Bacteria adapt all possible ways to survive when exposed to drugs. Depending upon the type of bacteria (gram positive/ gram negative) the approaches vary. The most common of these in general include:

Not permitting the drug to enter

• Either by closing porin channels
• My making alteration in outer membrane proteins to reduce permeability
• By secreting extracellular enzymes to deactivate the drug

By secreting intracellular enzymes for deactivation of drug

• Extended-spectrum beta-lactamases secretion
• Aminoglycoside-modifying enzyme secretion

• Efflux the drug out of the bacterial cell
• By making biofilms formation (when single bacteria or a small population is under threat they colonize and form a protective layer around them, called biofilm)
• By altering the binding sites of drug
• By transferring resistant genetic material to neighboring non-resistant microbes