Efficacies of piperacillin-tazobactam and cefepime in rats with experimental intra-abdominal abscesses due to an extended-spectrum beta-lactamase-producing strain of Klebsiella pneumoniae.

The in vivo activities of piperacillin-tazobactam and cefepime were compared with those of ticarcillin-clavulanate, ceftazidime, cefotaxime, and imipenem in a rat model of intra-abdominal abscess with a strain of Klebsiella pneumoniae elaborating an extended-spectrum beta-lactamase (TEM-26). With the exception of ceftazidime, all of the antimicrobial agents significantly reduced bacterial counts within abscesses at the end of therapy compared with those in untreated controls. Residual viable cell counts (mean +/- standard deviation in log10 CFU/gram) were as follows: control, 8.76 +/- 0.97; ceftazidime, 8.00 +/- 0.76; piperacillin-tazobactam, 3.87 +/- 1.72; ticarcillin-clavulanate, 3.74 +/- 1.34; cefepime, 3.15 +/- 1.19; cefotaxime, 2.61 +/- 0.77; imipenem, 2.41 +/- 0.93. Imipenem was more effective than either of the inhibitor combinations (P < 0.05). Cefotaxime was unexpectedly effective given its poor in vivo activity against this organism in our earlier studies, which used a different dose and total duration of therapy (L. B. Rice, J. D. C. Yao, K. Klimm, G. M. Eliopoulos, and R. C. Moellering, Jr., Antimicrob. Agents Chemother. 35:1243-1244, 1991). These observations suggest that the effectiveness of cephalosporins in the treatment of experimental infections caused by extended-spectrum beta-lactamase-producing K. pneumoniae may be highly dependent on dosing regimens, even for a specific organism and site of infection

Efficacy of ceftriaxone plus tazobactam in a rat model of intraabdominal abscess due to Bacteroides fragilis

Using a rat model of intraperitoneal abscess due to Bacteroides fragilis, we evaluated therapy with the combination of ceftriaxone plus the /Mactamase inhibitor tazobactam in comparison with ceftriaxone or cefotaxime alone. When treatment was begun five hours after bacterial challenge, final bacterial counts within abscesses at 3-5 days of treatment were as follows (mean±s.D., log 10 cfu/g): ceftriaxone plus tazobactam, 415 ±1-25; cefotaxime, 4-77 ±1-80; ceftriaxone alone, 5-68 ± 104; untreated controls, 914+ 113. In spite of pharmacokinetic differences between the two drugs, coadministration of tazobactam significantly enhanced activity of ceftriaxone in this model