The images show the 2D structures of the penicillins used in the UK. The beta-lactam ring is evident. Note how the additional functional groups influence the susceptibility to beta-lactamases.
Overview of Ticarcillin
Ticarcillin is a broad-spectrum, semi-synthetic penicillin antibiotic with bactericidal activity. Similar to carbenicillin in action, ticarcillin inactivates the penicillin-sensitive transpeptidase C-terminal domain by opening the lactam ring. This inactivation prevents the cross-linkage of peptidoglycan strands, thereby inhibiting the third and last stage of bacterial cell wall synthesis. This leads to incomplete bacterial cell wall synthesis and eventually causes cell lysis.