the fungi Flashcards
list the medically important fungi
- aspergillus spp
- fusarium spp
- agents of mucormycosis
- dimorphic fungi (histo/blastomycosis/coccidioides)
- dermatophytes/superficial mycoses
what are fungi?
EUKARYOTES that grow without roots, stems or leaves
do not have chlorophyll for photosynthesis
reproduce via SPORE formation
rigid cells walls made of chitin, mannan, cellulose (no peptidoglycan)
have nucleus, nuclear membrane, ER, golgi, mitochondria
what is the cell membrane of fungi made of
sterols
antifungal target
what makes up the cell wall of fungi
chitin, mannan, cellulose
what are yeasts
unicellular (ovid or round)
replicate by budding
smooth, bacteria-like colonies
(type of fungus)
what are molds
multiple cells forming microscopic filamentous mycelium
type of fungus
name 2 yeasts
candida
cryptococcus
name 1 mold
aspergillus
name 2 dimorphic species
histoplasmosis
blastomycosis
coccidioimycosis
superficial fungi
dermatophytes: tinea, Malassezia furfur
yeast
systemic/deep fungi
histoplasma
coccidioides
opportunistic fungi
aspergillus
candida
cryptococcus
pneumocystis
list the medically important yeasts
candida
cryptococcus
pneumocystis jirovecii
candida spp
c. albicans = most common
OPPORTUNISTIC
most common fungal pathogen affecting humans
wide range of disease: superficial musculocutaneous disease to invasive (i.e vulvovaginal cadidiasis, oropharyngeal colonization in healthy adults; systemic infections with 30-40% mortality)
management of candida infection
limited by delay in diagnosis
remove IV lines, catheters, foreign bodies if possible
early IV antifungal targeted versus the specific candida
consult ID
what is candidemia
systemic blood infection of candida
very serious MEDICAL EMERGENCY
cryptococcus spp
environmental yeast (bird poop)
inhalation of basidiospores from enviro leads to disease beginning in lungs
hematogenous spread to brain/bone/skin/joints
pathogenic species = C. NEOFORMANS var. neoformans (classic) and var. grubii, as well as C. GATTII (vancouver island)
greater prevalence in immunocompromised patients
CNS and/or pulmonary involvement; morbidity and mortality rates remain high
describe C. gattii infection in an immunocompetent host
results in “walled off” pulmonary disease (“uncommon pneumonia”)
Pneumocystis jirovecii
P. carinii
yeast-like fungus
all mammals harbour at least one species of pneumocystis
reproduce in mammals lung alveoli (reservoir = mammalian host)
environmental reservoir is undetermined
transmitted via AIRBORNE route–> requires short period of exposure and low inoculum
most people are seropositive by 2-4 years old
leading opportunistic infection in AIDS patients–> defining condition–>nonproductive cough, chest tightness, night sweats, low grade fever, tachypnea
aspergillus spp
environmental mold (requires environmental substrate for growth
5-6 are pathogenic
A. fumigatus, A. falvus, A. terreus, A. niger
sinusitis, skin infection are most common
filamentous fungi
which aspergillus species is most invasive and pathogenic
A. fumigatus
what is the toxin assocaited with A. flavus
aflatoxin
what medication is A. terreus resistant to?
amphotericin B (susceptible to newer azoles)
describe A. niger infection
uncommon cause of invasive disease
superficial agent of otic disease
associated with colonization
what are the seven types of disease/disease classifications for aspergillus spp?
- allergic syndrome
- colonization and superficial syndrome (pulm)
- direct inoculation
- invasive pulmonary aspergillus
- tracheobronchitis
- sinusitis
- disseminated infection
describe aspergillus allergic syndrome
allergic bronchopulmonary aspergillosis (ABPA)
exposure to fungus causes allergic respiratory symptoms
affects people with asthma of CF
can also cause allergic sinusitis
describe pulmonary colonization by aspergillus
pulmonary aspergilloma
colonization of a free fungal ball in residual lung cavity (80% are post-TB)
minimal inflammation
evolution to cavitation
typical symptom is HEMOPTYSIS
list two other conditions associated with aspergillus colonization
- otomycosis–> A. niger colonization of external ear
2. keratitis –> secondary to trauma or corneal surgery
what two places/ways does direct inoculation of aspergillus usually occur
nosocomial or associated with construction work
describe invasive pulmonary aspergillosis
“IPA”
most common–> usually fatal opportunistic infections
immunocompromised patients are at risk
usually have extrapulmonary dissemination i.e to brain
response to therapy is less than 20% and mortality is greater than 90%
what patients typically get tracheobronchitis from aspergillus
AIDS patients or those undergoing lung transplant
fusarium spp
found in soil and organic debris
human disease is rare
in healthy hosts, infection usually occurs after trauma (direct inoculation)
can happen in immunocompromised hosts after inhalation or minor trauma
infections: keratitis, onchomycosis (nails), endiphthalmitis (internal coats of eye), skin/MSK infection
how might disseminated fusarium infection present clinically
may present with fever and myalgias unresponsive to antibacterials
skin lesions in 60-80% of patients (papules or deep, painful nodules that begin as flat but can become necrotic)
agents of mucormycosis
includes fungi of order MUCORALES (i.e Rhizopus spp, Absidia spp, and Mucor spp_)
these are molds that grow as HYPHAL forms (“lid lifters”)
common in environment, rapid growth, prolific spore formation
low virulence in humans–> disease caused in severely immunocompromised patients, people with diabetes mellitus, trauma or transplant
fungus gains access through respiratory tract
hyphae invade tissue and have affinity for BLOOD VESSELS
describe clinical conditions associated with mucomycosis infection
rhinocerebral, pulmonary, cutaneous, GI, CNS mucormycosis
list the dimorphic fungi and give their shared traits
histoplasmosis
blastomycosis
coccidioimycosis
grow as FILAMENTOUS molds in the environment (at 24-30 degrees)
are YEAST LIKE in TISSUES (at 35-37 degrees)
ALL are pathogenic–> contaminant level 3
begin as inhalation of spores but are not communicable
arise due to exposure to nitrogen rich soil, bird or bat poop, caves
name diseases that can resemble TB
histoplasmosis and coccidioimycosis
histoplasmosis
HISTOPLASMA CAPSULATUM
infection is common but overt disease is not
primary lesion is in the LUNGS
large spectrum of clinical presentations from asymptomatic to acute disseminated infection
acute disseminated infection presents as: rapid, debilitating GI symptoms, bone marrow suppression, hepatosplenomagaly (young children, AIDS, immunocompromised)
chronic disseminated presents as: low grade fever, weight loss, weakness, hepatosplenomegaly, focal disease (fatal if untreated)–> if pulmonary can resemble; is granulomatous
blastomycosis (blastomyces)
blastomyces dermatitidis
most = soil exposure, decomposing organic matter, hunting, trapping
about 50% of those infected show symptoms–> if symptomatic, symptoms arise 3-15 weeks post exposure due to incubation period
symptoms = flu-like (fever, chills, cough, muscles aches, joint and chest pain)
can disseminate and become serious
coccidioides (coccidioides immitis)
found in soil and transmitted by inhalation of dust-borne infective ARTHROCONIDIA
primary infection is flu-like (or asymptomatic)
60% are self-limiting
1/5 cases have erythema nodosum
may heal completely with residual pulmonary fibrosis
rarely fatal unless disseminated
many have GRANULOMA formation (resembles TB)
incubation period of 10-16 days
what are dermatophytes and superficial mycoses
closely related group of FILAMENTOUS fungi that are able to digest and obtain nutrients from KERATIN
chronic process of infection
3 genera: differentiated phenotypically by CONIDIA formation
transmission by direct/indirect contact to infected sites of human, animal or contaminated fomites
can remain infectious for months/years in shredded skin
higher incidence in tropical/subtropical areas
tinea spp
example of dermatophyte infection
SKIN MYCOSES categorized by anatomical area affected
tinea capitis
scalp, eyebrows, eyelashes
worldwide endemicity
spectrum of clinical presentation
highly contagious
TRICHOPHYTON spp and MICROSPORON spp
tinea pedis
“athlete’s foot”
chronic or subclinical tow web infection
constant shedding of infectious skin scales
TRICHOPHYTON spp or EPIDERMOPHYTON spp
tinea unguium/onchomycosis
toenails
common (3% of elderly)
TRICHOPHYTON
tinea cruris
groin
common in males, usually spread from feet
TRICHOPHYTON spp and EPIDERMOPHYTON
tinea manum
hands
tinea corporis
skin (“RINGWORM”)
ringworm = host reaction to enzymes release from fungus during digestive process–> ECZEMATOUS response
no invasion of living tissue–> colonization of STRATUM CORNEUM
tinea barbae
beard
what is tinea versicolor? is it a dermatophyte?
NOT a dermatophyte–> a YEAST
i.e Malassezia furfur
normal skin flora that can become opportunistic
multiple macules–> patches of hyperpigmentation (back/chest/abdomen/forehead)
relatively common (2-8%)
adolescents and young adults in warm/humid climates
yeast feed on dead skin and skin oils
Tx = topical antifungals
