Ertapenem: no effect on aerobic gram-negative susceptibilities to imipenem.
OBJECTIVE
To describe any potential effect on in vitro susceptibility to imipenem for aerobic gram-negative bacteria following the addition of ertapenem to the formulary of a large teaching hospital.


METHODS
Changes in imipenem susceptibilities for aerobic gram-negative bacteria were compared among clinical isolates from 2002 to 2007 using a Poisson model. Changes in the susceptibility of imipenem to P. aeruginosa, K. pneumoniae, K. oxytoxa, E. coli, and S. marcescens were compared over time using a chi-squared test for trend. Carbapenem use was measured using a defined daily dose per 1000 patient days. Change in utilization was compared for all years. The prevalence of ESBL-producing K. pneumoniae, K. oxytoxa, and E. coli over time was compared.


RESULTS
Susceptibility to imipenem did not change after the addition of ertapenem and this most notably includes P. aeruginosa (p=0.43). Additionally, an increase in the incidence of ESBL K. pneumoniae from 2002 (4%) to 2007 (18%) p<0.0001 occurred with significant increases in both imipenem and ertapenem use in that time frame (p<0.001).


CONCLUSIONS
The continued use of ertapenem over 5 years with predominant use of imipenem did not select for P. aeruginosa resistance to imipenem. The rising rate of community and healthcare associated ESBL K. pneumoniae increased total carbapenem use.
Goff
Debra A
DA
College of Pharmacy, The Ohio State University Medical Center, Department of Pharmacy, 410 West. 10th Ave., 368 Doan Hall, Columbus, OH 43210, USA. debbie.goff@osumc.edu
Mangino
Julie E
JE
D004347:Drug Interactions; D024881:Drug Resistance, Bacterial; D000077727:Ertapenem; D006088:Gram-Negative Aerobic Bacteria / Q000187:drug effects* / Q000201:enzymology; D016905:Gram-Negative Bacterial Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology; D006785:Hospitals, University; D006801:Humans; D015378:Imipenem / Q000494:pharmacology* / Q000627:therapeutic use; D001618:beta-Lactamases / Q000096:biosynthesis*; D047090:beta-Lactams / Q000494:pharmacology*
D047090:beta-Lactams; D015378:Imipenem; D001618:beta-Lactamases; D000077727:Ertapenem