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Medical microbiology > Opportunisitic mycoses > Flashcards

Opportunisitic mycoses Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

T or F: Opportunistic mycoses are of high virulence in patients who are immunologically compromised

A

false, low virulence

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2
Q

Pathogenic fungi found in immunocompetent hosts

A

Subcutaneous
Systemic
Cutaneous

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3
Q

Pathogenic fungi found in immunocompromised hosts

A

Opportunistic

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4
Q

T or F: number of organisms and its virulence is directly proportional to the probability of acquiring the disease

A

true

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5
Q

T or F: host resistance is directly proportional to the probability of acquiring the disease

A

False

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6
Q

opportunistic fungi from the environment

A

saprophytic

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7
Q

opportunistic fungi which is a commensal organism, normal flora and found inside the body

A

endogenous

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8
Q

most serious opportunistic infection

A

candida
aspergillus
mucor species (zygomyces)

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9
Q

Two classifications of candida species

A

C. albicans

Non-c. albicans

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10
Q

exhibits production of germ tube (rapid screening test to differentiate non albi and albi due to different treatments)

A

candida albicans (and C. dubliniensis??; germ tube supposed to differentiate albi and non-albi)

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11
Q

Characteristics of candida species

A

endogenous and saprophytic
part of normal flora
dimorphic

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12
Q

what is the cause of aquiring disease of candida species in immunocompromised?

A

low host resistance not number of organisms

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13
Q

characteristic feature of cutaneous candidiasis

A

satellite lesions

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14
Q

candida in culture or tissue is shown as

A

oval budding yeast cells

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15
Q

T or F: candida species forms pseudohyphae

A

True

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16
Q

candida species unique because it produces only yeast cells and no pseudohyphal forms

A

C. glabrata

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17
Q

clinical findings of candida infections

A 
oral thrush
interdigital candidiasis (of feet)
intertriginous/flexural candidiasis of the groin 
balanitis
vaginal candidiasis
candida onychomycosis (chronic)
generalized candidiasis
candida endopthalmitis
hepatic candidiasis
superficial candidiasis
candidiasis of the kidney
esophageal candidiasis
candida meningitis
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18
Q

patchy, whitish, pseudomembrane lesion (angular lesion) found in gums, tongue, palate and lips in immunocompromised patients secondary to candida species

A

Oral thrush

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19
Q

describe lesions found in intertriginous/flexural candidiasis fo the groin

A

erythematous and reddish

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20
Q

candidiasis of the penis

A

balanitis

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21
Q

candidiasis affecting retina wherein eye damage may happen in immunocompromised patients

A

candida endopthalmitis

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22
Q

what indicates candidiasis of the liver?

A

presence of calcifications

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23
Q

what specimen is used to observe candidiasis of the kideny

A

urine (hyphal and yeast forms are seen)

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24
Q

specimens used for laboratory diagnosis of candidiasis

A 
 Swabs
 Spinal fluid
 Scrapings from superficial lesions (cultures: confirmatory)
 Tissue biopsies
 Mounted in 10% KOH 
 Urine
 Blood
 Exudates

*sputum=no value

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25
Q

what are seen in gram stained smears of candida species?

A

pseudohyphae (@ lower layer) and budding cells (@ surface; spherical to ovoid blastoconidia)

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26
Q

Why is serology rarely used for lab diagnosis of candida species?

A

limited specificity and sensitivity

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27
Q

At which temperature are candida species cultured?

A

37C

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28
Q

agar used for candida species

A 
SDA
CHROMagar Candida (sophisticated, expensive)
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29
Q 
What is the color of the ff in CHROMagar:
o C. glabrata or C. krusei
o C. tropicalis
o C. albicans
o C. parapsilosis
A

o Pink: C. glabrata or C. krusei
o Blue: C. tropicalis
o Turquoise: C. albicans
o White: C. parapsilosis

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30
Q

Basidiomycetous yeasts with large polysaccharide capsules

A

Cryptococcus sp.

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31
Q

T or F: Cryptococcus has hyphal form and no yeast form

A

false; yeast form meron, hyphal wala

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32
Q

C. neoformans are found in

A

dry pigeon feces

33
Q

Cryptococcus gattii is found in

A

trees of tropical areas (less pathogenic species)

34
Q

Describe colonies of cryptoccus

A

whitish mucoid colonies within 2-3 days

35
Q

In direct microscopy what is observed in cryptococcus species

A

spherical budding yeast cells (more virulent) surrounded by non-staining capsules

36
Q

T or F: All cryptococcus specieas are urease positive

A

True

37
Q

T or F: Cryptococcus sp produces infection in normal hosts

A

False, only in immunocompromised

38
Q

How does C. gatii and neoformans differ from non-pathogenic species?

A

Their ability to grow at 37C

They both produce laccase (phenol oxidase)

39
Q

component of gatii and neoformans which catalyzes the formation of melanin from appropriate phenolic substrates (e.g. Catecholamines)

A

laccase (phenol oxidase)

40
Q

antigenic structures of cryptococcus

A 
capsular polysaccharide (enzyme immunoassay or by the agglutination of latex particles): so large and impenetrable na stinastain yung background instead of organism
melanin
41
Q

highly virulent disease caused by inhalation (main mode) or inoculation of cryptococcus neoformans

A

cryptococcosis

42
Q

different manifestations of cryptococcosis

A

cutaneous cryptococcosis
cryptomeningitis
disseminated cryptococcosis

43
Q

indicative of disease progression into a more severe skin lesion of cryptococcosis

A

if papule ulcerates

44
Q

specimens for lab diagnosis of cryptococcosis

A 
spinal fluid (KOH with india ink is used)
tissue (lung: GMS is used)
exudates
sputum
blood
urine
45
Q

T or F: histology with GMS shows hyphal forms of cryptococcus

A

False, only encapsulated yeast cells

46
Q

Which species is difficult to differentiate cryptococcus from in SDA culture?

*dark cream colored, smooth, moist, shining and mucoid colonies

A

Candida

47
Q

T or F: Cryptococcus is inhibited by cycloheximide

A

true

48
Q

color of neoformans and gatii in birdseed agar

A

brown pigment

49
Q

indirect test for capsular antigen of cryptococcus

A

Cryptococcus Aglutination Latex Serologic test (CALAS)

*only for CSF/blood/ serum

50
Q

most common cause of aspergillosis

A

A. fumigatus (thrives in wide range of temps 50C and inhibited by cycloheximide)

51
Q

aspergillus species associated with old stock nuts and aflatoxin

A

A. flavus

52
Q

What is characteristic of Aspergillus species

A

conidial head

*high amount of spores
branching, septate mycelium

53
Q

T or F: Aspergillus is purely in yeast form

A

false, mold form with true (aerial) hyphae (has septations)

54
Q

where phialides produce basipetal chains of conidia

A

terminal vesicles on long conidiophores

55
Q

modes of transmission of aspergillosis

A

respiratory (main mode), ingestion, direct inoculation

56
Q

Clinical findings of aspergillosis

A

allergy (benign), aspergilloma and extrapulmonary colonization (rarely invasive), invasive aspergillosis (causes abscesses and necrotic lesion)

57
Q

form of aspergillosis allergy wherein there is colonization of bronchial tree without invasion of lung parenchyma

A

allergic bronchopulmonary aspergillosis

*characterized by asthma, recurrent chest infiltrates,
eosinophilia, and both type I (immediate) and type III
(Arthus) skin test hypersensitivity to Aspergillus antigen

58
Q

Other forms of aspergillosis allergy

A

farmers lung

extrinsic allergic alveolitis (massive conidia in immunocompetent person)

59
Q

characteristic of aspergilloma and extrapulmonary colonization which occurs when inhaled conidia enter an existing cavity, and produce abundant hyphae

A

fungus ball

60
Q

what puts you at risk of aspergilloma?

A

previous cavity disease (tuberculosis, sarcoidosis, emphysema)

61
Q

What puts you at risk of invasive aspergillosis?

A

lymphocytic or myelogenous leukemia and lymphoma, stem cell transplant recipients, AIDS and corticosteroids

62
Q

In invasive aspergillosis, what does the hyphae invade and eventually cause?

A

lumens and walls of blood vessels causing thrombosis, infarction and necrosis

63
Q

Specimens for id aspergillus infection

A

Sputum
other respiratory tract specimens
lung biopsy tissue

(blood: rarely positive)

64
Q

used in direct examination of aspergillus sp

A

KOH and calcofluor white

*GMS in histologic sections

65
Q

has a clavate head, pitted conidiophore with conidiospores

A

A. flavus

66
Q

black, globular head with smooth conidiophore

A

A. niger

67
Q

clavate head with smooth conidiophore

A

A. fumigatus

68
Q

when are antibody tests not helpful in aspergillosis?

A

when diagnosing invasive aspergillosis

69
Q

a diagnostic direct test (serologic) for aspergillus

A

Serologic test for circulating cell wall galactomannan

70
Q

this was previously thought to be a protozoan, lacks capsule, irregularly round and causes pneumonia in immunocompromised and major cause of death in AIDS patients

A

Pneumocystis jiroveci: humans
P. carinii: rats

*genetically diverse (with different stains)

71
Q

T or F: P. jiroveci can be found in immunocompetent

A

False

72
Q

two forms of p. jiroveci which is extracellular

A

thin walled trophozoites

thick walled cysts

73
Q

symptoms of P. carinii pneumonia

A

 Dyspnea
 Non-productive cough
 Fever
 PCP if untreated, it leads to death

74
Q

Chest radiography of p. jiroveci infection shows

A

bilateral infiltrates

75
Q

Specimens used for diagnosing jiroveci infx

A

 Bronchoalveolar lavage
 Lung biopsy tissue
 Induced sputum

76
Q

stains used for microscopic examination of pneumocystis

A

 Giemsa, toluidine blue
 Methenamine silver
 Calcofluor white

77
Q

Higher sensitivity of id pneumoccy than conventional microscopy

A

IF microscopy using monoclonal abs

78
Q

T or F: P. jiroveci can be cultured and serology is useful

A

False

Medical microbiology (14 decks)

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