Antimicrobial Agents Practice Questions

Q: Which of the following is the chemoprophylaxis of choice in a person who is on a journey to endemic malarial region?

Atovaquone-proguanil. ***Atovaquone-proguanil*** - **First-line choice** for malaria chemoprophylaxis in travelers to endemic regions according to WHO and CDC guidelines - Highly effective against **drug-resistant *P. falciparum***, including chloroquine and mefloquine-resistant strains - **Excellent tolerability** with minimal side effects compared to other antimalarials - **Convenient dosing schedule**: started 1-2 days before travel and continued for only **7 days after** leaving the endemic area (shorter post-travel duration than alternatives) - Well-tolerated with few contraindications, making it suitable for most travelers *Doxycycline* - Effective alternative for malaria prophylaxis as a **tetracycline antibiotic** - Provides additional protection against **leptospirosis** and traveler's diarrhea - However, associated with **photosensitivity reactions** (sunburn risk), **GI upset**, and **esophageal irritation** - Contraindicated in **pregnancy** and **children <8 years** due to effects on teeth and bone - Requires daily dosing starting 1-2 days before until **4 weeks after travel** (longer duration) *Mefloquine* - Once-weekly dosing offers convenience for long-term travelers - Effective against most *P. falciparum* strains - Major limitation: significant **neuropsychiatric side effects** including anxiety, depression, dizziness, and rarely psychosis - Contraindicated in those with **psychiatric history**, seizure disorders, or cardiac conduction abnormalities - Must be started **2-3 weeks before travel** to assess tolerance *Chloroquine* - Historically the first-line agent but now limited by widespread **chloroquine resistance** - Only effective in few remaining areas with **chloroquine-sensitive *P. vivax*** or *P. falciparum* (parts of Central America, Middle East) - Well-tolerated with once-weekly dosing - Not appropriate for most endemic malarial regions in Africa, Southeast Asia, or South America

Q: Which of the following aminoglycosides is most cochleotoxic:-

Gentamycin. ***Gentamycin*** - **Gentamycin** is known to be the most **cochleotoxic** aminoglycoside, causing irreversible damage to the hair cells in the cochlea [1]. - This toxicity can lead to **permanent hearing loss** and **tinnitus** due to its selective accumulation in inner ear fluids [2]. *Streptomycin* - While streptomycin can cause ototoxicity, its primary adverse effect is vestibulo-toxicity, affecting **balance** more than hearing [2]. - It mainly targets the hair cells of the semicircular canals and otolithic organs, leading to **vertigo** and ataxia [3]. *Amikacin* - Amikacin is also an ototoxic aminoglycoside but is generally considered **less cochleotoxic** than gentamycin. - Its ototoxic effects are comparable to gentamicin, but it is often reserved for infections resistant to other aminoglycosides. *Minocycline* - Minocycline is a **tetracycline antibiotic**, not an aminoglycoside, and is not associated with significant ototoxicity. - Its side effects typically include photosensitivity, gastrointestinal upset, and **vestibular dysfunction** (dizziness, vertigo) in some patients, distinct from cochlear damage.

Q: Empirical drug of choice for treatment of meningococcal meningitis is:-

Ceftriaxone. ***Ceftriaxone*** - As a **third-generation cephalosporin**, **Ceftriaxone** provides excellent coverage against common bacterial causes of meningitis, including *Neisseria meningitidis*. - It achieves high concentrations in the **cerebrospinal fluid (CSF)**, making it highly effective for CNS infections. *Cefotetan* - **Cefotetan** is a **second-generation cephalosporin** that has limited CSF penetration and less reliable coverage against common meningitis pathogens. - While it has activity against some gram-negative bacteria, it is not considered a first-line agent for empirical treatment of meningitis. *Cefoxitin* - **Cefoxitin** is also a **second-generation cephalosporin** with limited ability to cross the blood-brain barrier, making it unsuitable for treating meningitis. - Its spectrum of activity is more focused on anaerobic bacteria and some gram-negative organisms, not typically the main culprits in meningitis. *Gentamicin* - **Gentamicin** is an **aminoglycoside antibiotic** that has poor penetration into the CSF and is less effective as a monotherapy for meningitis. - It is often used in combination with other antibiotics, but not as an empirical monotherapy for suspected meningococcal meningitis.

Q: Bivalent HPV vaccine contains which types?

Type 16,18. ***Type 16,18*** - The **bivalent HPV vaccine** (Cervarix) specifically targets HPV types 16 and 18, which are responsible for the majority of **cervical cancers**. - These two types are considered **high-risk HPV strains** due to their strong oncogenic potential. *Type 6,16* - This combination is partially correct as **HPV 16** is a high-risk type, but **HPV 6** is primarily associated with **genital warts** and is included in the quadrivalent and nonavalent vaccines, not the bivalent. - The bivalent vaccine aims solely for **oncogenic types 16 and 18** for cervical cancer prevention. *Type 11,18* - This combination incorrectly includes **HPV 11**, which, like HPV 6, causes **genital warts** and is not a target of the bivalent vaccine. - While **HPV 18** is a key oncogenic target, HPV 11 does not contribute to the efficacy of the bivalent vaccine against cervical cancer. *Type 6,11* - These HPV types are known to cause approximately 90% of **genital warts** and are considered **low-risk types**, not associated with cervical cancer. - The bivalent vaccine's primary goal is **cervical cancer prevention** by targeting high-risk oncogenic types, rendering this option incorrect.

Q: DOC for Herpes simplex encephalitis:

Acyclovir. ***Acyclovir*** - **Acyclovir** is the drug of choice for treating **Herpes simplex encephalitis (HSE)** due to its potent antiviral activity against **herpes simplex virus (HSV)**. - It works by inhibiting viral DNA synthesis, thereby reducing viral replication and decreasing morbidity and mortality associated with HSE. *Amphotericin B* - **Amphotericin B** is an **antifungal medication** primarily used for severe systemic fungal infections. - It has no antiviral activity against **HSV** and is therefore ineffective in treating **Herpes simplex encephalitis**. *Inosine pranobex* - **Inosine pranobex** is an **immunomodulatory agent** that is sometimes used for viral infections, but it is not the drug of choice for acute, life-threatening conditions like **Herpes simplex encephalitis**. - Its effectiveness for **HSE** is not established, and it cannot replace potent antiviral therapy. *Intravenous immunoglobulins* - **Intravenous immunoglobulins (IVIG)** are used for immune deficiencies or certain autoimmune and inflammatory conditions. - While they can provide passive immunity, **IVIG** are not a primary treatment for acute viral infections like **HSE** and do not directly inhibit viral replication.

Q: Components of acellular pertussis vaccine

PT + FHA + Pertactin. ***PT + FHA + Pertactin*** - The most common contemporary **acellular pertussis vaccines (DTaP and Tdap)** typically include **detoxified pertussis toxin (PT)**, **filamentous hemagglutinin (FHA)**, and **pertactin (PRN)** as key antigenic components. - These components elicit a protective immune response against *Bordetella pertussis* by targeting virulence factors essential for bacterial adherence and pathogenesis. *FHA + Pertactin* - This option is incomplete as it misses the crucial **pertussis toxin (PT)**, which is a major virulence factor and a primary component of acellular pertussis vaccines. - While FHA and pertactin are important for immunity, they alone are insufficient to provide comprehensive protection against all aspects of pertussis infection. *PT + Pertactin* - This combination is incomplete, as it omits **filamentous hemagglutinin (FHA)**, an important adhesin that contributes significantly to *Bordetella pertussis* colonization and is a standard component of acellular vaccines. - A comprehensive vaccine strategy aims to include multiple antigens to achieve broader and more robust immunity. *PT + FHA + PRN + FIM* - While some research vaccines and earlier formulations might have included **fimbriae (FIM)**, modern and widely available acellular pertussis vaccines (DTaP/Tdap) in many regions primarily rely on **PT, FHA, and pertactin (PRN)** as the core three components. - The inclusion of fimbriae is not universal across all acellular pertussis vaccines currently in use, though some formulations do include FIM types 2 and 3 for enhanced protection.

Q: According to current WHO guidelines, the first-line drug of choice for managing uncomplicated vivax malaria is:

Chloroquine. ***Chloroquine*** - **Chloroquine plus primaquine** remains the **WHO first-line treatment** for uncomplicated *P. vivax* malaria in areas where chloroquine resistance has not been established. - Chloroquine is highly effective against the blood stages of *P. vivax* with **rapid parasite clearance** and excellent tolerability. - In the majority of endemic regions, *P. vivax* remains **chloroquine-sensitive**, making it the preferred first-line agent. - Primaquine is added to eliminate hypnozoites and prevent relapse, but chloroquine remains the primary blood schizonticide. - Only in areas with **documented chloroquine resistance** (parts of Papua New Guinea, Indonesia) does WHO recommend switching to **artemisinin-based combination therapy (ACT)**. *Artesunate* - Artesunate is the cornerstone of **ACTs for *P. falciparum* malaria**, not monotherapy for vivax. - For vivax, artesunate-based ACTs are reserved for **chloroquine-resistant areas** or when used as combination therapy. - While effective, it is **not the first-line choice** globally for uncomplicated vivax malaria where chloroquine remains effective. *Artemether* - Artemether (typically as artemether-lumefantrine) is another ACT option. - Like artesunate, it is used for vivax malaria only in **chloroquine-resistant regions** or for *P. falciparum*. - Not the standard first-line for uncomplicated vivax malaria per WHO guidelines. *Clindamycin* - Clindamycin is used as an **adjunct therapy** in combination with quinine for severe malaria or in special populations (e.g., pregnant women). - It is **never used as monotherapy** and is not a first-line option for uncomplicated vivax malaria.

Q: Drug of choice for roundworm

Albendazole. ***Albendazole*** - **Albendazole** is a broad-spectrum anthelminthic and is the drug of choice for treating common roundworm infections like *Ascaris lumbricoides*. - It works by inhibiting microtubule polymerization in parasitic worms, leading to their immobility and death. *Mebendazole* - **Mebendazole** is also an effective anthelminthic used for roundworm infections, but **albendazole** is generally preferred due to its single-dose efficacy and broader spectrum. - While effective, it may be used as an alternative if albendazole is not available or contraindicated. *Metronidazole* - **Metronidazole** is an antibiotic and antiprotozoal agent used primarily for anaerobic bacterial infections and parasitic protozoa like *Giardia* and *Trichomonas*. - It is **ineffective** against helminthic infections such as roundworms. *Praziquantel* - **Praziquantel** is primarily used to treat infections caused by **flukes** (trematodes) and **tapeworms** (cestodes). - It is **not effective** against roundworms (nematodes).

Q: Standard dose of rifampicin for adults (≥50 kg) in RNTCP is -

600 mg. ***600 mg*** - For adults weighing **50 kg or more**, the standard daily dose of **rifampicin** under the **Revised National Tuberculosis Control Programme (RNTCP)** is 600 mg. - This dosage is crucial for achieving optimal therapeutic concentrations and ensuring effective treatment of **tuberculosis**. *300 mg* - This is **not a standard RNTCP dose** for any specific weight category in adults. - Administering only 300 mg to an adult weighing ≥50 kg would be a significant **underdose**, leading to treatment failure and potential drug resistance. *100 mg* - 100 mg is a significantly **subtherapeutic dose** for rifampicin in adults, regardless of weight. - Such a low dose would be entirely ineffective in treating tuberculosis and would promote the development of **drug-resistant strains**. *450 mg* - While 450 mg is the correct dose for patients in the **30-49 kg weight band** under RNTCP, it is not the standard dose for individuals weighing 50 kg or more. - Using 450 mg for a patient ≥50 kg would result in **under-dosing**, compromising treatment efficacy.

Q: A 2-year-old infant is diagnosed with meningitis. A lumbar puncture reveals numerous neutrophils and gram-positive cocci in pairs that appear encapsulated. She is admitted to the hospital and started on intravenous (IV) beta-lactams. Which of the following targets would most likely play a role in the development of resistance to this antibiotic in the most likely etiologic agent of this child's meningitis?

Penicillin-binding protein. ***Penicillin-binding protein*** - The most likely pathogen causing meningitis in a 2-year-old with gram-positive cocci in pairs and capsules is *Streptococcus pneumoniae*. Resistance in *S. pneumoniae* to beta-lactam antibiotics (like penicillin and cephalosporins) primarily arises from **mutations in its penicillin-binding proteins (PBPs)**, which reduce their affinity for these drugs. - Beta-lactam antibiotics exert their effect by binding to and inactivating bacterial **PBPs**, which are essential for **cell wall synthesis**. *Reverse transcriptase* - **Reverse transcriptase** is an enzyme found in **retroviruses** and is involved in converting RNA into DNA; it is not present in bacteria. - This target is associated with resistance to **antiretrovirals** (e.g., in HIV treatment), not bacterial antibiotics. *Bactoprenol* - **Bactoprenol** is a lipid carrier molecule involved in the transport of peptidoglycan precursors across the bacterial cell membrane for cell wall synthesis. - While crucial for cell wall synthesis, it is not a direct target for beta-lactam antibiotics, nor is it the primary mechanism for beta-lactam resistance in *S. pneumoniae*. *DNA gyrase* - **DNA gyrase** is a bacterial enzyme responsible for relieving supercoiling during DNA replication. - It is the primary target for **fluoroquinolone antibiotics**, and mutations in DNA gyrase can lead to fluoroquinolone resistance, but it is not relevant to beta-lactam resistance.

Question 1

Which of the following is the chemoprophylaxis of choice in a person who is on a journey to endemic malarial region?

Accepted Answer

Atovaquone-proguanil

Answer

Doxycycline

Answer

Mefloquine

Answer

Chloroquine

Question 2

Which of the following aminoglycosides is most cochleotoxic:-

Accepted Answer

Gentamycin

Answer

Streptomycin

Answer

Amikacin

Answer

Minocycline

Question 3

Empirical drug of choice for treatment of meningococcal meningitis is:-

Accepted Answer

Ceftriaxone

Answer

Cefotetan

Answer

Cefoxitin

Answer

Gentamicin

Question 4

Bivalent HPV vaccine contains which types?

Accepted Answer

Type 16,18

Answer

Type 6,16

Answer

Type 11,18

Answer

Type 6,11

Question 5

DOC for Herpes simplex encephalitis:

Accepted Answer

Acyclovir

Answer

Amphotericin B

Answer

Intravenous immunoglobulins

Answer

Inosine pranobex

Question 6

Components of acellular pertussis vaccine

Accepted Answer

PT + FHA + Pertactin

Answer

FHA + Pertactin

Answer

PT + Pertactin

Answer

PT + FHA + PRN + FIM

Question 7

According to current WHO guidelines, the first-line drug of choice for managing uncomplicated vivax malaria is:

Accepted Answer

Chloroquine

Answer

Clindamycin

Answer

Artesunate

Answer

Artemether

Question 8

Drug of choice for roundworm

Accepted Answer

Albendazole

Answer

Mebendazole

Answer

Metronidazole

Answer

Praziquantel

Question 9

Standard dose of rifampicin for adults (≥50 kg) in RNTCP is -

Accepted Answer

600 mg

Answer

300 mg

Answer

100 mg

Answer

450 mg

Question 10

A 2-year-old infant is diagnosed with meningitis. A lumbar puncture reveals numerous neutrophils and gram-positive cocci in pairs that appear encapsulated. She is admitted to the hospital and started on intravenous (IV) beta-lactams. Which of the following targets would most likely play a role in the development of resistance to this antibiotic in the most likely etiologic agent of this child's meningitis?

Accepted Answer

Penicillin-binding protein

Answer

Reverse transcriptase

Answer

Bactoprenol

Answer

DNA gyrase

Antimicrobial Agents — MCQs

Antimicrobial Agents — MCQs

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