•In this work, some bacteriological and immunological studies were carried out on E. coli and S. aureus strains for evaluation of the effect of ~- lactam antibiotics treatment on the bacterialsusceptibility to Phagocytic cell activity.•At first, 4 typed bacterial strains of E. coli and 4 typed bacterialstrains of S. aureus isolated from clinical cases were used as thetest organisms. They were cultivated on MacConkey’s agar and Nutrient agar with (7-10%) NaCI, respectively.•Disc diffusion antimicrobial susceptibility test was done byusing all strains then amoxicillin and piperacillin were chosen assuccessive days.5th Group: Infected with E.coli strain 01 at day and treated withflorfenicol 10% in a dose of (20mg/kg b.wt.) for 5successive days.