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Thursday, June 24, 2010

Cephalosporins

The first-generation cephalosporins, epitomized by cephalothin and cefazolin, have good activity against gram-positive bacteria and relatively modest activity against gram-negative microorganisms.
The second-generation cephalosporins have somewhat increased activity against gram-negative microorganisms but are much less active than the third-generation agents
Third-generation cephalosporins generally are less active than first-generation agents against gram-positive cocci, but they are much more active against the Enterobacteriaceae, including b-lactamase-producing strains
Fourth-generation cephalosporins, such as cefepime, have an extended spectrum of activity compared with the third generation and have increased stability from hydrolysis by plasmid and chromosomally mediated b-lactamases
The first-generation cephalosporins are excellent agents for skin and soft tissue infections owing to S. aureus and S. pyogenes
The second-generation cephalosporins generally have been displaced by third-generation agents. They have inferior activity against penicillin-resistant S. pneumoniae compared with either the third-generation agents or ampicillin and therefore should not be used for empirical treatment of meningitis or pneumonia. The oral second-generation cephalosporins can be used to treat respiratory tract infections
The third-generation cephalosporins, with or without aminoglycosides, have been considered to be the drugs of choice for serious infections caused by Klebsiella, Enterobacter, Proteus, Providencia, Serratia, and Haemophilus spp
The fourth-generation cephalosporins are indicated for the empirical treatment of nosocomial infections where antibiotic resistance owing to extended-spectrum b-lactamases or chromosomally induced b-lactamases are anticipated.

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