Veterinary Microbiology and Mycology Practical by Dr. Sameh Abuseir

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What staining technique is used to visualize mycobacteria in specimens?

Ziehl-Neelsen staining (correct)

Auramine staining

Gram staining

Acid-fast staining

At what concentration of mycobacteria per ml can they be visualized under direct microscopy?

5 x 105

5 x 106

5 x 104 (correct)

5 x 103

How do mycobacteria appear when stained with Ziehl-Neelsen stain?

Green rods on a white background

Red rods on a blue background (correct)

Yellow rods on a black background

Blue rods on a red background

Which type of tuberculosis usually yields a large number of mycobacteria in specimens?

Avian tuberculosis in poultry Signup and view all the answers

What is the colonial morphology of M.tuberculosis on glycerol-containing media described as?

'Rough, tough and buff' colonies Signup and view all the answers

Which fluorescent dye can be used to examine mycobacteria under a UV microscope when small numbers are present?

Auramine Signup and view all the answers

What is the term used to describe the sparse, thin growth of M.bovis on glycerol-containing media?

Dysgonic Signup and view all the answers

Which type of mycobacteria produces yellowish-orange carotenoid pigments?

Chromogenic Signup and view all the answers

What is the term applied to mycobacteria that produce pigment only if exposed to light?

Photochromogenic Signup and view all the answers

What is one procedure for isolating and cultivating mycobacteria from clinical material like nodules?

Grind tissue with sand, add NaOH, centrifuge, neutralize sediment, and inoculate onto slants Signup and view all the answers

What is the principal basis for identifying mycobacteria?

Cultural, morphologic, and biochemical characteristics Signup and view all the answers

What method is being used to replace the complex and time-consuming phenotypic approach for identifying mycobacteria?

Using specific probes Signup and view all the answers

What is the purpose of the acid-fast stain technique?

To differentiate between acid-fast and non acid-fast bacteria Signup and view all the answers

Why must the stain (carbol fuchsin) be driven into the cells with heat in the acid-fast stain technique?

To ensure the color binds to the waxy lipid in acid-fast bacteria Signup and view all the answers

What makes acid-fast cell walls more durable compared to other bacteria?

Incorporation of mycolic acid Signup and view all the answers

How are non acid-fast bacteria affected by decolorization with acid-alcohol in the staining process?

They lose the carbol fuchsin stain Signup and view all the answers

What is the primary method used to differentiate between acid-fast and non acid-fast bacteria after staining?

Applying methylene blue counterstain Signup and view all the answers

How does mycolic acid contribute to the pathogenicity of some bacteria?

By making their cell walls more durable Signup and view all the answers