Cephalosporins: rationale for clinical use.
 Cephalosporins, the most widely used class of antibiotics, are more resistant than penicillins to inactivation by beta-lactamases.
 Based on their spectrum of activity against gram-negative bacteria, cephalosporins are classified into three generations.
 The generation classification, however, does not correlate with activity against gram-positive bacteria or anaerobes.
 First-generation cephalosporins have a narrow gram-negative spectrum but are most active against gram-positive bacteria, particularly Staphylococcus aureus.
 Third-generation compounds have excellent activity against gram-negative bacteria.
 The cephamycins, a second-generation subgroup that includes cefoxitin, cefotetan and cefmetazole, have the best activity against anaerobes.
