Review of in Vitro Activity of Third-generation Cephalosporins and Other Newer Beta-lactam Antibiotics Against Clinically Important Bacteria

The third-generation cephalosporins and some newer beta-lactam compounds such as the monobactams and carbapenems, when compared with first- and second-generation cephalosporins, have an extended spectrum of activity and generally greater activity against gram-negative bacilli of clinical importance. The increased spectrum includes the Enterobacteriaceae and Pseudomonas aeruginosa. Although the third-generation cephalosporins have some activity against P. aeruginosa, of those drugs now available in the United States, ceftazidime and cefoperazone are much more active than the others, and ceftazidime is more active than cefoperazone. The activity of the third-generation compounds against Acinetobacter species and other Pseudomonas species is limited. These compounds inhibit the growth of Hemophilus and Neisseria species (including beta-lactamase-producing isolates), nonenterococcal streptococci, and anaerobic gram-positive cocci. They also inhibit the growth of methicillin-susceptible Staphylococcus aureus and coagulase-negative staphylococci but generally are not as active against these organisms as are the first-generation cephalosporins. They do not inhibit methicillin-resistant S. aureus. The activity of third-generation cephalosporins against anaerobes varies, but moxalactam and ceftizoxime are similar in activity to cefoxitin, a second-generation compound. The third-generation cephalosporins do not inhibit the growth of Listeria. A majority of organisms resistant to cephalothin and cefamandole (first- and second-generation cephalosporins) and to aminoglycosides are inhibited by third-generation cephalosporins.