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.
Section of Microbiology, Department of Morphological and Clinical Sciences, University of Pavia, Varese, Italy. medlin95@ipv36.unipv.it
L
L
Pagani
R
R
Migliavacca
F
F
Luzzaro
E
E
Giacobone
M
M
Perilli
P
P
Micheletti
G
G
Amicosante
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