Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

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

Blakes mycology part 2 Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards USMLE® Step 1 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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Asexual reproduction

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Vegetative growth

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Mold identification

A

Growth rate
Colonial morphology
Microscopic morphology

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Preparation for microscopic observations

A

Tape preparation
Wet mount (tease prep)
Microslide culture

Lactophenol cotton (or aniline) blue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Tease mount and tape prep

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Deferential media

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Typical media selections

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Some Cryptococcus and Aspergillus are inhibited by

A

some Cryptococcus and Aspergillus inhibited by cycloheximide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

T. rubrum has a

A

Red pigment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

T.mentagrophytes can range from

A

red to orange to reddish brown.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

T. mentagrophytes are

A

T. mentagrophytes is urease positive and can penetrate hair.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Hair perforation test for

A

T. mentagrophytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

T.rubrum is

A

Urease negative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Microconidia for Microsporum species

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Microconidia in Trichophyton species

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Direct detection of fungi

A

Calcofluor white
KOH
Histology stains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Other direct detection methods

NAT

A

Nucleic acid amplification
not available for most fungi
NAT for Histoplasma, Blastomyces, Coccidioides: culture confirmation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Serodiagnosis

A

Useful for systemic fungi
False-negatives: immunocompromised
False-positives: cross-reactivity
Complement fixation and immunodiffusion should be used in conjunction with antibody detection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

EXO antigent test

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Immunodiffusion

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Yeast general charateristics

A

Unicellular organisms that
reproduce asexually by budding
(Blastoconidia) or sexually.

Easy to see microscopically, but unable to identify to species level.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Microscopic analysis

A

Certain environmental stimuli can produce different morphologies that provide useful information for physician

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Candida albicans features

A

Germ tube
Pseudohyphae
Chlamydospores

32
Q

Cryptococcus spp

A

Capsule

33
Q

Structures seen in yeast

A

Blastoconidia
Chlamydospores and pseudohyphae are most common in Candida albicans

34
Q

Agents of yeast infection

A

The most commonly seen/significant isolates are:
Candida albicans (and other species)
Cryptococcus neoformans and C. gattii
Trichosporon
Malessezia furfur

35
Q

Candida

most common

other species

is a what

extended antibiotic use and chemo

A

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
Q

Candida conditions

A
37
Q

Intertriginous candidiasis
(cutaneous)
Chronic paronychia
Candidial Onychomycosis
Perleche

A

Candida albicans

38
Q

Common Candida Infections

A

Thrush
Vulvovaginitis
Pulmonary infections
Eye infection
Endocarditis
Meningitis
Fungemia

39
Q

Candida laboratory diagnosis

A

Gram stains
Germ tubes/pseudohyphae
Chlamydospores (chlamydoconidia)
Culture

40
Q

Germ tube procedure

A

Inoculate a small amount of yeast cells into
about 0.5 mL serum.
Incubate and examine on 40x after two to four hours

41
Q

Chromagar what

A

Candida

42
Q

C.glabrata what

A

mauve to dark mauve- light purple color

43
Q

C.krusei color

A

light rose to pink with a whitish border

44
Q

Candida auris

emerging what

four geographic clades

A

-Emerging fungal pathogen (considered a global health threat)
Four geographic clades
-South Asian, South African, South American, and East Asian

45
Q

Candida auris diseases

and causes what

A
  1. Can cause invasive disease
  2. Has caused outbreaks
    Can persist on surfaces
    Routine disinfectants (Quaternary Ammonium Compounds) may not be effective
46
Q

Candida auris

difficult to what

A
  1. 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
Q

Candida auris is frequently what

A
  1. 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
Q

Cryptococcus neoformans is what

A

Saprobe in nature (pigeons)
Immunocompromised: dissemination common with or w/o meningitis

49
Q

Cryptococcus infections

A

-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
Q

Disseminated infections in cryptococcus infections

Symptoms

Specimens

A

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
Q

Cryptococcus lab diagnosis

A

-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
Q

Malassezia furfur

A

Causes tinea versicolor (pityriasis versicolor)

Superficial brownish scars

Disseminates in infants

53
Q

Malassezia furfur

Rare but important agent of

Attention to medical practices when administering what

A

-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
Q

culture of Malessezia

A

-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
Q

Trichosporon beigelii

A

-Yeast-like organism
-Immunocompromised patients/leukemia
-Usually superficial/Rarely disseminated
It also causes white piedra

56
Q

Usually identify to species

from

in
patient is not

A

-From sterile sources
-In serious ill/compromised patients
-Patient not responding to therapy

57
Q

Presumptive identification

C.albicans-

Cryptococcus-

Commercially blank

A

-C. albicans – germ tubes
-Cryptococcus – India Ink and antigenic typing

-Commercially manufactured kits are available

58
Q

Cornmeal agar

A

Cornmeal agar (chlamydospores in Candida)

59
Q

Sabouraud Dextrose Agar

A

will grow most yeast and molds

60
Q

Chromagar

A

Chromagar (for Candida)

61
Q

Niger seed

A

Niger seed (for Cryptococcus

62
Q

Oil overlay for

A

Oil overlay for Malessezia with olive oil in sabouraud dextrose media

63
Q

Mycosel for

A

Mycosel for filamentous fungi

64
Q

Other ID methods

A

Sugar assimilation
API, RapID Yeast Plus Panel, Vitek, MALDI-TOF

65
Q

Vitek

A

Yeast card

66
Q

Antifungal agents

A

-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
Q

Polyenes: Amphotericin B

A

Binds ergosterol, increases cell permeability, leading to leakage of cellular contents and cell death

68
Q

Azoles

A

fluconazole, itraconazole, voriconazole, posaconazole
Impair ergosterol synthesis in the cytoplasmic membrane

69
Q

Nucleoside analog

A

flucytosine
Disrupts pyrimidine metabolism in the cell nucleus

70
Q

Echinocandin

A

caspofungin and micafungin
Inhibits formation of 1,3 glucan which is part of the cell wall

71
Q

Allylamine

A

– terbinafine
Disrupts the fungal cell membrane (squalene oxidase)

72
Q

Susceptibility testing methods yeast

A

frequently performed for yeast
Usually from sterile sites and upon Physician request
IVD method, Sensititre YeastOne

73
Q

Suceptibility testing for molds

A

molds performed at reference laboratories
Sterile site infections
Therapeutic failure

74
Q

Sensititre

A

Yeast one

75
Q

Dixon media

A

Media for M furfur with glycerol mono oleate

Spaghetti and meatballs

Medical Microbiology II - 4336 (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions