How do bacteria acquire antibiotic resistance?

Bacteria acquire antibiotic resistance primarily through mutations or horizontal gene transfer. Mutations occur in the bacterial genome that can lead to changes in proteins or enzymes, enabling bacteria to survive in the presence of antibiotics. For example, a mutation might alter a target site of an antibiotic, reducing the drug's effectiveness. Horizontal gene transfer, on the other hand, allows bacteria to share genetic material with one another. This can occur through transformation (uptake of free DNA), transduction (transfer of DNA by a virus), or conjugation (direct transfer between bacteria through a pilus). This sharing can rapidly spread resistance traits throughout a bacterial population, making it a significant factor in the development of antibiotic-resistant strains.

While environmental changes and living in biofilms can influence bacterial behavior and survival, they do not directly confer antibiotic resistance. Likewise, direct contact with antibiotics can exert selection pressure that favors resistant strains, but it does not constitute a mechanism by which resistance is acquired. The true mechanism lies in the genetic alterations or transfers that occur, which enable bacteria to withstand the effects of antibiotics.