Which statement most accurately defines antibiotic resistance and explains the role of antibiotic use in its emergence?

• A. Antibiotic resistance is primarily an environmental phenomenon where antibiotics chemically alter bacterial cell walls causing temporary tolerance, and antibiotic use is unrelated to the genetic frequency of resistance because resistance is transient and nonheritable.
• B. Antibiotic resistance is created de novo by exposure to antibiotics which directly induces specific resistance mutations in bacterial genomes in most clinical cases, therefore widespread use is the main generator of novel resistance genes across populations even when none existed previously.
• C. Antibiotic resistance refers to host immune system failure to clear an infection, and heavy antibiotic use strengthens host immunity over time which paradoxically leads to more chronic infections but not genetic changes in bacteria.
• D. Antibiotic resistance is a genetic trait that makes drugs less effective and antibiotic use selects for pre-existing resistant cells rather than creating new resistance; antibiotics remove susceptible competitors so resistant variants increase in frequency.

Answer: (D)