Antibiotic resistance can occur through several mechanisms: 1. Enzymatic inhibition - bacteria produce enzymes that can degrade antibiotics such as beta-lactamases which break down beta-lactam antibiotics. 2. Alteration of bacterial membranes - changes to outer membrane permeability or efflux pumps can reduce antibiotic uptake or increase antibiotic export from bacteria. 3. Modification of antibiotic target sites - mutations may alter the binding sites of antibiotics on ribosomes, cell walls, or metabolic enzymes, preventing the antibiotics from working.