Antimicrobial Agents — MCQs
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Daily suppressive therapy for HSV-1 and HSV-2 is :
Which one of the following groups of drugs is ineffective against gram positive bacteria?
Regarding active immunization against Typhoid fever, consider the following statements : 1. The typhoid polysaccharide vaccine is injectable and can be given subcutaneously or intramuscularly. 2. The typhoid polysaccharide vaccine is required to be given in two doses and administered on 0 and 7th day. 3. The typhoid oral Ty21a vaccine requires to be given in three doses on 0, 3rd and 7th days. 4. Protective immunity with typhoid vaccines is achieved immediately after the vaccine is received. Which of the statements given above is/are correct ?
A recently married woman presents with dysuria and increased urinary frequency of two-days duration. On physical examination, her body temperature is 38°C and her vital signs are normal. Her gynaecologic examination does not reveal any vaginal discharge, vaginitis or cervicitis. Her urine analysis reveals 14 WBC per high power field and many gram negative rods. Which of the following is the most appropriate pharmacotherapy ?
Which of the following statements is true about antibiotic therapy?
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?
In a case of paucibacillary leprosy, treatment is considered adequate if the patient has received the six monthly doses of combined therapy within:
A pregnant woman in 2nd trimester of pregnancy from North Eastern State has been diagnosed with uncomplicated P. falciparum. She should be treated with:
Covaxin is a/an
The recommended dose of cotrimoxazole for treatment of pneumonia in a child weighing 16 kg is
Antimicrobial Agents Indian Medical PG Practice Questions and MCQs
Question 1301: Daily suppressive therapy for HSV-1 and HSV-2 is :
- A. Acyclovir 400 mg thrice daily
- B. Valacyclovir 1 g once daily (Correct Answer)
- C. Acyclovir 400 mg once daily
- D. Valacyclovir 1 g twice daily
Explanation: ***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 1302: Which one of the following groups of drugs is ineffective against gram positive bacteria?
- A. Glycopeptides
- B. Fluoroquinolones
- C. First generation cephalosporins
- D. Monobactams (Correct Answer)
Explanation: 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].
Question 1303: Regarding active immunization against Typhoid fever, consider the following statements : 1. The typhoid polysaccharide vaccine is injectable and can be given subcutaneously or intramuscularly. 2. The typhoid polysaccharide vaccine is required to be given in two doses and administered on 0 and 7th day. 3. The typhoid oral Ty21a vaccine requires to be given in three doses on 0, 3rd and 7th days. 4. Protective immunity with typhoid vaccines is achieved immediately after the vaccine is received. Which of the statements given above is/are correct ?
- A. 2 and 3 only
- B. 1 and 2 only
- C. 1 only (Correct Answer)
- D. 1, 3 and 4
Explanation: ***1 only*** - The **typhoid polysaccharide vaccine** (ViCPS vaccine) is an **injectable vaccine**, typically administered **intramuscularly**. While subcutaneous administration might occur in specific situations, intramuscular is the standard route. - This statement accurately describes the general nature and administration route of the typhoid polysaccharide vaccine. *2 and 3 only* - The **typhoid polysaccharide vaccine (ViCPS) is usually given as a single dose** for primary immunization, not two doses on day 0 and 7. Boosters may be given every 2-3 years. - The **oral Ty21a vaccine requires three or four doses** (depending on the formulation and guidelines) taken on alternate days, typically on days 1, 3, and 5 (for a 3-dose regimen) or 1, 3, 5, and 7 (for a 4-dose regimen), not specifically on days 0, 3rd, and 7th. *1 and 2 only* - As explained, Statement 2 is incorrect because the **typhoid polysaccharide vaccine is generally a single-dose vaccine** for initial immunization. - Therefore, this option containing an incorrect statement cannot be the correct answer. *1, 3 and 4* - Statement 3 is incorrect as the **oral Ty21a vaccine dosing schedule is typically on alternate days** (e.g., 1, 3, 5 or 1, 3, 5, 7), not specifically 0, 3rd, and 7th. - Statement 4 is incorrect because **protective immunity from typhoid vaccines is not achieved immediately**; it takes about 1-2 weeks for the immune system to develop a sufficient response.
Question 1304: A recently married woman presents with dysuria and increased urinary frequency of two-days duration. On physical examination, her body temperature is 38°C and her vital signs are normal. Her gynaecologic examination does not reveal any vaginal discharge, vaginitis or cervicitis. Her urine analysis reveals 14 WBC per high power field and many gram negative rods. Which of the following is the most appropriate pharmacotherapy ?
- A. Trimethoprim-sulfamethoxazole
- B. Amoxicillin
- C. Ciprofloxacin
- D. Nitrofurantoin (Correct Answer)
Explanation: ***Nitrofurantoin*** - **Nitrofurantoin** is a first-line agent for **uncomplicated cystitis** due to its good efficacy, low resistance rates, and minimal systemic side effects. - Its concentration in the urine is high, making it effective against common urinary pathogens like **Gram-negative rods**. - **Note:** The patient has a temperature of 38°C, which is borderline. Current guidelines suggest that **fever may indicate upper tract involvement** (pyelonephritis), where nitrofurantoin would be less appropriate due to poor tissue penetration. However, with **normal vital signs** and localized symptoms, this may represent uncomplicated cystitis with mild pyrexia. *Ciprofloxacin* - **Fluoroquinolones** like ciprofloxacin are highly effective and achieve excellent tissue penetration, making them ideal for **complicated UTIs or pyelonephritis**. - The presence of **fever (38°C)** could justify fluoroquinolone use, as it may indicate upper tract involvement. - However, fluoroquinolones are increasingly reserved for complicated cases due to concerns about promoting **antibiotic resistance** and potential side effects (e.g., tendon rupture, C. difficile). - **Current IDSA guidelines** recommend fluoroquinolones when pyelonephritis is suspected. *Trimethoprim-sulfamethoxazole* - While effective for UTIs, **trimethoprim-sulfamethoxazole** resistance rates have increased significantly, particularly among *E. coli* strains. - It can be used for uncomplicated cystitis when local resistance rates are <20%, but is less preferred than nitrofurantoin in many settings. *Amoxicillin* - **Amoxicillin** is not recommended as first-line treatment for acute cystitis due to high rates of **bacterial resistance**, particularly from common uropathogens like *E. coli*. - Its efficacy against **Gram-negative rods** is limited, especially with prevalent beta-lactamase production.
Question 1305: Which of the following statements is true about antibiotic therapy?
- A. It enhances the intracellular killing of organisms by phagocytes
- B. It has its greatest effect on multiplying organisms (Correct Answer)
- C. It facilitates killing of organisms by activation of complements
- D. It enhances the uptake of organisms by phagocytes
Explanation: ***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.
Question 1306: 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?
- A. 1, 2 and 3
- B. 1 and 4
- C. 2, 3 and 4
- D. 1 and 2 only (Correct Answer)
Explanation: ***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].
Question 1307: In a case of paucibacillary leprosy, treatment is considered adequate if the patient has received the six monthly doses of combined therapy within:
- A. 9 months (Correct Answer)
- B. 12 months
- C. 6 months
- D. 15 months
Explanation: ***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.
Question 1308: A pregnant woman in 2nd trimester of pregnancy from North Eastern State has been diagnosed with uncomplicated P. falciparum. She should be treated with:
- A. Chloroquine and Primaquine
- B. Artesunate and Sulphadoxine
- C. Artemether and Lumefantrine (Correct Answer)
- D. Artesunate, Sulphadoxine and Pyrimethamine
Explanation: ***Artemether and Lumefantrine*** - This combination is a **fixed-dose artemisinin-based combination therapy (ACT)** specifically recommended by WHO for treating uncomplicated *P. falciparum* malaria in the **second and third trimesters of pregnancy**. - ACTs are highly effective against *P. falciparum* and have a favorable safety profile compared to other antimalarials during this period of pregnancy. *Chloroquine and Primaquine* - **Chloroquine** is primarily used for treatment of *P. vivax* and *P. ovale* malaria, as *P. falciparum* has widespread resistance. - **Primaquine** is contraindicated in pregnancy due to the risk of **hemolysis** in the fetus if there is G6PD deficiency and is used for radical cure of *P. vivax* and *P. ovale*. *Artesunate and Sulphadoxine* - While **artesunate** is an artemisinin derivative, **sulphadoxine** is often combined with pyrimethamine (as SP, sulphadoxine-pyrimethamine) for intermittent preventive treatment in pregnancy (IPTp) but is not the first-line for *uncomplicated P. falciparum* treatment in the second trimester, especially with increasing resistance. - This combination lacks the **lumefantrine** component, which provides a longer duration of action and higher efficacy when combined with artemether. *Artesunate, Sulphadoxine and Pyrimethamine* - The combination of **sulphadoxine-pyrimethamine (SP)** alone or with artesunate can be used for intermittent preventive treatment in pregnancy (IPTp), but it is generally *not* the first-line treatment for **uncomplicated P. falciparum malaria** in the 2nd trimester due to resistance concerns and the superior efficacy of Artemether-Lumefantrine. - **Pyrimethamine** is a folate antagonist and generally avoided in significant doses during pregnancy if alternatives are available, although it is part of SP for IPTp.
Question 1309: Covaxin is a/an
- A. Inactivated whole virus vaccine (Correct Answer)
- B. Live attenuated vaccine
- C. Nucleic acid vaccine
- D. Protein subunit vaccine
Explanation: ***Inactivated whole virus vaccine*** - Covaxin is an **inactivated** vaccine, meaning it uses a **killed version of the SARS-CoV-2 virus** that cannot cause disease but can still stimulate an immune response. - This type of vaccine presents the **entire viral structure** to the immune system, leading to a broad immune response against various viral proteins. *Live attenuated vaccine* - A live attenuated vaccine uses a **weakened form of the virus** that can still replicate but does not cause severe disease. - While effective, live attenuated vaccines often carry a small risk of reversion to virulence, which is not the case for Covaxin. *Nucleic acid vaccine* - Nucleic acid vaccines (like mRNA or DNA vaccines) deliver **genetic material** (e.g., mRNA for the spike protein) into host cells to produce viral proteins, triggering an immune response. - Covaxin does not use genetic material directly for antigen production. *Protein subunit vaccine* - Protein subunit vaccines contain only specific, purified viral proteins (e.g., the spike protein) that are highly immunogenic. - Unlike subunit vaccines, Covaxin presents the immune system with the **entire inactivated virus**, not just isolated proteins.
Question 1310: The recommended dose of cotrimoxazole for treatment of pneumonia in a child weighing 16 kg is
- A. Four paediatric tablets twice a day
- B. Two paediatric tablets twice a day
- C. One paediatric tablet twice a day
- D. Three paediatric tablets twice a day (Correct Answer)
Explanation: ***Three paediatric tablets twice a day*** - A paediatric cotrimoxazole tablet contains **20 mg trimethoprim + 100 mg sulfamethoxazole**. - The recommended dose for pneumonia is **4 mg/kg trimethoprim + 20 mg/kg sulfamethoxazole** twice daily. - For a 16 kg child: Required dose = **64 mg trimethoprim + 320 mg sulfamethoxazole** per dose. - Three tablets provide **60 mg trimethoprim + 300 mg sulfamethoxazole**, which is the closest appropriate dose to the calculated requirement. *One paediatric tablet twice a day* - This provides only **20 mg trimethoprim + 100 mg sulfamethoxazole** per dose. - This is **grossly inadequate** for a 16 kg child, providing less than one-third of the required dose. - Such underdosing risks treatment failure and antibiotic resistance. *Two paediatric tablets twice a day* - This provides **40 mg trimethoprim + 200 mg sulfamethoxazole** per dose. - While better than one tablet, this is still **subtherapeutic** for a 16 kg child with pneumonia. - This represents only about 60% of the recommended dose. *Four paediatric tablets twice a day* - This provides **80 mg trimethoprim + 400 mg sulfamethoxazole** per dose. - This is **slightly higher** than required but would risk unnecessary adverse effects. - Three tablets is the more appropriate choice for this weight range.
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