Molecular correlation for the treatment outcomes in bloodstream infections caused by Escherichia coli and Klebsiella pneumoniae with reduced susceptibility to ceftazidime.

Abstract

Data are limited on outcomes of treatment with extended-spectrum cephalosporins (ESCs) for infections caused by Enterobacteriaceae that produce extended-spectrum beta-lactamases (ESBLs). This study describes the largest treatment experience of a nonoutbreak series of bloodstream infections caused by strains of Escherichia coli (23 episodes) and Klebsiella pneumoniae (13 episodes) with a ceftazidime minimal inhibitory concentration of > or =2 microg/mL. E. coli isolates produced a greater variety of beta-lactamase types than did K. pneumoniae isolates, among which ESBL production was predominant. Five ESBL types were identified: TEM-12, TEM-71, TEM-6, SHV-12, and SHV-5. Most patients were treated empirically with an ESC-based regimen. A favorable response to treatment with a nonceftazidime ESC was observed when the causative pathogen produced either TEM-6 or TEM-12; ceftazidime treatment was associated with failure of therapy in all patients. Despite the limited clinical success, ESCs are currently not recommended for the treatment of serious infections caused by ESBL-producing strains.