Fungus 2 Flashcards
themes in superficial mycoses
- 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
dermatophytosis
- caused by dermatophytes
- infect superficial keratinized structures
- skin, hair, nails
- produce keratinases that allow invasion of the cornified cell layer
dermatophytosis pathogenesis
-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
dermatophytosis diagnosis
- 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
dermatophytosis treatment and prevention
- 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
themes in subQ mycoses
- 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
sporotrichosis
- sporothrix schenckii and other species
- thermally dimorphic
- found on vegetation
- often seen in gardeners, particularly of roses
sporotrichosis pathogenesis
- 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
sporotrichosis diagnosis exam
- 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
sporotrichosis diagnosis lab
- 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
sporotrichosis treatment and prevention
- 3-6 mo of itraconazole or other oral azoles for normal form
- for more serious types, admit for AmpB
- garden gloves
themes in systemic mycoses
- 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
coccidio
- 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
coccidio pathogenesis
- 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
exposure
-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
coccidio pathogensis 2
- 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
pathogenesis 3
- symptomatic disease may appear as valley fever or desert rheumatism
- fever
- arthralgia
- erythema nodosum
- erytheme multiforme
- chest pain
pathogenesis 4
- 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
coccidio diagnosis
- 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
coccidio treatment
- 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
themes in opportunistic mycoses
- diseases and severity are widely varied, depending on the patients pre-existing conditions
- optimal treatment addresses both the infection and the underlying problem
cryptococcosis
-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
crypto 2
- 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
crypto pathogenesis
- 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
crypto pathogenesis 2
- 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
crypto diagnosis exam
- 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
crypto meningitis
- 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
crypto diagnosis in lab
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
crypto treatmetn
-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
