Beta-lactams

a group of antibiotics that contains beta-lactam ring in their molecular structure and includes penicillins, carbapenems, monobactams, and cephalosporins

• Inhibit cell wall synthesis by blocking peptidoglycan crosslinking

  • β-lactam mimics the D-ala-D-ala structure of bacterial peptidoglycan residue.

  • β-lactam irreversibly binds to penicillin-binding proteins (PBPs) which act as transpeptidases → stalled cross-linking of peptidoglycan in cell wall (β-lactam cannot be cleaved) → inability to synthesize new cell wall during replication → bacterial death (bactericidal effect)

• Activate autolytic enzymes

• Only when meninges are inflamed

• Exceptions: ceftriaxone and aztreonam always have good CNS penetration.

• Primarily renal (via tubular secretion)

• Exceptions

  • Primarily biliary: nafcillin

  • Both renal and biliary: other anti-staphylococcal penicillins (e.g., oxacillin, dicloxacillin), ceftriaxone

• Jarisch-Herxheimer reaction (e.g., in treatment of syphilis)

• Hypersensitivity reactions