Introduction: Excessive group 2 carbapenem use may result in decreased bacterial susceptibility.
Objective: We evaluated the impact of a carbapenem stewardship program, restricting imipenem and
meropenem use. Methods: Ertapenem was mandated for ESBL-producing Enterobacteriaceae infections
in the absence of non-fermenting Gram-negative bacilli (GNB) from April 2006 to March 2008. Group
2 carbapenems were restricted for use against GNB infections susceptible only to carbapenems and suspected
GNB infections in unstable patients. Cumulative susceptibility tests were done for nosocomial
pathogens before and after restriction using Clinical and Laboratory Standards Institute (CLSI) guidelines.
Vitek System or conventional identifi cation methods were performed and susceptibility testing done
by disk diffusion according to CLSI. Antibiotic consumption (t-test) and susceptibilities (McNemar’s test)
were determined. Results: The defi ned daily doses (DDD) of group 2 carbapenems declined from 61.1 to
48.7 DDD/1,000 patient-days two years after ertapenem introduction (p = 0.027). Mean ertapenem consumption
after restriction was 31.5 DDD/1,000 patient-days. Following ertapenem introduction no signifi
cant susceptibility changes were noticed among Gram-positive cocci. The most prevalent GNB were
P. aeruginosa, Klebsiella pneumoniae, and Acinetobacter spp. There was no change in P. aeruginosa susceptibility
to carbapenems. Signifi cantly improved P. aeruginosa and K. pneumoniae ciprofl oxacin susceptibilities
were observed, perhaps due to decreased group 2 carbapenem use. K. pneumoniae susceptibility
to trimethoprim-sulfamethoxazole improved. Conclusion: Preferential use of ertapenem resulted in reduced
group 2 carbapenem use, with a positive impact on P. aeruginosa and K. pneumoniae susceptibility.
Keywords: carbapenems; drug resistance; bacterial ecology.