Ampicillin was the first semi-synthetic penicillin; it resulted from the aminopenicilins synthesized in 1958. It was developed in response to the need of finding wider spectrum derivates from penicillin, given the emergence of resistant strains. As all beta-lactam antibiotics, ampicillin is capable of penetrating gram positive and some gram negative and anaerobic bacteria. It inhibits the synthesis of the bacterial cell wall in its last two stages, joining penicillin-binding proteins, which conducts to destruction of the cell wall, and cell lysis. It is a widely used antibiotic in the market with a very good effect.