Antimicrobial Agents Practice Questions

Q: Inactivated SA 14-14-2 vaccine is an example of which type of vaccine?

Live attenuated vaccine. ***Live attenuated vaccine*** - The **SA 14-14-2 vaccine** is a **live attenuated Japanese Encephalitis (JE) vaccine** developed through serial passage and attenuation of the wild-type SA 14 strain. - The designation "14-14-2" refers to the specific **attenuated strain** after multiple passages, not to an inactivation process. - This vaccine uses **weakened (attenuated) virus** that can replicate minimally, providing robust and long-lasting immunity similar to natural infection. - It is widely used in **China, India, and other Asian countries** in national immunization programs. *Inactivated vaccine* - While there is also an **inactivated version** of the SA 14-14-2 strain (vero cell-derived inactivated JE vaccine), the term "SA 14-14-2 vaccine" by itself typically refers to the **live attenuated formulation**. - Inactivated vaccines contain killed viral particles that cannot replicate. *Toxoid vaccine* - **Toxoid vaccines** are based on inactivated bacterial toxins (toxoids), not viral antigens. - Examples include vaccines for **tetanus** and **diphtheria**, which target toxins produced by bacteria. - This type does not apply to viral vaccines like Japanese Encephalitis. *Subunit vaccine* - **Subunit vaccines** contain only specific purified antigenic components (proteins, polysaccharides) rather than whole organisms. - Examples include **Hepatitis B vaccine** (HBsAg) and **HPV vaccine**. - The SA 14-14-2 vaccine uses the whole attenuated virus, not subunits.

Q: Which of the following antifungal agents is primarily used topically?

Nystatin. ***Nystatin*** - **Nystatin** is commonly used as a **topical** or **oral swish-and-swallow** antifungal agent for candidal infections of the skin, mucous membranes, and gastrointestinal tract. - It works by binding to **ergosterol** in fungal cell membranes, leading to pore formation and cell death. *Itraconazole* - **Itraconazole** is an **oral** or **intravenous** antifungal agent primarily used for systemic fungal infections or onychomycosis, not typically for topical application. - It works by inhibiting **cytochrome P450-dependent enzymes**, which are essential for ergosterol synthesis. *Griseofulvin* - **Griseofulvin** is an **oral** antifungal used to treat dermatophyte infections of the skin, hair, and nails, especially when topical treatments are ineffective. - It binds to **keratin** in newly formed tissue, making it resistant to fungal invasion. *Voriconazole* - **Voriconazole** is a broad-spectrum **systemic (oral or IV)** antifungal agent, particularly useful for invasive aspergillosis and other serious fungal infections. - It is a **triazole antifungal** that inhibits fungal cytochrome P450 enzymes involved in ergosterol synthesis.

Q: Which of the following is effective against Pseudomonas and is used in burns patients?

Silver sulfadiazine. ***Silver sulfadiazine*** - This antimicrobial agent is widely recognized for its effectiveness against a broad spectrum of bacteria, including **Pseudomonas aeruginosa**, a common pathogen in **burn wounds**. - Its mechanism involves the gradual release of **silver ions** and **sulfadiazine**, which together inhibit bacterial growth and prevent infection in burn patients. *Sulphadoxine* - Sulphadoxine is a **long-acting sulfonamide antibiotic** primarily used in combination with pyrimethamine for the treatment of **malaria**. - It does not have a primary role in the topical management of **burn wounds** or specific efficacy against **Pseudomonas**. *Sulphamethoxazole* - Sulphamethoxazole is a **medium-acting sulfonamide** commonly combined with trimethoprim (**co-trimoxazole**) to treat various bacterial infections, including **urinary tract infections** and respiratory infections. - While it has antibacterial properties, it is not typically used topically for **burns** and is not specifically favored for **Pseudomonas** coverage in this context. *Silver sulphazine* - This is a **non-existent medication** - a deliberate distractor with incorrect spelling. - The correct medication is **silver sulfadiazine** (not "sulphazine"), making this a common exam trap to test precise knowledge of antimicrobial nomenclature.

Q: What is the recommended drug for treatment of mild leptospirosis?

Tetracycline. ***Tetracycline (Doxycycline)*** - **Doxycycline** (a tetracycline antibiotic) is the **first-line treatment for mild leptospirosis** - It has excellent activity against **spirochetes** including *Leptospira* species - Typically given as **doxycycline 100 mg twice daily for 7 days** - Also effective as **prophylaxis** in high-risk exposures - Alternative oral agents include **amoxicillin** or **ampicillin** for mild cases *Penicillin* - While **penicillin** is highly effective against *Leptospira*, this specifically refers to **IV Penicillin G for severe leptospirosis** - For **severe disease with organ involvement**, IV Penicillin G (1.5 million units every 6 hours) is the drug of choice - Oral penicillins (amoxicillin/ampicillin) can be used for mild cases but doxycycline is generally preferred - The question asks about general treatment, where **doxycycline is the standard first-line choice for mild cases** *Erythromycin* - Erythromycin is **not recommended** as primary treatment for leptospirosis - It has **poor activity** against *Leptospira* compared to tetracyclines and beta-lactams - Not included in standard treatment guidelines for this infection *Azithromycin* - Azithromycin has **limited documented efficacy** in leptospirosis - It is **not a first-line agent** and is not routinely recommended in treatment guidelines - May be considered as an alternative in specific situations with allergies, but tetracyclines or penicillins are strongly preferred

Q: A diabetic patient developed cellulitis due to S. aureus, which was found to be methicillin resistant on the antibiotic sensitivity testing. All of the following antibiotics will be appropriate except ?

Imipenem. ***Imipenem*** - **Imipenem** is a carbapenem antibiotic that is effective against many Gram-positive and Gram-negative bacteria, but it is **not active against MRSA (methicillin-resistant *Staphylococcus aureus*)**. - MRSA strains are resistant to all beta-lactam antibiotics, including penicillins, cephalosporins, and carbapenems like imipenem, due to the presence of the **mecA gene** which encodes for an altered penicillin-binding protein (PBP2a). *Vancomycin* - **Vancomycin** is a glycopeptide antibiotic that is a primary choice for treating **MRSA infections**, including cellulitis. - It inhibits cell wall synthesis by binding to the D-Ala-D-Ala precursor, preventing cross-linking, and is specifically active against **Gram-positive bacteria**. *Teicoplanin* - **Teicoplanin** is another glycopeptide antibiotic, similar to vancomycin, and is also considered a suitable agent for treating **MRSA infections**. - It works by inhibiting bacterial cell wall synthesis and has a **longer half-life** than vancomycin, allowing for less frequent dosing. *Linezolid* - **Linezolid** is an oxazolidinone antibiotic known for its activity against **Gram-positive bacteria**, including **MRSA** and vancomycin-resistant enterococci (VRE). - It inhibits protein synthesis by binding to the 50S ribosomal subunit, preventing the formation of the initiation complex.

Q: Ivermectin is indicated in the treatment of:

Scabies. ***Scabies*** - **Ivermectin** is an effective oral antiparasitic agent used to treat **scabies**, particularly in cases of widespread infestation, crusted scabies, or when topical treatments fail. - It acts by paralyzing and killing the **Sarcoptes scabiei mites** responsible for the infestation. *Dermatophytosis* - **Dermatophytosis** (ringworm) is a **fungal infection** of the skin, hair, or nails. - It is typically treated with **antifungal medications** (e.g., azoles, terbinafine), not ivermectin. *Tuberculosis* - **Tuberculosis** is a bacterial infection caused by **Mycobacterium tuberculosis**, primarily affecting the lungs. - Treatment involves a multi-drug regimen of **antibiotics** (e.g., rifampin, isoniazid), for several months. *Syphilis* - **Syphilis** is a sexually transmitted bacterial infection caused by **Treponema pallidum**. - The primary treatment for syphilis is **penicillin**, usually administered via injection.

Q: A 25-year-old female has been diagnosed to be suffering from tuberculosis categorized as category II (sputum +ve) case of relapse. According to the previous RNTCP (Revised National Tuberculosis Control Programme) guidelines, the treatment regimen recommended under DOTS was:

2(HRSZE)3 + 1(HRZE)3 + 5(HRE)3. ***2(HRSZE)3 + 1(HRZE)3 + 5(HRE)3*** - This regimen reflects the standard **Category II DOTS regimen** under the **previous RNTCP guidelines** for **sputum-positive relapse cases**, which was an 8-month treatment protocol. - The intensive phase consisted of **2 months of daily Streptomycin, Isoniazid, Rifampicin, Pyrazinamide, and Ethambutol (HRSZE)**, followed by **1 month of daily Isoniazid, Rifampicin, Pyrazinamide, and Ethambutol (HRZE)**, and a continuation phase of **5 months of Isoniazid, Rifampicin, and Ethambutol (HRE)** given three times weekly. - **Note:** Under current NTEP (National TB Elimination Programme) guidelines, previously treated cases undergo drug susceptibility testing, and fixed Category II regimens are no longer the standard approach. *3(HRZE)3 + 2(HRE)3 + 4(HR)3* - This is an incorrect combination of drugs and durations that does not match any standard DOTS category under previous RNTCP guidelines. - Category II relapse cases required a five-drug intensive phase including Streptomycin, not a four-drug regimen. *3(HRSZE)3 + 1(HRZE)3 + 6(HRE)3* - While this option includes the correct five-drug intensive phase, the duration is incorrect—the intensive phase with Streptomycin should be **2 months, not 3 months**. - The continuation phase of 6 months (instead of 5 months) also makes the total treatment duration longer than the standard 8-month Category II protocol. *2(HRZE)3 + 5(HR)3* - This regimen represents the **Category I (new cases) regimen** under previous RNTCP guidelines, which used only four drugs in the intensive phase. - It **lacks Streptomycin**, which was essential for Category II (relapse/failure/treatment after default) cases, and the continuation phase lacks Ethambutol, which was included in Category II continuation.

Q: Contact lens staining occurs in which ATT drug?

Rifampicin. ***Rifampicin*** - **Rifampicin** causes **red-orange discoloration** of bodily fluids, including tears. - This discoloration can **permanently stain soft contact lenses**, making this an important patient counseling point. *INH (Isoniazid)* - **INH** is primarily associated with **hepatotoxicity** and **peripheral neuropathy** due to pyridoxine deficiency. - It does not cause significant discoloration of bodily fluids or contact lens staining. *Pyrazinamide* - **Pyrazinamide** is known for causing **hyperuricemia** and **hepatotoxicity**. - It does not lead to discoloration of bodily fluids or contact lenses. *Thioacetazone* - **Thioacetazone** (not a first-line ATT drug) is associated with severe **cutaneous hypersensitivity reactions**, including Stevens-Johnson syndrome. - It does not cause the characteristic discoloration or contact lens staining seen with rifampicin.

Q: Minimum TB resistance is seen with which drug?

Ethambutol. ***Ethambutol*** - Among the first-line anti-TB drugs, **Ethambutol** has the **lowest rates of resistance development** - Resistance to Ethambutol is **less common** than to other first-line drugs like Isoniazid or Rifampicin - This makes it a valuable component of TB treatment regimens, particularly in maintaining effectiveness of combination therapy - Ethambutol resistance does occur but is relatively uncommon compared to other first-line agents *Isoniazid* - **Isoniazid resistance** is very common, occurring in approximately 10-15% of TB cases globally - Resistance arises from mutations in genes like *katG* and *inhA*, affecting drug activation and target binding - Despite resistance concerns, it remains a cornerstone drug due to its high efficacy when susceptibility is present *Rifampicin* - **Rifampicin resistance** is less common than Isoniazid but still significant - **Rifampicin-resistant TB (RR-TB)** is a marker for multidrug-resistant TB (MDR-TB) and indicates more severe disease - Development of Rifampicin resistance necessitates longer treatment regimens with second-line drugs *Streptomycin* - Historically one of the first antibiotics used for TB, but **resistance developed relatively quickly and is now widespread** - Due to the **high prevalence of resistance**, Streptomycin is no longer considered a first-line drug in most treatment programs - Has the highest resistance rates among the options listed

Q: Not True about Bedaquiline

Contraindicated in pregnancy. ***Contraindicated in pregnancy*** - While bedaquiline's safety in pregnancy is not fully established, it is generally **not absolutely contraindicated** if the potential benefits outweigh the risks, especially in cases of MDR-TB. - Current guidelines suggest that it can be used with caution, and a woman taking bedaquiline should use **effective contraception** throughout treatment. *Inhibits mycobacterial ATP synthase* - This statement is **true**. Bedaquiline specifically targets the **F0F1-ATP synthase enzyme** in *Mycobacterium tuberculosis*. - By inhibiting this enzyme, bedaquiline disrupts the **energy production** pathway of the bacteria, leading to bacterial death. *Given in > 10 years aged patients* - This statement is **true**. Bedaquiline is approved for use in patients with **multidrug-resistant tuberculosis (MDR-TB)** who are **12 years of age and older**. - Its use in younger children is still under investigation, though some compassionate use cases exist. *Given for MDR-TB patients* - This statement is **true**. Bedaquiline is a key drug in the treatment of **multidrug-resistant tuberculosis (MDR-TB)** and **extensively drug-resistant tuberculosis (XDR-TB)**. - It is often used as part of a **combination regimen** to overcome drug resistance to first-line agents.

Question 1

Inactivated SA 14-14-2 vaccine is an example of which type of vaccine?

Accepted Answer

Live attenuated vaccine

Answer

Toxoid vaccine

Answer

Inactivated vaccine

Answer

Subunit vaccine

Question 2

Which of the following antifungal agents is primarily used topically?

Accepted Answer

Nystatin

Answer

Itraconazole

Answer

Griseofulvin

Answer

Voriconazole

Question 3

Which of the following is effective against Pseudomonas and is used in burns patients?

Accepted Answer

Silver sulfadiazine

Answer

Sulphadoxine

Answer

Sulphamethoxazole

Answer

Silver sulphazine

Question 4

What is the recommended drug for treatment of mild leptospirosis?

Accepted Answer

Tetracycline

Answer

Erythromycin

Answer

Penicillin

Answer

Azithromycin

Question 5

A diabetic patient developed cellulitis due to S. aureus, which was found to be methicillin resistant on the antibiotic sensitivity testing. All of the following antibiotics will be appropriate except ?

Accepted Answer

Imipenem

Answer

Vancomycin

Answer

Teicoplanin

Answer

Linezolid

Question 6

Ivermectin is indicated in the treatment of:

Accepted Answer

Scabies

Answer

Dermatophytosis

Answer

Tuberculosis

Answer

Syphilis

Question 7

A 25-year-old female has been diagnosed to be suffering from tuberculosis categorized as category II (sputum +ve) case of relapse. According to the previous RNTCP (Revised National Tuberculosis Control Programme) guidelines, the treatment regimen recommended under DOTS was:

Accepted Answer

2(HRSZE)3 + 1(HRZE)3 + 5(HRE)3

Answer

3(HRZE)3 + 2(HRE)3 + 4(HR)3

Answer

3(HRSZE)3 + 1(HRZE)3 + 6(HRE)3

Answer

2(HRZE)3 + 5(HR)3

Question 8

Contact lens staining occurs in which ATT drug?

Accepted Answer

Rifampicin

Answer

INH

Answer

Thioacetazone

Answer

Pyrazinamide

Question 9

Minimum TB resistance is seen with which drug?

Accepted Answer

Ethambutol

Answer

Rifampicin

Answer

Streptomycin

Answer

Isoniazid

Question 10

Not True about Bedaquiline

Accepted Answer

Contraindicated in pregnancy

Answer

Inhibits mycobacterial ATP synthase

Answer

Given in > 10 years aged patients

Answer

Given for MDR-TB patients

Antimicrobial Agents — MCQs

Antimicrobial Agents — MCQs

On this page

Practice by Chapter

Want unlimited practice?