Comparative Activity of Newer Antibiotics Against Gram-Negative Bacilli
CONTRIBUTION • Comparative activity of newer antibiotics against gram-negative bacilli CYNTHIA C. KNAPP, MS AND JOHN A. WASHINGTON, MD • The in vitro activities of cefoperazone, cefotaxime, ceftriaxone, ceftazidime, azlocillin, mezlocillin, piperacillin, ticarcillin/clavulanate, aztreonam, imipenem, and ciprofloxacin were concurrently deter- mined against over 1,000 isolates of gram-negative bacilli from clinical specimens of patients at the Cleve- land Clinic. Cephalosporins, penicillins, and aztreonam were active against species of Enterobacteriaceae other than Citrobacter freundii, Enterobacter aerogenes, and Enterobacter cloacae. Ceftazidime was the most active cephalosporin against Pseudomonas aeruginosa. Against the Enterobacteriaceae, the rank order of activity of penicillins was ticarcillin/clavulanate > piperacillin > mezlocillin > azlocillin. Against P. aer- uginosa, the rank order of activity of penicillins was piperacillin > ticarcillin/clavulanate > azlocillin > mezlocillin. Aztreonam was less active v P. aeruginosa than ceftazidime, cefoperazone, or piperacillin. The most active antimicrobials against all isolates tested were imipenem and ciprofloxacin. • INDEX TERMS: ANTIBIOTICS, LACTAM; GRAM-NEGATIVE BACTERIA • CLEVE CLIN J MED 1989; 56:161-166 HE RECENT introduction of ciprofloxacin for and penicillins, as well as the monobactam, aztreonam, clinical use follows closely a period of active re- and the carbapenem, imipenem.1-3 search in and development of expanded spec- We compared the susceptibility of more than 1,000 trum p-lactam antibiotics, including cephalo- clinical bacterial isolates to four expanded spectrum Tsporins, penicillins, monobactams, and carbapenems. cephalosporins (cefoperazone, cefotaxime, ceftriaxone, Although numerous published studies compare the ac- and ceftazidime), four expanded spectrum penicillins tivity of ciprofloxacin with other quinolones, only a (azlocillin, mezlocillin, piperacillin, and ticarcil- limited number of studies compare the activity of ci- lin/clavulanate), aztreonam, imipenem, and ciproflox- acin.
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