Epidemiological and clinical features for cefepime heteroresistant Escherichia coli infections in Southwest China

Phenotypic heteroresistance (PHR) is common in a weight of microbes and plays an important role in the evolution of antibiotic resistance. However, PHR to cefepime (FEP-PHR) among invasive Escherichia coli (E. coli) has not been reported. This study aimed to report the characteristics of invasive E. coli with FEP-PHR traits and further to investigate the predisposing factors for its acquisition. A retrospective case-control study was conducted in a teaching hospital in Southwest China. A total of 319 successive and non-duplicate E. coli strains were isolated from blood and other sterile body fluids between July 2011 and August 2013. Among the seventy (70/319, 21.9 %) isolates harboring FEP-PHR traits, 30 (42.9 %) isolates were isolated from blood, 14 (20.0 %) isolates were isolated from bile, and 13 (18.6 %) isolates were isolated from drainage. FEP-PHR isolates were verified by population analysis profile (PAP) assays. Male gender, receipt of total parenteral nutrition, cephalosporins exposure, and production of extended spectrum betalactamases (ESBL) were independent risk factors for the acquisition of invasive E. coli with FEP-PHR traits. Pulsedfield gel electrophoresis (PFGE) revealed clonal diversity among the FEP-PHR isolates. The prevalence of heteroresistance to cefepime among invasive E. coli isolates merits great attention and heteroresistance may lead to the emergence of resistance strains. Therefore, systematical analysis of risk factors, careful interpretation of antibiotic susceptibility results and appropriate prescription of therapeutic strategy could help to prevent misreporting and therapeutic failure.