Which of the following was most likely the mechanism of mycobacterial resistance to ethambutol in this patient?

Correct Answer: C

Rationale: Rationale: The correct answer is C because ethambutol targets arabinosyl transferase, an enzyme involved in mycobacterial cell wall synthesis. Resistance is commonly due to gene-induced changes in this enzyme, reducing drug efficacy. A: Topoisomerase II is not targeted by ethambutol. B: Increased metabolism wouldn't affect drug's target. D: Multiefflux pump activity is not related to ethambutol resistance.

Correct Answer: C

Rationale: Step 1: Fluconazole is metabolized by fungal cytochrome P-450 enzymes. Step 2: Gene-induced changes in these enzymes can lead to decreased drug efficacy. Step 3: Resistance to fluconazole commonly involves alterations in cytochrome P-450 enzymes. Step 4: Therefore, gene-induced changes in fungal cytochrome P-450 enzymes are most likely the mechanism of resistance in this patient. Summary: A is incorrect as topoisomerase II is not a target of fluconazole. B is incorrect as increased metabolism would not lead to resistance. D is incorrect as decreased activity of multiefflux pump would increase drug accumulation, not resistance.

Correct Answer: D

Rationale: The correct answer is D, "All of the above." Enalapril, Lisinopril, and Losartan are all medications known as ACE inhibitors or ARBs, which work by relaxing blood vessels and reducing the workload on the heart, thus effectively treating hypertension. Enalapril and Lisinopril are ACE inhibitors, while Losartan is an ARB. These medications help lower blood pressure by blocking certain enzymes or receptors, leading to vasodilation and decreased cardiac workload. Therefore, all three choices are correct as they all target the same mechanism of action in treating hypertension.

Correct Answer: B

Rationale: The correct answer is B: Stimulating beta-2 adrenergic receptors in the lungs. Albuterol is a beta-2 adrenergic agonist, which means it binds to and activates beta-2 adrenergic receptors in the lungs. By stimulating these receptors, albuterol causes smooth muscle relaxation, leading to bronchodilation and improved airflow in the lungs. This mechanism of action is beneficial in treating asthma by relieving bronchospasms and symptoms of shortness of breath. Choice A is incorrect because albuterol does not inhibit histamine release from mast cells. Choice C is incorrect as albuterol does not increase acetylcholine release in the lungs; in fact, it has the opposite effect by promoting bronchodilation. Choice D is incorrect as albuterol does not block leukotriene receptors; leukotriene receptor antagonists like montelukast are used for that purpose.

Correct Answer: A

Rationale: The correct answer is A: Celecoxib. Celecoxib is a nonsteroidal anti-inflammatory drug (NSAID) commonly prescribed to treat acute pain and inflammation in conditions like osteoarthritis and rheumatoid arthritis. It works by inhibiting the COX-2 enzyme, reducing inflammation and pain. Furosemide (B) is a diuretic used to treat fluid retention, not pain or inflammation. Gabapentin (C) is an anticonvulsant primarily used for nerve pain and seizures, not inflammation. Clonazepam (D) is a benzodiazepine used for anxiety and seizures, not for pain and inflammation.