This would depend on the type of bacteria that is invading. Penicillin is considered beta-lactam antibiotic, beta-lactam antibiotics have a beta lactam ring in their structure. Penicillin's MoA (mechanism of action) is that it disrupts the formation of the peptidoglycan cell wall of the bacteria, by binding to the penicillin binding protein. This is considered bacteriocidal. Bacteria can evade this by using beta-lactamases which is an enzyme which can break down beta-lactam rings.
