A chronic Pseudomonas aeruginosa lung infection is treated with tobramycin. Which resistance mechanism most directly allows the bacteria to persist despite initially effective antibiotic concentrations?

💡 Explanation

Upregulation of efflux pump expression directly reduces intracellular antibiotic concentration, because it actively transports tobramycin out of the bacterial cell. Therefore, the bacteria persist due to decreased drug effectiveness, rather than ribosomal modification, enzymatic inactivation, or limited drug entry.

• What causes lymph flow reduction during severe dehydration, impacting interstitial fluid drainage?
• Why does administering antipyretics reduce fever, but not during exercise-induced hyperthermia?
• An orally administered drug undergoes significant first-pass metabolism. If the intestinal CYP3A4 enzyme is inhibited, which consequence follows?
• If a drug inhibits the hydrolysis of cGMP in retinal photoreceptors, which consequence follows for phototransduction in the eye?
• If a chronic pain patient's descending modulation pathway from the brainstem to the spinal cord malfunctions, which consequence follows regarding nociceptor signal transmission?
• If a researcher introduces a drug that inhibits osteoclast activity in a 70-year-old patient with age-related bone loss, what effect dominates on bone density over the long term?