PBP-Mediated Mechanisms of β-Lactam Resistance in Staphylococcus aureus, Enterococci, and Streptococcus pneumoniae

β-lactam antibiotics are fundamental to antimicrobial treatment. They inhibit bacterial cell-wall synthesis, and are particularly important for treating Gram-positive bacterial infections. Bacteria have evolved several mechanisms of β-lactam resistance, among which alterations in penicillin-binding proteins (PBPs) are particularly important in the Gram-positive pathogens discussed here. This review summarizes PBP functions and PBP-mediated resistance mechanisms in Staphylococcus aureus, Enterococci, and Streptococcus pneumoniae, aiming to inform drug development and guide new therapeutic strategies against resistance.