Antimicrobial Agents — MCQs
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What is the drug of choice (DOC) for the treatment of subacute sclerosing panencephalitis (SSPE)?
Which of the following is not true about the Vi polysaccharide vaccine for typhoid?
Which statement is true regarding the influenza vaccine?
In areas with chloroquine-sensitive P. vivax, what is the preferred drug for treating the blood stages?
What is the recommended regimen for post-exposure prophylaxis for HIV?
Which of the following medications is not indicated for the treatment or prophylaxis of seasonal influenza?
What is the Hib conjugate vaccine made of?
Flu-like symptoms are a side effect of which anti-TB drug?
Which of the following is the longest acting carbapenem?
Quinine primarily acts on which stage of the Plasmodium life cycle?
Antimicrobial Agents Indian Medical PG Practice Questions and MCQs
Question 1521: What is the drug of choice (DOC) for the treatment of subacute sclerosing panencephalitis (SSPE)?
- A. Abacavir
- B. Inosine pranobex (Correct Answer)
- C. Glatiramer
- D. Interferon
Explanation: ***Inosine pranobex*** - **Inosine pranobex (Isoprinosine)** is considered the **oral drug of choice** for treating **subacute sclerosing panencephalitis (SSPE)**, particularly in the early stages, as it has shown success in delaying disease progression. - This drug works by **modulating the immune system** and enhancing T-cell function, which helps control the persistent measles virus infection in the CNS. - **Note:** Best outcomes are achieved when inosine pranobex is combined with **intrathecal/intraventricular interferon-alpha**, but as a single oral agent, inosine pranobex is the primary choice. *Abacavir* - **Abacavir** is an **antiretroviral drug (NRTI)** used in the treatment of **HIV infection**. - It inhibits reverse transcriptase and has **no role** in treating measles virus-induced SSPE. *Glatiramer* - **Glatiramer acetate** is an **immunomodulatory drug** used in **multiple sclerosis (MS)**. - It works by mimicking **myelin basic protein** to reduce immune attacks on myelin, but is **not effective** against viral infections like SSPE. *Interferon* - **Interferon-alpha** (particularly **intrathecal/intraventricular** administration) has been used in **SSPE** as **combination therapy** with inosine pranobex, showing improved outcomes. - However, when given systemically alone, it has **significant side effects** and **variable efficacy**. - As a single answer option without specifying the route, **inosine pranobex** is preferred as the primary oral DOC.
Question 1522: Which of the following is not true about the Vi polysaccharide vaccine for typhoid?
- A. Given intramuscularly
- B. Given at birth (Correct Answer)
- C. Revaccination at 3 years
- D. Single dose is given
Explanation: ***Given at birth*** - The **typhoid Vi polysaccharide vaccine is not administered at birth**. It is recommended for individuals **2 years of age**. - Vaccines given at birth protect against diseases with significant **neonatal risk**, such as Hepatitis B and BCG (tuberculosis). - This is the **FALSE** statement, making it the correct answer to this "not true" question. *Single dose is given* - The Vi polysaccharide vaccine is administered as a **single 0.5 mL dose**. - This single dose provides protection against *Salmonella typhi* for approximately 3 years. - This statement is **TRUE**. *Revaccination at 3 years* - For ongoing protection, **revaccination is recommended every 3 years** for individuals at continued risk of typhoid exposure. - The booster dose maintains adequate protective antibody levels. - This statement is **TRUE**. *Given intramuscularly* - The Vi polysaccharide vaccine is administered via the **intramuscular (IM) route**, typically in the deltoid muscle. - This is the standard recommended route of administration. - This statement is **TRUE**.
Question 1523: Which statement is true regarding the influenza vaccine?
- A. The live attenuated vaccine is given by nasal spray.
- B. All statements are correct. (Correct Answer)
- C. The inactivated vaccine is used most commonly.
- D. The inactivated vaccine is given intramuscularly in the deltoid.
Explanation: ***All statements are correct.*** - Each of the preceding statements is factually accurate regarding influenza vaccines. - The **inactivated vaccine** is widely used, the **live attenuated vaccine** is administered via nasal spray, and the **inactivated vaccine** is given intramuscularly [1]. *The inactivated vaccine is used most commonly.* - The **inactivated influenza vaccine (IIV)**, given by injection, is the most frequently administered type of influenza vaccine. - It is recommended for most age groups and is safe for individuals with chronic medical conditions, pregnant women, and the elderly. *The live attenuated vaccine is given by nasal spray.* - The **live attenuated influenza vaccine (LAIV)**, also known as FluMist, is administered as a **nasal spray** [1]. - This vaccine is suitable for healthy individuals aged 2-49 years and is not recommended for pregnant women or individuals with certain immune compromising conditions. *The inactivated vaccine is given intramuscularly in the deltoid.* - The standard route of administration for the **inactivated influenza vaccine (IIV)** is via **intramuscular injection**, most commonly into the **deltoid muscle** in adults and older children [1]. - This method ensures proper absorption and an effective immune response, a common practice for many vaccines.
Question 1524: In areas with chloroquine-sensitive P. vivax, what is the preferred drug for treating the blood stages?
- A. Mefloquine
- B. Artesunate
- C. Quinine
- D. Chloroquine (Correct Answer)
Explanation: ***Correct Option: Chloroquine***- **Chloroquine** remains the **first-line treatment** for **chloroquine-sensitive P. vivax** infections due to its high efficacy and safety profile [1, 2].- It rapidly clears **blood-stage parasites**, alleviating acute symptoms of malaria [3].- In areas where P. vivax remains sensitive, chloroquine is preferred due to low cost, good tolerability, and proven effectiveness [1, 2].*Incorrect Option: Mefloquine*- **Mefloquine** is typically reserved for areas with **chloroquine-resistant P. falciparum** or for prophylaxis in such regions.- Its use is generally avoided when less toxic and equally effective options like chloroquine are available for sensitive strains.- Associated with more neuropsychiatric side effects.*Incorrect Option: Artesunate*- **Artesunate** is an **artemisinin derivative**, primarily used for severe malaria or in areas with **multi-drug resistant P. falciparum**.- While effective, it is not the preferred first-line agent for chloroquine-sensitive P. vivax due to the availability of simpler, equally effective treatments.- Typically used in combination therapy (ACT) for resistant strains.*Incorrect Option: Quinine*- **Quinine** is an older antimalarial, often used for **severe malaria** or in cases of **chloroquine-resistant P. falciparum**.- It has a higher incidence of side effects compared to chloroquine (cinchonism, hypoglycemia) and is not the preferred choice for chloroquine-sensitive P. vivax.- Requires longer treatment duration with more monitoring.
Question 1525: What is the recommended regimen for post-exposure prophylaxis for HIV?
- A. Zidovudine + Lamivudine + Lopinavir/ritonavir for 28 days
- B. Tenofovir disoproxil fumarate + Emtricitabine + Raltegravir for 28 days
- C. Single dose Tenofovir + Emtricitabine + Raltegravir
- D. Tenofovir disoproxil fumarate + Emtricitabine + Dolutegravir for 28 days (Correct Answer)
Explanation: ***Tenofovir disoproxil fumarate + Emtricitabine + Dolutegravir for 28 days*** - This is the **current first-line recommended regimen** for **HIV post-exposure prophylaxis (PEP)** according to WHO (2021), CDC, and Indian NACO guidelines. - It includes two **nucleoside reverse transcriptase inhibitors (NRTIs)** and an **integrase strand transfer inhibitor (INSTI)**. - **Dolutegravir** is preferred over Raltegravir due to **superior efficacy, better tolerability, higher barrier to resistance, once-daily dosing**, and fewer drug interactions. - The duration of **28 days** is crucial for effective PEP to cover the window period for potential HIV integration and replication. *Tenofovir disoproxil fumarate + Emtricitabine + Raltegravir for 28 days* - This was the **previous standard PEP regimen** and is still an acceptable alternative if Dolutegravir is contraindicated or unavailable. - Raltegravir requires **twice-daily dosing** compared to Dolutegravir's once-daily regimen, which may affect adherence. - The 28-day duration is correct, but Raltegravir is no longer the first-line INSTI choice in current guidelines. *Single dose Tenofovir + Emtricitabine + Raltegravir* - A **single dose** of these medications is insufficient for **post-exposure prophylaxis (PEP)** as HIV replication needs to be suppressed over an extended period to prevent seroconversion. - PEP typically requires a **28-day course** to be effective. *Zidovudine + Lamivudine + Lopinavir/ritonavir for 28 days* - While this is an older, effective **antiretroviral regimen**, it is **not the preferred first-line PEP regimen** due to a higher incidence of side effects, particularly with zidovudine (anemia, nausea). - Modern guidelines favor regimens with **Tenofovir/Emtricitabine + Dolutegravir** due to better tolerability and superior efficacy.
Question 1526: Which of the following medications is not indicated for the treatment or prophylaxis of seasonal influenza?
- A. Amantadine
- B. Rimantadine
- C. Oseltamivir
- D. Acyclovir (Correct Answer)
Explanation: ***Acyclovir*** - **Acyclovir** is an antiviral medication specifically used to treat infections caused by **herpes viruses** (e.g., HSV, VZV), not influenza viruses. - It works by inhibiting **viral DNA polymerase**, a mechanism distinct from how anti-influenza drugs act. - **This drug has never been indicated for influenza** - it is the correct answer to this "not indicated" question. *Amantadine* - **Amantadine** is an M2 ion channel inhibitor that **was indicated** for influenza A treatment and prophylaxis. - Although no longer recommended due to widespread **resistance** among circulating influenza strains, it remains a drug that was formally indicated for seasonal influenza. *Rimantadine* - **Rimantadine** is also an M2 ion channel inhibitor, structurally related to amantadine, with a similar mechanism of action. - Like amantadine, it **was indicated** for influenza treatment or prophylaxis but is no longer recommended due to high rates of **resistance** in circulating influenza A viruses. *Oseltamivir* - **Oseltamivir** is a **neuraminidase inhibitor** currently approved and recommended for the treatment and prophylaxis of both influenza A and B. - It reduces viral spread by preventing the release of new virions from infected cells and remains a first-line agent for seasonal influenza.
Question 1527: What is the Hib conjugate vaccine made of?
- A. Capsular polysaccharide
- B. Purified protein with carrier
- C. Cell wall polysaccharide
- D. Capsular polysaccharide with carrier (Correct Answer)
Explanation: ***Capsular polysaccharide with carrier*** - The Hib conjugate vaccine uses a **polysaccharide capsule** from *Haemophilus influenzae* type b (Hib) covalently linked to a **protein carrier** [1]. - This conjugation allows activated B cells to present the polysaccharide to T helper cells, inducing a strong **T-cell dependent immune response** and **immunological memory**, especially in infants [1]. *Capsular polysaccharide* - A vaccine made only of **capsular polysaccharide** would be a **polysaccharide vaccine**, which induces a **T-cell independent immune response**. - This type of vaccine is **poorly immunogenic in infants** and does not generate long-lasting memory. *Purified protein with carrier* - This describes components of some **protein subunit vaccines**, but not specifically the Hib vaccine, which targets the polysaccharide capsule. - While it employs a carrier protein, the primary antigen is the **polysaccharide**, not a purified bacterial protein. *Cell wall polysaccharide* - The Hib vaccine specifically targets the **capsular polysaccharide**, which is distinct from the general cell wall polysaccharides found in the bacterial outer membrane. - The **capsule** is the primary virulence factor and target for protective immunity in Hib.
Question 1528: Flu-like symptoms are a side effect of which anti-TB drug?
- A. Rifampicin (Correct Answer)
- B. Isoniazid
- C. Pyrazinamide
- D. Ethambutol
Explanation: ***Rifampicin*** - **Flu-like syndrome** (fever, chills, myalgia, and headache) is a dose-dependent side effect of **rifampicin**, particularly with intermittent dosing. - This reaction is due to **immunological mechanisms**, involving antibodies against rifampicin. *Isoniazid* - The most significant side effect of isoniazid is **hepatotoxicity**, which can range from mild elevated liver enzymes to severe hepatitis. - It can also cause **peripheral neuropathy**, particularly in malnourished patients or those with risk factors, preventable with pyridoxine (vitamin B6) supplementation. *Pyrazinamide* - **Hepatotoxicity** is a major concern with pyrazinamide, often leading to elevated liver enzymes and, in some cases, severe liver damage. - It frequently causes **hyperuricemia**, which can precipitate acute gouty arthritis due to decreased excretion of uric acid. *Ethambutol* - The most characteristic adverse effect of ethambutol is **optic neuritis**, causing decreased visual acuity, red-green color blindness, and visual field defects. - Regular **ophthalmological monitoring** is crucial during treatment to detect this reversible side effect early.
Question 1529: Which of the following is the longest acting carbapenem?
- A. Imipenem
- B. Meropenem
- C. Doripenem
- D. Ertapenem (Correct Answer)
Explanation: ***Ertapenem*** - **Ertapenem** has the **longest half-life** among the carbapenems, allowing for once-daily dosing. - Its prolonged action is due to its **chemical structure**, which provides high protein binding and reduced renal clearance compared to other carbapenems. *Imipenem* - **Imipenem** has a **relatively short half-life** and requires co-administration with cilastatin to prevent its renal metabolism by dehydropeptidase-1. - Its short duration of action necessitates **frequent dosing**, typically every 6 to 8 hours. *Meropenem* - **Meropenem** has a **shorter half-life** than ertapenem, generally requiring dosing every 8 hours. - Although it does not require cilastatin, its pharmacokinetic profile is not as extended as ertapenem's. *Doripenem* - **Doripenem** also has a **shorter half-life** than ertapenem, necessitating administration every 8 hours. - Its spectrum of activity is similar to meropenem, but it does not offer the same extended duration of action.
Question 1530: Quinine primarily acts on which stage of the Plasmodium life cycle?
- A. Exoerythrocytic
- B. Pre-erythrocytic
- C. Erythrocytic (Correct Answer)
- D. None of the options
Explanation: ***Correct: Erythrocytic*** - Quinine primarily acts as a **blood schizonticide**, targeting the asexual erythrocytic stages of the *Plasmodium* parasite. - Its mechanism involves interfering with the parasite's ability to detoxify **heme**, leading to accumulation of toxic byproducts and parasite death within **red blood cells**. - This is why quinine is effective in treating **acute malaria attacks** during the symptomatic phase of the disease. *Incorrect: Exoerythrocytic* - The **exoerythrocytic stage** occurs in the liver, where sporozoites develop into merozoites. - Quinine has **minimal or no activity** against these liver stages, meaning it does not prevent initial infection or relapse from hepatic dormant forms (hypnozoites). - Drugs like **primaquine** target this stage. *Incorrect: Pre-erythrocytic* - The **pre-erythrocytic stage** is another term for the exoerythrocytic or liver stage of the parasite life cycle, occurring before the parasite enters red blood cells. - Medications that target this stage are known as **causal prophylactics**, which quinine is not. - Quinine has **no significant activity** at this stage. *Incorrect: None of the options* - This option is incorrect as quinine specifically targets the **erythrocytic stage**, making that option the correct answer. - Quinine's effectiveness in treating malaria stems from its action during the **symptomatic phase** of the disease, which corresponds to the erythrocytic cycle in red blood cells.
Practice by Chapter
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