Antimicrobial Agents — MCQs
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Which of the following statements about cephalosporins is false?
DEC (diethylcarbamazine) is used for the treatment of:
A 25-year-old male university student presented with a history of multiple tick bites 45 days prior, followed by recurring episodes of high-grade fever, headache, myalgias, arthralgias, nausea, and occasional vomiting. Each episode lasted approximately 6-7 days with symptom-free intervals of 9-10 days. Physical examination revealed mild splenomegaly and skin lesions. A Wright stain of the patient's peripheral blood smear was performed. What is the first oral drug of choice for this patient?
In the treatment of superficial bacterial skin infections, what is the standard concentration of tetracycline ointment typically prescribed for topical application?
What is an example of an entry inhibitor?
Which one of the following statements is false regarding the use of adefovir dipivoxil?
The multidrug regimen under the National Leprosy Eradication Programme for the treatment of all multibacillary leprosy would include which medications?
According to WHO guidelines for community health workers, which drug is commonly used in the management of acute respiratory infections?
Ketoconazole is useful in all except:
What is the primary reason for using silver sulphadiazine cream in the treatment of burn wounds?
Antimicrobial Agents Indian Medical PG Practice Questions and MCQs
Question 1611: Which of the following statements about cephalosporins is false?
- A. Cefoperazone has got antipseudomonal effect.
- B. Cephalosporins act by inhibiting cell wall synthesis.
- C. Ceftazidime is a 3rd generation cephalosporin.
- D. Cefoxitin has no activity against anaerobes. (Correct Answer)
Explanation: ***Cefoxitin has no activity against anaerobes.*** - This statement is **false** because **cefoxitin** is a second-generation cephalosporin known for its **excellent activity against anaerobic bacteria**, particularly *Bacteroides fragilis*. - Its anaerobic coverage makes it useful for treating infections where these organisms are suspected, such as intra-abdominal and pelvic infections. *Ceftazidime is a 3rd generation cephalosporin.* - This statement is **true**. **Ceftazidime** is a third-generation cephalosporin characterized by its broad-spectrum activity, including significant coverage against **Pseudomonas aeruginosa**. - Its primary clinical utility is often in treating difficult Gram-negative infections. *Cefoperazone has got antipseudomonal effect.* - This statement is **true**. **Cefoperazone** is a third-generation cephalosporin that exhibits **antipseudomonal activity**, similar to ceftazidime. - It is often used for treating infections caused by **Pseudomonas aeruginosa** and other difficult Gram-negative bacteria. *Cephalosporins act by inhibiting cell wall synthesis.* - This statement is **true**. Like other beta-lactam antibiotics, **cephalosporins** exert their bactericidal effect by **inhibiting bacterial cell wall synthesis**. - They bind to and inactivate **penicillin-binding proteins (PBPs)**, which are essential enzymes involved in peptidoglycan cross-linking, leading to compromised cell wall integrity and bacterial lysis.
Question 1612: DEC (diethylcarbamazine) is used for the treatment of:
- A. Dracunculiasis (Dracunculus medinensis)
- B. Schistosomiasis (Schistosoma species)
- C. Taeniasis (Taenia species)
- D. Filariasis (Wuchereria bancrofti and Brugia malayi) (Correct Answer)
Explanation: ***Filariasis (Wuchereria bancrofti and Brugia malayi)*** - **Diethylcarbamazine (DEC)** is the drug of choice for treating **lymphatic filariasis** caused by *Wuchereria bancrofti* and *Brugia malayi*. - DEC works by killing the **microfilariae** and adult worms in the lymphatic system. *Dracunculiasis (Dracunculus medinensis)* - Treatment for **dracunculiasis** primarily involves mechanical removal of the worm by winding it around a stick, with supportive care like analgesics and antibiotics for secondary infections. - DEC is **ineffective** against *Dracunculus medinensis*. *Schistosomiasis (Schistosoma species)* - The standard treatment for all forms of **schistosomiasis** is **praziquantel**. - DEC has **no significant efficacy** against *Schistosoma* species. *Taeniasis (Taenia species)* - **Taeniasis**, caused by tapeworms like *Taenia saginata* and *Taenia solium*, is effectively treated with **praziquantel** or **niclosamide**. - DEC is **not indicated** for the treatment of tapeworm infections.
Question 1613: A 25-year-old male university student presented with a history of multiple tick bites 45 days prior, followed by recurring episodes of high-grade fever, headache, myalgias, arthralgias, nausea, and occasional vomiting. Each episode lasted approximately 6-7 days with symptom-free intervals of 9-10 days. Physical examination revealed mild splenomegaly and skin lesions. A Wright stain of the patient's peripheral blood smear was performed. What is the first oral drug of choice for this patient?
- A. Doxycycline (Correct Answer)
- B. Amoxicillin
- C. Cefuroxime
- D. Erythromycin
Explanation: ***Doxycycline*** - The patient's presentation is classic for **tick-borne relapsing fever (TBRF)** caused by *Borrelia* species. - The **pathognomonic feature** is the **relapsing pattern**: recurring fever episodes (6-7 days) separated by **afebrile intervals** (9-10 days), which distinguishes TBRF from Lyme disease. - **Wright stain of peripheral blood smear** during febrile episodes typically reveals **spirochetes** (unlike Lyme disease where spirochetes are rarely visible in blood). - **Doxycycline 100 mg twice daily** is the **first-line oral treatment** for TBRF, with excellent activity against *Borrelia* spirochetes. - Also covers potential tick-borne coinfections (Ehrlichia, Anaplasma). *Amoxicillin* - While effective for **Lyme disease**, amoxicillin is **less effective for TBRF** compared to tetracyclines. - Used as an alternative in **pregnant women or children <8 years** when doxycycline is contraindicated. - Does not cover rickettsial coinfections that doxycycline would treat. *Cefuroxime* - This **second-generation cephalosporin** can be used as an alternative for Lyme disease. - However, it is **not the first-line choice** for the relapsing fever pattern seen in this case. - Doxycycline remains superior due to broader coverage and better efficacy for TBRF. *Erythromycin* - **Erythromycin** has **poor efficacy** against *Borrelia* species and is **not recommended** for TBRF or Lyme disease. - Higher relapse rates and treatment failures make it an inappropriate choice. - Modern macrolides (azithromycin) have better activity but still inferior to doxycycline.
Question 1614: In the treatment of superficial bacterial skin infections, what is the standard concentration of tetracycline ointment typically prescribed for topical application?
- A. 0.10%
- B. 0.50%
- C. 5%
- D. 1% (Correct Answer)
Explanation: ***1%*** - **Tetracycline 1% ointment** is the standard and effective concentration for topical application in superficial bacterial skin infections [1]. - This concentration ensures adequate therapeutic levels of the antibiotic at the site of infection while minimizing systemic absorption. *0.10%* - A concentration of **0.10% tetracycline** is generally too low to be effective against most common bacterial skin infections. - This insufficient concentration could lead to treatment failure and potentially contribute to antibiotic resistance. *0.50%* - While higher than 0.10%, **0.50% tetracycline** is still considered a suboptimal concentration for treating superficial bacterial skin infections. - It might not achieve the necessary bactericidal or bacteriostatic effects required for successful eradication of the infection. *5%* - A **5% concentration of tetracycline** is typically too high for topical application and could increase the risk of local irritation or sensitization. - While potentially more potent, it is not the standard and usually offers no significant therapeutic advantage over the 1% concentration for superficial infections, while increasing potential side effects.
Question 1615: What is an example of an entry inhibitor?
- A. Abacavir
- B. Amprenavir
- C. Enfuvirtide (Correct Answer)
- D. Etravirine
Explanation: ***Enfuvirtide*** - **Enfuvirtide** is a **fusion inhibitor** that blocks **HIV-1** from entering target cells by binding to the gp41 subunit of the viral envelope glycoprotein. - It works by preventing the conformational change in gp41 required for fusion of the viral and cellular membranes. *Abacavir* - **Abacavir** is a **nucleoside reverse transcriptase inhibitor (NRTI)**. - NRTIs incorporate into the growing viral DNA chain, causing chain termination and preventing viral replication. *Etravirine* - **Etravirine** is a **non-nucleoside reverse transcriptase inhibitor (NNRTI)**. - NNRTIs bind directly to the reverse transcriptase enzyme, altering its structure and inhibiting its function. *Amprenavir* - **Amprenavir** is a **protease inhibitor (PI)**. - Protease inhibitors prevent the cleavage of viral polyproteins into functional proteins, which is essential for the assembly of new infectious virions.
Question 1616: Which one of the following statements is false regarding the use of adefovir dipivoxil?
- A. It is used as a first-line treatment for HIV. (Correct Answer)
- B. It is generally well tolerated when taken orally.
- C. It is an acyclic nucleotide analogue.
- D. It is effective in treating chronic hepatitis B infection.
Explanation: ***It is used as a first-line treatment for HIV.*** - **Adefovir dipivoxil** is primarily indicated for the treatment of **chronic hepatitis B** infection, not HIV [1]. - While it has some *in vitro* activity against HIV, it is **not recommended** for HIV treatment due to its suboptimal efficacy and potential for **nephrotoxicity** at the higher doses required for HIV [2]. *It is generally well tolerated when taken orally.* - **Adefovir dipivoxil** is indeed generally **well-tolerated** at the doses used for hepatitis B, with common side effects being mild and transient [2]. - However, **higher doses** can lead to significant **nephrotoxicity**, which is why it's not preferred for HIV treatment [2]. *It is an acyclic nucleotide analogue.* - **Adefovir dipivoxil** is a **prodrug** of adefovir, which is an **acyclic nucleotide analogue** (specifically, an adenosine monophosphate analogue) [1]. - This structure allows it to mimic natural nucleotides and interfere with **viral reverse transcriptase** or **DNA polymerase** [1]. *It is effective in treating chronic hepatitis B infection.* - **Adefovir dipivoxil** is an **antiviral medication** specifically approved and effective in treating **chronic hepatitis B virus (HBV) infection** [1]. - It works by inhibiting HBV DNA polymerase, thereby reducing **viral replication** [1].
Question 1617: The multidrug regimen under the National Leprosy Eradication Programme for the treatment of all multibacillary leprosy would include which medications?
- A. Rifampicin and dapsone
- B. Clofazimine, rifampicin, and dapsone (Correct Answer)
- C. Ethionamide, rifampicin, and dapsone
- D. Propionamide, rifampicin, and dapsone
Explanation: ***Clofazimine, rifampicin, and dapsone*** - The standard multidrug therapy (MDT) for **multibacillary (MB) leprosy** under the National Leprosy Eradication Programme (NLEP) includes **rifampicin**, **dapsone**, and **clofazimine** [1], [2]. - This combination is crucial for effective treatment, preventing drug resistance, and minimizing relapse rates over a 12-month course [1]. *Rifampicin and dapsone* - This combination alone is typically used for **paucibacillary (PB) leprosy**, which involves fewer skin lesions and bacilli. - It lacks **clofazimine**, which is essential for adequate coverage and efficacy against the higher bacterial load seen in multibacillary leprosy [1]. *Ethionamide, rifampicin, and dapsone* - **Ethionamide** is primarily an antitubercular drug and is not part of the standard first-line regimen for leprosy [3]. - Its inclusion would be considered an off-label use or reserved for specific circumstances like **drug-resistant leprosy**, which is not the general case for all multibacillary leprosy. *Propionamide, rifampicin, and dapsone* - **Propionamide** is not a drug used in the treatment of leprosy. - This option introduces an incorrect and clinically irrelevant drug into the regimen.
Question 1618: According to WHO guidelines for community health workers, which drug is commonly used in the management of acute respiratory infections?
- A. Cotrimoxazole (Correct Answer)
- B. Chloramphenicol
- C. Benzyl penicillin
- D. Gentamycin
Explanation: ***Cotrimoxazole*** - **Cotrimoxazole (trimethoprim-sulfamethoxazole)** was historically recommended by WHO for community health workers in resource-limited settings for the treatment of **acute respiratory infections (ARIs)**. - It is effective against common bacterial pathogens causing ARIs, such as *Streptococcus pneumoniae* and *Haemophilus influenzae*. - **Note:** Current WHO IMCI (Integrated Management of Childhood Illness) guidelines now recommend **amoxicillin** as first-line treatment for pneumonia in children, though cotrimoxazole remains an alternative in specific contexts or where amoxicillin is unavailable. *Chloramphenicol* - **Chloramphenicol** is a potent broad-spectrum antibiotic but is generally reserved for severe infections due to potential side effects like **bone marrow suppression** (aplastic anemia). - It is not a first-line drug for routine community-level management of uncomplicated ARIs according to WHO guidelines. *Benzyl penicillin* - **Benzyl penicillin** (Penicillin G) is effective against many streptococcal infections but has a narrower spectrum compared to cotrimoxazole. - Its use in the community setting for ARIs is limited due to the need for **parenteral administration**, making it impractical for community health workers managing outpatient cases. *Gentamycin* - **Gentamycin** is an aminoglycoside antibiotic primarily used for severe Gram-negative bacterial infections, often in hospital settings. - It is administered parenterally and is not recommended by WHO for routine community-based treatment of ARIs due to the risk of **nephrotoxicity** and **ototoxicity**, and its limited effectiveness against common ARI pathogens.
Question 1619: Ketoconazole is useful in all except:
- A. T. cruris
- B. T. capitis (Correct Answer)
- C. T. versicolor
- D. T. corporis
Explanation: ***T. capitis*** - **Ketoconazole** is generally not considered the first-line or most effective treatment for **Tinea capitis** due to its poor penetration into hair follicles. - **Oral griseofulvin** or **terbinafine** are preferred systemic antifungals for **Tinea capitis** because they can reach the infected hair shafts more effectively. *T. cruris* - **Ketoconazole** is an effective antifungal for **Tinea cruris**, which is a fungal infection of the groin, as it can be applied topically. - Its broad-spectrum antifungal activity makes it suitable for treating various superficial dermatophyte infections. *T. versicolor* - **Ketoconazole** is highly effective in treating **Tinea versicolor** (also known as Pityriasis versicolor), a superficial fungal infection caused by *Malassezia* species. - It can be used both topically (shampoo, cream) and orally to reduce the fungal burden. *T. corporis* - **Ketoconazole** is an appropriate topical antifungal agent for **Tinea corporis**, commonly known as ringworm of the body. - Its ability to inhibit ergosterol synthesis makes it effective against the dermatophytes responsible for this infection.
Question 1620: What is the primary reason for using silver sulphadiazine cream in the treatment of burn wounds?
- A. It provides a cooling effect on the skin.
- B. It has antibacterial properties against Pseudomonas.
- C. It is effective against MRSA.
- D. It provides broad-spectrum coverage against both Pseudomonas and MRSA. (Correct Answer)
Explanation: ***It provides broad-spectrum coverage against both Pseudomonas and MRSA.*** - **Silver sulphadiazine** is a topical antimicrobial agent commonly used in burn care due to its **broad-spectrum activity** against a wide range of bacteria, including common burn wound pathogens like *Pseudomonas aeruginosa* and MRSA [1]. - This broad-spectrum coverage helps **prevent and treat wound infections**, which are a significant cause of morbidity and mortality in burn patients [1]. *It provides a cooling effect on the skin.* - While applying any cream might initially feel cool, the primary therapeutic benefit of **silver sulphadiazine** is its **antimicrobial action**, not its cooling properties. - **Cooling** is generally achieved with cool water application immediately post-burn, not sustained cream use. *It has antibacterial properties against Pseudomonas.* - While it is effective against *Pseudomonas*, this statement is **incomplete** as it is not the sole reason for its widespread use. - Its utility in burn care stems from its activity against a **broader range of pathogens**, not just *Pseudomonas* [1]. *It is effective against MRSA.* - This statement is also **incomplete** because its effectiveness against MRSA is only one part of its broader antimicrobial spectrum. - The primary advantage is its **combined efficacy** against both gram-positive and gram-negative bacteria, including both MRSA and *Pseudomonas* [1].
Practice by Chapter
Beta-Lactam Antibiotics
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Aminoglycosides
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Macrolides and Ketolides
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Tetracyclines
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Quinolones
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Sulfonamides and Trimethoprim
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Antimycobacterial Drugs
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Antifungal Agents
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Antiviral Drugs
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Antiparasitic Agents
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Principles of Antimicrobial Selection
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Antimicrobial Resistance
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