Laboratory Diagnosis, Specimen Collection & Serologic Test

Question 1

What is the first step in specimen collection?

Answer 1

Aseptic technique

Aseptic technique is crucial to prevent contamination during specimen collection.

Question 2

What type of specimen is most important if the infection is disseminated?

Answer 2

Blood

Blood specimens provide an accurate measure of determining the etiology of disseminated fungal infections.

Question 3

What is the optimal incubation temperature for blood cultures?

Answer 3

30 deg C

Blood cultures should be incubated at 30 degrees Celsius for up to 21 days.

Question 4

What is a biphasic broth-agar system?

Answer 4

Contains both solid and liquid media

This system allows organisms to grow in both solid and liquid environments.

Question 5

What technique is optimal for isolation of H. capsulatum?

Answer 5

Lysis centrifugation technique (Isolator)

This technique lyses cells containing the organism and gathers concentrates for culture.

Question 6

Which specimens are included under respiratory secretions?

Answer 6

Sputum, Bronchoalveolar lavage (BAL), Bronchial washings, Tracheal aspirate

These are common specimens for fungal culture and should use media with antibiotics.

Question 7

What is the recommended method for collecting cerebrospinal fluid (CSF)?

Answer 7

Filtered through a 0.45 um membrane pore filter

This method allows for the collection of organisms present in the CSF.

Question 8

How should urine specimens be processed?

Answer 8

Centrifuge → smear → culture (sediments)

Urine specimens should be processed within 2 hours or refrigerated, but not kept for more than 6 hours.

Question 9

What is the procedure for collecting hair specimens?

Answer 9

Pluck hair by roots (forceps or tweezers)

Care must be taken to avoid damaging infected hair, and Woods lamp can be used for visualization.

Question 10

What type of culture media should be used for cutaneous specimens?

Answer 10

Media with antibiotics

Antibiotics are used to prevent bacterial contamination in fungal cultures.

Question 11

What are the main components required in culture media for fungi?

Answer 11

• Amino acids or urea (source of Nitrogen)
• Glucose (source of Carbohydrate)

These components are essential for fungal growth in culture media.

Question 12

What is the advantage of using agar plates for fungal culture?

Answer 12

Better aeration and large surface area for better isolation

Agar plates allow for more oxygen to enter, promoting fungal growth.

Question 13

What type of agar is used for the primary recovery of dimorphic fungi?

Answer 13

Brain-Heart Infusion Agar (BHI Agar)

BHI Agar is suitable for the primary recovery of both saprophytic and dimorphic fungi.

Question 14

What is the purpose of Potato Dextrose Agar?

Answer 14

General purpose basal medium for the cultivation of yeasts & molds

It aids in cultivating various fungi and can help differentiate pathogenic from non-pathogenic strains.

Question 15

What does Chromagar Candida differentiate?

Answer 15

Major clinically significant Candida species

This chromogenic agar allows each Candida species to produce characteristic colonies and pigmentation.

Question 16

What is the function of the India Ink method?

Answer 16

Direct microscopic examination of fungal morphology

This method helps in identifying encapsulated organisms like C. neoformans.

Question 17

Fill in the blank: Specimen rejection criteria can include _______.

Answer 17

Hemolysis, improper transport temperature, incorrect patient identifiers

These criteria ensure the integrity of specimens for accurate diagnosis.

Question 18

True or False: The culture media must include antimicrobials for sterile specimens.

Answer 18

False

Antimicrobials are primarily used for non-sterile specimens to prevent bacterial contamination.

Question 19

What is the recommended storage condition for CSF specimens?

Answer 19

Keep at room temperature or at 37 deg C

Refrigeration may kill fungal elements present in the specimen.

Question 20

What is the purpose of adding a drop of 10% KOH to a specimen?

Answer 20

To clear the background and make fungi prominent

KOH is useful for cutaneous specimens.

Question 21

What does the negative staining method do?

Answer 21

Stains the background while keeping the target element colorless

Question 22

What type of organisms is the negative staining method perfect for?

Answer 22

Encapsulated organisms

Example: capsule of C. neoformans.

Question 23

What does Calcofluor white stain bind to?

Answer 23

Chitin and cellulose in the cell wall of organisms

Question 24

What color indicates the presence of fungi and parasites when using Calcofluor white?

Answer 24

Apple-green/bluish-white

Question 25

What are the components of Lactophenol Cotton Blue (LPCB)?

Answer 25

* Lactic acid * Phenol * Cotton blue

Question 26

What is the purpose of the Basic Tease Mount method?

Answer 26

To separate the individual growth of the organism

Question 27

What should be used instead of cotton swabs when collecting samples?

Answer 27

Dacron/rayon swabs

Question 28

What is the result of using cotton swabs in Calcofluor white staining?

Answer 28

Cotton fibers may intensely fluoresce, causing interference

Question 29

What does the Gomori’s/Grocott Methenamine Silver stain indicate?

Answer 29

Black cell wall of fungi

Question 30

What does the Periodic Acid Schiff (PAS) stain target?

Answer 30

Carbohydrates in fungal cell walls

Question 31

What does the Papanicolau stain demonstrate?

Answer 31

Better demonstration of B. dermatitidis than wet mounts

Question 32

At what temperature should dermatophyte cultures be incubated before reporting as negative?

Answer 32

Room temperature for 6 weeks

Question 33

What is the risk group for dimorphic fungi?

Answer 33

Risk Group 3 (may cause lethal diseases)

Question 34

What is the typical growth rate for yeast?

Answer 34

Can grow after 24 hours to 4 days

Question 35

What are the types of fungal growth textures?

Answer 35

* Cottony or wooly * Velvety or silky * Powdery or granular * Moist, creamy, pasty

Question 36

What does the Slide Culture/Microculture method preserve?

Answer 36

Fungi in their original living state

Question 37

What is the Germ Tube Test used for?

Answer 37

To differentiate Candida albicans from other Candida species

Question 38

What indicates a positive result in the Rapid Urease Test for C. neoformans?

Answer 38

Color change from peach to magenta

Question 39

What is the sensitivity and specificity of the Latex Agglutination test for Cryptococcosis?

Answer 39

Sensitivity - 90.9%; Specificity - 95%

Question 40

What does a positive precipitation band indicate in serological tests?

Answer 40

Presence of antibodies

Question 41

What is the main disadvantage of serological tests?

Answer 41

False positives due to cross-reactivity

Question 42

What does the Enzyme Linked Immunosorbent Assay (ELISA) detect?

Answer 42

Qualitative or screening assay for various fungal infections

Question 43

What is the purpose of molecular identification in fungal diagnostics?

Answer 43

To identify organisms using PCR methods

Question 44

What is a major disadvantage of using culture methods for fungal diagnosis?

Answer 44

Time-consuming; mold cultures may take several weeks to grow

Question 45

What does the 1,3 β-D-Glucan Assay (Fungitell) detect?

Answer 45

High levels of 1,3 β-D-glucan in various fungal species

Question 46

What is the purpose of the Mannan Ag & Anti-Mannan Ab Assay?

Answer 46

It is used for the presumptive diagnosis of Invasive candidiasis ## Footnote This assay detects the presence of mannan and anti-mannan antibodies.

Question 47

Which metabolites are detected in the diagnosis of Candida?

Answer 47

D-Arabinitol and Secreted Aspartyl Proteinase ## Footnote These are metabolites associated with Candida infections.

Question 48

What cells are involved in the elimination of mannan by immune complexes?

Answer 48

Kuppfer cells ## Footnote Kuppfer cells are specialized macrophages located in the liver.

Question 49

What are the causative agents of Cryptococcosis?

Answer 49

C. neoformans and C. gattii ## Footnote These fungi are responsible for the disease known as cryptococcosis.

Question 50

What type of antibodies does the Aspergillosis test detect?

Answer 50

IgE antibodies ## Footnote This indicates an allergic response to Aspergillus species.

Question 51

What does the E-TEST Agar MIC Method help determine?

Answer 51

The Minimum Inhibitory Concentration (MIC) of antifungal agents ## Footnote This method assists physicians in selecting appropriate antifungal treatments.

Question 52

What is the significance of the clear zone in the E-TEST?

Answer 52

It indicates the edge of the ellipse that meets a specific MIC measurement ## Footnote The clear zone shows the effectiveness of the antifungal agent.

Question 53

Which test is widely used for Candida albicans?

Answer 53

Sensititre Yeast One ## Footnote This is a microbroth dilution MIC test for various Candida species.

Question 54

What types of testing methods are included in the summary for fungal diagnosis?

Answer 54

* Microscopic * Culture * Serological * Molecular * Sensitivity tests * Aftercare ## Footnote These methods encompass a range of diagnostic techniques for fungal infections.

Question 55

What is the purpose of the FungiTest?

Answer 55

It identifies which concentration of drugs is susceptible ## Footnote This test uses a microbroth dilution breakpoint method.

Question 56

What does a pink (+) result indicate in the FungiTest?

Answer 56

Resistant ## Footnote A blue (-) result indicates sensitivity.

Question 57

What is the recommended waste management practice for highly infectious waste?

Answer 57

Disinfect at source and autoclave culture plates and tubes ## Footnote If autoclaving is not possible, soaking in a disinfectant is advised.

Question 58

What are the disposal methods for hazardous waste?

Answer 58

* Hazardous waste landfill * Safe burial * Incineration ## Footnote These methods ensure safe disposal of infectious waste.

Question 59

Fill in the blank: The culture for Candida krusei shows susceptibility to _______.

Answer 59

5Fc (Flucytosine) ## Footnote Other drugs show varying levels of susceptibility.

Question 60

What is the significance of a drug concentration of S <0.5 ug/mL for Itraconazole?

Answer 60

It indicates sensitivity to the drug ## Footnote This is important for effective treatment strategies.