EFFICACIES OF PIPERACILLIN-TAZOBACTAM AND CEFEPIME IN RATS WITH EXPERIMENTAL INTRAABDOMINAL ABSCESSES DUE TO AN EXTENDED-SPECTRUM BETA-LACTAMASE-PRODUCING STRAIN OF KLEBSIELLA-PNEUMONIAE

The in vivo activities of piperacillin-tazobactam and cefepime were co mpared 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-lactama se (TEM-26), With the exception of ceftazidime, all of the antimicrobi al agents significantly reduced bacterial counts within abscesses at t he end of therapy compared with those in untreated controls, Residual viable cell counts (mean +/- standard deviation in log(10) CFU/gram) w ere as follows: control? 8.76 +/- 0.97; ceftazidime, 8.00 +/- 0.76; pi peracillin-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 inhibito r combinations (P < 0.05), Cefotaxime was unexpectedly effective given its poor in vivo activity against this organism in our earlier studie s, which used a different dose and total duration of therapy (L. B. Ri ce, J. D. C. Yao, K. Klimm, G. M. Eliopoulos, and R. C. Moellering, Jr ,, Antimicrob. Agents Chemother, 35:1243-1244, 1991), These observatio ns suggest that the effectiveness of cephalosporins in the treatment o f experimental infections caused by extended-spectrum beta-lactamase-p roducing K. pneumoniae may be highly dependent on dosing regimens, eve n for a specific organism and site of infection.