Antimicrobial Agents Practice Questions

Q: A 17 year old girl had been taking a drug for the treatment of acne for the last 2 years, which has led to pigmentation. Which drug could it be?

Minocycline. ***Minocycline*** - **Minocycline** is a **tetracycline** antibiotic commonly used for acne and is notorious for causing various forms of **pigmentation**, including blue-gray discoloration of the skin, scars, and teeth, especially with long-term use. - This pigmentation is due to the formation of **insoluble chelates** of minocycline with iron and melanin within tissues. *Doxycycline* - While also a **tetracycline**, **doxycycline** is less commonly associated with significant **skin pigmentation** compared to minocycline at standard acne treatment doses. - Its side effect profile for pigmentation usually involves **photosensitivity** or **tooth discoloration** in children, not generally diffuse skin discoloration in adolescents. *Clindamycin* - **Clindamycin** is a **lincosamide antibiotic** primarily used topically or orally for acne, but it does not cause **pigmentation** as a known side effect. - Its main systemic side effect concern is **Clostridioides difficile-associated diarrhea (CDAD)**. *Azithromycin* - **Azithromycin** is a **macrolide antibiotic** and is not typically associated with **skin pigmentation** as a side effect. - It is sometimes used for acne, but its side effects are primarily **gastrointestinal** (nausea, vomiting, diarrhea).

Q: Treatment for filariasis is

Diethyl Carbamazine. ***Diethyl Carbamazine*** - **Diethyl Carbamazine (DEC)** is the drug of choice for treating lymphatic filariasis, acting against both microfilariae and adult worms. - It works by paralyzing the microfilariae and making them more susceptible to destruction by the host's immune system. *Chloroquin* - **Chloroquine** is an antimalarial drug used to treat malaria, a protozoal infection transmitted by mosquitoes, not filariasis. - Its primary mechanism involves interfering with the parasite's ability to detoxify heme. *Praziquantel* - **Praziquantel** is an anthelmintic agent primarily used to treat infections caused by **schistosomes** and **other flukes** and **tapeworms**. - It works by increasing the permeability of the worm's cell membranes to calcium, leading to paralysis and expulsion. *Tetracycline* - **Tetracycline** is a broad-spectrum antibiotic used to treat bacterial infections; it is not effective against **parasitic worms** like filaria. - It inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit.

Q: Which of the following is the preferred drug for prophylactic treatment of rheumatic heart disease?

Benzathine penicillin. ***Benzathine penicillin*** - **Benzathine penicillin** is the **drug of choice** for the **prophylactic treatment of rheumatic heart disease** due to its prolonged action and superior compliance. - A single intramuscular injection provides therapeutic drug levels for **3-4 weeks**, making it ideal for **secondary prophylaxis** against recurrent Group A streptococcal infections. - **Superior adherence** compared to daily oral regimens, which is crucial for preventing rheumatic fever recurrence. *Phenoxymethylpenicillin* - **Phenoxymethylpenicillin** (Penicillin V) can be used as an **alternative** for RHD prophylaxis when IM injections are refused or impractical, requiring **daily oral dosing** (250 mg twice daily). - However, it is **less preferred** than benzathine penicillin due to **compliance issues** with daily dosing and the risk of missed doses compromising prophylaxis effectiveness. - The need for sustained, consistent blood levels makes the long-acting IM formulation significantly more reliable. *Ampicillin* - **Ampicillin** is a broader-spectrum penicillin used for treating various bacterial infections, but it is **not routinely used** for the prophylaxis of rheumatic heart disease. - Its shorter half-life and lack of long-acting formulations make it unsuitable for the sustained blood levels required for effective secondary prophylaxis against Group A Streptococcus. *Penicillin G* - **Penicillin G** (benzylpenicillin) is an injectable penicillin, but its half-life is **much shorter** than benzathine penicillin, requiring **frequent** intravenous or intramuscular administration (every 6-12 hours). - While effective for treating acute streptococcal infections, its short duration of action makes it **impractical** for the long-term, sustained prophylactic regimen needed to prevent recurrent rheumatic fever.

Q: Drug of choice for chemoprophylaxis in meningococcal meningitis is -

Rifampicin. ***Rifampicin*** - **Rifampicin** is a primary agent for **chemoprophylaxis** against **meningococcal meningitis** due to its effective penetration into the cerebrospinal fluid and elimination of nasopharyngeal carriage of *Neisseria meningitidis*. - It is often favored for its **convenient oral administration** and short treatment course, making it suitable for close contacts of patients. *Tetracycline* - **Tetracycline** is not the **drug of choice** for **meningococcal prophylaxis** because of potential resistance patterns and side effects, especially in children and pregnant women. - While broad-spectrum, its efficacy against *Neisseria meningitidis* carriage is generally less reliable than recommended agents. *Erythromycin* - **Erythromycin** is not the preferred antibiotic for **meningococcal chemoprophylaxis** due to its variable efficacy in eradicating the nasopharyngeal carriage of *Neisseria meningitidis*. - Other agents like rifampicin or ceftriaxone are more consistently effective. *Streptomycin* - **Streptomycin** is an **aminoglycoside antibiotic** primarily used for **tuberculosis** and severe bacterial infections, but it is not effective for **meningococcal prophylaxis**. - It has a narrow spectrum against *Neisseria meningitidis* and does not achieve adequate concentrations in the nasopharynx to prevent carriage.

Q: Most common drug used in Leprosy is :

Dapsone. ***Correct Answer: Dapsone*** - **Dapsone** is the most commonly used and foundational drug in **multidrug therapy (MDT)** for leprosy [1] - It is included in **all WHO-recommended MDT regimens** for both paucibacillary and multibacillary leprosy [1] - Acts as a **bacteriostatic agent** against **Mycobacterium leprae** by interfering with **folate synthesis** [3] - Well-tolerated with a favorable safety profile for long-term use [2] - Has been the backbone of leprosy treatment for decades [1] *Incorrect: Ethionamide* - **Ethionamide** is primarily a **second-line agent for tuberculosis**, especially in multidrug-resistant TB (MDR-TB) - Not a standard drug for leprosy due to higher toxicity and availability of more effective options - Has no role in routine leprosy treatment regimens *Incorrect: Ofloxacin* - **Ofloxacin** is a **fluoroquinolone antibiotic** with some activity against **Mycobacterium leprae** - Used only as an **alternative agent** in special circumstances (e.g., drug resistance or intolerance) - Not part of standard first-line MDT regimens for leprosy *Incorrect: Clofazimine* - **Clofazimine** is an important component of **multibacillary (MB) leprosy treatment** in WHO MDT regimens [2] - While essential for MB leprosy, it is **not used in paucibacillary (PB) leprosy** regimens [1] - **Dapsone** is more commonly used overall as it appears in **all MDT regimens** (both PB and MB), making it the most common drug in leprosy treatment [1]

Q: Anti-leprosy drug causing ichthyosis is?

Clofazimine. ***Clofazimine*** - **Clofazimine** is a common anti-leprosy drug known to cause side effects such as skin discoloration (reddish-brown), **ichthyosis** (dry, scaly skin), and gastrointestinal symptoms. - Its mechanism of action involves DNA binding and generation of reactive oxygen species, but the exact cause of ichthyosis is thought to be related to its accumulation in the skin. *Dapsone* - **Dapsone** is a primary drug for leprosy treatment but is more commonly associated with side effects like methemoglobinemia, hemolysis (especially in G6PD deficiency), and peripheral neuropathy. - It does not typically cause **ichthyosis**; its dermatological side effects often include hypersensitivity reactions. *Clarithromycin* - **Clarithromycin** is an antibiotic from the macrolide class, primarily used for bacterial infections, and is not a first-line drug for leprosy. - While it can cause gastrointestinal upset and QT prolongation, **ichthyosis** is not a recognized side effect of clarithromycin. *Rifampicin* - **Rifampicin** is a crucial drug in multi-drug therapy for leprosy and is known for its ability to cause orange-red discoloration of body fluids, hepatotoxicity, and flu-like symptoms. - **Ichthyosis** is not a known side effect of rifampicin.

Q: A person wants to visit a malaria endemic area of low level chloroquine resistant falciparum malaria. The best chemoprophylaxis is -

Atovaquone + Proguanil. ***Atovaquone + Proguanil*** - **Atovaquone + Proguanil (Malarone)** is the **preferred first-line chemoprophylaxis** for areas with **chloroquine-resistant *P. falciparum***, including low-level resistance. - It has **excellent efficacy** against resistant strains with minimal documented resistance, and is **well-tolerated** with fewer side effects compared to mefloquine. - Approved by WHO and CDC as a **primary option** for travelers to chloroquine-resistant malaria areas. - The daily dosing regimen, while requiring more frequent administration, actually allows for a **shorter pre-travel start time** (1-2 days before vs. 1-2 weeks for mefloquine) and **shorter post-travel duration** (7 days vs. 4 weeks). *Mefloquine* - While **effective against chloroquine-resistant *P. falciparum***, mefloquine is increasingly used as a **second-line option** due to significant **neuropsychiatric side effects** (anxiety, depression, vivid dreams, rarely psychosis). - It requires weekly dosing starting 2 weeks before travel and continuing 4 weeks after, making the total prophylaxis period longer. - **Contraindicated** in individuals with psychiatric disorders, seizure disorders, or cardiac conduction abnormalities. *Sulfadoxine + Pyrimethamine* - This combination is primarily used for **intermittent preventive treatment (IPT)** in pregnant women and infants in endemic areas, **not for travel prophylaxis**. - Widespread **parasitic resistance** to both components has made it unreliable for chemoprophylaxis in most regions. - Not recommended by international guidelines for routine traveler prophylaxis. *Chloroquine* - **Completely ineffective** in areas with **chloroquine-resistant *P. falciparum*** as stated in the question. - Would provide **no protection** and lead to treatment failure if infection occurs.

Q: Antibiotic treatment of choice for treating cholera in an adult is a single dose of:

Doxycycline. ***Doxycycline***- **Doxycycline** is the recommended first-line antibiotic for cholera in adults due to its effectiveness in reducing stool volume and duration of diarrhea, and it is often given as a **single oral dose**.- Its broad-spectrum activity and good oral bioavailability make it a practical choice for treating **Vibrio cholerae** infections, especially in outbreak settings.*Co-trimoxazole*- While **co-trimoxazole (trimethoprim-sulfamethoxazole)** can be effective against some strains of Vibrio cholerae, resistance has become more common, limiting its use as a first-line agent.- Its efficacy as a single-dose treatment for cholera is generally less established compared to doxycycline.*Furazolidone*- **Furazolidone** has been used in the past for cholera treatment, but its use has declined due to concerns about side effects and the development of resistance.- It is not typically recommended as the first-line treatment for cholera in adults, particularly as a single dose.*Tetracycline*- **Tetracycline** is historically effective against cholera, but modern guidelines often prefer doxycycline due to its improved tolerability, once-daily dosing, and similar efficacy profile.- The older tetracyclines often require multiple doses per day, which can impact patient compliance compared to a single-dose regimen of doxycycline.

Q: A fungicidal drug that can be used orally for the treatment of onychomycosis is :

Terbinafine. ***Terbinafine*** - **Terbinafine** is a highly effective **fungicidal** agent prescribed orally for **onychomycosis** due to its ability to concentrate in the nail bed. - It works by inhibiting **squalene epoxidase**, an enzyme essential for fungal ergosterol synthesis, leading to fungal cell death. *Griseofulvin* - **Griseofulvin** is a **fungistatic** drug that inhibits fungal cell division rather than directly killing the fungi. - While it can treat onychomycosis, its effectiveness is generally lower, and treatment courses are longer compared to terbinafine. *Amphotericin B* - **Amphotericin B** is an intravenous **antifungal** primarily used for severe systemic fungal infections, not typically for **onychomycosis**. - Its mechanism involves binding to ergosterol in the fungal cell membrane, creating pores and leading to cell lysis. *Clotrimazole* - **Clotrimazole** is an **azole** antifungal primarily used topically for superficial fungal infections like **tinea corporis** or **vaginal candidiasis**. - It is not effective as an oral treatment for onychomycosis due to poor systemic absorption and extensive first-pass metabolism.

Q: What is the treatment of choice for penicillin-resistant gonorrhea?

Ceftriaxone (a third-generation cephalosporin). ***Ceftriaxone (a third-generation cephalosporin)*** - **Ceftriaxone** is the recommended treatment for uncomplicated gonorrhea, including penicillin-resistant strains, given as a single intramuscular dose (500 mg IM). - It works by inhibiting bacterial cell wall synthesis and has excellent activity against *Neisseria gonorrhoeae*. - **Current guidelines recommend dual therapy:** Ceftriaxone plus azithromycin (or doxycycline) to prevent resistance development and cover potential co-infection with *Chlamydia trachomatis*. *Erythromycin (a macrolide antibiotic)* - While macrolides like azithromycin are used in combination with ceftriaxone, **erythromycin alone** is not effective first-line therapy for gonorrhea. - Its primary use in STIs is for chlamydia in specific situations, but not as monotherapy for gonorrhea. *Streptomycin (an aminoglycoside antibiotic)* - **Streptomycin** is an older antibiotic primarily used for tuberculosis and plague, but it is not effective against gonorrhea. - It works by inhibiting protein synthesis but lacks the necessary spectrum and tissue penetration for *Neisseria gonorrhoeae*. *Ciprofloxacin (a fluoroquinolone antibiotic)* - **Ciprofloxacin** was previously used for gonorrhea, but widespread resistance has developed globally, making it unreliable. - Due to high rates of fluoroquinolone resistance, it is **no longer recommended** for empiric treatment of gonorrhea by CDC/WHO guidelines.

Question 1

A 17 year old girl had been taking a drug for the treatment of acne for the last 2 years, which has led to pigmentation. Which drug could it be?

Accepted Answer

Minocycline

Answer

Doxycycline

Answer

Clindamycin

Answer

Azithromycin

Question 2

Treatment for filariasis is

Accepted Answer

Diethyl Carbamazine

Answer

Chloroquine

Answer

Praziquantel

Answer

Tetracycline

Question 3

Which of the following is the preferred drug for prophylactic treatment of rheumatic heart disease?

Accepted Answer

Benzathine penicillin

Answer

Phenoxymethylpenicillin

Answer

Ampicillin

Answer

Penicillin G

Question 4

Drug of choice for chemoprophylaxis in meningococcal meningitis is -

Accepted Answer

Rifampicin

Answer

Tetracycline

Answer

Erythromycin

Answer

Streptomycin

Question 5

Most common drug used in Leprosy is :

Accepted Answer

Dapsone

Answer

Ethionamide

Answer

Ofloxacin

Answer

Clofazimine

Question 6

Anti-leprosy drug causing ichthyosis is?

Accepted Answer

Clofazimine

Answer

Dapsone

Answer

Clarithromycin

Answer

Rifampicin

Question 7

A person wants to visit a malaria endemic area of low level chloroquine resistant falciparum malaria. The best chemoprophylaxis is -

Accepted Answer

Atovaquone + Proguanil

Answer

Sulfadoxine + Pyrimethamine

Answer

Mefloquine

Answer

Chloroquine

Question 8

Antibiotic treatment of choice for treating cholera in an adult is a single dose of:

Accepted Answer

Doxycycline

Answer

Co-trimoxazole

Answer

Furazolidone

Answer

Tetracycline

Question 9

A fungicidal drug that can be used orally for the treatment of onychomycosis is :

Accepted Answer

Terbinafine

Answer

Griseofulvin

Answer

Amphotericin B

Answer

Clotrimazole

Question 10

What is the treatment of choice for penicillin-resistant gonorrhea?

Accepted Answer

Ceftriaxone (a third-generation cephalosporin)

Answer

Erythromycin (a macrolide antibiotic)

Answer

Streptomycin (an aminoglycoside antibiotic)

Answer

Ciprofloxacin (a fluoroquinolone antibiotic)

Antimicrobial Agents — MCQs

Antimicrobial Agents — MCQs

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