Treatment options for extended-spectrum beta-lactamase-producers

A review of antibiotic options for the treatment of infections caused by ex tended-spectrum beta-lactamase-producing isolates is presented. The use of the third-generation cephalosporin, cefotaxime, for infections caused by is olates producing ceftazidimase-type extended-spectrum p-lactamases is contr oversial, despite in vitro susceptibility to the antibiotic in many instanc es. The fourth-generation cephalosporin, cefipime, although active against most extended-spectrum beta-lactamases, is reported to show a marked inocul um effect. The cephamycins, such as cefoxitin, are generally effective agai nst Enterobacteriaceae producing TEM- and SHV-derived extended-spectrum bet a-lactamases, but Klebsiella pneumoniae strains are prone to cephamycin res istance as a result of porin loss. The use of beta-lactamase inhibitor comb inations is variable. Sulbactam is less effective than clavulanate for the inhibition of SHV-derived extended-spectrum beta-lactamases and a marked in oculum effect has been noted, while the efficacy of tazobactam against SHV- derived extended-spectrum beta-lactamase producers is controversial. Furthe rmore, extended-spectrum beta-lactamases are often encoded by multi-resista nt plasmids carrying genes conferring resistance to aminoglycosides, chlora mphenicol, sulfonamides, trimethoprim and other antimicrobials, severely li miting even alternative therapies. Extensive susceptibility testing before the institution of antibiotic therapy is thus vital. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.