1. Amoxicillin works by inhibiting cell wall synthesis during the stage of active multiplication and is a broad spectrum drug. The organisms that we tested with Amoxicillin, both Gram + & - were all resistant to this drug. The Zone of Inhibition was 0mm for E. Coli, S. Aureus, P. aeruginosa, S. marcescens. 2. Ampicillin’s mode of action is to penetrate Gram + and some Gram – cells. It has an Amino group which helps it to penetrate the outer membrane of Gram- bacteria. It inhibits bacteria from making cell walls and leads to cell lysis and is a broad spectrum drug. All bacteria that we tested, Gram -and Gram + were resistant to this drug. E.Coli was resistant to this drug, its Zone of Inhibition was 0mm. S. Aureus was resistant to this drug, its Zone of Inhibition was 8mm. P.Aeruginosa was resistant to this bacteria, its Zone of Inhibition was 0mm. S.marcescens was resistant to this drug, its Zone of Inhibition was 0mm. 3. Cephalothin’s mode of action is to prevent cell wall synthesis and is narrow spectrum. E.coli was resistant to this d...