57. Fungi Details

Question 1

what is the 3rd to 4th most common cause of blood stream infection?

Answer 1

candida

Question 2

what is the most common cause of infectious pneumonic mortality in leukemic recipeints?

Answer 2

aspergillus

Question 3

what fungi are among the most common AIDS defining infections in HIV-infected patients?

Answer 3

pneumocystis (jirovecii or carinii) and cryptococcus neoformans

Question 4

fungal cell wall contains what important molecule?

Answer 4

ergosterol

Question 5

what really strong molecule do fungi contain that allows them to cut through tissues really easily?

Answer 5

chitin

Question 6

what are unicellular fungi that reproduce by asexual process (generation time in hours)?

Answer 6

yeast

Question 7

what are fungi whose vegetatie form is a mass of individual hyphae?

Answer 7

filamentous (mold)

Question 8

hyphal elements grow by what?

Answer 8

apical extension

Question 9

what are the common morphologic forms of fungi?

Answer 9

yeast (budding)

filamentous (mold, hyphae)

branching hyphae (dichotomous or right angled)
septation of hyphae (septate like aspergillis or non-septate like zygomycetes)

Question 10

if you see yeast w/hyphae, pseudoyphae and budding, what is it?

Answer 10

candida

Question 11

if you see germ tubes, what is it?

Answer 11

candida albicans

Question 12

what is the major encapsulated yeast? (the only clinical one)?

Answer 12

cryptococcus neoformans

Question 13

if you see branching septate hyphae from bronciolavage, what is it?

Answer 13

aspergillis

Question 14

if you see non-septate branching hyphae, what is it?

Answer 14

zygomycete

Question 15

what is dimorphism?

Answer 15

lots of fungi exist in tow different morphologic forms.

Eg fungus exists in room temperature as a filamentous fungus but is a yeast in tissue or the lab

• temperature dependent (37C) and nutrient dependent

Question 16

what are the dimorphic fungi?

Answer 16

histoplasma capsulatum - here and ohio river valley

blastomyces dermatitidis - here, north central US and southeast US

coccidioides immitis - southwest

paracoccidioides brasiliensis

pencillium marneffei - southeast asia

sporothrix schenckii

Question 17

candida as a dimorphic fungi?

Answer 17

opposite! yeast in nature and filamentous/yeast in lab/tissue

Question 18

cryptococcus neoformans produces a _____ capsule composed principally of what?

Answer 18

heteropolysaccharide, glucuronoxylomannan (has a protective effect vs host)

** capsular antigen is used in detection of organism in CSF

Question 19

fungi cell wall?

Answer 19

rigid heteropolysaccharide that gives shape and stability but is not a barrier to the env’t

multi-layered:

• glucans (1,3-B-glucans, 1,6-B-glucans)
• mannans
• chitin

Question 20

what is a major component of aspergillis cell wall that is not found in candida?

Answer 20

galactomannan

Question 21

cellular and humoral host responses are directed toward what part of the fungi?

Answer 21

cell wall (PAMPs)…when you are neutropenic you cna’t contain the organisms and are at huge risk for infection

Question 22

5 possible virulence factors of fungi?

Answer 22

cell surface receptors ( epithelial cells, endothelial cells, vascular catheters)

hydrolytic enzymes (hydrolyze complex proteinaceous and lipid substrates)

host mimicry (produciton of macromolecules that are homologous with human molecules)

polysaccharide capsule (inhibits phagocytosis)

melanin production (inhibits oxidative killing mechanisms)

Question 23

fungi in budding yeast forms only?

Answer 23

cryptococcosis, histoplasmosis, blastomycosis, and sporotrichosis

Question 24

budding yeast forms and hyphae?

Answer 24

candidiasis and tinea versicolor

Question 25

hyphae?

Answer 25

aspergillosis, zygomycosis and dermatophytosis

Question 26

spherule?

Answer 26

coccidioidomycosis

Question 27

H and E stain and fungi?

Answer 27

used to differentiate host response but not sensitive for detection of fungi

Question 28

periodic acid-schiff (PAS) and fungi?

Answer 28

stains the acid polysaccharide cell wall of fungi very pink

Question 29

gomorri’s methenamine silver (GMS) and fungi?

Answer 29

deposits silver on the funal cell wall and increases sensitivity of detection

Question 30

mucicarmine or alcian blue specifically stains the polysaccharide capsule of whta?

Answer 30

cryptococcus neoformans

Question 31

fontana masson stains what?

Answer 31

melanin present in the cell wall of some fungi

Question 32

superficial fungal infection?

Answer 32

tinea versicolor - no inflammation, cosmetic

skin scraping = spaghetti and meatballs

malassexia furfur

Question 33

mucocutaneous fungal infection?

Answer 33

inflammation occurs, but fungi don’t invade deeply viable tissue

dermatophytosis

athletes foot - painful and can tontract w/papulosquamous infection (can feel it and silvery keratinotic structure)

Question 34

subcutaneous fungal infection?

Answer 34

localized infection, following trauma

• chromoblastomycosis (can infect subcutaneous tissue like the dermis, epidermis, subQ fat)
• mycetoma (can go into muscle, tendon and bone)
• sporotrichosis (lymphocutaneous from rose thorns)

Question 35

deep mycoses?

Answer 35

opportunistic: caused by common fungal due to compromised host (PMN-dependent) like candidiasis, aspergillosis, or zygomycosis
pathogenic: caused by more virulent species (CMI-dependent) like histoplasmosis