Which of the following describes intrinsic resistance in bacteria?

Intrinsic resistance refers to the inherent characteristics of a bacterial species that contribute to its ability to withstand certain antimicrobial agents. This means that some bacteria naturally possess mechanisms that make them resistant to specific drugs even in the absence of prior exposure to those drugs.

For instance, certain species of bacteria have structural features or metabolic pathways that inherently prevent antibiotics from effectively targeting them. A classic example is the intrinsic resistance of Gram-negative bacteria, which possess an outer membrane that restricts the penetration of many antibiotics.

The other options describe different mechanisms of resistance. Resistance acquired through horizontal gene transfer refers to the ability of bacteria to obtain resistance genes from other bacteria, which can happen through mechanisms such as transformation, transduction, or conjugation. Resistance due to environmental changes refers more to adaptive responses or changes in bacterial behavior in response to external conditions, not to intrinsic features. Resistance developed through antibiotic pressure involves the selection of resistant strains that occurs after exposure to antibiotics, which is a different concept than intrinsic resistance. Thus, the correct description of intrinsic resistance is clearly linked to the expected characteristics of specific bacterial species.