Q: Which of the following equations correctly represents the calculation of therapeutic index?

$$\text{Therapeutic Index} = \frac{\text{Toxic Dose}}{\text{Effective Dose}}$$

Question 1

Which of the following best describes the structure of a typical virion?

Accepted Answer

A nucleic acid genome surrounded by a protein capsid, sometimes enclosed in a lipid envelope

Question 2

A virus infects only certain species and cell types. What is the primary reason for this specificity?

Accepted Answer

The presence of specific receptor molecules on the host cell surface that match viral attachment proteins

Question 3

Which of the following is NOT a basic shape of viral capsids?

Accepted Answer

Spherical

Question 4

Which statement correctly compares the lytic and lysogenic cycles of bacteriophage replication?

Accepted Answer

The lysogenic cycle involves integration of viral DNA into the host genome, while the lytic cycle results in immediate host cell lysis

Question 5

Which of the following best describes a prion?

Accepted Answer

An infectious protein that lacks nucleic acids

Question 6

A patient develops a rapidly progressive neurodegenerative disease after eating contaminated beef. Which disease is most likely, and what is the causative agent?

Accepted Answer

Variant Creutzfeldt-Jakob disease caused by prions

Question 7

Which of the following is a method used to destroy prions?

Accepted Answer

Autoclaving at $$134^\circC $$for 18 minutes under increased pressure

Question 8

Which of the following best describes the relationship between incidence and prevalence in epidemiology?

Accepted Answer

Incidence is the number of new cases in a given time period, while prevalence is the total number of cases at a specific time

Question 9

A disease that is constantly present at a low level in a specific geographic area is best described as:

Accepted Answer

Endemic

Question 10

Which of the following is a characteristic of a broad-spectrum antimicrobial drug?

Accepted Answer

It targets a wide variety of pathogens, increasing the risk of disrupting normal microbiota

Question 11

Which of the following equations correctly represents the calculation of therapeutic index?

Accepted Answer

$$	ext{Therapeutic Index} = \frac{	ext{Toxic Dose}}{	ext{Effective Dose}}$$

Question 12

Which of the following is NOT a mechanism by which bacteria can become resistant to antimicrobial drugs?

Accepted Answer

Increasing the permeability of the cell membrane to the drug

Question 13

Which of the following best describes the principle of selective toxicity?

Accepted Answer

The drug harms the pathogen more than the host

Question 14

A patient is given a vaccine that contains a live, attenuated virus. Which of the following is a potential advantage of this type of vaccine?

Accepted Answer

It often induces a strong, long-lasting immune response with contact immunity

Question 15

Which of the following is a correct statement about passive immunotherapy?

Accepted Answer

It provides immediate protection by administering pre-formed antibodies

Question 16

Which of the following is an example of a mechanical vector in disease transmission?

Accepted Answer

A housefly carrying bacteria on its legs from feces to food

Question 17

Which of the following best describes the difference between signs and symptoms of a disease?

Accepted Answer

Signs are objective and measurable, while symptoms are subjective and felt by the patient

Question 18

Which of the following is a limitation of Koch's postulates in determining the cause of a disease?

Accepted Answer

Some pathogens cannot be cultured in the laboratory

Question 19

Which of the following is a characteristic of latent diseases?

Accepted Answer

The pathogen remains inactive for a period before causing symptoms

Question 20

Which of the following best explains how R plasmids contribute to antimicrobial resistance?

Accepted Answer

They carry genes that encode resistance to one or more antimicrobial drugs and can be transferred between bacteria

Microbiology Study Guide: Viruses, Infectious Diseases, Immunization, and Antimicrobial Drugs

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