mecA is a biomarker gene responsible for resistance to methicillin and other β-lactam antibiotics. After acquisition of mecA, the gene must be integrated and localized in the S. aureus chromosome. mecA encodes penicillin-binding protein 2a (PBP2a), which differs from other penicillin-binding proteins as its active site does not bind methicillin or other β-lactam antibiotics. As such, PBP2a can continue to catalyze the transpeptidation reaction required for peptidoglycan cross-linking, enabling cell wall synthesis even in the presence of antibiotics. As a consequence of the inability of PBP2a to interact with β-lactam moieties, acquisition of mecA confers resistance to all β-lactam antibiotics in addition to methicillin.Sahebnasagh R, Saderi H, Owlia P. Detection of methicillin-resistant Staphylococcus aureus strains from clinical samples in Tehran by detection of the mecA and nuc genes. The First Iranian International Congress of Medical Bacteriology; 4–7 September; Tabriz, Iran. 2011. 195 pp.
