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Erica's ID 3 > Mycology I: Opportunistic fungi > Flashcards

Mycology I: Opportunistic fungi Flashcards

1
Q

5 groups of medically important fungi

A
  1. Yeast
  2. Black molds (Dematiaceous)
  3. Hyaline molds
  4. Mucorales
  5. Dimorphs
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2
Q

Cryptococcous

A

HIV = neoformans (avian excrement)

Normal immune systems = gattii (eucalyptus trees)

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3
Q

Complications of cryptococcous neoformans

A

Meningoencephalitis (non-inflammatory, almost no white/phagocytic cells).

Pulmonary nodules
Disseminated disease: skin, brain abscess, etc. Not a pustule like staph.

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4
Q

Treat cryptococcous with ___?

A

Amphotericin B is the KEY!!

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5
Q

Test for cryptococcous?

A

Direct cryptococcal antigen test - can get from CSF and use a dipstick

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6
Q

White halo with india ink

A

Yeast capsule prevents dye - Cryptococcous

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7
Q

How to differentiate neoformans from the other kinds of cryptococcous

A

Neoformans = grows on birdseed agar (melanin production by phenol oxidase)

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8
Q

Do you need to treat candida in a urine sample?

A

If it’s just colonization, nope.If it’s invasive it will usually be with some other ascending infection related to obstruction.

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9
Q

Do you need a special media to grow candida?

A

Nope, grows on everything

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10
Q

Cryptococcous virulence

A

Capsule inhibits phagocytosis

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11
Q

What explains the neurotropism of cryptococcous?

A

The high levels of dopamine - a substrate to make melanin

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12
Q

Route of entry of cryptococcous

A

Inhalation

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13
Q

CRAG

A

Cryptococcal antigen test - detects the capsular polysaccharide; cheap and fast

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14
Q

CGB agar

A

differentiate gattii from neoformans because gattii will turn blue on CGB agar

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15
Q

3 species of candida associated with majority of invasive infections

A

Candida albicans
Candida parapsilosis
Candida glabrata

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16
Q

What is Candida krusei notable for?

A

Fluconazole resistance

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17
Q

Invasive candidiasis is a disease of _____ _____

A

medical progress

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18
Q

Key feature of C. albicans

A

Germ-tube positive

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19
Q

Virulence of Candida

A

Normal flora… so they overgrow when the host immune system sucks.

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20
Q

Host risks associated with candida

A
  • Intensive medical care (indwelling catheters)

- Immunocompromised hosts (premature infants, neutropenia)

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21
Q

Symptoms of clinical candidiasis

A

Fever +/- leukocytosis; skin papules indicate disseminated infection

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22
Q

3 syndromes of invasive candidiasis

A
  1. Isolated candidemia = easiest to recognize. Indwelling catheters
  2. Candidemia + visceral disease = eye** (endophthalmitis), kidney, brain, lung, etc
  3. Isolated visceral disease = no detectable bloodstream infection
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23
Q

Diagnosis of candida

A
  • Direct microscopy
  • Culture takes 1-5 days
  • Histo but granulomatous reaction is not typical
  • B-D-glucan antigen test! Present in most fungal cell walls
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24
Q

Is the B-D-glucan antigen test specific to candida?

A

Nope, but it is sensitive. Use it in high risk patients

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25
What is 1st line tx of candida?
Echinocandins
26
What treats endophthalmitis?
Fluconazole
27
4 species of aspergillum
1. Aspergillus fumigatus - majority 2. A. flavus 3. A. terreus 4. A. niger
28
What kind of environment does aspergillus enjoy?
- moist such as hay or water-damaged dwellings and old buildings
29
Mycology of aspergillus
Septate hypae
30
Rapid growing, fuzzy/velvety
Aspergillus
31
Pigmented center with white apron
Aspergillus
32
Colors for the different species
``` Blue-green = Fumigatus Brown = Terreus Black = niger Yellow = Flavus ```
33
What must the hyphae do to be identified on microscopic examination?
Sporulate
34
how do you get aspergillus?
Inhalation - usually grow and survive in an abnormal lung (like old TB cavities)
35
Pathogenesis of aspergillus in immunocompromised hosts?
- Angioinvasive --> ischemic necrosis --> clot formation --> infarction
36
Host risk factors for aspergillus
- Neutropenia (such as with AML) | - Old cavitary lung lesions
37
Chronic aspergillosis
- normal hosts | - may have wt loss, hemoptysis, and may look like malignancy
38
Acute invasive aspergillosis
- Fever + abnormal CXR/CT - Wedge shaped infarction - Rapidly expanding nodules - Disseminated aspergillosis from hematogenous spread
39
Cutaneous aspergillosis
- Seen with inoculation sites
40
Sino-orbital aspergillosis
- Identical in presentation to mucormycosis but happens in neutropenic hosts.
41
Diagnosis of aspergillosis
Direct microscopy (won't stain well) - Narrow hyphae (10-15 micrometers) - Septate, branching at 45 degree angles Serologic: - Aspergillus galactomannan antigen - B-D glucan antigen test
42
Tx for aspergillus
- Combo med surg >> med treatment alone | - Voriconazole, posaconazole, isavuconazole, amphotericin B, echinocandins
43
Disease producing species of mucormycosis
- Rhizopus arrhizus - Mucor - Rhizomucor
44
Substance that is 100% on glycemic index produces this fungus...
White bread - produces mucorales
45
Mycology of mucormycosis
- Rapid growing, wooly, white colony | - Hyphae are broad, ribbon-like, nonseptate, with 90 degree branching
46
What makes rhizopus grow in the presence of glucose and acid?
ketone reductase & free iron
47
Pathogenesis of mucorales
- Angioinvasive | - Spores can be inhaled
48
Host risk factors
- DKA | - Iron overload treatment with deferoxamine (iron chelator). Fungi can use the free iron... wheeee!
49
Rhinocerebral mucormycosis
Necrotic ulcer on plate followed by orbital invasion and extension into cavernous sinus and brain
50
Diabetic patient with facial swelling and black thing on the roof of their mouth
Rhinocerebral mucormycosis. They be dead soon bro.
51
Cutaneous mucormycosis
Seen with contaminated wounds
52
Diagnosis of mucormycosis
- Clinical presentation - Culture - Biopsy to see the broad hyphae that are non-septate and right angle branching
53
Tx of mucormycosis
- Combined med/surg (debridement + liposomal ampho B) | - Rhinocerebral is an EMERGENCY
54
PCP
Looks like protozoan because it is a fungus that lacks ergosterol
55
3 stages of PCP
1. Trophozoite 2. Pre-cyst 3. Thick-walled cyst (up to 8 intracystic bodies)
56
Perihilar reticulonodular infiltrates
PCP
57
What does a PCP culture show?
Nothing, you can't do it
58
When you use a GMS stain on PCP what do yousee?
Small non-budding yeasts that look like candida
59
Tx for PCP
TMP/SMX OR TMP + dapsone Clinda + primaquine, atovaquone, pentamidine, and trimetrexate
60
Black moulds
Dematiaceous fungi
61
What causes the "black" in black moulds?
Melanin within the cell walls and spores
62
What does black mould look like?
Narrow septate hyphae that branch at 45 degree angles Indistinguishable from aspergillus in tissue biopsies
63
How do colonies of black mould differ from any other colonies?
The brown-black color is on both the front and back
64
How do you get black moulds?
Direct inoculation events in normal hosts - soil or decayed vegetation
65
Clinical features of black moulds
Subcutaneous nodules that are slowly progressive and non-painful. Cerebral abscess - fever + HA + seizure
66
Diagnosis of black moulds
- Culture | - May have positive B-D-glucan antigen test
67
Tx of black moulds
- Surgical debridement | - Ampho B

Erica's ID 3 (13 decks)

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