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Medical Microbiology II - 4336 > Blakes mycology part 2 > Flashcards

Blakes mycology part 2 Flashcards

1
Q

Identification of fungi

A

Molds are usually identified regardless of the source
Molds that fail to sporulate may be reported but not identified if dimorphism has been ruled out
Usually identified based on macroscopic & microscopic morphology

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2
Q

Asexual reproduction

A

Conidiophore vesicle—> Metulae—-> Phialides —–> Mature conidiophore —-> Conidia

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3
Q

Vegetative growth

A

Germling—> Foot cells—-> Formation of mycelium—-> Stalk

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4
Q

Safety

All molds must be handled in

plates should be

yeast are handled on

A

All molds must be handled in Class II biological safety cabinet
Plates should be sealed
Yeasts can be handled on benchtop

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5
Q

Mold identification

A

Growth rate
Colonial morphology
Microscopic morphology

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6
Q

Preparation for microscopic observations

A

Tape preparation
Wet mount (tease prep)
Microslide culture

Lactophenol cotton (or aniline) blue

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7
Q

Tease mount and tape prep

A
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8
Q

Cultivation

Incubate at blank

common media

Mycosel has what

A

Incubate at room temperature unless looking for yeast phase
Common media: Sabouraud dextrose, potato flake, BHI, mycosel (cycloheximide)
dermatophyte test medium

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9
Q

Deferential media

A

Differential: cottonseed conversion, urea,
trichophyton agars 1-7
Corn meal agar

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10
Q

Typical media selections

A

All-purpose: SABS or potato-based (PFA, PDA)
Selective: Mycosel (contains cycloheximide)*
Enriched: BHI (for Histoplasma)

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11
Q

Some Cryptococcus and Aspergillus are inhibited by

A

some Cryptococcus and Aspergillus inhibited by cycloheximide

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12
Q

Penicillium marneffei

A

from specimen
-Gram stain from blood culture bottle showing hyphae (mold form that exists at room temperature). Since blood cultures are incubated at 37 degrees Celsius, you would not expect to see hyphae unless the bottle had been left at room temperature for some time.
-Gram stain from blood culture showing yeast forms. This is what you would expect to see if the bottle was placed into the incubator with minimal delay.

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13
Q

Trichophyton species

The most common species are
both can produce a

A

The most common species are T. rubrum and T. mentagrophytes

-pigment

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14
Q

T. rubrum has a

A

Red pigment

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15
Q

T.mentagrophytes can range from

A

red to orange to reddish brown.

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16
Q

T. mentagrophytes are

A

T. mentagrophytes is urease positive and can penetrate hair.

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17
Q

Hair perforation test for

A

T. mentagrophytes

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18
Q

T.rubrum is

A

Urease negative

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19
Q

Macroconidium for Microsporum species

A

Large thick walled and divided into many cells by transverse septa. Tend to be spindle or boat-shaped

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20
Q

Microconidia for Microsporum species

A

Relatively few or absent if present they are tear-shaped and bome singly on the hyphae

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21
Q

Trichophyton species Macroconidium

A

Few or absent in some species. If present, they are elongated and cigar or pencil shaped. The walls are thin and smooth. Divided by septa into 3-8 cells

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22
Q

Microconidia in Trichophyton species

A

Usually numerous and bome singly along the hyphae or in grape like clusters

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23
Q

Direct detection of fungi

A

Calcofluor white
KOH
Histology stains

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24
Q

Many fungi are diagnosed

note the Aspergillus fumigatus

A

-Many fungal infections are diagnosed microscopically before culture by visualizing fungal elements.
-Note the Aspergillus fumigatus infection seen in the following slides. The specimen was pleural fluid.

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25
Other direct detection methods NAT
Nucleic acid amplification not available for most fungi NAT for Histoplasma, Blastomyces, Coccidioides: culture confirmation
26
Serodiagnosis
Useful for systemic fungi False-negatives: immunocompromised False-positives: cross-reactivity Complement fixation and immunodiffusion should be used in conjunction with antibody detection
27
EXO antigent test
28
Immunodiffusion
29
Yeast general charateristics
Unicellular organisms that reproduce asexually by budding (Blastoconidia) or sexually. Easy to see microscopically, but unable to identify to species level.
30
Microscopic analysis
Certain environmental stimuli can produce different morphologies that provide useful information for physician
31
Candida albicans features
Germ tube Pseudohyphae Chlamydospores
32
Cryptococcus spp
Capsule
33
Structures seen in yeast
Blastoconidia Chlamydospores and pseudohyphae are most common in Candida albicans
34
Agents of yeast infection
The most commonly seen/significant isolates are: Candida albicans (and other species) Cryptococcus neoformans and C. gattii Trichosporon Malessezia furfur
35
Candida most common other species is a what extended antibiotic use and chemo
Candida: most common yeast isolated C. albicans most common species Other species: C. glabrata, C. tropicalis, C. parapsilosis, C. krusei Candida is normal flora Extended antibiotic use and chemotherapy can lead to the overgrowth of yeast and infection
36
Candida conditions
37
Intertriginous candidiasis (cutaneous) Chronic paronychia Candidial Onychomycosis Perleche
Candida albicans
38
Common Candida Infections
Thrush Vulvovaginitis Pulmonary infections Eye infection Endocarditis Meningitis Fungemia
39
Candida laboratory diagnosis
Gram stains Germ tubes/pseudohyphae Chlamydospores (chlamydoconidia) Culture
40
Germ tube procedure
Inoculate a small amount of yeast cells into about 0.5 mL serum. Incubate and examine on 40x after two to four hours
41
Chromagar what
Candida
42
C.glabrata what
mauve to dark mauve- light purple color
43
C.krusei color
light rose to pink with a whitish border
44
Candida auris emerging what four geographic clades
-Emerging fungal pathogen (considered a global health threat) Four geographic clades -South Asian, South African, South American, and East Asian
45
Candida auris diseases and causes what
1. Can cause invasive disease 2. Has caused outbreaks Can persist on surfaces Routine disinfectants (Quaternary Ammonium Compounds) may not be effective
46
Candida auris difficult to what
3. Difficult to identify by standard lab methods No phenotypic methods easily distinguish from other Candida Most frequently misidentified as C. haemulonii MALDI-TOF is the best method
47
Candida auris is frequently what
4. Frequently multi-drug resistant 90% resistant to fluconazole (in the US) 30% resistant to amphotericin B (in the US) <5% resistant to echinocandins (in the US)
48
Cryptococcus neoformans is what
Saprobe in nature (pigeons) Immunocompromised: dissemination common with or w/o meningitis
49
Cryptococcus infections
-Manifestation depends on host immune status -Initially, may present as a pulmonary infection. -May travel to the central nervous system (neurotropic) where it may be able to cross the blood-brain barrier which is facilitated by a thick polysaccharide capsule and other virulence factors such as phenyloxidase.
50
Disseminated infections in cryptococcus infections Symptoms Specimens
Patients with disseminated infection may have painless papular skin lesions that may ulcerate. Symptoms are similar to bacterial meningitis Specimens: Blood and Spinal Fluid
51
Cryptococcus lab diagnosis
-India ink, gram stain -Culture; bird seed agar (niger seed) Urease test, -Serologic: Based on detection of antigens (not antibodies). Latex test detects capsular polysaccharide antigens, lateral flow test also available now Caffeic acid test
52
Malassezia furfur
Causes tinea versicolor (pityriasis versicolor) Superficial brownish scars Disseminates in infants
53
Malassezia furfur Rare but important agent of Attention to medical practices when administering what
-Rare but important agent of pulmonary infection or fungemia in neonates, especially pre-term infants. -Attention to medical practices when administering lipid-containing emulsions to infants can greatly reduce the incidence
54
culture of Malessezia
-Culture is usually performed in cases of suspected fumgemia (babies). -M. furfur is a lipophilic yeast, therefore in vitro growth must be stimulated by natural oils or other fatty substances. -The most common method used is to overlay Sabouraud's dextrose agar containing cycloheximide with olive oil or alternatively to use a more specialized media like Dixon's agar which contains glycerol mono-oleate (a suitable substrate for growth).
55
Trichosporon beigelii
-Yeast-like organism -Immunocompromised patients/leukemia -Usually superficial/Rarely disseminated It also causes white piedra
56
Usually identify to species from in patient is not
-From sterile sources -In serious ill/compromised patients -Patient not responding to therapy
57
Presumptive identification C.albicans- Cryptococcus- Commercially blank
-C. albicans – germ tubes -Cryptococcus – India Ink and antigenic typing -Commercially manufactured kits are available
58
Cornmeal agar
Cornmeal agar (chlamydospores in Candida)
59
Sabouraud Dextrose Agar
will grow most yeast and molds
60
Chromagar
Chromagar (for Candida)
61
Niger seed
Niger seed (for Cryptococcus
62
Oil overlay for
Oil overlay for Malessezia with olive oil in sabouraud dextrose media
63
Mycosel for
Mycosel for filamentous fungi
64
Other ID methods
Sugar assimilation API, RapID Yeast Plus Panel, Vitek, MALDI-TOF
65
Vitek
Yeast card
66
Antifungal agents
-Polyenes: Amphotericin B Binds ergosterol, increases cell permeability, leading to leakage of cellular contents and cell death -Azoles: fluconazole, itraconazole, voriconazole, posaconazole Impair ergosterol synthesis in the cytoplasmic membrane -Nucleoside analog – flucytosine Disrupts pyrimidine metabolism in the cell nucleus -Echinocandin – caspofungin and micafungin Inhibits formation of 1,3 glucan which is part of the cell wall -Allylamine – terbinafine Disrupts the fungal cell membrane (squalene oxidase)
67
Polyenes: Amphotericin B
Binds ergosterol, increases cell permeability, leading to leakage of cellular contents and cell death
68
Azoles
fluconazole, itraconazole, voriconazole, posaconazole Impair ergosterol synthesis in the cytoplasmic membrane
69
Nucleoside analog
flucytosine Disrupts pyrimidine metabolism in the cell nucleus
70
Echinocandin
caspofungin and micafungin Inhibits formation of 1,3 glucan which is part of the cell wall
71
Allylamine
– terbinafine Disrupts the fungal cell membrane (squalene oxidase)
72
Susceptibility testing methods yeast
frequently performed for yeast Usually from sterile sites and upon Physician request IVD method, Sensititre YeastOne
73
Suceptibility testing for molds
molds performed at reference laboratories Sterile site infections Therapeutic failure
74
Sensititre
Yeast one
75
Dixon media
Media for M furfur with glycerol mono oleate Spaghetti and meatballs

Medical Microbiology II - 4336 (20 decks)

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