FREE AP-MICRO Specimen Processing and Stains Questions and Answers

Question 1

A cerebrospinal fluid (CSF) specimen from a patient with suspected meningitis is received in the microbiology lab.
A direct smear is prepared using India ink.
The technologist observes encapsulated yeast cells.
Which of the following is the most likely organism?

Accepted Answer

Cryptococcus neoformans

Answer

Candida albicans

Answer

Aspergillus fumigatus

Answer

Histoplasma capsulatum

Question 2

A Gram stain of a sputum specimen reveals >25 squamous epithelial cells and <10 polymorphonuclear cells per low-power field. What is the most appropriate action for the technologist to take?

Accepted Answer

Request a new, more deeply expectorated specimen.

Answer

Inoculate the specimen onto all routine culture media.

Answer

Perform an acid-fast stain on the specimen.

Answer

Report the Gram stain results as 'normal oral flora'.

Question 3

In the Ziehl-Neelsen acid-fast staining procedure, what is the function of the carbolfuchsin?

Accepted Answer

Primary stain

Answer

Mordant

Answer

Decolorizer

Answer

Counterstain

Question 4

A laboratory receives a tissue biopsy for fungal culture and direct examination. Which stain is a rapid and highly sensitive fluorochrome that binds to chitin and cellulose in fungal cell walls, causing them to fluoresce brightly under a UV microscope?

Accepted Answer

Calcofluor white

Answer

Lactophenol cotton blue

Answer

Periodic acid-Schiff (PAS)

Answer

Gomori methenamine silver (GMS)

Question 5

A microbiologist is performing a Gram stain. After the decolorization step with alcohol/acetone, what is the state of Gram-positive and Gram-negative bacteria?

Accepted Answer

Gram-positive are purple, Gram-negative are colorless.

Answer

Gram-positive are purple, Gram-negative are pink.

Answer

Both are colorless.

Answer

Both are purple.

Question 6

A CSF specimen is sent to the lab for bacterial culture and must be held for one hour before processing. What is the proper storage condition for this specimen?

Accepted Answer

Kept at room temperature (20-25°C)

Answer

Refrigerated at 2-8°C

Answer

Frozen at -20°C

Answer

Incubated at 35-37°C

A cerebrospinal fluid (CSF) specimen from a patient with suspected meningitis is received in the microbiology lab.A direct smear is prepared using India ink.The technologist observes encapsulated yeast cells.Which of the following is the most likely organism?

A cerebrospinal fluid (CSF) specimen from a patient with suspected meningitis is received in the microbiology lab.
A direct smear is prepared using India ink.
The technologist observes encapsulated yeast cells.
Which of the following is the most likely organism?