Comparative activity of piperacillin/tazobactam against clinical isolates of extended-spectrum beta-lactamase-producing Enterobacteriaceae.
beta-Lactam resistance on the part of the Enterobacteriaceae causes serious therapeutic problems in our institutions due to their production of extended-spectrum beta-lactamases (ESbetaLs). We studied the in vitro activity of beta-lactam/beta-lactamase inhibitor combinations and third-generation cephalosporins and monobactams against 71 clinically relevant Enterobacteriaceae which produced TEM- and SHV-derivative ESbetaLs. Of the single drugs and combinations tested, piperacillin/tazobactam proved to be the most effective. Piperacillin/tazobactam was highly active against Proteus mirabilis, with minimum inhibitory concentrations (MICs) ranging from 0.125 to 16 microg/ml; Escherichia coli (MICs from 2 to 16 microg/ml) and Serratia marcescens (MICs from 4 to 8 microg/ml), while its activity against Klebsiella pneumoniae ESbetaL producers turned out to be closely related to the type and the amount of enzyme produced, the MIC ranging from 1 to 128 microg/ml. The antibacterial activity of piperacillin/tazobactam was stronger than that of ticarcillin/clavulanate, ceftriaxone, cefotaxime, ceftazidime and aztreonam, and the combination shared favorable in vitro activity properties against the ESbetaL producers with imipenem which, however, should be kept as reserve product.
Pagani
L
L
Section of Microbiology, Department of Morphological and Clinical Sciences, University of Pavia, Varese, Italy. medlin95@ipv36.unipv.it
Migliavacca
R
R
Luzzaro
F
F
Giacobone
E
E
Perilli
M
M
Micheletti
P
P
Amicosante
G
G
D002969:Clavulanic Acids / Q000494:pharmacology; D004359:Drug Therapy, Combination / Q000494:pharmacology*; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000201:enzymology*; D006801:Humans; D020128:Inhibitory Concentration 50; D008826:Microbial Sensitivity Tests; D010397:Penicillanic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D010878:Piperacillin / Q000494:pharmacology; D000077725:Piperacillin, Tazobactam Drug Combination; D013982:Ticarcillin / Q000494:pharmacology; D065093:beta-Lactamase Inhibitors; D047090:beta-Lactams / Q000037:antagonists & inhibitors*
D002969:Clavulanic Acids; D065093:beta-Lactamase Inhibitors; D047090:beta-Lactams; D000077725:Piperacillin, Tazobactam Drug Combination; C043215:ticarcillin-clavulanic acid; D010397:Penicillanic Acid; D013982:Ticarcillin; D010878:Piperacillin