Try to describe the antibacterial mechanism of β -lactam antibiotics and the mechanism of bacterial resistance to them.

Answer: The antibacterial mechanisms of β -lactam antibiotics are as follows: ① Binding PBPs (PBPS inhibits its function, such as inhibiting trans-peptide, hindering mucin cross-linking, leading to bacterial cell wall defects and barrier function loss. Due to the high osmotic pressure inside bacteria, bacterial cells swell, deform, rupture and die. ② Initiating autolytic enzyme activity.

The mechanisms of bacterial resistance to β -lactam antibiotics are: PBPs difference or PBPs change, the difference of outer membrane barrier or membrane pore protein makes drugs unable to penetrate the site of action, β -lactamase hydrolysis or drug binding, active efflux enhancement, and bacteria lack autolytic enzyme.