Antimicrobial Agents Practice Questions

Q: Which of the following is NOT an advantage of amoxicillin over ampicillin?

Spectrum includes H. influenzae & Shigella. ***Spectrum includes H. influenzae & Shigella*** - Amoxicillin and ampicillin both have a similar spectrum of activity against *Haemophilus influenzae* and *Shigella* species. Neither drug possesses a distinct advantage over the other in this regard for these specific pathogens. - Therefore, stating that amoxicillin's spectrum *includes* these bacteria as an advantage over ampicillin implies a unique characteristic, which is incorrect. *Better bioavailability & faster action* - **Amoxicillin** has superior oral **bioavailability** compared to ampicillin, leading to higher and more consistent blood levels. - This improved absorption often translates to a **faster onset of action** and allows for less frequent dosing. *Incidence of diarrhea is lower* - **Amoxicillin** is associated with a **lower incidence of diarrhea** and other gastrointestinal side effects compared to ampicillin. - This is partly due to its better absorption, meaning less unabsorbed drug reaches the colon to disrupt normal flora. *Food does not interfere with its absorption* - The absorption of **amoxicillin is largely unaffected by food**, allowing it to be taken without regard to meals. - In contrast, ampicillin's absorption can be significantly reduced when taken with food, making amoxicillin more convenient.

Q: Which of the following conditions is not treated by penicillin G?

Rickettsial infection. ***Rickettsial infection*** - **Rickettsial infections**, such as Rocky Mountain spotted fever or typhus, are caused by **obligate intracellular bacteria** that are not susceptible to penicillin G. - The primary treatment for rickettsial infections is **doxycycline**, due to its ability to penetrate host cells and inhibit bacterial protein synthesis. *Bacterial meningitis* - **Bacterial meningitis**, particularly caused by susceptible strains of *Neisseria meningitidis*, *Streptococcus pneumoniae*, and *Haemophilus influenzae*, can be effectively treated with **high-dose intravenous penicillin G** [1]. - Penicillin G's ability to cross the **blood-brain barrier** in inflamed meninges makes it a suitable option, though ceftriaxone is now more commonly used empirically due to resistance concerns [2]. *Syphilis* - **Penicillin G** remains the **drug of choice** for all stages of syphilis, caused by *Treponema pallidum*. - For primary, secondary, and early latent syphilis, a **single intramuscular dose of benzathine penicillin G** is curative. *Anthrax* - While **ciprofloxacin** and **doxycycline** are often considered first-line for anthrax, **penicillin G** can also be an effective treatment for susceptible strains of *Bacillus anthracis*. - It is particularly used in cases of less severe cutaneous anthrax or to de-escalate treatment once susceptibility is confirmed.

Q: Which of the following is a topical sulfonamide ?

Mafenide. ***Mafenide*** - **Mafenide** is a **sulfonamide antibiotic** primarily used **topically** as a cream for preventing and treating **wound infections**, particularly in **burn patients**. - It works by inhibiting bacterial growth and has good penetrative capabilities in **necrotic tissue** and **eschar**. - It is **water-soluble** and can penetrate burn eschar effectively. *Sulfadoxine* - **Sulfadoxine** is a **long-acting oral sulfonamide** frequently used in combination with **pyrimethamine** for conditions like **malaria** and **toxoplasmosis**. - It is administered **systemically**, not topically. *Sulfamethopyrazine* - **Sulfamethopyrazine** (also known as sulfalene) is another **long-acting sulfonamide** primarily used **orally** for conditions such as **malaria** and **urinary tract infections**. - Its clinical application is **systemic**, not topical. *Sulfisoxazole* - **Sulfisoxazole** is a **short-acting oral sulfonamide** used systemically for **urinary tract infections** and other bacterial infections. - It is **rapidly absorbed** and excreted, making it suitable for systemic use, not topical application.

Q: Drug for prophylaxis of malaria in chloroquine resistant P.falciparum ?

Mefloquine. ***Mefloquine*** - **Mefloquine** is a well-established and effective drug for prophylaxis against **chloroquine-resistant Plasmodium falciparum**. - It is often used in regions with high chloroquine resistance, although it can have significant neuropsychiatric side effects. *Quinine* - **Quinine** is primarily used for the *treatment* of severe or complicated malaria, especially in cases of multidrug resistance. - It is not typically recommended for malaria **prophylaxis** due to its relatively short half-life and potential for side effects with chronic use. *Halofantrine* - **Halofantrine** is an *antimalarial treatment* drug, not a prophylactic agent. - Its use is limited due to potential for **cardiotoxicity** (QT prolongation) and poor bioavailability. *Artesunate* - **Artesunate** is an **artemisinin derivative** and a potent antimalarial drug used for the *treatment* of acute malaria, particularly severe cases. - It has a very short half-life and is not suitable for **prophylaxis**.

Q: What is the initial loading dose of chloroquine base for treating uncomplicated malaria in children?

10 mg/kg (maximum 600 mg). ***10 mg/kg (maximum 600 mg)*** - The standard **initial loading dose** of chloroquine base for uncomplicated malaria in children is **10 mg/kg body weight**, with a maximum cap of **600 mg** to prevent toxicity. - This is followed by **5 mg/kg** at 6 hours, 24 hours, and 48 hours (total course of 25 mg/kg over 3 days). - This represents **WHO-recommended** weight-based dosing for pediatric malaria treatment. *5 mg/kg* - **5 mg/kg** is the dose for the **subsequent doses** (at 6, 24, and 48 hours after the initial dose), not the initial loading dose. - The initial dose must be higher (10 mg/kg) to rapidly achieve therapeutic blood levels. *15 mg/kg* - **15 mg/kg** exceeds the recommended initial dose and increases the risk of **chloroquine toxicity**. - Chloroquine has a narrow therapeutic index, and overdosing can cause serious **cardiovascular** (arrhythmias, hypotension) and **neurological** effects (seizures, visual disturbances). *25 mg/kg* - **25 mg/kg** represents the **total cumulative dose** over the entire 3-day treatment course, not the initial single dose. - Giving this amount as a single dose would result in severe toxicity and is contraindicated.

Q: Which of the following statements about clofazimine is incorrect?

Does not interfere with DNA synthesis. ***Does not interfere with DNA synthesis*** - Clofazimine's primary mechanism of action involves **DNA binding** and **interference with bacterial DNA synthesis**. - It also generates **reactive oxygen species** and disrupts membrane function, contributing to its bactericidal effect. - **This statement is INCORRECT** - clofazimine does interfere with DNA synthesis. *Used in lepra reaction* - Clofazimine is a crucial component in the treatment of **leprosy**, particularly effective in managing **Type 2 lepra reactions (erythema nodosum leprosum)** due to its anti-inflammatory effects. - It helps to reduce the severity and duration of these acute inflammatory episodes. *Used in treatment of leprosy* - Clofazimine is a **core component of multidrug therapy (MDT) for leprosy**, particularly in multibacillary leprosy. - It is recommended by the **WHO** as part of the standard treatment regimen for leprosy. *Causes ichthyosis and hyperpigmentation* - Clofazimine commonly causes **hyperpigmentation of the skin, conjunctiva, and bodily fluids**, often appearing reddish-brown to black. - Less commonly, it can also lead to **ichthyosis (dry, scaly skin)** as a side effect.

Q: Which drug is commonly used to treat chronic hepatitis B infection?

Entecavir. ***Entecavir*** - **Entecavir** is an oral **nucleoside analog reverse transcriptase inhibitor** specifically approved and widely used for the treatment of **chronic hepatitis B virus (HBV) infection**. - It works by inhibiting HBV DNA polymerase, thereby reducing **viral replication** and preventing disease progression. *Atazanavir* - **Atazanavir** is a **protease inhibitor** primarily used in the treatment of **HIV infection**. - It is not indicated for the treatment of **hepatitis B virus infection**. *Zanamivir* - **Zanamivir** is a **neuraminidase inhibitor** used in the treatment and prevention of **influenza A and B viruses**. - It has no activity against **hepatitis B virus**. *Abacavir* - **Abacavir** is a **nucleoside reverse transcriptase inhibitor (NRTI)** used to treat **HIV infection**. - While it is an NRTI, it does not have significant efficacy against **hepatitis B virus** and is not used for its treatment.

Q: An Englishman travels to a place which is resistant to chloroquine and mefloquine. What should he take as prophylaxis?

Atovaquone-proguanil. ***Atovaquone-proguanil*** - This combination, known as **Malarone**, is the most appropriate prophylactic agent for areas with **multi-drug resistant malaria**, including resistance to chloroquine and mefloquine [1], [2]. - It targets multiple stages of the parasite life cycle, providing excellent protection and is generally well-tolerated with specific **WHO and CDC recommendations** for chloroquine and mefloquine resistant areas [1], [3]. *Primaquine* - **Primaquine** is primarily used for **causal prophylaxis** against *P. vivax* and *P. ovale* to prevent relapse, not as primary prophylaxis [2]. - It is not typically recommended as the primary prophylactic agent in areas with **chloroquine and mefloquine resistance** and requires **G6PD testing** due to risk of hemolysis [1]. *Proguanil* - While proguanil is used for malaria prophylaxis, **proguanil alone** is not effective enough for prophylaxis in areas with multi-drug resistant malaria. - It is typically used in **combination with atovaquone** rather than as monotherapy for effective protection [3]. *Doxycycline* - **Doxycycline** is also an effective prophylactic agent for areas with **chloroquine and mefloquine-resistant malaria** and is commonly recommended [1], [2]. - While effective, it can cause **photosensitivity** and **gastrointestinal upset**, making atovaquone-proguanil the preferred first-line choice.

Q: What is the most serious side effect associated with Raltegravir?

Rhabdomyolysis. ***Rhabdomyolysis*** - Raltegravir, an **integrase strand transfer inhibitor (INSTI)**, can cause muscle-related side effects, including **rhabdomyolysis** and **myopathy**. [2] - Patients may present with muscle pain, weakness, and elevated **creatine kinase (CK)** levels. *Headache* - While headache can be a general side effect of many medications, it is not a **distinguishing or severe adverse effect commonly associated with Raltegravir** that would require specific monitoring. - Other more prominent side effects are typically prioritized in counseling and monitoring for this drug. *Hyperglycemia* - **Hyperglycemia** is not a commonly reported or significant side effect of Raltegravir. - While some antiretrovirals, particularly certain **protease inhibitors (PIs)** and **nucleoside reverse transcriptase inhibitors (NRTIs)**, are associated with altered glucose metabolism, INSTIs like Raltegravir generally have a more favorable metabolic profile. [1] *Hypertension* - Hypertension is generally **not a recognized or common side effect** of Raltegravir. - Cardiovascular events and hypertension are more frequently associated with other classes of antiretroviral drugs or as comorbidities in HIV-positive patients, rather than directly with INSTIs.

Q: First generation cephalosporins are active against?

Gram positive bacteria. ***Gram positive bacteria*** - First-generation cephalosporins, such as **cefazolin** and **cephalexin**, primarily exhibit excellent activity against many **Gram-positive cocci**, including **staphylococci** and **streptococci**. - They are commonly used for skin and soft tissue infections and surgical prophylaxis due to this Gram-positive coverage. *Gram negative bacteria* - While first-generation cephalosporins have *some* activity against limited Gram-negative bacteria (e.g., *E. coli*, *Klebsiella pneumoniae*, *P. mirabilis*), their spectrum is generally weak and unreliable compared to later generations of cephalosporins. - They are not the drug of choice for serious Gram-negative infections. *Anaerobes* - First-generation cephalosporins have **poor activity** against most **anaerobic bacteria**. - For infections involving anaerobes, other antibiotics like **metronidazole**, **clindamycin**, or later-generation cephalosporins (e.g., cefoxitin, cefotetan) are generally preferred. *Dermatophytes* - Dermatophytes are **fungi** that cause skin, hair, and nail infections. - Cephalosporins are **antibacterial agents** and have **no activity** against fungi. Antifungal medications are required to treat dermatophyte infections.

Question 1

Which of the following is NOT an advantage of amoxicillin over ampicillin?

Accepted Answer

Spectrum includes H. influenzae & Shigella

Answer

Incidence of diarrhea is lower

Answer

Food does not interfere with its absorption

Answer

Better bioavailability & faster action

Question 2

Which of the following conditions is not treated by penicillin G?

Accepted Answer

Rickettsial infection

Answer

Bacterial meningitis

Answer

Syphilis

Answer

Anthrax

Question 3

Which of the following is a topical sulfonamide ?

Accepted Answer

Mafenide

Answer

Sulfadoxine

Answer

Sulfamethopyrazine

Answer

Sulfisoxazole

Question 4

Drug for prophylaxis of malaria in chloroquine resistant P.falciparum ?

Accepted Answer

Mefloquine

Answer

Quinine

Answer

Halofantrine

Answer

Artesunate

Question 5

What is the initial loading dose of chloroquine base for treating uncomplicated malaria in children?

Accepted Answer

10 mg/kg (maximum 600 mg)

Answer

5 mg/kg

Answer

15 mg/kg

Answer

25 mg/kg

Question 6

Which of the following statements about clofazimine is incorrect?

Accepted Answer

Does not interfere with DNA synthesis

Answer

Used in lepra reaction

Answer

Used in treatment of leprosy

Answer

Causes ichthyosis and hyperpigmentation

Question 7

Which drug is commonly used to treat chronic hepatitis B infection?

Accepted Answer

Entecavir

Answer

Zanamivir

Answer

Atazanavir

Answer

Abacavir

Question 8

An Englishman travels to a place which is resistant to chloroquine and mefloquine. What should he take as prophylaxis?

Accepted Answer

Atovaquone-proguanil

Answer

Primaquine

Answer

Doxycycline

Answer

Proguanil

Question 9

What is the most serious side effect associated with Raltegravir?

Accepted Answer

Rhabdomyolysis

Answer

Hyperglycemia

Answer

Hypertension

Answer

Headache

Question 10

First generation cephalosporins are active against?

Accepted Answer

Gram positive bacteria

Answer

Gram negative bacteria

Answer

Anaerobes

Answer

Dermatophytes

Antimicrobial Agents — MCQs

Antimicrobial Agents — MCQs

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