Why are bacteria refractory to antimicrobials?

Abstract

The incidence of antibiotic resistance in pathogenic bacteria is rising. Antibiotic resistance can be achieved via three distinct routes: inactivation of the drug, modification of the target of action, and decreasing the concentration of drug that can reach the target. It has long been recognized that specific antibiotic resistance mechanisms can be acquired through mutation of the bacterial genome or by the addition of genes through horizontal gene transfer. Recent attention has also brought to light the importance of different physiological states for the survival of bacteria in the presence of antibiotics. It is now apparent that bacteria have complex, intrinsic resistance mechanisms that oftentimes are not detected in the standard antibiotic sensitivity tests performed in clinical laboratories. Paramount among these intrinsic mechanisms is the development of resistance in bacteria found in surface-associated aggregates or biofilms.