CMLA Microbiology Basics 3

Question 1

The catalase test differentiates which two groups of Gram-positive cocci?

Accepted Answer

Staphylococcus vs. Streptococcus

Answer

Staphylococci are catalase-positive (produce bubbles with hydrogen peroxide) while Streptococci are catalase-negative, making this the first key differentiation test.

Question 2

Which of the following viruses requires a helper virus to replicate?

Accepted Answer

Hepatitis D virus

Answer

Hepatitis D virus (delta agent) is a defective RNA virus that requires the surface antigen of Hepatitis B virus (HBsAg) for its own replication and packaging.

Question 3

A wet mount preparation showing motile, pear-shaped organisms with two nuclei is most consistent with:

Accepted Answer

Giardia lamblia

Answer

Giardia lamblia trophozoites appear pear-shaped with bilateral symmetry, two nuclei, and characteristic tumbling motility on wet mount preparations.

Question 4

Which sterilization method is most appropriate for heat-sensitive items such as plastic tubing?

Accepted Answer

Ethylene oxide gas

Answer

Ethylene oxide (EO) gas sterilizes at low temperatures, making it ideal for heat-sensitive materials like plastics, rubber, and electronic devices.

Question 5

When performing a Gram stain, what is the correct sequence of reagents?

Accepted Answer

Crystal violet → iodine → decolorizer → safranin

Answer

The correct Gram stain sequence is: crystal violet (primary stain), Gram's iodine (mordant), alcohol/acetone (decolorizer), then safranin (counterstain).

(CMLA) Certified Medical Laboratory Assistant Practice Test

(CMLA) Certified Medical Laboratory Assistant Practice Test

CMLA Microbiology Basics 3