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MYCOLOGY AND VIROLOGY > Laboratory Identification of Fungi > Flashcards

Laboratory Identification of Fungi Flashcards

1
Q

The diagnosis of fungal infections depends entirely on the

A

Selection and collection of an appropriate clinical specimen for microscopic analysis and culture

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2
Q

Many infections have a primary focus in what organ

A

Lungs

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3
Q

This specimen almost always included among the specimens selected for culture

A

Respiratory tract secretions

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4
Q

Dissemination to distant body sites may occur, and fungi may be recovered from nonrespiratory sites. True or false?

A

True

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5
Q

These steps are crucial for the recovery of fungi

A

Proper collection of specimens and rapid transport to the clinical laboratory

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6
Q

What happens to the viability of fungi over time?

A

Decrease

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7
Q

What to do when specimen processing will be delayed?

A

Specimens can be refrigerated for a short time

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8
Q

Specimens that cannot be refrigerated

A

Dermatologic specimens (skin, hair, nails), blood, and cerebrospinal fluid (CSF)

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9
Q

This are commonly are recovered on routine bacteriology media and fungal culture media

A

Yeasts

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10
Q

Respiratory tract secretions include

A

Sputum
Induced sputum
Bronchial washings
Bronchoalveolar lavage
Tracheal aspirations

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11
Q

The most common specimens collected for fungal culture

A

Respiratory tract secretions

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12
Q

How to ensure optimal recovery of fungi and prevent overgrowth by contaminants when using respiratory tract secretions?

A

Antibacterial antibiotics should be included in the battery of media used

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13
Q

Antifungal agent used when handling respiratory tract secretions

A

Cycloheximide

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14
Q

Function of cycloheximide when added to respiratory tract secretions

A

Prevents overgrowth by rapidly growing molds

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15
Q

How much specimen (respiratory tract secretions ) must be inoculated in each medium?

A

0.5mL

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16
Q

Cerebrospinal fluid collected for culture should be fil- tered through

A

0.45-μm membrane filter attached to a sterile syringe

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17
Q

CSF cultures should be examined for

A

Daily

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18
Q

What to do after CSF filtration is done?

A

After filtration, the filter is removed and placed on the surface of an appropriate culture medium with the inoculum side down. Alternatively, the specimen may be centrifuged and the concentrated sediment used to inoculate the culture medium

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19
Q

What should we do if CSF specimen is plated using a filter?

A

The filter should be moved to another location every other day

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20
Q

What should we do if less than 1 mL of CSF specimen is submitted for culture?

A

It should be centrifuged, and 1-drop aliquots of the sediment should be placed on several areas on the agar surface

21
Q

Media used for the recovery of fungi from CSF should contain

A

No antibacterial or antifungal agents

22
Q

Once submitted to the laboratory, CSF specimens should be processed

A

Promptly

23
Q

If prompt processing of CSF is not possible, what should we do?

A

Specimen should be kept at room temperature or placed in a 30°C incubator

24
Q

Why should CSF be kept at room temperature or placed in a 30°C incubator

A

Because most organisms continue to replicate in this environment

25
Q

Automated blood culture systems

A

BACTEC
Bact/ALERT
VersaTREK

26
Q

This has been proven optimal for the recovery of H. capsulatum and other filamentous fungi

A

Lysis-centrifugation system, the Isolator

27
Q

How does lysis-centrifugation system works?

A

With this system, red blood cells and white blood cells, which may contain the microorganisms, are lysed, and centrifugation concentrates the organisms before culturing. The concentrate is inoculated onto the surface of appropriate culture media

28
Q

When using lysis-centrifugation system, most fungi are detected within

A

First 4 days of incubation

29
Q

Isolates of H. capsulatum may require approximately how many days for recovery

A

10 to 14 days

30
Q

The optimal temperature for fungal blood cultures

A

30°C

31
Q

The suggested incubation time for fungal blood cultures

A

21 days

32
Q

Usually submitted for dermatophyte culture and are contaminated with bacteria or rapidly growing fungi or both

A

Hair, Skin, and Nail Scrapings

33
Q

How to collect specimens for Dermatophytes?

A

Samples collected from lesions may be obtained by scraping the skin or nails with a scalpel blade or microscope slide; infected hairs are removed by plucking them with forceps

34
Q

How to properly store Hair, Skin, and Nail Scrapings

A

These specimens should be placed in a sterile container; they should not be refrigerated

35
Q

Media that is satisfactory for the recovery of dermatophytes

A

Mycosel agar, which contains chloramphenicol and cyclo- heximide

36
Q

Dermatophytic cultures should be incubated for a minimum of _____ before being reported as negative

A

21 days at 30°C

37
Q

Vaginal samples should be transported to the laboratory within

A

24 hours of collection

38
Q

Why does vaginal swabs should be kept moist in sterile tubes?

A

This method of collection provides a specimen suitable for a wet preparation

39
Q

Vaginal cultures should be screened for yeasts and incubated

A

30°C for 7 days

40
Q

Urine samples collected for fungal culture should be processed

A

As soon after collection as possible

41
Q

Does the 24-hour urine sample acceptable for culture?

A

No

42
Q

How to ensure the recovery of fungi in urine specimen?

A

Media must contain antibacterial agent

43
Q

Why does media containing antibacterial agents must be used to ensure the recovery of fungi in urine?

A

Because urine often is contaminated with gram negative bacteria

44
Q

Tissue, Bone Marrow, and Sterile Body Fluids cultures should be incubated ar

A

30°C for 21 days

45
Q

Bone marrow may be placed directly onto the surface of appropriate culture media and incubated at

A

30°C for 21 days

46
Q

Sterile body fluids must be _____ before culturing

A

Concentrated by centrifugation

47
Q

All specimens should be cultured as soon as possible to ensure the recovery of fungi. True or false

A

True

48
Q

Specimens used to examine the presence of granules

A

Abscess fluid and Wound exudates

MYCOLOGY AND VIROLOGY (2 decks)

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