General Characteristics of MRSS

Methicillin-resistant Staphylococcus species (MRSS) refers to Staphylococcus species that possess resistance genes, making them resistant to methicillin and related antibiotics. 

The primary mechanism underlying methicillin resistance is the presence of the mecA or mecC gene, which is carried on a large mobile genetic element known as the Staphylococcal Cassette Chromosome mec (SCCmec). 

These resistance genes encode altered penicillin-binding proteins (PBPs), namely PBP2a and PBP2c, which exhibit a reduced affinity for β-lactam antibiotics. As a result, β-lactam antibiotics are less able to bind effectively to their target PBPs and inhibit cell wall synthesis. Consequently, the bacteria can continue synthesizing and maintaining their cell wall despite the presence of these antibiotics, thereby conferring resistance to β-lactam agents, including methicillin.