IT IS A BETA-LACTAM ANTIBIOTIC AND HAS A BACTERICIDAL ACTION AGAINST GRAM-POSITIVE AND GRAM NEGATIVE BACTERIA. IT EXERTS ITS KILLING ACTION ON GROWING AND DIVIDING BACTERIA BY INHIBITING BACTERIAL CELL-WALL SYNTHESIS, ALTHOUGH THE MECHANISMS INVOLVEDARE STILL NOT PRECISELY UNDERSTOOD. BACTERIAL CELL WALLS ARE HELD RIGID AND PROTECTED AGAINST OSMOTIC RUPTURE BY PEPTIDOGLYCAN.