Methicillin-resistant Staphylococcus aureus， MRSA bacterium also be referred to as multiply-resistant Staphylococcus aureus or oxacillin-resistant Staphylococcus aureus， ORSA， evolved the ability to survive treatment with beta-lactam antibiotics， including penicillin， methicillin， and cephalosporins. Common strains of MRSA are EMRSA15 and EMRSA16.EMRSA16 is best described epidemiologically & found to be identical to the ST36:USA200 strain. Under the new international typing system， ST36:USA200 strain is now called MRSA252. It is not entirely certain why this strain has become so successful， whereas previous strains have failed to persist. One explanation is the characteristic pattern of antibiotic susceptibility. Both the EMRSA15 and EMRSA16 strains are resistant to erythromycinand ciprofloxacin. It is known that Staphylococcus aureus can survive intracellularly， and these are precisely the antibiotics that best penetrate intracellularly； it may be that these strains of S. aureus are therefore able to exploit an intracellular niche. Most cases of CA-MRSA are caused by a CC8 strain designated ST8:USA300， which carries mec type IV， Panton-Valentine leukocidin， PSM-alpha and enterotoxins Q and K，and ST8:USA400. Other community-associated strains of MRSA are ST8:USA500 and ST59:USA1000.
應用類型
Direct ELISA， Western Blot， Immuneprecipitation， immunohistochemistry， affinity purification.
