Intrinsic resistance to antimicrobials is when bacteria naturally have structural or functional characteristics that resist activity of a particular antibiotic.

• A. Acquired
• B. Intrinsic
• C. Transient
• D. Adaptive

Answer: (B)

Intrinsic resistance is resistance that bacteria are born with due to their inherent structural or physiological traits. These characteristics are part of the organism’s baseline makeup, so they resist the action of specific antibiotics without needing prior exposure or gene acquisition. For example, some bacteria have outer membranes that prevent certain drugs from entering, lack the drug’s target or have targets with naturally low affinity, or possess efflux systems that pump the drug out of the cell. These features are stable features of the species or genus and do not require new genes or mutations to exist.

This differs from acquired resistance, which appears after exposure to an antibiotic and results from mutations or acquisition of new resistance genes that were not originally present. Transient or adaptive resistance involves temporary, reversible changes in response to environmental conditions or stress, not permanent inherited traits. The description given best matches intrinsic resistance because it emphasizes natural, built-in characteristics that resist activity of a particular antibiotic.