In this article. Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium that causes infections in different parts of the body. It's tougher to treat than most strains of staphylococcus aureus -- or staph -- because it's resistant to some commonly used antibiotics.n this article. Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium that causes infections in different parts of the body. It's tougher to treat than most strains of staphylococcus aureus -- or staph -- because it's resistant to some commonly used antibiotics.
Although enterococci have been known to be intrinsically resistant to cephalosporins for decades, the mechanism of cephalosporin resistance remains incompletely understood. Three determinants for cephalosporin resistance in E. faecalis have been described.
â¢ However, degree and extent of binding to different PBPs may be different for the cephalosporins. than for penicillins. For example, cephalothin causes lysis of Staph. aureus, whereas cephalexin. produces long filamentous forms in E. coli. â¢ In general, cephalosporins are less susceptible to b-lactamases compared to penicillins. 47. Cephalosporin!!!!!!!!!!!!!R1!!!!!!!!!!!!!!!!!!!!!!!!!R2!!!!!!!!!!!!!!!!!!!!!!!!R3. Table 18.