Antimicrobial Agents Practice Questions

Q: Which of the following is the treatment for complicated gonorrhoea due to penicillin-resistant Neisseria gonorrhoeae?

Ceftriaxone. ***Correct: Ceftriaxone*** - **Ceftriaxone** (a third-generation cephalosporin) is the current cornerstone of treatment for both uncomplicated and complicated gonorrhoea, especially given the high prevalence of **penicillin resistance** in *N. gonorrhoeae*. - For complicated infections (e.g., disseminated gonococcal infection, epididymo-orchitis, pelvic inflammatory disease), it is often given as a higher dose (e.g., 1g IV daily) and sometimes combined with **azithromycin** where co-infection with *Chlamydia* is possible. *Incorrect: Amoxicillin* - **Amoxicillin** is a penicillin-class antibiotic and is ineffective due to widespread resistance mediated by **plasmid-encoded beta-lactamases** (e.g., *penicillinase-producing Neisseria gonorrhoeae* or PPNG). - Penicillins are no longer recommended for the treatment of gonorrhoea in any setting because of this high resistance. *Incorrect: Tetracycline* - **Tetracycline** (or doxycycline) was historically used for gonorrhoea treatment but resistance has become common, rendering it unreliable as a first-line therapy. - It is currently used primarily to treat concurrent **Chlamydia trachomatis** infection, rather than gonorrhoea itself. *Incorrect: Vancomycin* - **Vancomycin** is a glycopeptide antibiotic primarily effective against **Gram-positive bacteria** (like MRSA) by interfering with cell wall synthesis. - *Neisseria gonorrhoeae* is a **Gram-negative bacterium**, and vancomycin is not effective for its treatment.

Q: Which of the following is the classical drug for clinical cure in malaria?

Chloroquine. ***Chloroquine*** - **Clinical cure** in malaria refers to the eradication of the **asexual erythrocytic forms** of the parasite, which are responsible for the clinical symptoms. - **Chloroquine** is the classical 4-aminoquinoline drug historically used as the prototype for clinical cure, acting specifically against asexual blood stages in chloroquine-sensitive *Plasmodium* species. - It remains the drug of choice for *P. vivax*, *P. malariae*, and *P. ovale* in areas without resistance. *Primaquine* - Primarily used for **radical cure** (preventing relapse) by eliminating **hypnozoites** (dormant liver stages) in *P. vivax* and *P. ovale*. - Also kills **gametocytes** (sexual stages) to reduce transmission, but does NOT provide clinical cure as it has minimal activity against asexual blood stages. *Artesunate* - A fast-acting artemisinin derivative that rapidly clears **asexual blood stages** and is used in Artemisinin-based Combination Therapy (ACT) as first-line treatment for *P. falciparum*. - While artesunate does achieve clinical cure in modern practice, chloroquine is the **classical prototype drug** traditionally associated with this concept in pharmacology teaching. *Sulfadoxine-pyrimethamine* - A **folate antagonist** combination used as alternative treatment or for Intermittent Preventive Treatment in Pregnancy (IPTp). - Widespread resistance limits its use for clinical cure, and it's not the classical drug associated with this concept.

Q: A male patient with a history of MSM presents with urethral discharge. There is penicillin resistance on testing. Which drug should be given?

Ceftriaxone. ***Ceftriaxone*** - **Ceftriaxone** (a third-generation cephalosporin) is the current primary treatment for uncomplicated **gonorrhea**, especially due to rising penicillin and fluoroquinolone resistance globally. - Given the patient's presentation (urethral discharge in an **MSM** patient) strongly suggesting gonorrhea, and documented **penicillin resistance**, ceftriaxone remains the drug of choice. *Amoxiclav* - **Amoxicillin/clavulanic acid** (Amoxiclav) is ineffective for the treatment of *Neisseria gonorrhoeae* due to widespread $\beta$-lactamase production and insufficient coverage against resistant strains. - It is more commonly used for community-acquired respiratory tract infections or skin infections. *Tetracycline* - **Tetracyclines** (like doxycycline) are the preferred treatment for co-occurring **Chlamydia trachomatis** infection, but are not the primary single agent for resistant gonococcal infection. - Although historically used, tetracyclines have limited efficacy against many contemporary **gonococcal strains** and are not recommended as monotherapy for resistant gonorrhea. *Vancomycin* - **Vancomycin** is a glycopeptide antibiotic primarily used for serious infections caused by **Gram-positive** bacteria, particularly **MRSA** and *Clostridium difficile*. - It has no meaningful role or efficacy in treating **Gram-negative** infections like **gonorrhea**.

Q: Patient came with fever headache and nuchal rigidity. LP shows gram-negative diplococci in gram stain. Which of the following will be used for chemoprophylaxis in close contacts of a patient with meningococcal meningitis?

Rifampicin. ***Rifampicin*** - **Rifampicin** is one of the preferred agents for chemoprophylaxis against meningococcal meningitis in close contacts because it effectively eliminates **Neisseria meningitidis** colonization from the nasopharynx. - The other common options for prophylaxis include **Ceftriaxone** (single IM dose, safe in pregnancy) or **Ciprofloxacin** (single oral dose). *Amoxicillin* - Amoxicillin is commonly used for **otitis media** and **sinusitis** but is ineffective for reliable elimination of nasopharyngeal colonization by **Neisseria meningitidis**. - It is not a recommended prophylactic agent for **meningococcal disease** in close contacts. *Doxycycline* - While a broad-spectrum antibiotic, **Doxycycline** is not the standard or preferred drug for routine **meningococcal prophylaxis**. - It is often used for atypical pneumonias or tick-borne diseases like **Rocky Mountain spotted fever**. *Ethambutol* - **Ethambutol** is a primary anti-mycobacterial drug, used exclusively in the treatment regimen for **Tuberculosis (TB)**. - It has no role or efficacy in the prophylaxis or treatment of **bacterial meningitis** caused by **Neisseria meningitidis**.

Q: All are used in treatment for the GIT parasite shown below except:

Albendazole. ***Albendazole*** - **CORRECTION:** The image displays *Giardia lamblia*, a flagellate protozoan characterized by its **pear-like shape** and multiple flagella. - **Albendazole IS actually used for Giardiasis** as an alternative agent with 80-90% efficacy. - However, it is **NOT a first-line agent** for *Giardia lamblia*. While it has activity against this protozoan, it is primarily known as an **antihelminthic drug** used for **nematode infections**. - First-line agents (metronidazole, tinidazole) are preferred due to better-established efficacy and shorter treatment courses. *Metronidazole* - **Metronidazole** is a **first-line treatment** for **Giardia lamblia** infections due to its high efficacy against anaerobic protozoa. - It works by producing **cytotoxic compounds** that damage parasitic DNA. - Standard regimen: 250mg three times daily for 5-7 days. *Tinidazole* - **Tinidazole** is another **first-line treatment** for **Giardia lamblia**, often preferred for its shorter treatment course and good tolerability. - It belongs to the same class as metronidazole (nitroimidazoles) and acts similarly by disrupting parasitic nucleic acid synthesis. - Single-dose regimen available: 2g as a single dose. *Paromomycin* - **Paromomycin** is an **aminoglycoside antibiotic** that has activity against various intestinal protozoa, including *Giardia lamblia*. - It is particularly useful in **pregnant patients** due to poor systemic absorption (luminal agent). - Efficacy is somewhat lower than nitroimidazoles (55-90% cure rate).

Q: All of the following drugs will act on the following stage of malarial parasite except:

Chloroquine. ***Chloroquine*** - **Chloroquine** is a potent **blood schizonticide** that specifically targets the asexual erythrocytic stages of malaria parasites (trophozoites and schizonts) by inhibiting heme detoxification. - It has **no significant activity against gametocytes** of *P. falciparum*, the stage visible in the image. - This is why chloroquine does **not act on the stage shown** in the image, making it the correct answer to this EXCEPT question. *Primaquine* - **Primaquine** is highly effective against **gametocytes** of all malaria species, including *P. falciparum*. - While it primarily targets the **hepatic stages** (hypnozoites) of *P. vivax* and *P. ovale* to prevent relapse, it also effectively kills **gametocytes** in the blood. - It **does act on the gametocyte stage** shown in the image. *Artemisinin* - **Artemisinin** derivatives are highly effective **blood schizonticides**, rapidly clearing asexual parasitic stages from red blood cells. - They also have **significant activity against gametocytes**, including early and mature stages of *P. falciparum*. - Artemisinin compounds **do act on the gametocyte stage** depicted in the image. *Mefloquine* - **Mefloquine** is a **blood schizonticide** used for treating and preventing malaria by killing the asexual erythrocytic stages. - While its primary action is against asexual forms, it has **some activity against immature gametocytes**, though less effective against mature forms. - Still considered to have **some effect** on gametocytes, unlike chloroquine which has essentially none.

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: A 30-year-old patient from a rural area presents with right upper quadrant pain, fever, and marked eosinophilia. He reports a history of consuming raw watercress from a local stream. Stool examination reveals the organism shown in the image below. What is the drug of choice for this infection?

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.

Question 1

Which of the following is the treatment for complicated gonorrhoea due to penicillin-resistant Neisseria gonorrhoeae?

Accepted Answer

Ceftriaxone

Answer

Vancomycin

Answer

Tetracycline

Answer

Amoxicillin

Question 2

Which of the following is the classical drug for clinical cure in malaria?

Accepted Answer

Chloroquine

Answer

Sulfadoxine-pyrimethamine

Answer

Artesunate

Answer

Primaquine

Question 3

A male patient with a history of MSM presents with urethral discharge. There is penicillin resistance on testing. Which drug should be given?

Accepted Answer

Ceftriaxone

Answer

Amoxiclav

Answer

Tetracycline

Answer

Vancomycin

Question 4

Patient came with fever headache and nuchal rigidity. LP shows gram-negative diplococci in gram stain. Which of the following will be used for chemoprophylaxis in close contacts of a patient with meningococcal meningitis?

Accepted Answer

Rifampicin

Answer

Amoxicillin

Answer

Doxycycline

Answer

Ethambutol

Question 5

All are used in treatment for the GIT parasite shown below except:

Accepted Answer

Albendazole

Answer

Metronidazole

Answer

Tinidazole

Answer

Paromomycin

Question 6

All of the following drugs will act on the following stage of malarial parasite except:

Accepted Answer

Chloroquine

Answer

Primaquine

Answer

Artemisinin

Answer

Mefloquine

Question 7

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 8

A 30-year-old patient from a rural area presents with right upper quadrant pain, fever, and marked eosinophilia. He reports a history of consuming raw watercress from a local stream. Stool examination reveals the organism shown in the image below. What is the drug of choice for this infection?

Accepted Answer

Triclabendazole

Answer

Albendazole

Answer

Praziquantel

Answer

Niclosamide

Question 9

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 10

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

Antimicrobial Agents — MCQs

Antimicrobial Agents — MCQs

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