[Mechanisms of antimicrobial resistance]

Most fundamental differences in the bacterial structure between the gram positive and negative bacteria are whether the organism has the outer membrane. The most essential mechanism of antimicrobial resistance in the gram negative bacteria are the alteration of membrane permeability to antibiotics. The outer membrane can perform as the barrier to prevent the cells from being exposed to antibiotics. On the other hand, the gram positive bacteria need to alternate the antimicrobial targets for reducing their binding affinity with antibiotics, because of defect of the outer membrane. On the basis of the structural difference between gram positive and negative bacteria, the mechanisms of bacterial resistance to beta-lactams, amino glycosides, macrolides, newer quinolones and vancomycin are discussed.