Acquisition of methicillin resistance and progression of multiantibiotic resistance in methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) produces specific penici llin-binding protein, PBP2', which shows remarkably low affinities to most beta-lactam antibiotics except those such as penicillin G and ampicillin. T he region surrounding mecA has been called additional DNA or mec and is tho ught to be of extraspecies origin. From the study of mec, we found that mec is a novel mobile genetic element and designated as staphylococcal cassett e chromosome mec (SCCmec). There are three types of SCCmec. In the past dec ades, MRSA has become resistant to many antibiotics, such as carbapenems, n ew quinolones. and minocycline etc. It seems to be a characteristic of MRSA to acquire multi-resistance by accumulating multiple resistance genes arou nd the mecA gene inside SCCmec.