MBPL3822 Chemotherapy CAT 1

**Jan/Apr 2022/23** --- ## Question 1 **Which one of the following antibiotics is likely to be most effective agent in the treatment of an infection due to enterococci if used in conjunction with penicillin G? (Application question)** **Choices:** - A. Streptomycin - B. Amikacin - C. Gentamicin - D. Tobramycin - E. Netilmicin **Answer:** C. Gentamicin **Explanation:** Gentamicin, when used in combination with penicillin G, shows synergistic activity against enterococci. The penicillin disrupts the cell wall, allowing better penetration of the aminoglycoside (gentamicin) into the bacterial cell, resulting in enhanced bactericidal activity. --- ## Question 2 **Regarding the antibacterial action of gentamicin, which one of the following statements is the MOST accurate? (Application question)** **Choices:** - A. Antibacterial activity is often reduced by the presence of an inhibitor of cell wall synthesis - B. Efficacy is directly proportionate to the time that the plasma level of the drug is greater than the minimal inhibitory concentration - C. Gentamicin continues to exert antibacterial effects even after plasma levels decrease below detectable levels - D. The antibacterial action of gentamicin is not concentration-dependent - E. The antibacterial action of gentamicin is time-dependent **Answer:** C. Gentamicin continues to exert antibacterial effects even after plasma levels decrease below detectable levels **Explanation:** Gentamicin exhibits a post-antibiotic effect (PAE) , meaning it continues to suppress bacterial growth even after drug concentrations fall below the minimum inhibitory concentration (MI C). This is characteristic of concentration-dependent antibiotics like aminoglycosides. --- ## Question 3 **A 24-year-old woman is diagnosed with genital herpes simplex virus infection. Which agent is indicated for use in this diagnosis?** **Choices:** - A. Zanamivir - B. Cidofovir - C. Ganciclovir - D. Valacyclovir **Answer:** D. Valacyclovir **Explanation:** Valacyclovir, famciclovir, penciclovir, and acyclovir are all indicated for herpes simplex virus infection. Cidofovir and ganciclovir are used for CMV retinitis. Zanamivir is indicated for influenza. --- ## Question 4 **A 72-year-old man is admitted to the hospital from a nursing home with severe pneumonia. He was discharged from the hospital 1 week ago after open heart surgery. The patient has no known allergies. Which of the following regimens is most appropriate for empiric coverage of methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa in this patient?** **Choices:** - A. Vancomycin + cefepime + ciprofloxacin - B. Vancomycin + cefazolin + ciprofloxacin - C. Telavancin + cefepime + ciprofloxacin - D. Daptomycin + cefepime + ciprofloxacin **Answer:** A. Vancomycin + cefepime + ciprofloxacin **Explanation:** Vancomycin provides adequate coverage against MRSA, and cefepime and ciprofloxacin provide adequate empiric coverage of Pseudomonas. Option B is incorrect because cefazolin does not have activity against Pseudomonas. Option C is incorrect because telavancin should be avoided if possible with drugs that prolong the QTc interval (ciprofloxacin). Daptomycin is inactivated by pulmonary surfactant and should not be used for pneumonia. --- ## Question 5 **Select the agent which evades acquired efflux and target-mediated resistance** **Choices:** - A. Tigecycline - B. Minocycline - C. Tetracycline - D. Doxycycline **Answer:** A. Tigecycline **Explanation:** Tigecycline is the first glycylcycline to be launched and is one of the very few new antimicrobials with activity against Gram-negative bacteria. It evades acquired efflux and target-mediated resistance to classical tetracyclines, but not chromosomal efflux in Proteeae and Pseudomonas. It has shown equivalence to imipenem/cilastatin in intra-abdominal infections and is useful for treating multiresistant pathogens. --- ## Question 6 **Superinfections are more common with** **Choices:** - A. Use of narrow spectrum antibiotics - B. Use of antibiotics that are completely absorbed from the small intestines - C. Short courses of antibiotics - D. Use of antibiotic combinations covering both gram positive and gram negative bacteria **Answer:** D. Use of antibiotic combinations covering both gram positive and gram negative bacteria **Explanation:** Broad-spectrum antibiotics or antibiotic combinations that cover both gram-positive and gram-negative bacteria disrupt the normal flora more extensively, allowing opportunistic organisms (like C. difficile or Candida) to overgrow, leading to superinfections. --- ## Question 7 **Which one of the following drugs is most likely to be effective against multi-drug-resistant (MDR) strains of M tuberculosis, including those resistant to streptomycin?** **Choices:** - A. Spectinomycin - B. Clarithromycin - C. Amikacin - D. Gentamicin - E. Meropenem **Answer:** C. Amikacin **Explanat