A catheterized patient develops a persistent urinary tract infection despite antibiotic treatment. Which mechanism explains why the *E. coli* biofilm exhibits resistance when planktonic bacteria are susceptible?

💡 Explanation

The biofilm enhances antibiotic resistance in *E. coli* because it upregulates efflux pump expression, actively pumping antibiotics out of the biofilm matrix. This reduces intracellular antibiotic concentration, therefore resistance develops in the biofilm, rather than increased permeability or target site affinity.

• Why does ultraviolet radiation exposure in light-skinned individuals often lead to sunburn, whereas darker-skinned individuals experience significantly less damage under similar conditions?
• In the context of aging skeletal muscle, what causes reduced force generation when oxidative stress damages the sarcoplasmic reticulum?
• Why does hypokalemia increase in a patient taking a loop diuretic targeting the ascending limb of the loop of Henle?
• Which mechanism causes weakened fracture repair during chronic stress?
• A football player sustains a concussion; if their cerebral metabolic rate of glucose (CMRglc) plummets severely during the acute phase, which consequence becomes most probable, overwhelming compensatory mechanisms?
• If a child presents with bowed legs and delayed tooth eruption, what process related to calcium absorption is most likely deficient in this case of rickets?