A bacterium that is unaffected by an antibiotic drug is said to be a bacterium.

A bacterium that is unaffected by an antibiotic drug is said to be antibiotic-resistant. Antibiotic resistance occurs when bacteria evolve mechanisms to withstand the effects of drugs that once killed them or inhibited their growth. This resistance can arise through various means such as genetic mutations or acquiring resistance genes from other bacteria. The prevalence of antibiotic-resistant bacteria is a significant public health concern as it can lead to infections that are more difficult to treat, necessitating the development of new antibiotics and the implementation of stronger infection control measures. Understanding and combating antibiotic resistance is crucial in the field of medicine and microbiology.