After diagnostic tests on ten isolates of S. marcescence, were made an examination of sensitivity to various antibiotics and checking the ability to produce β-lactamase of all isolates.        The outer membrane protein quantity was determined in μg/cm3 for all isolates. The results showed that S. marcescence have antibiotic multiresistant and all isolates had the ability to produce β-lactamase and its resistance may arise from more than two mechanisms like overproduction of antibiotic inactivation enzymes and the decrease of permeability by outer membrane protein.