A Study on Comparative in Vitro Activity of Carbapenem Sparers Against Extended-Spectrum Beta Lactamase–Producing Enterobacteriaceae

Background In the era of increasing carbapenem resistance, there is an urgent need to explore alternative options (carbapenem sparers) such as various betalactam/beta-lactamase (BL/BLI) agents, aminoglycosides, fosfomycin, and chloramphenicol to treat infections due to extended-spectrum beta lactamase (ESBL)-producing Enterobacteriaceae. We evaluated the in vitro activities of these agents in comparison to carbapenem against ESBL-producing Enterobacteriaceae blood culture isolates. Methods A retrospective analysis on the comparative susceptibility of ESBL-producing Escherichia coli and Klebsiella blood culture isolates against various antibiotics such as cefoperazone-sulbactam, piperacillin-tazobactam, cefepime-tazobactam (C/T), colistin, tigecyline, aminoglycosides, ciprofloxacin, and chloramphenicol was carried out in a tertiary care oncology setting over a span of 18 months (January 2013 to June 2014). Identification of the isolates and susceptibility testing were done using VITEK 2 compact autoanalyzer. Colistin sensitivity was done using Etest, as per Clinical and Laboratory Standards Institute (CLSI) 2013 guidelines. Results A total of 125 ESBL E coli and Klebsiella isolates were analyzed, (E coli, 67; Klebsiella, 58). Cefepime-tazobactam and carbapenem sensitivities were similar against E coli as well as Klebsiella isolates. E coli had good sensitivity to amikacin (70%) and chloramphenicol (88.5%). Among all BL/BLI agents, C/T had the highest sensitivity. Conclusions Betalactam/beta-lactamase agents and carbapenem had similar susceptibility against ESBL Enterobacteriaceae. Among the BL/BLI combinations, C/T had the highest susceptibility, followed by cefoperazone-sulbactam. Betalactam/beta-lactamase agents may have significant potential as carbapenem sparers.