Antimicrobial Agents Practice Questions

Q: Based on the above diagnosed patient of Myasthenia Gravis, which of the following antibiotics is LEAST likely to exacerbate the condition?

Cephalosporins. ***Cephalosporins*** - **Cephalosporins** are generally considered safe for patients with **myasthenia gravis (MG)** as they do not significantly interfere with neuromuscular transmission. - This makes them a suitable choice when antibiotic therapy is required in these patients, unlike many other antibiotic classes that can exacerbate MG symptoms. *Macrolides* - **Macrolides** (e.g., azithromycin, clarithromycin, erythromycin) can worsen **myasthenia gravis** by impairing neuromuscular transmission. - They produce a **nondepolarizing blockade** and can lead to acute exacerbation of muscle weakness. *Quinolones* - **Quinolones** (e.g., ciprofloxacin, levofloxacin) are known to exacerbate **myasthenia gravis**. - They achieve this by **blocking acetylcholine receptors** or presynaptically reducing acetylcholine release, leading to increased muscle weakness. *Aminoglycosides* - **Aminoglycosides** (e.g., gentamicin, tobramycin) are well-known for their potential to worsen **myasthenia gravis**. - They inhibit **presynaptic acetylcholine release** and directly depress postsynaptic excitability, causing or exacerbating neuromuscular blockade.

Q: Choice of drug for management of the parasitic infection shown below is:

Triclabendazole. ***Triclabendazole*** - The image displays an adult **Fasciola hepatica** (liver fluke), characterized by its **leaf-like shape** and the prominent **anterior cone** terminating in an oral sucker. - **Triclabendazole** is the drug of choice for treating **fascioliasis**, as it effectively kills both immature and mature forms of Fasciola hepatica. *Albendazole* - **Albendazole** is primarily used to treat a wide range of **intestinal nematode infections** (e.g., Ascaris, hookworm, whipworm) and some **cestode infections** (e.g., neurocysticercosis, echinococcosis). - It has **limited efficacy** against trematodes like Fasciola hepatica. *Praziquantel* - **Praziquantel** is a broad-spectrum antihelminthic drug effective against most **trematodes (flukes)**, including schistosomes and other liver flukes (e.g., Clonorchis, Opisthorchis), and **cestodes (tapeworms)**. - However, it is **ineffective against Fasciola hepatica**, making it unsuitable for this specific infection. *Niclosamide* - **Niclosamide** is an oral anthelmintic primarily used to treat **tapeworm infections (cestodiasis)**, including Taenia species and Hymenolepis nana. - It is **not effective against trematodes** like Fasciola hepatica.

Q: A 24-year-old patient presents with a 1-week history of vulvar itching and vaginal discharge. She says that she has had intercourse with two individuals in the past 6 months without the use of a condom. On physical examination, the vulva is edematous. Discharge is present on the vaginal walls and at the cervical os. Wet smear of vaginal secretions shows epithelial cells, white blood cells, and flagellate protozoa. You prescribe an antibiotic. What warning do you give about this particular treatment?

Avoid alcohol. ***Avoid alcohol*** - The patient's symptoms (vulvar itching, vaginal discharge, edematous vulva) and the presence of **flagellate protozoa** on a wet smear are classic for **Trichomoniasis**. The standard treatment for Trichomoniasis is **metronidazole**. - **Metronidazole** can cause a **disulfiram-like reaction** when taken with alcohol, leading to symptoms like flushing, nausea, vomiting, abdominal cramps, and headache. Patients must be warned to completely avoid alcohol during treatment and for at least 24-72 hours after the last dose. *Avoid sun overexposure* - This warning is typically given for medications that cause **photosensitivity**, such as tetracyclines (e.g., doxycycline) or some fluoroquinolones. - Metronidazole is not commonly associated with significant photosensitivity requiring this specific warning. *Avoid taking on an empty stomach* - While some medications can cause gastrointestinal upset if taken on an empty stomach (e.g., NSAIDs, certain antibiotics), metronidazole can generally be taken with or without food. - The more critical instruction for metronidazole relates to **alcohol consumption**. *Avoid taking with grapefruit juice* - Grapefruit juice can interact with certain medications by inhibiting **cytochrome P450 enzymes** (specifically CYP3A4), altering drug metabolism and increasing drug levels. - This interaction is generally not significant or routinely warned about for metronidazole.

Q: Daily suppressive therapy for HSV-1 and HSV-2 is :

Valacyclovir 1 g once daily. ***Valacyclovir 1 g once daily*** - **Valacyclovir 1 g once daily** is an effective and commonly prescribed regimen for daily suppressive therapy of HSV-1 and HSV-2 due to its good bioavailability and convenient once-daily dosing. - This dosage is particularly effective in reducing the frequency of outbreaks and the risk of transmission. *Acyclovir 400 mg thrice daily* - While **acyclovir** is an effective antiviral for HSV, the standard dose for suppressive therapy is typically **400 mg twice daily** (not thrice daily) to maintain adequate antiviral levels. - A thrice-daily regimen might be used for acute outbreaks but is generally not preferred for long-term daily suppression due to adherence challenges. *Acyclovir 400 mg once daily* - **Acyclovir 400 mg once daily** is generally considered insufficient for effective daily suppressive therapy for HSV infections. - This low frequency of dosing would likely not maintain adequate antiviral concentrations to consistently prevent outbreaks. *Valacyclovir 1 g twice daily* - **Valacyclovir 1 g twice daily** is often used for the treatment of acute HSV outbreaks (e.g., genital herpes episodes) or for severe cases of suppression, but it is not the standard daily suppressive dose. - For routine daily suppressive therapy, a 1g once-daily dose is usually sufficient and preferred for convenience and patient adherence.

Q: Which one of the following groups of drugs is ineffective against gram positive bacteria?

Monobactams. Monobactams - **Monobactams**, such as **aztreonam**, have a narrow spectrum of activity primarily targeting aerobic **Gram-negative bacteria** [1]. - They lack significant activity against **Gram-positive organisms** and **anaerobes** due to differences in cell wall structure and penicillin-binding proteins (PBPs) [1]. *Glycopeptides* - **Glycopeptides**, like **vancomycin**, are highly effective against a wide range of **Gram-positive bacteria**, including **MRSA** (methicillin-resistant *Staphylococcus aureus*) [3]. - They inhibit cell wall synthesis by binding to the D-Ala-D-Ala precursor, which is crucial for **Gram-positive cell wall integrity**. *Fluoroquinolones* - **Fluoroquinolones** are broad-spectrum antibiotics with activity against both **Gram-positive** and **Gram-negative bacteria** [4]. - While some newer agents (*e.g., levofloxacin, moxifloxacin*) have enhanced **Gram-positive coverage**, older agents (e.g., **ciprofloxacin**) are less potent against Gram-positives [4]. *First generation cephalosporins* - **First-generation cephalosporins** (e.g., **cefazolin**, **cephalexin**) exhibit good activity against many **Gram-positive bacteria**, including **staphylococci** and **streptococci** [2]. - They are commonly used for infections caused by **Gram-positive organisms** and as surgical prophylaxis [2].

Q: For the treatment of kala-azar, the daily dose of miltefosine in a 3-year-old child who weighs 15 kg is

40 mg. ***40 mg*** - Miltefosine dosage for children weighing 12 to 29 kg (including a 15 kg child) is typically **2.5 mg/kg body weight per day orally**. - For a 15 kg child, this translates to 2.5 mg/kg * 15 kg = **37.5 mg**, which is rounded to **40 mg** for practical dosing since miltefosine capsules come in 10 mg or 50 mg sizes. *20 mg* - This dose is lower than the recommended **2.5 mg/kg/day** for a 15 kg child, which would be 37.5 mg. - An underdose of miltefosine could lead to **treatment failure** and the development of drug resistance. *10 mg* - This dose is significantly lower than the recommended therapeutic dose for a 15 kg child, which requires approximately **37.5 mg daily**. - Such a low dose would be **ineffective** in treating kala-azar, risking worsening disease. *30 mg* - While closer than 10 mg or 20 mg, 30 mg is still below the calculated **37.5 mg/day** for a 15 kg child. - An insufficient dose may compromise the efficacy of treatment and lead to **suboptimal parasitic clearance**.

Q: Which of the following statements is true about antibiotic therapy?

It has its greatest effect on multiplying organisms. ***It has its greatest effect on multiplying organisms*** - Most **antibiotics** target processes essential for bacterial growth and replication, such as cell wall synthesis, protein synthesis, or DNA replication. - Therefore, their efficacy is highest against **actively multiplying bacteria**, as these processes are most vulnerable during periods of rapid growth. *It enhances the intracellular killing of organisms by phagocytes* - Antibiotics primarily act directly on bacteria, either **killing them (bactericidal)** or inhibiting their growth (bacteriostatic), rather than directly augmenting host immune cell functions like intracellular killing by phagocytes. - While antibiotics reduce the bacterial load, which aids phagocytosis, they do not directly enhance the phagocyte's intrinsic killing mechanisms. *It facilitates killing of organisms by activation of complements* - The **complement system** is part of the innate immune response and is activated by antibodies or microbial surface components; antibiotics do not directly activate this system. - Antibiotic action is independent of complement activation, although a reduced bacterial load can indirectly influence the overall immune response. *It enhances the uptake of organisms by phagocytes* - Enhancing the uptake of organisms by phagocytes (opsonization) is primarily mediated by host immune components such as **antibodies** and **complement proteins**, which coat bacteria to facilitate recognition. - Antibiotics do not directly opsonize bacteria or enhance phagocytic uptake; their role is to inhibit or kill bacteria directly.

Q: Consider the following drugs : 1. Rifampicin 2. Dapsone 3. Clofazimine 4. Minocycline Which of the above drugs are used in the standard treatment of pauci-bacillary leprosy in adults?

1 and 2 only. ***1 and 2 only*** - The **WHO standard treatment regimen** for **pauci-bacillary leprosy** in adults consists of only two drugs: **Rifampicin** and **Dapsone** [1]. - **Rifampicin 600 mg** is administered once monthly under supervision for 6 months, while **Dapsone 100 mg** is given daily for 6 months [3]. - This regimen is sufficient for PB leprosy, which has fewer bacilli and 1-5 skin lesions with no nerve involvement or only one nerve trunk involved [1], [2]. *1, 2 and 3* - This combination includes **Clofazimine**, which is part of the **multi-bacillary (MB) leprosy** regimen, not pauci-bacillary [2], [3]. - MB leprosy requires triple therapy (Rifampicin + Dapsone + Clofazimine) for 12 months due to higher bacterial load and more extensive disease. - Pauci-bacillary leprosy has a lower bacterial load and requires only a 6-month two-drug regimen [1]. *1 and 4* - **Minocycline** is used in **alternative regimens** for leprosy, particularly for patients with drug intolerance or in single-lesion PB leprosy (ROM regimen). - It is **not part of the standard first-line WHO treatment** for pauci-bacillary leprosy in adults. - The standard PB regimen requires **Rifampicin plus Dapsone**, not Rifampicin plus Minocycline. *2, 3 and 4* - This option misses **Rifampicin**, which is the **most crucial bactericidal drug** for all forms of leprosy (both PB and MB) [3]. - **Clofazimine** and **Minocycline** are not part of the standard PB leprosy regimen—Clofazimine is reserved for MB leprosy, and Minocycline is used only in alternative regimens. - Without Rifampicin, the treatment would be inadequate and risk development of drug resistance [3].

Q: In a case of paucibacillary leprosy, treatment is considered adequate if the patient has received the six monthly doses of combined therapy within:

9 months. ***9 months*** - For **paucibacillary (PB) leprosy**, the standard multi-drug therapy (MDT) regimen consists of six monthly doses of **rifampicin** and **dapsone**. - According to **WHO guidelines**, this six-dose regimen should be completed within a maximum period of **9 months** to ensure effective treatment and minimize drug resistance. - This timeframe allows for occasional missed doses while maintaining treatment efficacy. *12 months* - This duration is used for **multibacillary (MB) leprosy**, which requires 12 doses within 18 months. - For paucibacillary leprosy, 12 months is considered too long and may lead to suboptimal treatment outcomes. *6 months* - Completing all six doses within 6 months would mean no missed doses, which is theoretically possible. - However, this timeframe is too strict and does not account for real-world scenarios where patients might miss appointments or doses. - The WHO guideline of 9 months provides appropriate flexibility. *15 months* - Extending the treatment completion period to 15 months for PB leprosy is considered too long. - A prolonged treatment duration can increase the risk of **drug resistance** and may lead to poor compliance, as patients might discontinue treatment early. - This duration far exceeds WHO recommendations for paucibacillary leprosy.

Q: Which of the following drugs should be avoided in the first-line ART regimens because of its well recognized metabolic toxicities ?

Stavudine (d4T). ***Stavudine (d4T)*** - **Stavudine** is a **nucleoside reverse transcriptase inhibitor (NRTI)** that is well-known for its significant **metabolic toxicities**, including **lipoatrophy**, peripheral neuropathy, and lactic acidosis [1]. - Due to these severe side effects, it is no longer recommended for first-line ART regimens and its use is generally avoided. *Tenofovir (TDF)* - While Tenofovir (TDF) can cause **renal toxicity** and **bone mineral density loss** [2], it is generally considered a safer option than stavudine regarding severe metabolic toxicities like lipoatrophy. - TDF is commonly used in first-line ART regimens, often in combination with other drugs. *Zidovudine (AZT)* - **Zidovudine** is associated with side effects such as **bone marrow suppression** (leading to anemia and neutropenia), myopathy, and gastrointestinal upset, but not typically the severe metabolic toxicities seen with stavudine. - It is still used in some ART regimens, particularly for prevention of mother-to-child transmission. *Lamivudine (3TC)* - **Lamivudine** is generally well-tolerated with a favorable side effect profile, primarily mild gastrointestinal symptoms, and is rarely associated with significant metabolic toxicities. - It is a cornerstone drug in many first-line ART regimens due to its efficacy and safety.

Question 1

Based on the above diagnosed patient of Myasthenia Gravis, which of the following antibiotics is LEAST likely to exacerbate the condition?

Accepted Answer

Cephalosporins

Answer

Macrolides

Answer

Quinolones

Answer

Aminoglycosides

Question 2

Choice of drug for management of the parasitic infection shown below is:

Accepted Answer

Triclabendazole

Answer

Albendazole

Answer

Praziquantel

Answer

Niclosamide

Question 3

A 24-year-old patient presents with a 1-week history of vulvar itching and vaginal discharge. She says that she has had intercourse with two individuals in the past 6 months without the use of a condom. On physical examination, the vulva is edematous. Discharge is present on the vaginal walls and at the cervical os. Wet smear of vaginal secretions shows epithelial cells, white blood cells, and flagellate protozoa. You prescribe an antibiotic. What warning do you give about this particular treatment?

Accepted Answer

Avoid alcohol

Answer

Avoid sun overexposure

Answer

Avoid taking on an empty stomach

Answer

Avoid taking with grapefruit juice

Question 4

Daily suppressive therapy for HSV-1 and HSV-2 is :

Accepted Answer

Valacyclovir 1 g once daily

Answer

Acyclovir 400 mg thrice daily

Answer

Acyclovir 400 mg once daily

Answer

Valacyclovir 1 g twice daily

Question 5

Which one of the following groups of drugs is ineffective against gram positive bacteria?

Accepted Answer

Monobactams

Answer

Glycopeptides

Answer

Fluoroquinolones

Answer

First generation cephalosporins

Question 6

For the treatment of kala-azar, the daily dose of miltefosine in a 3-year-old child who weighs 15 kg is

Accepted Answer

40 mg

Answer

20 mg

Answer

10 mg

Answer

30 mg

Question 7

Which of the following statements is true about antibiotic therapy?

Accepted Answer

It has its greatest effect on multiplying organisms

Answer

It enhances the intracellular killing of organisms by phagocytes

Answer

It facilitates killing of organisms by activation of complements

Answer

It enhances the uptake of organisms by phagocytes

Question 8

Consider the following drugs :
1. Rifampicin
2. Dapsone
3. Clofazimine
4. Minocycline
Which of the above drugs are used in the standard treatment of pauci-bacillary leprosy in adults?

Accepted Answer

1 and 2 only

Answer

1, 2 and 3

Answer

1 and 4

Answer

2, 3 and 4

Question 9

In a case of paucibacillary leprosy, treatment is considered adequate if the patient has received the six monthly doses of combined therapy within:

Accepted Answer

9 months

Answer

12 months

Answer

6 months

Answer

15 months

Question 10

Which of the following drugs should be avoided in the first-line ART regimens because of its well recognized metabolic toxicities ?

Accepted Answer

Stavudine (d4T)

Answer

Tenofovir (TDF)

Answer

Zidovudine (AZT)

Answer

Lamivudine (3TC)

Antimicrobial Agents — MCQs

Antimicrobial Agents — MCQs

On this page

Practice by Chapter

Want unlimited practice?