Antimicrobial Agents Practice Questions

Q: Idoxuridine is used for treatment of?

HSV. ***HSV*** - **Idoxuridine** is a **pyrimidine analog** that inhibits viral DNA synthesis, making it effective against **herpes simplex virus (HSV)** infections, particularly **herpes keratitis** (ophthalmic use). - Its mechanism involves being incorporated into viral DNA, leading to errors in replication and transcription. - It is applied **topically** for ocular HSV infections due to systemic toxicity concerns. *Influenza* - **Idoxuridine** is not active against **influenza viruses**. - **Antiviral drugs** like **oseltamivir** or **zanamivir** are typically used for influenza treatment. *RSV* - **Idoxuridine** is not indicated for the treatment of **respiratory syncytial virus (RSV)**. - **Ribavirin** is the primary antiviral agent used for severe RSV infections, especially in immunocompromised patients. *HIV* - **Idoxuridine** has no significant activity against **human immunodeficiency virus (HIV)**. - **Antiretroviral therapy (ART)**, a combination of drugs targeting various stages of the HIV life cycle, is used for HIV treatment.

Q: Which drug would be most appropriate for treating a patient with suspected chlamydia-gonorrhea coinfection?

Doxycycline. ***Doxycycline*** - **Doxycycline** is a highly effective treatment for **chlamydia**, and its broad-spectrum activity also covers potential **gonorrhea coinfection** when used as part of a dual therapy regimen. - It is often prescribed alongside a **single dose of ceftriaxone** for presumed gonorrhea coinfection, as ceftriaxone targets gonorrhea while doxycycline targets chlamydia. *Ciprofloxacin* - **Ciprofloxacin** is a **fluoroquinolone** antibiotic, which is generally not recommended as first-line treatment for uncomplicated **gonorrhea** or **chlamydia** due to increasing resistance. - It has activity against *Neisseria gonorrhoeae*, but its effectiveness against *Chlamydia trachomatis* is suboptimal compared to macrolides or tetracyclines. *Norfloxacin* - **Norfloxacin** is another **fluoroquinolone** with a narrower spectrum of activity than ciprofloxacin and is primarily used for **urinary tract infections**. - It has **poor efficacy against chlamydia** and is not a recommended treatment for either organism in this context. *Nalidixic acid* - **Nalidixic acid** is a first-generation **quinolone** with a very limited spectrum, used mainly for **gram-negative urinary tract infections**. - It has **no significant activity against chlamydia** or gonorrhea and is therefore inappropriate for treating this suspected coinfection.

Q: What is the recommended single dose treatment for gonorrhea?

Ceftriaxone. ***Ceftriaxone*** - **Ceftriaxone** is the **recommended first-line single dose treatment** for uncomplicated gonorrhea, given as a **500 mg intramuscular injection**. - As per current guidelines (CDC 2020+), **ceftriaxone monotherapy** is preferred due to its high efficacy and the discontinuation of routine dual therapy. - Ceftriaxone, a third-generation cephalosporin, maintains excellent activity against *Neisseria gonorrhoeae* with minimal resistance reported. *Azithromycin* - **Azithromycin alone** is **not recommended** as single-dose monotherapy for gonorrhea due to increasing macrolide resistance and treatment failures. - While previously used in dual therapy with ceftriaxone, routine dual therapy was discontinued in 2020 guidelines. - Azithromycin remains the first-line treatment for **chlamydia** (1 g single dose), which often co-occurs with gonorrhea and should be treated separately if detected. *Tetracycline* - **Tetracycline** is **not effective** against current strains of *Neisseria gonorrhoeae* due to widespread resistance. - Tetracyclines are primarily used for bacterial infections like **chlamydia** (doxycycline 100 mg twice daily for 7 days), **acne**, and **rickettsial infections**. *Erythromycin* - **Erythromycin** is **not a recommended treatment** for gonorrhea due to high rates of resistance and poor efficacy. - It is used for conditions like **streptococcal pharyngitis** in penicillin-allergic patients and some **atypical pneumonias**.

Q: What is the treatment for Trichomonas vaginalis?

Metronidazole. ***Metronidazole*** - **Metronidazole** is the **first-line drug** for treating *Trichomonas vaginalis* infection. - It is effective against this **anaerobic protozoan** and can be administered as a single dose or a 7-day course. *Azithromycin* - **Azithromycin** is a **macrolide antibiotic** primarily used to treat bacterial infections, such as **chlamydia** or certain **respiratory tract infections**. - It is **not effective** against *Trichomonas vaginalis*, which is a parasitic protozoan. *Ciprofloxacin* - **Ciprofloxacin** is a **fluoroquinolone antibiotic** used for bacterial infections, especially **urinary tract infections** and complicated **gastrointestinal infections**. - It has **no activity** against *Trichomonas vaginalis*. *None of the options* - This option is incorrect because **Metronidazole** is a highly effective and widely accepted treatment for *Trichomonas vaginalis* infections.

Q: What is the drug of choice for the treatment of kala-azar?

Liposomal Amphotericin B. ***Liposomal Amphotericin B*** - It is currently considered the **drug of choice** for treating **visceral leishmaniasis (kala-azar)** due to its high efficacy and better tolerability profile compared to conventional amphotericin B. - The **liposomal formulation** allows for targeted delivery to macrophages, where *Leishmania* parasites reside, reducing systemic toxicity. *Amphotericin B* - While effective against *Leishmania*, conventional **Amphotericin B deoxycholate** is associated with significant **nephrotoxicity** and other severe side effects. - It is generally reserved for cases where liposomal amphotericin B is unavailable or as an alternative in specific clinical situations. *Quinine* - **Quinine** is an **antimalarial drug** primarily used for the treatment of *Plasmodium falciparum* malaria. - It has no significant efficacy against *Leishmania* species, which are the causative agents of kala-azar. *Paromomycin* - **Paromomycin** is an **aminoglycoside antibiotic** that can be used as an alternative treatment for visceral leishmaniasis, especially in combination therapies. - Although effective, it is generally not considered the first-line **drug of choice** globally, and its efficacy can vary by region.

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 mechanism of action of aminoglycoside antibiotics?

Inhibition of protein synthesis. ***Inhibition of protein synthesis*** - Aminoglycosides **bind irreversibly to the 30S ribosomal subunit** of bacteria, interfering with the initiation complex formation and causing misreading of mRNA. - This leads to the production of **non-functional proteins** and ultimately bacterial cell death, making them bactericidal. *Disruption of the cell membrane* - This mechanism is characteristic of **polymyxins** (e.g., colistin), which interact with bacterial cell membranes, increasing permeability and causing leakage of intracellular contents. - Aminoglycosides do not primarily target the cell membrane for their bactericidal action. *Inhibition of DNA replication* - This mechanism is associated with **fluoroquinolones**, which inhibit bacterial topoisomerase II (DNA gyrase) and topoisomerase IV. - Aminoglycosides do not interfere with DNA synthesis or replication. *Inhibition of bacterial cell wall synthesis* - This is the mechanism of action for **beta-lactam antibiotics** (e.g., penicillins, cephalosporins) and **glycopeptides** (e.g., vancomycin), which target peptidoglycan synthesis. - Aminoglycosides do not affect the bacterial cell wall but rather their intracellular protein machinery.

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 drug is contraindicated in G6PD deficiency?

Primaquine. ***Primaquine*** - **Primaquine** is an antimalarial drug that generates **severe oxidative stress** in red blood cells. - It is **definitively contraindicated** in **G6PD deficiency** as it consistently causes **acute hemolytic anemia**. - Among antimalarials, primaquine poses the **highest risk** and should **never be used** in G6PD-deficient patients. - It is used for radical cure of P. vivax and P. ovale malaria, but alternative regimens must be used in G6PD deficiency. *Chloroquine* - **Chloroquine** can cause hemolysis in **G6PD deficiency**, though the risk is **lower than primaquine**. - It is **not considered fully safe** and should be used with **caution** in G6PD-deficient patients. - At standard doses, the risk is moderate, but hemolysis can occur, especially in certain G6PD variants. - However, it is not absolutely contraindicated and may be used when benefits outweigh risks with close monitoring. *Quinine* - **Quinine** can also cause **hemolysis** in patients with **G6PD deficiency**. - The risk varies with G6PD variant severity and dosage. - In **severe G6PD deficiency**, quinine should be avoided when alternatives are available. - While less consistently problematic than primaquine, it still requires caution and monitoring. *All of the options* - This option is incorrect in the context of this question because **primaquine** is the **most consistently and severely contraindicated** drug. - While chloroquine and quinine can cause hemolysis, they have **variable risk profiles** and may be used cautiously in some situations, unlike primaquine which is **absolutely contraindicated**. - The question asks for "which drug" (singular), indicating primaquine as the primary answer due to its consistent and severe risk.

Question 1

Idoxuridine is used for treatment of?

Accepted Answer

HSV

Answer

Influenza

Answer

RSV

Answer

HIV

Question 2

Which drug would be most appropriate for treating a patient with suspected chlamydia-gonorrhea coinfection?

Accepted Answer

Doxycycline

Answer

Ciprofloxacin

Answer

Nalidixic acid

Answer

Norfloxacin

Question 3

What is the recommended single dose treatment for gonorrhea?

Accepted Answer

Ceftriaxone

Answer

Erythromycin

Answer

Tetracycline

Answer

Azithromycin

Question 4

What is the treatment for Trichomonas vaginalis?

Accepted Answer

Metronidazole

Answer

Azithromycin

Answer

Ciprofloxacin

Answer

None of the options

Question 5

What is the drug of choice for the treatment of kala-azar?

Accepted Answer

Liposomal Amphotericin B

Answer

Amphotericin B

Answer

Quinine

Answer

Paromomycin

Question 6

Which of the following is a topical sulfonamide ?

Accepted Answer

Mafenide

Answer

Sulfadoxine

Answer

Sulfamethopyrazine

Answer

Sulfisoxazole

Question 7

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

Accepted Answer

Mefloquine

Answer

Quinine

Answer

Halofantrine

Answer

Artesunate

Question 8

What is the mechanism of action of aminoglycoside antibiotics?

Accepted Answer

Inhibition of protein synthesis

Answer

Inhibition of DNA replication

Answer

Disruption of the cell membrane

Answer

Inhibition of bacterial cell wall synthesis

Question 9

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 10

Which drug is contraindicated in G6PD deficiency?

Accepted Answer

Primaquine

Answer

Chloroquine

Answer

Quinine

Answer

All of the options

Antimicrobial Agents — MCQs

Antimicrobial Agents — MCQs

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