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Micro/Immuno Part 3 > Fungus 2 > Flashcards

Fungus 2 Flashcards

1
Q

themes in superficial mycoses

A
  • caused by fungal growth on the superficial skin layer
  • does not require thermal dimorphism; often growing on cool exterior as hyphae
  • very common, symptoms are minor-itch or discoloration
  • treated with topical azoles, or oral griseofulvin
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2
Q

dermatophytosis

A
  • caused by dermatophytes
  • infect superficial keratinized structures
  • skin, hair, nails
  • produce keratinases that allow invasion of the cornified cell layer
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3
Q

dermatophytosis pathogenesis

A

-form chronic infections in warm, humid areas onf the body surface
-inflamed circular border of papules and/or vesicles, broken hairs, thickened, broken nails
-skin within border may be normal
-named for affected body part
capitis head
corporis ringworm
cruris jock itch
pedis foot
-transmitted by fomites or by autoinoculation from other sites on body
-some have hypersensitive dermatophytid reactions of vesicles on fingers
-completely immunogenic
-tinea common-10-20% of visits to derm
-no morbidity-itching can lead to bacterial superinfection

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4
Q

dermatophytosis diagnosis

A
  • exam-itching, redness, history of tight or wet clothing
  • microscopic:
  • scraping from affected skin or nail
  • KOH mount
  • examine for hyphae and spores
  • culture on sabourauds agar at room temp
  • microsporum show fluorescence when examined under Wood’s lamp
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5
Q

dermatophytosis treatment and prevention

A
  • topical antifungal-terbinafine- lamisil, undecylenic acid, miconazole, tolnaftate
  • treat all sites simultaneously
  • oral griseofulvin if can’t reach all spots
  • keep skin dry and cool
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6
Q

themes in subQ mycoses

A
  • introduced by trauma exposing subQ tissue to soil or vegetation
  • slow spread from trauma site toward trunk from lymphatics
  • thermal dimorphism
  • patient presents with history of ineffective antibiotic treatment
  • treated with oral azoles
  • in serious cases, may begin with short course of AmpB and surgery
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7
Q

sporotrichosis

A
  • sporothrix schenckii and other species
  • thermally dimorphic
  • found on vegetation
  • often seen in gardeners, particularly of roses
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8
Q

sporotrichosis pathogenesis

A
  • introduced into skin by thorn puncture
  • yeasts grow at site and form painless pustule or ulcer
  • draining lymphatics for suppurating subQ nodules
  • symptoms wax and wane over the years
  • may progress to disseminated disease and meningitis if immunocompromised
  • patients with COPD and long term corticosteroid use may develop pulmonary symptoms from inhaling the spores, difficult to distinguish from TB or histo
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9
Q

sporotrichosis diagnosis exam

A
  • painless pustule or ulcer on hand or arm, reddish, necrotic, nodular papules may extend along lymphatic from initial injury site
  • history of gardening, farming, landscaping, berry picking
  • history of ineffective antibiotic treatment
  • in AIDS, see nodules all over body
  • in COPD+alcoholism, resp distress
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10
Q

sporotrichosis diagnosis lab

A
  • tissue biopsy-round or cigar shaped budding yeasts
  • hard to see
  • culture at room temp from pus- hyphae with oval conidia in clusters at tip of slender conidiophores-daisy
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11
Q

sporotrichosis treatment and prevention

A
  • 3-6 mo of itraconazole or other oral azoles for normal form
  • for more serious types, admit for AmpB
  • garden gloves
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12
Q

themes in systemic mycoses

A
  • environmental-spores/fungi in soil
  • inhaled into lungs
  • thermal dimorphism
  • wide range of severity-asymptomatic clearance to death
  • not person to person
  • coccidio, histo, blasto:mimic TB
  • american dirt not foreign crowds
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13
Q

coccidio

A
  • coccidioides immitis and C posadasii
  • dimorphic-mold in soil, spherule in tissue
  • grow in the rainy season as mycelia-noninfectious
  • in the dry summer, forms hyphae with alternating arthrospores and empty cells
  • when disturbed by wind or excavation, readily release arthroconidia-infectious
  • spores carried and inhaled
  • endemic in southwest US and latin america,may travel home in returning patient or arrive in contaminated shipped material
  • caseload has spike because endemic areas have increasing number of geriatrics
  • can keep a previously healthy person out of school or work for a month
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14
Q

coccidio pathogenesis

A
  • arthrospores are inhaled, ID as low as single IU, though high dosage more likely to cause symptoms
  • within terminal bronchiole-change form
  • spherules:highly resistant to eradication by immune system
  • 30 um diameter
  • thick doubly refractive wall
  • wall ruptures to release endospores, develop into new spherules
  • spherules and endospores not infectious
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15
Q

exposure

A

-if low dose and healthy:asymptomatic clearance
(first three outcomes-60%)

if moderate dose and healthy CMI-asymptomatic containment; nonspecific flulike, containment; mild pneumonia, EN, containment

if high dose or immunosuppressed:serious pneumonia; dangerous dissemination

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16
Q

coccidio pathogensis 2

A
  • acute phase-innate immunity (macrophage response) attempts to clear infection, often successful
  • chronic phase-innate immunity inadequate for clearance; lymphocytes and histiocytes initiate granuloma and giant cell formation
  • if CMI is healthy, infection is contained in granulomas in lung, many eventually cleared asymptomatically
  • many patients who become ill have non-specific flulike symptoms that resolve at home
17
Q

pathogenesis 3

A
  • symptomatic disease may appear as valley fever or desert rheumatism
  • fever
  • arthralgia
  • erythema nodosum
  • erytheme multiforme
  • chest pain
18
Q

pathogenesis 4

A
  • if immunosuppressed, disseminated infection both by intracellular travel in macrophages and hematogenous spread
  • risk factors-advanced age, immunocompromise, late stage pregnancy, high level exposure, black of filipino race
  • may affect any organ, primarily seen in bones and meninges
  • induces immune anergy, may be rapidly fatal
19
Q

coccidio diagnosis

A
  • take biopsies of relevant tissues, CSF, blood, urine, stain with HandE or fungal stains, examine microscopically for spherules
  • cultures on sabourauds agar at 25 c, cottony while mold composed of hyphae with arthrospores-infectious!-BSL3
  • serology for exposure- IgG from blood or CSF, titer spikes if disseminating
  • some false neg
20
Q

coccidio treatment

A
  • high morbidity but low mortality
  • no treatment required for mild disease, oral azoles may be used, no data indicate faster or better resolution
  • must treat if predisposed to complications: severe immunosuppression, diabetes, CAD, pregnancy
  • persisting lung lesions or disseminated- AmpB and long term itraconazole
  • minimum of 6 months drug therapy, followups for at least a year
21
Q

themes in opportunistic mycoses

A
  • diseases and severity are widely varied, depending on the patients pre-existing conditions
  • optimal treatment addresses both the infection and the underlying problem
22
Q

cryptococcosis

A

-neoformans and gattii-5 serotypes- A,D, AD=neo, B, C=gattii

  • cryptococcosis, meningitis
  • C neoformans is environmental, found worldwide in soil contaminated with bird droppings, pigeons
  • oval yeasts with narrow based buds and wide polysaccharide capsule
23
Q

crypto 2

A
  • pathogenic strain grows at 37 C
  • not thermally dimorphic, but does have moldlike sexually reproducing form in environment-filobasidiella neoformans
  • no human to human except organ transplant or needle sticks
  • meningitis rare before 1946, use of steroids, survival with malignancy, and AIDS increased caseload
  • disseminated disease was inevitably fatal before AmpB
24
Q

crypto pathogenesis

A
  • transmitted by inhalation-pigeon droppings may be contagious for years
  • lung infection may be asymptomatic or lead to pneumonia
  • can be intracellular in alveolar macro
  • immunocompetent hosts restrict infections to lungs
  • successful host raises helper T, skin test conversion, antibodies to capsule
25
Q

crypto pathogenesis 2

A
  • deficient CMI, AIDS predisposing is not required for dissemination
  • leads to meningitis with skin nodules
  • C neoformans raises very little IF response or granuloma formation- organ damage is by tissue distortion from growing yeast
  • virulence factors-capsules, melanin in cell wall (antiphag) phospholipase B for invading tissue
26
Q

crypto diagnosis exam

A
  • hx of steroid use, malignant disease, transplantation, HIV
  • take biopsies
  • pulm-asymptomatic to ARDS, cough and chest pain
  • crypto + HIV-fever, cough, headache, weight loss, pos cultures from blood, CSF, urine
  • CNS-subacute meningitis or meningoencephalitis, antifungal required for survival
  • may be symptoms in prostate, eyes, medullary cavity of bones

-blunted IF complicates diagnosis and presentation is late in disease

27
Q

crypto meningitis

A
  • headache
  • altered mental status
  • nausea and vomiting
  • fever and stiff neck less common- no IF
  • may also be sensory issues with eyes or ears
  • if not acute pyogenic, may wait for CT/MRI before lumbar puncture

-cryptococcoma-focal neurologic defects

28
Q

crypto diagnosis in lab

A

CSF-stain with india ink to look for yeast with wide capsule

  • biopsies-stain the silver, periodic acid-Schiff, mucicarmine
  • culture at 37C from CSF, blood, urine, sputum for mucoid colonies on sabouraud agar, will produce melanin in culture on special media
  • serology-crag for antigen in blood and CSF
  • routing bloodwork may be normal
29
Q

crypto treatmetn

A

-immunocompetent may not need treatment, can use 6-12 mo fluconazole or itraconazole
-meningitis or cryptococcoma-
AmpB and flucytosine for 2 weeks followed by 10 weeks of flucoazole
AIDS-fluconazole for long term suppression- clearance may not be an option
-examine CSF weekly to determine progress, glucose and cell count will return to normal but protein anomalies may persist for years
-do not discontinue therapy until cultures consistently fail

Micro/Immuno Part 3 (12 decks)

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