•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 asexamples for ~- lactam antibiotics to be used for treatement of E.coli and S. aureus bacterial strains predisposing to undergo someimmunological studies on them.•E. coli and S. aureus strains were treated with amoxicillin by 18hs incubation with 1/3 (MIC) value which recorded (8 ug/ml)for E. coli and (4 ug/ml) for S. aureus•E. coli and S. aureus strains were treated with piperacillin andthis achieved by picking up the arisen colonies in the middle zone around Piperacillin disc on disc diffusion sensitivity plate.•Concerning culturing of peripheral blood mononuclear cellsafter its isolation from sheep jugular vein puncture which was asimple reproducible method for obtaining a high yield of viablephagocytic cells, assessment of cell viability and counting of thecells and adjustment the count of the cells, then the amoxicillinand piperacillin treated E. coli and S. aureus cells and untreated