Laboratory Science Microbiology Techniques

Question 1

What is the purpose of the Gram stain in clinical microbiology?

Accepted Answer

Differentiate bacteria into gram-positive and gram-negative based on cell wall structure

Answer

Identify fungal infections

Answer

Detect acid-fast organisms

Answer

Measure bacterial colony counts

Question 2

Which growth medium is selective for gram-negative enteric bacteria while inhibiting gram-positive organisms?

Accepted Answer

MacConkey agar

Answer

Blood agar

Answer

Chocolate agar

Answer

Sabouraud dextrose agar

Question 3

What does a positive catalase test (bubbling with H₂O₂) indicate?

Accepted Answer

The organism produces catalase enzyme, suggesting Staphylococcus (not Streptococcus)

Answer

The organism is gram-negative

Answer

The organism is acid-fast

Answer

The organism is oxidase-positive

Question 4

Which temperature is standard for incubating most clinical bacterial cultures?

Accepted Answer

35–37°C

Answer

25°C

Answer

42°C

Answer

55°C

Question 5

What is the purpose of a streak plate technique in microbiology?

Accepted Answer

Isolate individual bacterial colonies from a mixed culture

Answer

Measure bacterial growth rate

Answer

Identify bacterial species by color

Answer

Prepare specimens for staining

Question 6

Which test is used to differentiate Staphylococcus aureus from other coagulase-negative staphylococci?

Accepted Answer

Coagulase test

Answer

Optochin sensitivity test

Answer

Bile solubility test

Answer

CAMP test