Lec40 Fungi II Flashcards
When you see broad ribbon-like hyphae with right angle branching what should you think?
zygomycetes
What is pathogenesis of mucormycosis?
- invades into blood vessels
- destroys tissue
- wide, nonseptate ribbon-like hyphae with white right angle branching
- move from nasal/palate area up into brain
What are two other names for mucormycosis
- phycomycosis
- zygomycisis
What are the types of zygomycetes fungi? which most common?
- rhizopus, absidia, apophysomyces, mucor, rhizomucor, cunninghamella
- rhizopus oryzae and rhizopus rhizopodiformia cause most cases
What are risk fators for rhinocerebral mucormycosis?
- DM [especially DKA]
- desferoxamine therapy [treatment for iron overload]
- neutropenia
- bone marrow recipients
What is mech by with hyperglycemia DKA increase risk of mucormycosis?
- have impaired phagocytic chemotaxis toward organisms
- impaired killing by oxidative/non-oxidative mech
- increased level of serum iron because iron released from binding proteins in acidosis
- iron plays role in increasing virulence of the fungi
What is a mech by which mucormycosis can supply its own iron?
- rhizopus species use deferoxamine [an iron chelator] as a siderophore to be able to make previously unavailable iron available to the fungus
What are the two common manifestations of mucormycosis? where else can it manifest?
- rhinocerebral disease
- primary cutaneous infection
- can also manifest in lungs, GI, disseminated infection
What is path of primary cutaneous zygomycete infection? how is it transmitted? risk factors? symptoms?
- due to direct innoculation
- may follow surgery, burn wound, trauma, associated with non-sterile bandages
- characterized by black, necrotic lesions
How do you treat zygomycete infections?
- aggressive surgical debridement + adjunct therapy with amphotericin
- posaconazole oral for prevention
What are properties of aspergillis?
- septated hyphae with acute angle branching
- ubiquitous spore-bearing fungus, septate hyphae, 45 degree branching
- grows in air ducts, decaying wood, organic matter
- culture shows fruiting head on lactophenol blue stain
Can voriconazole treat zygomycetes?
no! just aspergillus
Who is at risk for aspergillus
- immunocompromised, recent transplant
- neutropenia
What is the most common invasive mold infection worldwide?
aspergillus
Where does aspergillus live in nature?
- in air ducts, decaying wood, organic matter, house plants, soil
What are most common aspergillus species?
- A. fumigatus [most common]
- A. flavus
- A. niger
- A terreus
- A nidulans
What are clinical manifestations of aspergillus?
- allergic bronchopulmonary aspergillosis [ABPA] [wheezing, cough]
- aspergilloma [fungus ball in lung, usually in pt who used to have TB]
- invasive pulm and systemic disease in immunocompromised
- primary cutaneous infections in immunocompromised
What makes aspergillus unique from zygomyctes?
- thinner
- more acute angle branching
- contain cross walls/septa
What are signs of invasive pulmonary aspergillosis? who get it?
- in people with depressed immune system
- central area of necrosis surrounded by hemorrhage = nodule
- mass of sepate with acute angle branching
- hyphae within blood vessel see in silver stain –> thinner than zygo.
- “coin” lesions = hemorrhage in lung
- most infections associated with lung
What are signs of primary cutaneous aspergillosis? pathogenesis?
- can be primary [from direct inoculation] or secondary [via dissemination from lung or other site]
- associated with adhesive tape and arm boards
- usually in pts with hematologic disease, neutropenia
- signs: erythmatous macules, papules, plaques evolving to ulcerations with central necrotic eschars
How is asperigillosis transmistted?
- via inhalation of conidia
What is pathogenesis of invasive aspergillosis infection and immune response?
- conidia inhaled and lodge in lower resp
- macrophages try to block conidia
- conidia germinate into hyphae
- neutrophils try to block
- hyphae invade tissues
- neutrophils try to block
- hyphae invade blood + disseminate
What is treatment for aspergillus?
- voriconazole [better side effect] or amphotericin for invasive disease
What determines survival of invasive aspergillus disese?
determined by immune recovery
How is pneumocystis jiroveci diagnosed?
- cannot be grown in culture
- diagnosed based on morphology or direct fluorescence antibody [DFA]
- stain with silver stain to see cells
what are signs of pneumocystis jiroveci pneumonia?
- patchy alveolar infiltrates
- filling of alveolar space with proteinacious material –> impaired gas exchange
- get large cysts that appear on lungs that can sometimes rupture
What is a possible severe complication of pneumocystis jiroveci?
pneumothorax
How does pneumocytis replicate?
- sexually or asexually
What is treatment for pneumocystis?
- trimethoprim-sulfamethoxazole [bactrim] at high dose [usually IV]
- add steroids for pts with significant hypoxia
- prophylaxis with TMP/SMX for pts with CD4 <200
What are side effects of bactrim?
- rash
- renal failure
- hyperkalemia
- bone marrow toxicity
- increased liver function test
What are examples of common topical dermatophytes?
- athletes foot
- dandruff
- ringworm
- pytiriasis versicolor
who gets pneumocystis?
- mostly HIV
- also other immunocompromised [transplant], people with high doses of steroids
What is tinea pedis?
- topical dermatophyte = athlete’s foot, in warm wet sneaker
- causes pruritic infection in intertriginous infection
How do you treat tinea pedis?
- topical antifungals: miconazole, tolnaftate
What are tinea cruris?
- similar to athletes foot lesions but in groin = jock itch
What is disease associated with trychophyton rubrum? how do you treat?
- fungal onchomycosis = toenail fungus
- difficult to treat with topical antifungals
- sometimes use systemic terbinafine [lamisil]
What is disease associated with tinea corporis?
= ringworm [a fungus not a worm]
What are taenia?
taenia = tapeworms = cestodes –> acquired by eating undercooked parasitized meat [beef, pork, fish, etc]
What causes ringworm?
- tinea corporis
- also tricophyton species [verrucosum]
What is pityriasis versicolor?
- superficial dermatophyte
- infection characterized by hypo or hyperpigmnetation
What causes pityriasis versicolor?
malassezia furfur
How do you diagnose malassezia furfur?
- diagnose of scraping stained with KOH shows both yeast and hyphal forms = spaghetti and meatballs
How do you treat pityriasis versicolor?
- topical antifungals: miconazole, tolnaftate
How can you diagnose topical dermatophytes?
- visualize hyphae by staining with KOH or calcafluor white
What are subcutaneous fungal infections?
- involve dermis and subcutaneous tissue
- mostly in tropics
- infection enters skin via local trauma
- rarely disseminate but more at risk for immunosuppressed
What is mycetoma “madura foot”?
- fungi like madurella
- could also be caused by actinomyces
What causes eumycetoma?
fungal agents –> madurella species [madurella mycetomatis, madurella grisea]
What causes actinomycetoma?
actinomyces including nocardia
What does eumycetoma mean?
fungal colony underneath surface of skin
How do you treat madurella grisea?
- treat with surgical removal, amputation
- sometimes treat with posaconazole
- poorly responsive to traditional antifungal therpay [itraconazole, amphotericin B]
Who gets eumycetoma? how does it present?
- slowly progressive subcutaneous infection
- fungal granules = black with coarse texture
- seen in farmers
What is sporotrichosis associated with?
rose gardening, rose thorns
What is pathogenesis of sporotrichosis?
- prick finger with rose thorn
- get fungus infection there, spreads up arm lymphangitically
What are signs of sporotrichosis?
- characteristic lymphangitic spread of red rash up the arm
What causes sporotrichosis?
sporothrix schenckii
How do you treat sporothrix schenckii?
- sporonox [itraconazole]
What is exophiala jeanselmei? how does it present?
- dematiaceous [pigmented] fungi
- cause of phaeohyphomycosis
- presents as solitary sometimes cystic subcutaneous nodule on distal extremity
What are the three dematiaceous fungi?
- exophiala jeanselmei
- hoartaea werneckii
- exophilaa spinifera
What caused recent fungal meningitis outbreak?
exserohilum rostratum
What are properties of Paecilomyces?
- ubiquitous saprophytic organism
- example of non-pigemented fungi [hyalohyphomycoses]
What disease is paecilomyces associated with?
- sometimes recovered as contaminant in pulmonary specimens
- device infections and infections in immunocompromised hosts
