Effects of Group 1 versus Group 2 Carbapenems on the Susceptibility of Acinetobacter baumannii to Carbapenems: A Before and After Intervention Study of Carbapenem-Use Stewardship

Objective: Antimicrobial stewardship programs have been proposed for reducing bacterial resistance in the hospital environment. The purpose of this study was to investigate the impact of a carbapenem-use stewardship program on the susceptibility of Acinetobacter baumannii to Group 2 carbapenems. Methods: A before and after intervention study was conducted at a university hospital from September 2008 to February 2013. Three study periods were defined: Phase I, pre-intervention (months 1-18); Phase II, a postintervention period during which ertapenem use was mandated but carbapenem use was not restricted (months 19-36); and Phase III, a postintervention period during which Group 2 carbapenem use was restricted (months 37-54). Results: During the study period, intervention resulted in diminished consumption of Group 2 carbapenems (antimicrobial use density (AUD): 21.3 +/- 6.0 in Phase I, 18.8 +/- 6.0 in Phase II, 16.1 +/- 4.4 in Phase III; P = 0.028) and increased consumption of ertapenem (AUD: 2.7 +/- 1.7 in Phase I, 7.2 +/- 4.5 in Phase II, 9.1 +/- 5.3 in Phase III; P<0.001). The use of autoregressive-error models showed that in contrast with ertapenem use, the use of Group 2 carbapenem during the previous one month was positively and significantly associated with a subsequent increase in the proportion of carbapenem-resistant A. baumannii (CRAB) (P = 0.031). Conclusions: Implementing a carbapenem-use stewardship program featuring the preferential use of ertapenem for treating appropriate indications of infection resulted in reduced use of Group 2 carbapenems and had a positive impact on the susceptibility of A. baumannii to carbapenems. This approach could be integrated into CRAB-control strategies in hospitals.