or in groups from the ends of lateral branches.
2 to 4 µ by 2 to 6µ in size
Yeast form
Use: Francis’ cystin blood agar or brain- heart infusion glucose blood agar
-develop grayish-yellow, soft-bacteria- like colonies
Sporotrichosis - Microscope
cigar shaped,
round, oval and budding cells,
Gram positive
Sporotrichosis - Treatment
- Saturated KOH (good treatment response) 4-6ml 3 times per day
- Itraconazole 400mg/day or terbinafine 250mg/day
- Treatment for 1 month after cured
Maduromycosis
- Eumycotic (true fungus)
- Affects feet
- Infection resembles actinomycetes (fungi like bacteria) infection
Maduromycosis vs actinomycotic mycetoma
-Organisms invade body for maduromycosis+actinomycotic mycetoma
-lesions in the
brain,
the meninges
bones.
Maduromycosis features
-Chronic
-swelling of tissue (tumefaction)
-feet, hands, butt
Allescheria boydii, can invade the blood stream in the rare instances and cause lesions of the
brain, meninges,
lungs, sinuses,
prostate, bones and other internal organs.
Maduromycosis Etiology
- minor scratch, splinter
- Six fungi spp <= Etiological agent
- Mostly Saprophytic fungi in soil/plant e.g. Allescheria boydii
Maduromycosis Pathogenesis
1) Papules form first
2) Then abscesses form and envelop the foot
3) Infection can extend deeper into tissue
- Club shaped hands/feet, discoloured skin, pitted scars, nodules with oily fluid, white/yellow/black granules
Maduromycosis - etiology
Ascomycetes:
allescheria
Leptosphaeria,
Fungi imperfecti: Madurella, cephalosporium, Phialophora pyrenochoeta, Monosporium opiospermum
Actinomycotic mycetoma
“Lumpy-jaw” - The initial nodules formed are firm and described as “woody” or “lumpy.“
Nocardia spp. & Streptomyces spp
Maduromycosis - Direct exam
Sample
Pus from multiple draining fistulas or aspirated from un opened fluctuant areas in petri dish
- Direct exam - look for “grains” - yellow, brown, black , white
-Using a drop of water or 10% KOH
Grains contain- wide hyphae with hyphal swelling Chlamydospores
**should not be mistaken for the granule seen in actinomyeotic mycetoma ***
Maduromycosis media
sabouraud’s glucose agar at rtp
Allescheria boydii
large, round to lobulated White to yellowish Rapid growth; white, cottony mycelium Asexual conidia Produced singly on conidiophore ends/sides of mycelium
Phialophora jeanselmei
Grain may be crescent shaped, round or ovoid Brown Olive-black colony -> overgrown with olive-gray mycelium - Budding on primary culture - Spores on conidiophore tips
Treatment - Maduromycosis
Sulfonamide may help the actinomycotic form.
There is no effective drug against the fungal form; surgical excision is recommended.
Phaeohyphomycosis
any infection caused by a dematiaceous organism (black yeast)
-subcutaneous, localized, or systemic
Paeohyomycosis vs Chromoblastomycosis and mycetoma
Phaeohyphomycosis is distinguished from chromoblastomycosis and mycetoma by the absence of specific histopathologic findings such as grains in tissue.
Paeohyomycosis - Etiology
Common etiological agents of subcutaneous infection include: Exophiala jeanselmei Phialophora richardsial Wangiella dermatitidis Alternaria spp. Bipolaris spp. Exserohilum spp.
Subcutaneous phaeohyphomycosis
-Cystic lesions
Paranasal sinus phaeohyphomycosis
Bipolaris, Exserohilum, and Alternaria
Cerebral phaeohyphomycosis
In immunosuppressed patients following the inhalation of conidia.
Direct examination
observation of pigmented hyphae in hematoxyline-eosin or unstained histopathologic sections
-> yellowish –brown septate, moniliform hyphae
Exophiala jeanselmei - Lab ID
Exophiala jeanselmei:
grow at 370C not at 400C
can utilize inorganic KNO3
grow slowly (7 to 21 days)
produces- shiny black, yeast like colonies initially.
With age, colonies become filamentous, velvety, and gray to olive to black.
Wangiella dermatitidis
Wangiella dermatitidis
cultures can grow at 400C and cannot utilize KNO3 in contrast to E.Jeanselmei
Cultural characteristics the same to E.Jeanselmei
- dematiceous (dark) budding yeasts -young colony
- dematiceous hyphae + conidiogenous cells (conidia forming) + tapered tips
Phialophora richardsial
Phialophora richardsial
- Dematiaceous (dark-hyphae) organism
- Rapid growth
- Olive brown to brownish gray colonies
- Brown elliptical conidia within phialides (projection from mycelia)
Chromoblastomycosis (chromomycosis,
verrucous dermatitis)
variety of dematiaceous fungi
- formation of warty cutaneous nodules which develop very slowly
- papillomatous vegetations (tumor)
- Lesions in lower extremities mostly
- Tissue trauma
Chromoblastomycosis - Etiology
Fonsecaea pedrosoi,
Fonsecaea compactum and
phialophora verrucosa are the three most familiar fungi
Chromoblastomycosis - Pathogenesis
- begins as a small, itchy papule which extends eccentrically and simulates a patch of ring worm
- Months later -new lesions appear along the paths of the superficial lymphatic drainage
- Cauliflower like appearance
Fibrosis
-Scar healing in connective tissue
Chromoblastomycosis - complications
Extensive fibrosis develops in the deeper tissues and the lymphatics become blocked producing elephantiasis of the extremity.
- Painless lesions unless secondary bacterial infection
- Spontaneous lesion healing sometimes
Chromoblastomycosis - lab ID
Skin scrapings -10% KOH and calcofluor white mounts Tissue sections -stained using H&E, and GMS Interpretation -Brown, sclerotic (cigar shaped, thick) bodies -Multiply by splitting not budding
Differentiate between Chromoblastomycosis and Phaeohyphomycosis
-causative agent is mycelial for Phaeohyphomycosis and gains presents where chromo has sclerotic bodies
Fonsecaea pedrosoi - strains
-slow- growing dark brown to black colonies
Microscopically, different strains of F.pedrosoi vary greatly based on method of conidial formation
three different methods of sporulation are recognized.
–ACP–
Arthrotheca type:
Terminal (end)cell/single lateral branches on hyphae
Swollen cells become knotted clubs that bear conidia
Cladosporium type:
Conidiophores of diff lengths bear conidia in branching chains
Single celled conidia connected via thick disjuncture
Phialophora type:
Flask-shaped conidiophores with - terminal cuplike structure bearing conidia groups
Fonsecaea compactum
- slow growth
- short mycelium
- terminal+lateral conidiophores with short+long branching chains of subspherical (not perfectly spherical) conidia
Phialophora verrucosa
-slow growth
-greenish-brown; mat-like aerial mycelium
-Microscopically: Lateral/terminal conidia from cups at conidiophores
Flask shaped conidiophores
Chromoblastomycosis - Treatment
Surgery Antifungal therapy (susceptibility varies depending on the genus) Amphotericin B Flucytosine Ketoconazole Heat
Rhinosporidiosis
Rhinosporidium seeberi
- Infection of the mucous membranes of the nose, eyes, ears, larynx and occasionally the vagina, penis and skin
- Organism has not been cultured/inoculated successuflly
- occurs spontaneously in horses, mules and cows
- May be carried via water
- Children+young adults
Rhinosporidiosis - Symptoms
First symptom: pain less itching sensation in the nose with profuse mucoid discharge.
Tumor masses then become pedunculated (attached) by constriction at base
-Globoid swellings on anterior area of nose
-If growth occurs in posterior nares/nostrils
—May project into posterior pharynx
Rhinosporidiosis - Complications
- Nasal obstruction, dyspnea due to swellings in posterior pharynx+larynx
- vaginal+rectal infections resemble condylomata, hemorroids/rectal polyp
- Lesions can persist for 35 yrs
Rhinosporodiosis - lab ID
Direct examination
Specimen: polypoid mass
Result: Sporangia and spores (round-ovoid spores 7 to 9 μ , spore filled sporangia)
Rhinosporidiosis - Treatment
Surgery
Ethylstilbamidine
(Local injection)
