Which of the following is a common mechanism by which bacteria develop antibiotic resistance?

• A. Drug inactivation (enzymes)
• B. Increased uptake of antibiotics
• C. Activation of immune cells
• D. Rapid growth without genetic change

Answer: (A)

Bacteria commonly resist antibiotics by making enzymes that inactivate the drug. These enzymes chemically modify or destroy the antibiotic so it can no longer reach or inhibit its target. For example, beta-lactamases hydrolyze the beta-lactam ring in penicillins and cephalosporins, rendering them ineffective. Other enzymes can modify aminoglycosides or chloramphenicol, reducing their activity. This enzymatic inactivation is a frequent and versatile resistance strategy because the genes encoding these enzymes are often carried on plasmids, enabling easy spread between bacteria.

In contrast, increasing uptake of an antibiotic would generally make the drug more effective, not resistant. Activation of immune cells is part of the host defense, not a bacterial resistance mechanism. Rapid growth without genetic change doesn’t explain how the antibiotic is neutralized or blocked, since resistance typically involves genetic changes or gene transfer that alter how the drug works.