Q: Which equation best represents the inhibition of folic acid synthesis by sulfonamides?

$$\text{PABA} + \text{pteridine} \xrightarrow{\text{dihydropteroate synthase}} \text{dihydropteroic acid}$$

Question 1

Which of the following best describes the principle of selective toxicity in antimicrobial therapy?

Accepted Answer

The drug should inhibit or kill microbial cells without causing significant harm to host tissues.

Question 2

Penicillin and cephalosporins both contain a beta-lactam ring. What is the primary function of this structure?

Accepted Answer

It disrupts the synthesis of peptidoglycan in bacterial cell walls.

Question 3

Which of the following drugs is most appropriate for treating a patient with a penicillin allergy who has a Gram-positive bacterial infection?

Accepted Answer

Cephalosporin

Question 4

A patient is diagnosed with tuberculosis. Which drug is specifically used to target Mycobacterium tuberculosis by disrupting mycolic acid synthesis?

Accepted Answer

Isoniazid

Question 5

Which of the following antibiotics is known for its broad spectrum of activity and can inhibit both Gram-positive and Gram-negative bacteria by targeting the 70S ribosome?

Accepted Answer

Tetracycline

Question 6

A patient with a severe urinary tract infection caused by a Gram-negative rod is treated with a drug that disrupts the LPS layer of the bacterial cell membrane. Which drug is most likely used?

Accepted Answer

Polymyxin

Question 7

Which of the following statements about sulfonamides is correct?

Accepted Answer

They are synthetic drugs that inhibit folic acid synthesis in bacteria.

Question 8

Which of the following best explains why biofilms are more resistant to antibiotics than individual bacterial cells?

Accepted Answer

Biofilms have a protective matrix and altered metabolic states that reduce antibiotic penetration and efficacy.

Question 9

A patient is prescribed erythromycin for a respiratory infection. What is a key advantage of erythromycin compared to other protein synthesis inhibitors?

Accepted Answer

It has the lowest toxicity among protein synthesis inhibitors.

Question 10

Which of the following drugs is most likely to cause kidney toxicity if used long-term?

Accepted Answer

Polymyxin

Question 11

Which of the following mechanisms is NOT a common target for antibacterial drugs?

Accepted Answer

Inhibition of host cell mitochondria

Question 12

A patient with MRSA (methicillin-resistant Staphylococcus aureus) is not responding to penicillin or methicillin. Which drug is considered a last line of defense?

Accepted Answer

Vancomycin

Question 13

Which of the following drugs is used to treat protozoan infections such as amoebiasis?

Accepted Answer

Metronidazole

Question 14

Which equation best represents the inhibition of folic acid synthesis by sulfonamides?

Accepted Answer

$$	ext{PABA} + 	ext{pteridine} \xrightarrow{	ext{dihydropteroate synthase}} 	ext{dihydropteroic acid}$$

Question 15

Which of the following is a major side effect associated with long-term tetracycline use?

Accepted Answer

Deposition in hard tissues impacting bone development

Question 16

Which of the following drugs is used as a topical treatment for superficial skin infections caused by streptococci and staphylococci?

Accepted Answer

Bacitracin

Question 17

Which of the following best explains why fluoroquinolones, such as ciprofloxacin, are effective broad-spectrum antibiotics?

Accepted Answer

They inhibit bacterial DNA gyrase and topoisomerase, preventing DNA replication.

Question 18

Which of the following is a reason why treatment of biofilm-associated infections often requires a combination of strategies?

Accepted Answer

Biofilms are 1,000 times less sensitive to antibiotics due to their structure and altered gene expression.

Question 19

Which of the following drugs is used to treat helminthic infections?

Accepted Answer

Mebendazole

Question 20

Which of the following antiviral drugs works by preventing the penetration of the virus into the host cell?

Accepted Answer

Tamiflu (oseltamivir)

Chemotherapeutic Agents and Antimicrobial Drugs: Mechanisms, Spectrum, and Applications

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