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Flashcards in the fungi Deck (50):
1

list the medically important fungi

1. aspergillus spp
2. fusarium spp
3. agents of mucormycosis
4. dimorphic fungi (histo/blastomycosis/coccidioides)
5. dermatophytes/superficial mycoses

2

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

3

what is the cell membrane of fungi made of

sterols
(antifungal target)

4

what makes up the cell wall of fungi

chitin, mannan, cellulose

5

what are yeasts

unicellular (ovid or round)

replicate by budding

smooth, bacteria-like colonies

(type of fungus)

6

what are molds

multiple cells forming microscopic filamentous mycelium

(type of fungus)

7

name 2 yeasts

candida

cryptococcus

8

name 1 mold

aspergillus

9

name 2 dimorphic species

histoplasmosis

blastomycosis

coccidioimycosis

10

superficial fungi

dermatophytes: tinea, Malassezia furfur

yeast

11

systemic/deep fungi

histoplasma

coccidioides

12

opportunistic fungi

aspergillus

candida

cryptococcus

pneumocystis

13

list the medically important yeasts

candida

cryptococcus

pneumocystis jirovecii

14

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)

15

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

16

what is candidemia

systemic blood infection of candida

very serious MEDICAL EMERGENCY

17

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

18

describe C. gattii infection in an immunocompetent host

results in "walled off" pulmonary disease ("uncommon pneumonia")

19

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

20

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

21

which aspergillus species is most invasive and pathogenic

A. fumigatus

22

what is the toxin assocaited with A. flavus

aflatoxin

23

what medication is A. terreus resistant to?

amphotericin B (susceptible to newer azoles)

24

describe A. niger infection

uncommon cause of invasive disease

superficial agent of otic disease

associated with colonization

25

what are the seven types of disease/disease classifications for aspergillus spp?

1. allergic syndrome
2. colonization and superficial syndrome (pulm)
3. direct inoculation
4. invasive pulmonary aspergillus
5. tracheobronchitis
6. sinusitis
7. disseminated infection

26

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

27

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

28

list two other conditions associated with aspergillus colonization

1. otomycosis--> A. niger colonization of external ear
2. keratitis --> secondary to trauma or corneal surgery

29

what two places/ways does direct inoculation of aspergillus usually occur

nosocomial or associated with construction work

30

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%

31

what patients typically get tracheobronchitis from aspergillus

AIDS patients or those undergoing lung transplant

32

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

33

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)

34

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

35

describe clinical conditions associated with mucomycosis infection

rhinocerebral, pulmonary, cutaneous, GI, CNS mucormycosis

36

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

37

name diseases that can resemble TB

histoplasmosis and coccidioimycosis

38

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

39

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

40

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

41

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

42

tinea spp

example of dermatophyte infection

SKIN MYCOSES categorized by anatomical area affected

43

tinea capitis

scalp, eyebrows, eyelashes

worldwide endemicity

spectrum of clinical presentation

highly contagious

TRICHOPHYTON spp and MICROSPORON spp

44

tinea pedis

"athlete's foot"

chronic or subclinical tow web infection

constant shedding of infectious skin scales

TRICHOPHYTON spp or EPIDERMOPHYTON spp

45

tinea unguium/onchomycosis

toenails

common (3% of elderly)

TRICHOPHYTON

46

tinea cruris

groin

common in males, usually spread from feet

TRICHOPHYTON spp and EPIDERMOPHYTON

47

tinea manum

hands

48

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

49

tinea barbae

beard

50

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