openstax microbiology test bank

Correct Answer: A

Rationale: The correct answer is A: Norwalk Virus. The Norwalk Virus belongs to the family Caliciviridae because it has characteristic features such as a nonenveloped, single-stranded RNA genome. The other options, Yellow fever virus, Rubella virus, and CMV, belong to different virus families and have distinct characteristics that differentiate them from Caliciviridae. Yellow fever virus is a Flavivirus, Rubella virus belongs to Togaviridae, and CMV is a member of the Herpesviridae family. Therefore, based on the genomic and structural characteristics of the Norwalk Virus, it is the correct choice for belonging to the Caliciviridae family.

Correct Answer: A

Rationale: The correct answer is A: Giardia lamblia. Giardia lamblia is a flagellated protozoan with two nuclei, known as the "falling leaf" appearance. It causes diarrhea in humans through ingestion of contaminated water or food. Entamoeba histolytica causes amoebic dysentery, characterized by bloody diarrhea and colitis. Trichomonas vaginalis is a sexually transmitted protozoan causing vaginal discharge but is not found in stool. Balantidium coli is a ciliated protozoan causing diarrhea but does not have flagellated forms.

Correct Answer: D

Rationale: The correct answer is D: Loefler. This staining method is used for identifying Corynebacterium diphtheriae, the causative agent of diphtheria. It involves using methylene blue and basic fuchsin to stain the bacteria. The yellow bacilli with blue grains at their ends indicate the characteristic appearance of C. diphtheriae when stained using the Loefler method. Choice A: Ziehl-Nielsen is used for acid-fast bacteria like Mycobacterium tuberculosis. Choice B: Kozlovsky is not a standard staining method in microbiology. Choice C: Romanovsky is used for blood smears to identify malaria parasites.

Correct Answer: D

Rationale: The correct answer is D: thimerosal. Thimerosal is a mercury-containing compound used as a preservative in vaccines. It helps prevent contamination and growth of bacteria and fungi in multi-dose vials. Choice A, analgesic, refers to pain relievers, not preservatives. Choice B, EDTA, is a chelating agent used to bind metal ions and is not a preservative. Choice C, codeine, is an opioid pain medication and not a preservative used in vaccines. Thimerosal is the correct answer as it specifically fits the description of a mercury-containing compound used in vaccines.

Correct Answer: D

Rationale: Interferon is a cell-specific protein that is produced and released from infected cells in response to viral infections. It acts extracellularly to interfere with viral replication, not to inactivate the virus itself. Interferon is not coded for by cellular DNA, but by viral RNA during infection. Therefore, the correct answer, D, is that interferon is not virus-specific but is cell-specific. This is because interferon can be produced by various cell types in response to different types of viral infections, making it a broad-spectrum antiviral defense mechanism.