Opportunistic Fungi Flashcards
are fungi motile?
no
fungi: prokaryotic or eukaryotic?
eukaryotic
why do antifungals have significant toxicity?
cross-reactivity with mammalian compounds/enzymes
what distinguishes fungi from prokaryotes?
membrane-bound nucleus and organelles
DNA morphology?
multiple linear chromosomes
fungi membranes not composed of cholesterol but instead…
ergosterol
drug that binds to ergosterol
amphotericin B
drug class that interferes with ergosterol biosynthesis
azoles
fungi cell wall components (not found in mammals)
chitin
B-glucan
mannoproteins
drugs that inhibit B-glucan synthase
echinocandins
two fungi recognized as part of the normal human microbiota
C. albicans
M. furfur
fungal energy source
heterotrophs –> organic material
NOT photosynthetic
absorptive, NOT phagotrophic
drugs that cross-react with P450 enzymes
azoles
fungi v. bacteria distinction: diaminopimelate, which one has it in their cell wall?
NO DAP in fungi
term for organism that lives on dead/decaying botanic matter
saprobe
a fungi that exists only as yeast
Cryptococcus neoformans
a DIMORPHIC fungus who’s yeast morphotype is the pathogenic, invasive form? mold?
Yeast: Histoplasma capsulatum
Mold: Candida albicans
which morphology grows by apical extension?
molds
unicellular oval structure that divides by budding or fission
yeast
a pathogenic fungus that exists only as a mold
Aspergillus
hyphae, mycelia
molds
both yeast/mold forms are invasive
candida
a form of yeast growth where cells remain attached and elongate
pseudohyphae
conversion to the host-adapted form is essential for pathogenesis in humans - especially systemic infections
dimorphism
dimorphic fungi (MSCHBC)
Malassezia (superficial) Sporothrix (subQ) Candida (opportunisitc) Histo (systemic) Blasto (systemic) Coccidio (systemic)
Yeast fungi ONLY (2C)
Cryptococcus (opportunistic) Candida glabrata (opportunistic)
Mold fungi ONLY (ADZ)
Aspergillus (opportunistic)
Dermatophytes (cutaneous)
Zygomycetes (subQ)
fusion of 2 gametangia –> zygote
zygomycetes
2 haploid nuclei fuse to form diploid –> meiosis in a sac “ASCUS” to form haploid
Ascomycetes
like asco but sac is called “BASIDIUM” –> haploid progeny mature on outer surface of sac (e.g.?)
Basidiomycetes
Cryptococcus
no sexual stage identified for these fungi
deuteromycetes
allergy
Type I, IgE-mediated
exposure via inhalation/ingestion/contact
re-exposure –enhanced rxn
morbidity via host response
major atmospheric fungi causing hypersensitivity (ACA)
Alternaria
Cladosporium
Aspergillus
cheese washer’s lung
Penicillium
paprika splitter’s lung
Mucor stolonifer
ingestion of seeds/nuts leading to hepatotoxicity (acute) and liver cancer (chronic)
aflatoxins from Aspergillus (most potent naturally occurring toxin)
ingestion of grains and breads leading to vasoconstriction, peripheral necrosis, gangrene
ergot alkaloids from Claviceps purpurea
grains and breads causing cytotoxic/systemic effects
trichothecenes from Fusarium
building materials (esp. damaged by water)
trichothecenes from Stachybotrys
superficial S.C. or cuticle infection e.g.
Malassezia
epidermis, finger/toe nails, hairs (dermatophytes) (TME)
Trichophyton
Microsporum
Epidermophyton
dermis, subQ, fascia, bone
fungi that cause sporotrichosis and zygomycosis
Fungal entry via resp tract –> hematogenous/lymph spread or direct extension (the big 3)
Systemic (deep)
Histo/Blasto/Coccidio
can cause disease in the immunocompetent
fungal entry via wounds/burns, or immunodeficiencies (CCAP)
Crypto
Candida
Aspergillus
Pneumocystis jiroveci
risk groups for immunodeficiency
cancer/AIDS/transplant
young/elderly
hospitalized
prolonged survival of the severely ill
Containment of fungi requires?
antigen-specific CD4 T-cells
activate MP’s via IFN-y stimulation
CMI or humoral, which is of primary importance in defending fungi?
CMI
for which fungi are neutrophils critical for defense?
Aspergillus
neutropenic pts, pts on chemo –> aspergillosis
this infection generally does not have sx, immune response, or physical discomfort
superficial mycoses
M. furfur
inhabits skin
lipophilic, dimorphic
disseminated disease in infants receiving TPN
M. furfur
dandruff, cradle cap, seborrheic dermatitis
M. furfur
can be early sign in HIV/AIDS pts
pathogenic form of M. furfur
HYPHAL (yeast is commensal)
asymptomatic disorder of host melanocytes
tinea versicolor
big 3 TME for cutaneous mycoses
Trichophyton
Microsporum
Epidermophyton
ectothrix/endothrix
growth w/in and outside hair shaft
paronychomycosis
fungal infection of nail beds
elderly
systemic abx
very contagious and transmittable infection
tinea
diagnostic methods for fungi
KOH –> lesion border
Wood’s lamp –> fluorescence of cell wall
Culture for DEFINITIVE DX (rarely used)
infection while working with potting soil, sphagnum moss, pricked by a rose thorn
sporotrichosis
sporothrix schenkii
“gardener’s disease”
Sporothrix schenkii
dimorphic
MOLD in env
yeast in tissues at 37C
small, hard, painless nodule that enlarges to a fluctuant mass that eventually ulcerates; may progress along lymphatics but rarely spreads beyond regional lymphatics
Lymphocutaneous sporotrichosis
inhalation of spores; may resemble TB
Pulmonary sporotrichosis
Zygomycosis fungi (RAM)
Rhizopus Absidia Mucor Rapidly invasive (2-7d) All types of presentations (cut, subQ, dissem, etc.)
common initial sites of zygomycosis infection
lungs/nasal sinuses
burn/trauma pts also susceptible on skin
life-threatening, fulminant infection seen in ACIDOTIC individuals (poorly controlled DM) –> DKA
also in neutropenic pts or pts receiving IRON chelation therapy
Rhinocerebral zygomycosis
the 5 fungi of fragility (opportunism only)
Crypto
Candida albicans/other spp
Aspergillus
Pneumocystis j
brudzinski’s / kerning’s signs indicate?
meningeal inflammation
encapsulated budding yeasts on INDIA INK
Cryptococcus neo
big immune defects (CMI and innate)
innate: neutrophils
CMI: CD4’s and MP’s
airborne fungi settling on burn/wound
aspergillus
soil introduced via trauma
Sporothrix schenkii
on own skin
Candida albicans
woman receives antibacterial treatment –> what fungal infection to worry about?
vaginal candidiasis
defects in humoral immunity (complement, antibody) associated with susceptibility?
generally not
defect in the oxidative killing capacity of phagocytes
CGD
lack of mature T and B lymphocytes; results in death <1 year
SCID
inherited grab bag
C-type lectin (receptor pathway components)
Signaling components
Cytokines and receptors
Inflam/autoimmune diseases leading to fungal susceptibility
RA, IBS, SLE, psoriasis
Drugs that increase susceptibility
cyclophosphamide
radiation –> neutropenia
steroids –> supp antimicrobial phagocyte action
infliximab/etanercept (block TNFa)
calcineurin inhibitors (block T cell activation)
–> cyclosporin A, tacrolimus
Mycophenolate mofetil –> blocks T and B cell proliferation and fxn for transplant
are ma’s antibodies protective against fungal infection?
negatron
other viruses that increase fungal susceptibility
Herpes
CMV, EBV, HIV (CD4/MP’s)
diabetes mellitus impact
hyperglycemia and acidosis
diminished phagocyte fxn
monomorphic budding yeast w/capsule, worldwide found in soil, fruit, juice, milk, bagpipes, GUANO, pigeons, spelunking
Cryptococcus neo
can disseminate via blood or lymph
disease distribution matching eucalyptus trees (reservoir) Australia, hawaii, california, BC, NW US
C. neo var. gattii (serotypes B and C)
more virulent can infect immunosufficient
C. neo major form causing human disease
var. grubii (serotype A)
aerosolization of unencapsulated yeasts w/no capsule inhaled to small airways; also sexual spores/condida
C. neoformans
respiratory/GI acquisition
pulmonary presentations of C. neoformans
DIP, pleural effusion, ARDS
disseminated presentations of C. neoformans
fungemia –>
meningitis (most serious; AIDS pts)
skin
prostate (reservoir)
potential reservoir for C. neoformans
prostate
leading cause of meningitis in AIDS pts? how to tx?
C. neoformans
lifelong fluconazole, antiretroviral therapy
virulence determinants of C. neoformans
growth at 37C
capsule (GXM is Cn ANTIGEN)
diagnostic criterion for cryptococcosis (hint: it’s a virulence determinant)
capsular antigen in SERUM or CSF
how is C. neo capsule production regulated?
moisture, CO2, iron
small yeast –> dry soil low CO2 and iron (easily aerosolized)
moist env w/high CO2 and iron deprivation = SWELLING –> more effective inhibition of host defenses
phenoloxidase activity as a virulence determinant of C. neo
CNS –> catecholamine-rich (phenoloxidase substrates) –> pigmented melanins –> free radical scavengers and thus resistance to oxidative stress
Melanin coat confers extreme resistance to other host stresses (drugs, pH, temperature, UV, phagocytes)
diagnosis of C. neo
CSF LA test
also blood, serum, sputum, urine
DEFINITIVE: culture (slow and least-sensitive)
all tests are highly specific
cryptococcal antigen (latex agglutination) test for C. neo
most SENSITIVE
CSF or serum for capsule
allows quantitative assessment of fungal burden
India ink test for C. neo
CSF
“HALO” surrounding fungal cells
quick/easy but NOT sensitive
Microscopic histology of tissue for C. neo
SOCCER BALL encapsulated yeasts (lung biopsy e.g.)
tx of C. neoformans (severe, mild, prophylactic, subclinical)
severe: amphotericin B + 5-flucytosine
after improvement/less sever: fluconazole
prophylaxis: fluconazole (high-risk pts or persistent sub-clinical infection) low CD4 count? –> for life
broad, ribbon-like, septate hyphae in tissue or necrotic debris
zygomycetes
primary risk factors for zygomycosis
trauma, break in skin, inhalation
rapidly invasive/destructive
usually not assoc with immunocomp
secondary risk factors for zygomycosis
typically defects in innate immunity neutropenia immunosuppressive therapy iron chelation acidosis (b/c acidification causes iron to fall off transferrin) DM, especially DKA
cryptococcal antigen measured (tells us what)?
capsular polysacc
fungal load
big cryptococcal disease
meningitis
how to dx cryptococcal meningitis?
india ink
culture and slide agglutination
tx cryptococcal meningitis in AIDS pt
acute amphotericin B
fluconazole prophylaxis
now ART to maintain CD4 levels
which C. neoformans variant is common in Europe?
neoformans (serotype D)
leading cause of meningitis in pts with AIDS
Cn
ABCD serotyping of Cn based on?
Capsule
cryptococcal capsule (or shed antigens) pathogenic mechanisms
antiphagocytic
depletion of complement
down-modulation of immune responses
the hyphal (mold) form invades tissue, the yeast form is commensal on the body surface
candida albicans
all filamentous forms: hyphae, pseudohyphae, germ tubes are considered?
invasive
oropharynx, GI, vagina, intertriginous, perioral, perianal colonization
not found on dry areas
albicans
albicans pathogenic action
skin, nail, mucosal in immunocompetent
invasive/disseminated in immunocompromised
RF’s for candidiasis
Abx/age chemo/neutropenia gastric acid suppression abd surgery CVC's, TPN, genetics
dermatitis, onychomycosis, paronycho, OE
candida
vulvovaginal, orophar (thrush), esoph, perianal
candida
extensive, chronic, tx-resistant superficial infection w/o dissemination accompanied by T-lymphocyte/MP defects but NORMAL HUMORAL responses
chronic mucocutaneous candidiasis
fungemia –> sepsis, endocarditis, UTI, meningitis, pneumonia, endophthalmitis
candida
infects virtually all individuals with AIDS
candida albicans
4th leading cause of nosocomial bloodstream infection
candida
approach to candida infection
culture –> determine spp –> susceptibility testing
candida virulence factors
morphogenesis
adhesins (mimic CR3/CR4 on host phagocytes)
BIOFILMS
hydrolytic enzymes
vulvar erythema, pruritis, thick CHEESY vaginal discharge, EXTERNAL dysuria
Vulvovaginal candidiasis (yeast infection)
Dx VVC
pelvic speculum exam –> WHITE plaques
vaginal fluid results: pH 4-4.5 (higher if bacterial)
calorimetric metabolic profiling
microscopic exam of KOH prep VVC shows?
filamentous hyphae, pseudo, germ tubes
glabrata –> only budding yeasts (no filamentous form)
Culture for VVC shows?
germ-tube test: + if albicans (differentiates from other candida spp)
adherent white plaques on tongue, buccal mucosa, or corner of mouth (angular shelties), asymptomatic or painful, can lead to esophagitis (in severe immunocompromised)
oropharyngeal candidiasis
dx based on clinical presentation
confirm via micro exam of KOH prep via skin scraping
a candida syndrome occurring in pts with CMI compromise (AIDS, premies), GI leakage, foreign body
disseminated candidiasis (bloodstream infection)
dx disseminated (bloodstream) candidiasis
culture blood, CSF, peritoneal fluid
definitive, significant, limited sensitivity
also Beta-D-glucan in blood/fluids via LIMULUS horseshoe crab assay (cell wall component marker for invasive)
also detection of antigen/metabolites/enzymes/PCR:rDNA
tx candida (mild/moderate/severe)
mild: topical antifungals/oral azoles
moderate: IV azoles or echinocandins
serious: IV echinocandins or amphotericin B (bloodstream)
probiotics also an option??
mucosal/cutaneous infection in immunocompetent pt (or baby/or pt with mono) may not receive tx
tx AIDS pt w/oropharyngeal candidiasis
tx AIDS pt w/candida esophagitis
nosocomial candidemia?
topical antifungal
topical antifungal + oral azoles
IV antibiotics (amphoB)
candida spp (2) resistant to fluconazole
glabrata/krusei
albicans susceptible
exists as mold only, airborne –> inhalation –> hypersensitivity w/germination to form invasive hyphae
aspergillus spp
Aspergillus syndromes (infection w/viable fungi not necessary)
allergy/hypersensitivity pneumonitis/ABPA
mycotoxicosis –> aflatoxins (seeds, nuts, corn; india/africa)
cavitary colonization –> aspergillomas –> hemoptysis
invasive pulmonary aspergillosis –> hemoptysis
dissemination
risk factors and tx of aspergillomas
TB, emphysema, smoking, a-1-antitrypsin def surgical excision (cavity action)
RF’s for invasive/disseminated aspergillosis
neutropenia
transplant
AID/CGD
chemo/steroids
colonization via aspergillus assoc w?
cavitary lesions
corticosteroids impair function of WAT?
macrophages –> high risk for IPA and disseminated aspergillosis
aspergillus virulence factors
allergens
toxins
hydrolytic enzymes
aspergillus dx
best: microscopic histology or beta-D-glucan marker for invasiveness; or aspergillis galactomannan assay
also culture of tissue/fluid to look for BRANCHING SEPTATE HYPHAE, but variable and low sensitivity
branching septate hyphae
aspergillus
xray or CT of IPA shows?
halo sign (early: represents HEMORRHAGE)
air-crescent sign (late: rim of cavitation as NP’s recover)
highly suggestive but not diagnostic
pts with IPA aren’t nec coming in coughing up a bunch of sputum, bc they don’t have full innate defenses
tx of aspergillosis (DOC?)
DOC: voriconazole
high-dose Ampho-B
transplant: vori + echinocandin
drug for aspergillus prophylaxis in immunocompromised pts?
Posaconazole
2 morphologic forms of Pj
trophozoites –> nonrefractive, active, motile (predominant)
cysts –> refractive, non-motile, thick-walled
no ergosterol, yes cholesterol not susceptible to amphoB susceptible to anti-parasitic agents (TMP-SMX) life-cycle similar to parasites fragile cell wall no in vitro culturable form
Pj attributs atypical for a fungus
evidence for Pj is a fungus
chitin and B-glucans in cell wall
sensitive to echinocandins
genes/arrangements
rDNA –> gold std
room air, apple orchard
pneumocystis j
ID’d from the lungs of infected people/animals but CANNOT be cultured in vitro
Pj
most common disease of Pj? route of infection?
pneumonia
common env exposure (very early in life)
respiratory
other Pj facts
don’t know a lot about this guy
host specificity suggests a non-human reservoir is unlikely
don’t know infectious form
trophozoites damage pneumocytes and cause loss of cells lining alveoli –> FOAMY eosinophilic exudate fill alveoli –> HONEYCOMB –> gas exchange compromised –> pO2 descends
diffuse interstitial pneumonia
can also disseminate
70-80% of AIDS pts infected; COD in 15-20%
P. jiroveci (extreme opportunist)
dx P. jiroveci
gold std: histo via biopsy/BAL/sputum
Beta-D-glucan in blood/fluids (nonspecific)
NO CULTURE (can’t)/SEROLOGY (everyone is seropositive)
tx P. jiroveci
acute: TMP-SMX
high-risk prophylaxis: TMP-SMX
also dapsone (and anti-parasite drugs)
STEROIDS to dampen host inflammatory response; along with antimicrobials, ESPECIALLY w/fluid accum in lungs!
candida infection typically exogenous/endogenous?
endogenous
germ tube induction in serum diagnostic for?
candida albicans
sporothrix form at 37 deg?
yeast
mold at room temp
thermoregulated morphogenesis
unlike candida, which can be present in all forms
if you see only yeast on histo it’s probably…
candida glabrata
cutaneous candidiasis sx
redness, pain, pruritis
most common dissemination site for candida
kidney
PICU (neonates) candidiasis?
elderly?
C. parapsilosis
C. glabrata
fluorescence on wood’s lamp via?
cell wall
what bacteria can cause disease similar to the subcutaneous mycoses?
mycobacteria