MechanismofActionofMacrolidesMacrolides bind reversibly to a site on the5oS subunit of thebacterial ribosome.They block the translocation of theribosomeBacteriasurviveexposuretomacrolides,whicharethereforebacteriostatic. At higher doses, however, macrolides maybecomebactericidalMacrolidespenetrateGram(+)bacteriaabout1ootimesmorethantheydoGram(-)bacteria
Mechanism of Action of Macrolides Macrolides bind reversibly to a site on the 50S subunit of the bacterial ribosome. They block the translocation of the ribosome Bacteria survive exposure to macrolides, which are therefore bacteriostatic. At higher doses, however, macrolides may become bactericidal Macrolides penetrate Gram(+) bacteria about 100 times more than they do Gram(-) bacteria
Resistanceto MacrolidesResistance to erythromycin is a serious problem. For example,moststrainsofStaphylococcihavebecomeresistantMechanismsofresistanceinclude.modificationof the ribosomefollowinga geneticmutation·activepumping ofthe drug out of the bacterium.modification of the ribosome by a bacterial enzyme·destruction of themacrolides by esterase enzymesThe mechanisms of resistance are common to all macrolides,sothatcross-resistance is observed
Resistance to Macrolides Resistance to erythromycin is a serious problem. For example, most strains of Staphylococci have become resistant Mechanisms of resistance include: •modification of the ribosome following a genetic mutation •active pumping of the drug out of the bacterium •modification of the ribosome by a bacterial enzyme •destruction of the macrolides by esterase enzymes The mechanisms of resistance are common to all macrolides, so that cross-resistance is observed