Retrospective review of antimicrobial selection for treatment of Enterobacter in a teaching hospital

Purpose: Enterobacter spp are intrinsically resistant to 1st and 2nd generation cephalosporins through constitutive chromosomal AmpC beta-lactamases. Avoidance of 3rd generation cephalsoporins has been believed to be necessary due to the association of hyperproducing AmpC mutations. This retrospective review evaluated antimicrobial treatment selection in patients with Enterobacter spp infections, specifically focusing on the use of third generation cephalosporins.

Methods: All microbiology cultures positive for Enterobacter spp were retrospectively identified from the microbiology laboratory database at West Virginia University Healthcare from January to October 2010. Electronic medical records were reviewed for site of infection, date of culture collection, date of culture results, and antimicrobial choice. Infections were divided into 3 categories: urine, wound, and deep-seeded (including osteomyelitis, meningitis, pneumonia, and bacteremia). Duplications of infections, determined as a recurrent positive culture within 14 days time, were removed from evaluation. The choice of antimicrobial treatments was determined at 48 hours after culture resulting. This information was further divided into antimicrobial classes.

Results: Enterobacter spp infections were identified in a total of 128 patients, 49 with urine cultures, 21 with wound cultures, and 58 with deep-seeded cultures. Cephalosporins were the chosen treatment in 28% of urine cultures, 21% of wound cultures, and 19% deep-seeded cultures in those patients that received single antimicrobial coverage.

Conclusions: Validating our concern, a significant number of Enterobacter spp infections are treated with cephalosporins at our institution. Staff awareness is pertinent at this time regarding antibiotic treatment choices. Efficacy of cephalosporin treatment for Enterobacter spp needs to be validated by further evaluation to determine clinical outcomes.