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.
Some 3rd-generation cephalosporins have relatively poor activity against gram-positive cocci. Oral cefixime and ceftibuten have little activity against S. aureus and, if used for skin and soft-tissue infections, should be restricted to uncomplicated infections due to streptococci. These cephalosporins have many clinical uses, as does the 4th-generation cephalosporin (see Table: Some Clinical Uses of 3rd- and 4th-Generation Cephalosporins).