Laboratory Diagnosis, Specimen Collection & Serologic Test Flashcards
What is the first step in specimen collection?
Aseptic technique
Aseptic technique is crucial to prevent contamination during specimen collection.
What type of specimen is most important if the infection is disseminated?
Blood
Blood specimens provide an accurate measure of determining the etiology of disseminated fungal infections.
What is the optimal incubation temperature for blood cultures?
30 deg C
Blood cultures should be incubated at 30 degrees Celsius for up to 21 days.
What is a biphasic broth-agar system?
Contains both solid and liquid media
This system allows organisms to grow in both solid and liquid environments.
What technique is optimal for isolation of H. capsulatum?
Lysis centrifugation technique (Isolator)
This technique lyses cells containing the organism and gathers concentrates for culture.
Which specimens are included under respiratory secretions?
Sputum, Bronchoalveolar lavage (BAL), Bronchial washings, Tracheal aspirate
These are common specimens for fungal culture and should use media with antibiotics.
What is the recommended method for collecting cerebrospinal fluid (CSF)?
Filtered through a 0.45 um membrane pore filter
This method allows for the collection of organisms present in the CSF.
How should urine specimens be processed?
Centrifuge → smear → culture (sediments)
Urine specimens should be processed within 2 hours or refrigerated, but not kept for more than 6 hours.
What is the procedure for collecting hair specimens?
Pluck hair by roots (forceps or tweezers)
Care must be taken to avoid damaging infected hair, and Woods lamp can be used for visualization.
What type of culture media should be used for cutaneous specimens?
Media with antibiotics
Antibiotics are used to prevent bacterial contamination in fungal cultures.
What are the main components required in culture media for fungi?
- Amino acids or urea (source of Nitrogen)
- Glucose (source of Carbohydrate)
These components are essential for fungal growth in culture media.
What is the advantage of using agar plates for fungal culture?
Better aeration and large surface area for better isolation
Agar plates allow for more oxygen to enter, promoting fungal growth.
What type of agar is used for the primary recovery of dimorphic fungi?
Brain-Heart Infusion Agar (BHI Agar)
BHI Agar is suitable for the primary recovery of both saprophytic and dimorphic fungi.
What is the purpose of Potato Dextrose Agar?
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.
What does Chromagar Candida differentiate?
Major clinically significant Candida species
This chromogenic agar allows each Candida species to produce characteristic colonies and pigmentation.
What is the function of the India Ink method?
Direct microscopic examination of fungal morphology
This method helps in identifying encapsulated organisms like C. neoformans.
Fill in the blank: Specimen rejection criteria can include _______.
Hemolysis, improper transport temperature, incorrect patient identifiers
These criteria ensure the integrity of specimens for accurate diagnosis.
True or False: The culture media must include antimicrobials for sterile specimens.
False
Antimicrobials are primarily used for non-sterile specimens to prevent bacterial contamination.
What is the recommended storage condition for CSF specimens?
Keep at room temperature or at 37 deg C
Refrigeration may kill fungal elements present in the specimen.
What is the purpose of adding a drop of 10% KOH to a specimen?
To clear the background and make fungi prominent
KOH is useful for cutaneous specimens.
What does the negative staining method do?
Stains the background while keeping the target element colorless
What type of organisms is the negative staining method perfect for?
Encapsulated organisms
Example: capsule of C. neoformans.
What does Calcofluor white stain bind to?
Chitin and cellulose in the cell wall of organisms
What color indicates the presence of fungi and parasites when using Calcofluor white?
Apple-green/bluish-white
What are the components of Lactophenol Cotton Blue (LPCB)?
- Lactic acid
- Phenol
- Cotton blue
What is the purpose of the Basic Tease Mount method?
To separate the individual growth of the organism
What should be used instead of cotton swabs when collecting samples?
Dacron/rayon swabs
What is the result of using cotton swabs in Calcofluor white staining?
Cotton fibers may intensely fluoresce, causing interference
What does the Gomori’s/Grocott Methenamine Silver stain indicate?
Black cell wall of fungi
What does the Periodic Acid Schiff (PAS) stain target?
Carbohydrates in fungal cell walls
What does the Papanicolau stain demonstrate?
Better demonstration of B. dermatitidis than wet mounts
At what temperature should dermatophyte cultures be incubated before reporting as negative?
Room temperature for 6 weeks
What is the risk group for dimorphic fungi?
Risk Group 3 (may cause lethal diseases)
What is the typical growth rate for yeast?
Can grow after 24 hours to 4 days
What are the types of fungal growth textures?
- Cottony or wooly
- Velvety or silky
- Powdery or granular
- Moist, creamy, pasty
What does the Slide Culture/Microculture method preserve?
Fungi in their original living state
What is the Germ Tube Test used for?
To differentiate Candida albicans from other Candida species
What indicates a positive result in the Rapid Urease Test for C. neoformans?
Color change from peach to magenta
What is the sensitivity and specificity of the Latex Agglutination test for Cryptococcosis?
Sensitivity - 90.9%; Specificity - 95%
What does a positive precipitation band indicate in serological tests?
Presence of antibodies
What is the main disadvantage of serological tests?
False positives due to cross-reactivity
What does the Enzyme Linked Immunosorbent Assay (ELISA) detect?
Qualitative or screening assay for various fungal infections
What is the purpose of molecular identification in fungal diagnostics?
To identify organisms using PCR methods
What is a major disadvantage of using culture methods for fungal diagnosis?
Time-consuming; mold cultures may take several weeks to grow
What does the 1,3 β-D-Glucan Assay (Fungitell) detect?
High levels of 1,3 β-D-glucan in various fungal species
What is the purpose of the Mannan Ag & Anti-Mannan Ab Assay?
It is used for the presumptive diagnosis of Invasive candidiasis
This assay detects the presence of mannan and anti-mannan antibodies.
Which metabolites are detected in the diagnosis of Candida?
D-Arabinitol and Secreted Aspartyl Proteinase
These are metabolites associated with Candida infections.
What cells are involved in the elimination of mannan by immune complexes?
Kuppfer cells
Kuppfer cells are specialized macrophages located in the liver.
What are the causative agents of Cryptococcosis?
C. neoformans and C. gattii
These fungi are responsible for the disease known as cryptococcosis.
What type of antibodies does the Aspergillosis test detect?
IgE antibodies
This indicates an allergic response to Aspergillus species.
What does the E-TEST Agar MIC Method help determine?
The Minimum Inhibitory Concentration (MIC) of antifungal agents
This method assists physicians in selecting appropriate antifungal treatments.
What is the significance of the clear zone in the E-TEST?
It indicates the edge of the ellipse that meets a specific MIC measurement
The clear zone shows the effectiveness of the antifungal agent.
Which test is widely used for Candida albicans?
Sensititre Yeast One
This is a microbroth dilution MIC test for various Candida species.
What types of testing methods are included in the summary for fungal diagnosis?
- Microscopic
- Culture
- Serological
- Molecular
- Sensitivity tests
- Aftercare
These methods encompass a range of diagnostic techniques for fungal infections.
What is the purpose of the FungiTest?
It identifies which concentration of drugs is susceptible
This test uses a microbroth dilution breakpoint method.
What does a pink (+) result indicate in the FungiTest?
Resistant
A blue (-) result indicates sensitivity.
What is the recommended waste management practice for highly infectious waste?
Disinfect at source and autoclave culture plates and tubes
If autoclaving is not possible, soaking in a disinfectant is advised.
What are the disposal methods for hazardous waste?
- Hazardous waste landfill
- Safe burial
- Incineration
These methods ensure safe disposal of infectious waste.
Fill in the blank: The culture for Candida krusei shows susceptibility to _______.
5Fc (Flucytosine)
Other drugs show varying levels of susceptibility.
What is the significance of a drug concentration of S <0.5 ug/mL for Itraconazole?
It indicates sensitivity to the drug
This is important for effective treatment strategies.
