The latest penams and cephems are largely less effective against wild type bacteria as they are a compromise between potency and resistance to b -lactamases. In other words, cilistatin inhibits DHP-1. Bacteria are continuously synthesizing and degrading their cell wall. When the kinetic balance is disrupted due to decreased synthesis, the wall is digested by the bacterial autolysins. No ATP is required.
Compounds diffuse passively through porins.