Which statement best describes intrinsic resistance?

Which statement best describes intrinsic resistance?

• A. Bacteria naturally have structural or functional characteristics that resist activity of a particular antibiotic
• B. Bacteria gain resistance through mutation or gene transfer
• C. Resistance develops after exposure to antibiotics
• D. It is caused by biofilms

Answer: (B)

Intrinsic resistance means a bacterium is naturally resistant to a drug because of its inherent structural or physiological traits. This resistance is present before any antibiotic exposure, arising from features like the composition of the cell envelope, absence of the drug’s target, or constant efflux activity that prevents the drug from reaching effective levels. Because it’s built into the organism, it does not require mutation or gene transfer to exist, and it isn’t caused by exposure to antibiotics. In contrast, resistance that appears after exposure is acquired. That kind of resistance comes from changes gained through mutations or through acquiring resistance genes from other organisms via horizontal gene transfer. So when a bacterium becomes resistant after antibiotics are used, that’s acquired resistance rather than intrinsic. Biofilms can also impede antibiotic effectiveness by creating a protective environment, but this is a separate phenomenon from intrinsic resistance.

Intrinsic resistance means a bacterium is naturally resistant to a drug because of its inherent structural or physiological traits. This resistance is present before any antibiotic exposure, arising from features like the composition of the cell envelope, absence of the drug’s target, or constant efflux activity that prevents the drug from reaching effective levels. Because it’s built into the organism, it does not require mutation or gene transfer to exist, and it isn’t caused by exposure to antibiotics.

In contrast, resistance that appears after exposure is acquired. That kind of resistance comes from changes gained through mutations or through acquiring resistance genes from other organisms via horizontal gene transfer. So when a bacterium becomes resistant after antibiotics are used, that’s acquired resistance rather than intrinsic.

Biofilms can also impede antibiotic effectiveness by creating a protective environment, but this is a separate phenomenon from intrinsic resistance.