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Microbiology Part 2 > Lec39 Fungi > Flashcards

Lec39 Fungi Flashcards

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1
Q

What are the medical classifications of fungi?

A
  • systemic dimorphic endemic fungi
  • opportunistic fungi
  • superficial dermatophytes
  • subcutaneous mycoses
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2
Q

What are examples of systemic dimorphic endemic fungi?

A
  • histoplasma
  • coccidioides
  • blastomyces
  • paracoccidioides
  • penicillium
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3
Q

What are examples of opportunistic fungi?

A
  • candida
  • cryptococcus
  • aspergillus
  • mucorales
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4
Q

What are examples of superficial dermatophytes?

A
  • trichophyton

- malassezia

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5
Q

What are examples of subcutaneous mycoses?

A
  • sporothrix

- madurella

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6
Q

What are general properties of systemic dimorphic endemic fungi

A
  • can disseminate throughout blood stream, can exist as yeast and mold, often associated with certain geographic areas
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7
Q

What is the structure of fungi?

A
  • type of eukaryote
  • has true nucleus and organelles [dif from bacteria]
  • has cell wall made of primarily chitin
  • cell membrane is made of ergosterol instead of cholesterol
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8
Q

What should you think when you see cryptococcus neoformans?

A

meningitis in HIV pt

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9
Q

What is mech of action echinocandins?

A

inhibit synthesis of fungal cell wall

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10
Q

What is mech of action azoles/allylamines?

A

inhibit ergosterol syntehsis of cell membrane of fungi

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11
Q

What is mech of action flucytosine?

A

inhibits nucleic acid synthesis

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12
Q

What fungus is associated with pts receiving total parenteral nutrtition [TPN] through some sort of central line?

A

candida albicans

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13
Q

What are properties of candida albincans

A
  • unicellular yeast –> replicates by budding + mitotis
  • form pseudohyphae
  • can be used to form germ tube
  • can also form true hyphae
  • sometimes form chlamydospores
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14
Q

What are pseudohyphae?

A

chains of individual budding cells with constrictions = similar to hyphae but never completely separated

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15
Q

What is a germ tube?

A

elongated hyphal appendage from yeast cell to first constriction
sign of candida albicans

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16
Q

What are hyphae?

A

continuous tubes with septae separating each nuclei, no indentation at site of constriction

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17
Q

What is a chlamydospore?

A
  • the life stage that survives in nutrient deficient media or in poor conditions
  • terminal doublewalled cell arising from hyphae
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18
Q

What is immune rxn to mucosal candida?

A
  • cell mediated immunity predominates for mucosal, chronic muco-cutaneous or GI candidiasis
  • thus if you have lack of cell mediated immune [HIV] get mucosal candida [oral/esophageal]
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19
Q

What are common sites of candida in pt with normal immune?

A
  • vulvovaginal candidiasis [especially after antibiotics eradicate normal flora]
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20
Q

What disease associated with vulvovaginal candidiasis?

A

yeast infection! especially after antibiotics eradicate normal flora

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21
Q

What disease associated with cutaneous candidiasis?

A
  • diaper rash in infants
  • rash in warm/moist areas [like under breast] especially in diabetic or person just recently had antibiotics
  • fungal infection in nail plate [rarely]
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22
Q

Which species of candida most common in blood stream infection?

A

C. albicans = 46% MAJOR ONE
C. glabrata = 20%
C. parapsilosis = 14%
C. tropicalis = 12%

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23
Q

What is pathogenesis of candida bloodstream infection? What are some endpoint diseases?

A

pt recently on antibiotics, currently has catheter
- can cause: yeast form on heart valve, miliary abscesses in kidney, disseminated skin lesion, splenic candidiasis, endophtalmitis

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24
Q

37 yo F with severe aplastic anemia, neutropenic, thrombocytopenic, received anti-thymocyte globulin and cyclosporine, find multiple hepatosplenic abcesses and white lesions on liver

A

candida albicans

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25
Q

Who generally gets systemic candidiasis?

A

pts with - prolonged neutropenia, catheters, parenteral nutrition, broad spectrum antibiotics

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26
Q

Who gets mucutaneous disease?

A

can happen in immunocompetent hosts but way more frequent in pts with AIDS

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27
Q

How do you treat candida?

A

fluconazole when possible

amphotericin or echinocandins for non-albicans

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28
Q

How do you diagnose candida?

A

blood culture or direct visualization on biopsy, KOH test [germ tube]

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29
Q

What are properties of cryptococcus neoformans?

A
  • encapsulated fungus

- found in environment [in pigeon droppings]

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30
Q

What are clinical signs of cryptoccus neoformans?

A
  • wide range -> mainly asymptomatic colonization of respiratory airway –> can also get dissemination with fatal infections [nodular pulm infiltrates, non-blanching rash, skin lesion with umbilication]
  • likes to invade CNS –> fungal meningitis
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31
Q

How does cryptococus neoformans enter body?

A
  • enters primarily via lungs from aerosolization of pigeon droppings
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32
Q

What are the virulence factors of cryptococcus?

A
  • capsule [main one]
  • phenotypic switching
  • melanin
33
Q

What is role of capsule in cryptococcus infection?

A
  • prevent phagocytosis
  • reduces production of inflammatory cytokines
  • depletes complement components
34
Q

What is role of phenotypic switching in cryptococcus?

A
  • changes in polysaccharide capsule and cell wall after yeasts resistance to phagocytosis and immune responses
35
Q

What is role of melanin in cryptococcus?

A
  • pigment with antioxidant activity
  • moderates cell wall integrity and charge, interferes with antifungal susceptibility
  • inhibits antibody-mediated phagocytosis
  • protects from extrem temp
36
Q

What stains do you use to culture cryptococcus?

A
  • PAS

- silver stain

37
Q

How do you treat cryptococcus?

A

amphotericin [with 5FC for serious illness] then as get better transition to oral fluconazole

38
Q

How do you diagnose cryptococcus?

A
  • serum test for cryptococcal capsular antigen of blood or CSF [rapid test]
  • visualization of organism on biopsy or CSF [india ink see capsule]
  • blood or CSF cultures
39
Q

Who gets serious cryptococcus infection?

A

most serious infections = pts with AIDS

40
Q

What are properties of histoplasma capsulatum?

A
  • dimorphic fungus

- primarily

41
Q

How is histoplasma capsulatum tranmitted / who gets it?

A
  • primary infection from inhalation of microconidia
  • high concentration of it found in bat poop
  • associated with severe disease in immunocompetent with heavy exposure [spelunking, construction work]
42
Q

What happens to those with defects in cellular immunity and histoplasmosis?

A
  • defect in cellular immunity can result in reactivation/dissemination
  • have 80% mortality in untreated disseminated histoplasmosis
43
Q

What are sigs of acute histoplasmosis?

A
  • acute pulm illness
  • may see disseminated pulm scarring on CT, looks like miliary TB
  • pericarditis
  • spreads to liver/spleen/bone marrow in disseminated –> get pancytopenia
44
Q

How is histoplasmosis diagnosed?

A
  • urine histoplasma antigen [more sensitive for AIDS than non-AIDS pts] = major way
  • bone marrow biopsy [tendency to infect liver, spleen, and bone marrow]
  • blood cultures [silver stain]
  • CSF antigen
  • liver or lymph node biopsy
45
Q

Where is highest prevalence of histoplasma in US?

A

along ohio river vallery

46
Q

How do you treat histoplasma?

A
  • treat with amphotericin then transition to

- itraconazole or voriconazole

47
Q

Where is blastomycosis endemic?

A

south america, middle US

- has geo overlap with histoplasmosis

48
Q

How is blastomyces dermatidis acquired?

A
  • natural habitat is soil, decaying wood, river banks
  • saprophytic mold in soil at 25C
  • acquire through inhalation mold-form conidia [spores] into alveoli [rarely by direct cutaneous inoculation]
49
Q

What are properties of blastomyces?

A
  • dimorphic fungus in moist soil

- yeast phase divides with broad based budding = cells are still attached have broad wall between them

50
Q

What are the pulm manifestations of blastomycosis

A
  • wide spectrum
  • can have asymptomatic self limiting pulm infection
  • focal pulm infection resembling bacterial pneumonia
  • subacute to chronic pneumonia with mass-like lesions, multiple nodular lesions, lobar infiltrates, cavitary lesions in immunocompetent
51
Q

What are cutaneous manifestations of blastomyces dermatidis?

A
  • cutaneous lesions generally result from hematogenous spread
  • pathology = mix of granulomatous and neutrophilic response [microabcesses]
  • get lesions wingle or multiple papules, nodules, microabcesses
52
Q

What are clinical manifestations of blastomycosis generally?

A
  • most disease is pulm, can have some cutaneous disease
53
Q

How do you diagnose blastomyces?

A
  • by culture or visualization of yeast phase with broad based budding
54
Q

how do you treat blastomyces?

A
  • amphotericin B

- traconazole, flluconazole

55
Q

Where is coccidioides immitis infection found? what are two diseases of its infection?

A
  • in southwest US desert [texas, NM], mexico, central and south america
  • called: coccidioidomycosis and san joaquin valley fever
56
Q

Where does coccidioides live? How is it transmitted?

A
  • propagates in soil in desert
  • grows as mold at 25C and produces mycelia that give rise to barrel-shaped arthroconidia = infectious unit
  • arthroconidia become aerosolized and inhaled by humans
  • within human arthroconidia differentiates into large endosporulating spherule
57
Q

What is the coccidioides spherule?

A
  • the form of the fungus that exists in humans
  • composed of large sphere containing many endospores
  • releases endospores which disseminate infection
58
Q

What are clinical manifestations of coccidioidomycosis?

A
  • primary pulm infection [some asymptomatic]
  • mild flu-like symptoms 10-16 days post exposure = cough, fever, chest pain, headache, chills, anorexia
  • in 5% have san joaquin valley fever
59
Q

What are symptoms of san joaquin valley fever?

A
  • erythema nodosum
  • erythema multiforme
  • arthralgias “desert rheumatism”
  • conjunctivitis
  • hypersentitivity rxn to fungal proteins
60
Q

What are some examples of activities that give pts higher inoculum and thus more likely to get symptomatic disease?

A
  • archaeological excavation
  • construction project
  • military exercise
61
Q

Who gets disseminated coccidioides infection?

A
  • immunocompromised

- genetically high risk groups [filipino, African american, native american]

62
Q

How do you diagnose coccidioides infetion?

A

culture of pulmonary specimens –> spherule is diagnostic

63
Q

how do you treat coccidioides?

A
  • amphotericin B

- then fluconazole in immunocompromised

64
Q

What is mariner’s wheel morphology?

A
  • characteristic finding of paracoccidioides fungus
65
Q

What are properties of paracoccidioides brasiliensis?

A
  • characterstic mariners wheel appearance representing multiple budding in mold phase
  • often oval to round cell
  • buds have narrow stalks compared to blastomycosis
  • dimorphic fungus
66
Q

Where is paracoccidioides brasiliensis endemic?

A
  • south america from mexico to argentina, highest rates in brazil
67
Q

Who gets paracoccidioides primarily?

A
  • much higher prevalence in males [estrogen may inhibit]
68
Q

What are clinical manifestations of paracoccidiodes brasiliensis?

A
  • primary lung infection
  • can have long latency with reactivation > 10 yrs
  • patchy nodular densities/consolidations in lung
  • lymphadenopathy
  • cutaneous fistule
69
Q

How is paracoccidiodes transmitted?

A
  • primary infection via lung then dissemination
70
Q

How do you diagnose paracoccidioides?

A
  • culture of biopsied material or BAL specimens
71
Q

What is treatment for paracoccidioides?

A
  • itraconazole [main] or trimpethoprim-sulfamethoxazole

- amphotericin B if severe

72
Q

Where is peniillium marneffei endemic?

A
  • tropical asia –> thialand, north india, china, hong kong, vietnam, taiwan
73
Q

What is penicillium marneffei infection associated wtih?

A
  • opportunistic infection with AIDS
74
Q

Whare are properties of P. marneffei?

A
  • thermal dimorphism
  • mycelium with septate hyphae at 25C
  • yeast with binary fission replication at 37C
  • saprophytic
75
Q

What is reservoir for penicillium marneffei?

A
  • zoonotic [bamboo rat]
76
Q

What are clinical features of peniccilium marneffei?

A
  • primary pulm pathogen
  • produces chronic pulm infection
  • in immunosuppressed disseminates hematogenously –> hepatomegaly, skin lesions [umbilicated appearance] , generalized lymphadenopathy, fever, weight loss
77
Q

How do you diagnose peniillium marneffei?

A
  • visualization of yeast phase –> characterized by binary fission
78
Q

How do you treat penicillium marneffei?

A

amphotericin and 5-FC

Microbiology Part 2 (30 decks)

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