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ID Review > Mycology > Flashcards

Mycology Flashcards

1
Q

What is a dermatophyte?

A

Fungus with the ability to obtain nutrients from keratin and therefore infects skin, hair, or nails.

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2
Q

What is hyaline vs dematiaceous?

A

Hyaline is see through, dematiaceous is pigmented.

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3
Q

Is it a yeast, mold, or dimorphic: Candida

A

Yeast

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4
Q

Is it a yeast, mold, or dimorphic: Cryptococcus

A

Yeast

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5
Q

Is it a yeast, mold, or dimorphic: Geotrichum

A

Yeast

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6
Q

Is it a yeast, mold, or dimorphic: Saccharomyces

A

Yeast

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7
Q

Is it a yeast, mold, or dimorphic: Rhodotorula

A

Yeast

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8
Q

Is it a yeast, mold, or dimorphic: Trichosporon

A

Yeast

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9
Q

Is it a yeast, mold, or dimorphic: Malassezia

A

Yeast

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10
Q

Is it a yeast, mold, or dimorphic: Histoplasma

A

Dimorphic

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11
Q

Is it a yeast, mold, or dimorphic: Blastomyces

A

Dimorphic

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12
Q

Is it a yeast, mold, or dimorphic: Coccidioides

A

Dimorphic

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13
Q

Is it a yeast, mold, or dimorphic: Paracoccidioides

A

Dimorphic

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14
Q

Is it a yeast, mold, or dimorphic: Talaromyces marneffei

A

Dimorphic

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15
Q

Is it a yeast, mold, or dimorphic: Sporothrix Schenckii

A

Dimorphic

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16
Q

Is it a yeast, mold, or dimorphic: Rhizopus

A

Mold

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17
Q

Is it a yeast, mold, or dimorphic: Rhizomucor

A

Mold

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18
Q

Is it a yeast, mold, or dimorphic: Mucor

A

Mold

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19
Q

Is it a yeast, mold, or dimorphic: Alternaria

A

Mold

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20
Q

Is it a yeast, mold, or dimorphic: Bipolaris

A

Mold

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21
Q

Is it a yeast, mold, or dimorphic: Curvularia

A

Mold

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22
Q

Is it a yeast, mold, or dimorphic: Exserohilum

A

Mold

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23
Q

Is it a yeast, mold, or dimorphic: Fonsecaea

A

Mold

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24
Q

Is it a yeast, mold, or dimorphic: Scedosporium

A

Mold

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25
Q

Is it a yeast, mold, or dimorphic: Microsporum

A

Mold

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26
Q

Is it a yeast, mold, or dimorphic: Trichophyton

A

Mold

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27
Q

Is it a yeast, mold, or dimorphic: Epidermophyotn

A

Mold

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28
Q

Is it a yeast, mold, or dimorphic: Aspergillus

A

Mold

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29
Q

Is it a yeast, mold, or dimorphic: Fusarium

A

Mold

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30
Q

Is it a yeast, mold, or dimorphic: Acremonium

A

Mold

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31
Q

Is it a yeast, mold, or dimorphic: Scopulariopsis

A

Mold

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32
Q

Is it a yeast, mold, or dimorphic: Penicillum

A

Mold

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33
Q

How are molds sub divided?

A

Zygomycetes, dematiaceous, dermatophytes, hyaline hyphomycetes

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34
Q

What are zygomycetes?

A

This is a phylum of fungi that have broad irregularly 90 degree/right angle branched hyphae with rare septations.

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35
Q

Name the hyaline hypomycetes [5]

A

Aspergillus, fusarium, acremonium, scopulariopsis, pencillium

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36
Q

Name the dermatophyes [3]

A

Microsporum, trichophyton, Epidermophyton

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37
Q

Name the dematiaceous molds [6]

A

Alternaria, Bipolaris, Curvularia, Exserohilum, Fonsecaea, Scedosporium

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38
Q

Name the Zygomyctes [3]

A

Rhizopus, Rhizomucor, Mucor

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39
Q

Name the thermally dimorphic molds [6]

A

Histoplasma, Blastomyces, Coccidioides, Paracoccidioises, Talaromyces marneffei, Sporothix

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40
Q

Name the Non-Candida yeasts [6]

A

Cryptococcus, geotrichum, saccharomyces, rhodotorula, trichosporon, malassezia

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41
Q

Name the 6 types of candida

A

Albicans, brusei, parapsilosis, glabrata, tropicalis, lusitanie

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42
Q

What is the most common and 2nd most common cause of BSI with yeast?

A

Candida is the most common, Cryptococcus is the second most common.

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43
Q

How is candida differentiated from Cryptococcus microscopically?

A

Candida forms pseudohyphae and is oval shaped. Cryptococcus is larger, round, has a visible capsule and NEVER forms pseudohyphae

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44
Q

What does malassezia require to grow?

A

Oil or tween

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45
Q

C. albicans resistance pattern

A

Susceptible to fluconazole and echinocandins.

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46
Q

C. tropicalis resistance pattern

A

Susceptible to fluconazole and echinocandins.

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47
Q

C. Dubliniensis resistance pattern

A

Susceptible to fluconazole and echinocandins.

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48
Q

C. guilliermondii resistance pattern

A

Susceptible to fluconazole and echinocandins.

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49
Q

C. glabrata resistance pattern

A

Resistant to fluconazole. Susceptible to echinocandins but resistance is rising. 2nd most common candida infection

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50
Q

C. parapsilosis resistance pattern

A

Susceptible to fluconazole, increased MIC to echinocandins

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51
Q

C. parapsilosis causes what sort of disease?

A

Central line and implantable device diseases due to biofilm formation.

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52
Q

C. krusei resistance pattern

A

Resistant to fluzonazole, susceptible to echinocandins. May be resistant to amphotericin B and flucytosine

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53
Q

What types of patients get C. krusei infection?

A

Those with hematologic malignancy 2/2 azole prophylaxsis

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54
Q

C. lusitaniae resistance pattern

A

Resistant to amphotericin B but susceptible to fluzonazole and echinocandins.

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55
Q

C. auris resistance pattern

A

Resistant to fluconazole, ampho B, echinocandins

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56
Q

What is C. auris often mislabeled as?

A

Saccharomyces or C. haemulonii

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57
Q

Can candida cause pneumonia?

A

It is very uncommon and needs a biopsy for confirmation.

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58
Q

Micro shows yeast with pseudohyphae with clusters of blastoconidia at the septa. Diagnosis?

A

Candida

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59
Q

What infections does cryptococcus cause?

A

Meningitis, pneumonia, skin infections, sepsis

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60
Q

Micro shows round budding yeast with no hyphae. Diagnosis.

A

Cryptococcus

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61
Q

Who is at risk for cryptococcus infections?

A

HIV with CD4 <100, transplant recipients, those on steroids, those with malignancy and liver disease

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62
Q

What infections doe Geotrichum cause?

A

BSI, pneumonia

63
Q

Micro shows arthroconidia that are in chains. Rectangle or barrel shaped. True hyphae are seen. Diagnosis?

A

Geotrichum

64
Q

Risk factors for Geotrichum?

A

Neutropenia, heart valve surgery in immunocompromised host.

65
Q

What infections does rhodotorula cause?

A

BSI, and CLABSI.

66
Q

Micro shows unicellular blastoconidia, globose to elongated in shape. No hypae or pseudohypae. Growth is orange, red, or coral colored. Diagnosis?

A

Rhodotorula

67
Q

What is rhodotorula associated with?

A

Central lines in immunocompromised

68
Q

How does saccharomyces cause infection?

A

Associated with probiotic use. BSI. Rare infection.

69
Q

Micro shows unicellular globuse and ellipsoid to elongated blastoconida with multipolar budding. Diagnosis?

A

Saccharomyces.

70
Q

Micro shows round to oval nonbudding with comma-shaped focal thickening on the wall. Diagnosis?

A

Pneumocystis jirovecii

71
Q

Micro shows small oval budding yeast at 37 degrees celsius and septate hyphae with round/pear shaped microconidia and large tuberculate macroconidia at 25-30 degrees celsius. Diagnosis?

A

Histoplasmosis.

72
Q

Micro shows broad-based budding yeast at 37 degrees celsius and septate branched hyphae with intercalary or terminal chlamydospores at 25-30 degrees celsius. Diagnosis?

A

Blastomycosis

73
Q

Micro shows round thic-walled spherules containing endospores at 37 degrees celsius and septate branched hyphae with thick-walled arthroconidia at 25-30 degrees celsius. Diagnosis?

A

Coccidioides

74
Q

Micro shows large round thick-walled yeast with ship’s-wheel appearance budding at 37 degrees celsius and septate branched hyphae with intercalary or terminal chlamydospores at 25-30 degrees celsius. Diagnosis?

A

Paracoccidioides

75
Q

Where is paracoccidioides endemic?

A

South America

76
Q

What type of infection does talaromyces marneffei cause?

A

Skin, CNS, bone infections

77
Q

Micro shows small oval non-budding yeast at 37 degrees celsius with smooth conidiophores with 4-5 terminal metulae. each metulae bearing 4-6 phialides at 25-30 degrees celsius.

A

talaromyces marneffei

78
Q

Where is talaromyces marneffei endemic?

A

Southwest and Southern China and Southeast Asia

79
Q

What fungus has a biopsy that resembles squamous cell cancer?

A

Blastomyces

80
Q

What causes rose handler’s disease?

A

Sporothrix

81
Q

Micro shows small fusiform budding yeast at 37 degrees celsius and narrow septate hyphae with tapering conidiophores at right angles at 25-30 degrees. Diagnosis?

A

Sporothrix

82
Q

Micro shows thick-walled budding yeast at 37 degrees ant septate hyphae with round conidiophores at right angle at 25-30 degrees. Diagnosis?

A

Emonsia

83
Q

What disease does emmonsia cause?

A

Pneumonia and skin infection

84
Q

Who gets emmonsia?

A

Those with CD4 <100, this with malignancy, transplant patients. Those in South Africa

85
Q

Micro shows branched sporangiophores with no rhizoid structure. Diagnosis?

A

Mucor

86
Q

Micro shows nonbranching sporeangiophore originatinf from hyphae with rhizoid structure directly below the sporangiophore. Diagnosis?

A

Rhizopus

87
Q

Micro shows brnaching sporangiophore with rhizoid structure away from the origin of sporangiophore. Diagnosis?

A

Rhizomucor

88
Q

Who are at high risk for mucor? [5]

A

Uncontrolled DM, hematoligic malignancy, transplant, iron over-loard, or those on iron chelation.

89
Q

What is the treatment for mucor?

A

Ampho B for severe infections. Psoaconazole or isavuconazole for step-down after induction or for mild/moderate infection.

90
Q

Do dimorphic fungi ever represent contaminates?

A

No.

91
Q

Do hyaline hyphomycetes ever represent contaminants?

A

Yes! Get lab confirmation.

92
Q

Micro shows septate hyphae with conidiophore ending in phialides radiating around vesicle. Diagnosis?

A

Aspergillus

93
Q

Micro shows septate hyphae with canoe-shaped macroconidia. Diagnosis?

A

Fusarium

94
Q

Which fungus is able to sporulate inside the body and disseminate through the blood and yield positive blood cultures?

A

Fusarium

95
Q

How does fusarium present?

A

Seen during engraftment phase post stem cell transplant with skin lesions and fevers. Often starts with cellulitis surrounding toenails.

96
Q

Fusarium treatment?

A

Ampho B and vorizonazole prior to species level identification.

97
Q

Aspergillus treatment?

A

Voriconazole.

98
Q

General treatment methods for hyphomycete infections?

A

Ampho B for severe, voriconazole/isavuconazole for mild/moderate.

99
Q

In general what is treatment for dematiaceous molds

A

Surgical debridement, ampho B or voriconazole

100
Q

How are dematiaceous molds differentiared in tissue from hyaline hyphomyctes?

A

Fontana-Mason stain [stains the melanin in dematiaceous molds]

101
Q

What fungi might grow in a patient on amphotericin? [8]

A

C. lusitaniae, C. auris, fusarium, aspergillus terreus, Scedosporium apiospermum, Lomentospora prolificans, Sporothrix schenckii, Pseudallesdheria boydii

102
Q

Utility of blood culture with yeasts?

A

Most yeast grow well in blood cultures.

103
Q

Utility of blood culture with dimorphic fungi?

A

Can be positive in severe disseminated disease but this is a slow and insensitive method.

104
Q

Micro shows dark septate hyphae with alternating septated conidia. Diagnosis?

A

Alternaria

105
Q

Who gets alternaria?

A

Those with hematologic malignancy HSCT, and neutropenia.

106
Q

Micro shows dark septate hyphae with elongated septate conidia that taper at both poles. Diagnosis?

A

Bipolaris [tapers at both poles…bipolar]

107
Q

Who gets bipolaris infection

A

Those with hematologic malignancy, HSCT, neutropenia.

108
Q

Micro shows dark sepatate hyphae, septate curved conidia. Diagnosis?

A

Curvularia

109
Q

Who gets culvularia?

A

Those with hematologic malignancy, HSCT, neutropenia.

110
Q

Micro shows septate hyphae with swollen elongated conidia. Diagnosis?

A

Scedosporium/Lomentospora

111
Q

Who gets Scedosporium/Lomentospora?

A

Immunocompromised patients.

112
Q

Micro shows dark budding yeast like cells that eventually produce spetate hyphae and flask-shaped conidiogenous cells. Diagnosis?

A

Exserohilum

113
Q

What fungus is associated with outbreaks during natural disasters?

A

Exserohilum

114
Q

What fungus was associated with contaminated steroid injections?

A

Exserohilum

115
Q

What type of agar do most fungi grow on?

A

Emmons modification of sabourauds dextrose agar or potato dextrose agar

116
Q

What temp should fungi be incubated at?

A

25 degrees celsius to assist in identification of dimorphic molds

117
Q

How long will it take for fungal cultures to become positive?

A

4 weeks for many, 3 days for candida.

118
Q

What is a lactophenol cotton blue stain?

A

Identifies fungal structures from colonies on cultures [NOT tissue stains]. Lactic acid is a clearing agent and preserves fungal structures. Cotton blue stains.

119
Q

What is a calcofluor white stain?

A

Binds to cellulose and chitin and fluoresces when exposed to long wave UV light.

120
Q

How is pneumocystis usually idenitifed?

A

Direct fluorescent antibody stain.

121
Q

What is a giemsa stain used for?

A

Typically to detect intracellular organisms such as malaria, chlamydia. Also detects yersinia. In mycology it detects intracellular histoplasma in bone marrow or blood smears

122
Q

How does a gomori methamine silver stain work?

A

Mucopolysaccharide components of the fungal cell wall react with silver nitrate reducing it to metalic silver rendering a brown-black compound. Fungi look black on a green back round.

123
Q

How does a periodic acid-schiff stain work in fungi?

A

Periodic acid attacks carbohydrates containing 1,2-glycol or OH group with conversion to 1,2-aldehydes which then react with the fuchsin-sulfurous acid to form a magenta color.

124
Q

Utility of PAS stain?

A

Pan stain similar to GMS

125
Q

What is a mucicarmine stain used for?

A

Histologic visualization of mucopolysaccharides in the capsule of cryptococcus neoformans/gattii. Differentiates cryptococcus from other yeasts in tissues. Can also stain Rhinosporidium and Blastomyces dermatitiddis

126
Q

How does a fontana-masson silver stain work?

A

Oxidizes melanin and melanin-like pigments as it reduces silver giving a visible black color.

127
Q

What is a fontana-masson stain used for?

A

Differentiates fungi that produce melanin and dematiaceous molds from those who do not. It will also be positive with capsule-deficient [and therefore mucicarmine negative] cryptococci.

128
Q

What is T2Candida assay?

A

Uses Magnetic resonance to detect candida. It is 91% sensitive and 99% specific.

129
Q

What candida can T2 detect? [5]

A

Albicans, tropicalis, parapsilosis, krusei, glabrata.

130
Q

What is 1,3 beta-D-Glucan?

A

Cell wall component of many fungi. Typically used as a candida marker.

131
Q

What will make beta-d-glucan positive?

A

IVIG, IV penicillin, pneumocysitis, histoplasma

132
Q

What fungi is beta-d-glucan NEGATIVE?

A

cryptococcosis, zygomycetes

133
Q

What is galactomannan?

A

It is a polysaccharide constituent of Apergillus cell walls?

134
Q

What can make galactomannan false positive?

A

Fusarium, penicillium, histoplasma, zosyn, augmentin used to be positive if made before 2010. [May be positive up to 5 days after stoping abx.]

135
Q

What can make galactomannan false negative?

A

Antifungal use.

136
Q

What can make cryptococcal antigen false positive?

A

Rarely Trichosporon asahii, Rothia, Capnocytophaga.

137
Q

What is the utility of the quantitative histoplasmosis assay?

A

Helps ascertain severity of the infection and monitors for antigen clearance.

138
Q

On what is histoplasmosis antigen performed?

A

Blood, urine [most common], CSF

139
Q

What are the sensitivities of histoplasmosis antigen?

A

90% positive in BAL, 75% in CSF

140
Q

What can lead to a false positive histoplasmosis antigen?

A

Blastomycosis [so high that often the histoplasmosis urine antigen is used to diagnosis blastomycosis], talaromycosis, paracoccidioidomycosis, coccidioidomycosis

141
Q

What can cause false negative histoplasmosis antigen?

A

Localized disease [only pulm], immunosuppression

142
Q

What can cause false negative histoplasmosis antigen?

A

Localized disease [only pulm], immunosuppression

143
Q

How do histoplasma antibodies work?

A

Uses immunodiffusion to report M or H precipitin bands. M band becomes positive soon after exposure and is positive in most patients. H band is seen in <20% of cases but is specific for disseminated infection, chronic cavitary pulmonary histo, or severe acute pulmonary histo.

144
Q

Does H band clear? M band?

A

Yes, 6 months after infection. M band persists for years.

145
Q

What does the presence of M band alone indicate?

A

Early or chronic disease.

146
Q

What titer is sensitive for acute infection with M and H bands?

A

1:32 or higher.

147
Q

What can cause a false positive histoplasmosis antibody?

A

Coccidioidomycosis, blastomycosis, some granulomatous disease such as sarcoid and TB.

148
Q

What can cause false negative histoplasmosis antibody?

A

Immunosuppression.

149
Q

What can cause cross reactivity with blastomyces antibodies?

A

Histoplasma capsulatum exposure. NOT A GOOD TEST AND IS RARELY USED.

150
Q

How long does it take for coccidoides IgM and IgG to show up in the serum? How long does it take for it to go back down?

A

IgM: 1 week; persists 2-3 months
IgG: 3-6 weeks; persists 2 years

151
Q

What coccidio complement fixation antibody titer is suggestive of dissemination?

A

> 1:16

152
Q

What is the utility of CF antibody titer for coccidio?

A

It has prognostic, diagnostic, and response to therapy.

153
Q

What is the utility of CSF coccidio antibodies?

A

It is highly specific for meningitis

154
Q

What is the utility of a coccidio antigen?

A

Useful in immunocompromised moreso in the setting of negative serologies and can serve as a surogate marker of fungal burden in severe disease and be used to monitor response to therapy.

ID Review (25 decks)

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