The mecA gene is a gene found in bacterial cells. The mecA gene allows a bacterium to be resistant to antibiotics such as methicillin, penicillin and other penicillin-like antibiotics.
The most commonly known carrier of the mecA gene is the bacterium known as MRSA. Apart from Staphylococcus aureus and other Staphylococcus species, it can also be found in Streptococcus pneumoniae strains resistant to penicillin-like antibiotics. In Staphylococcus species, mecA is spread on the SCCmec genetic element.
The mecA gene does not allow the ringlike structure of penicillin-like antibiotics to bind to the enzymes that help form the cell wall of the bacterium (transpeptidases), and hence the bacteria is able to replicate as normal. The gene encodes the protein PBP2A (penicillin binding protein 2A). PBP2A has a low affinity for beta-lactam antibiotics such as methicillin and penicillin. This enables transpeptidase activity in the presence of beta-lactams, preventing them from inhibiting cell wall synthesis.