Changes in antibiotic usage and susceptibility in nosocomial Enterobacteriaceae and Pseudomonas isolates following the introduction of ertapenem to hospital formulary

Abstract

There is concern that widespread usage of ertapenem may promote cross-resistance to other carbapenems. To analyse the impact that adding ertapenem to our hospital formulary had on usage of other broad-spectrum agents and on susceptibilities of nosocomial Enterobacteriaceae and Pseudomonas isolates, we performed interrupted time-series analyses to determine the change in linear trend in antibiotic usage and change in mean proportion and linear trend of susceptibility pre- (March 2004-June 2005) and post- (July 2005-December 2008) ertapenem introduction. Usage of piperacillin-tazobactam (P=0·0013) and ampicillin-sulbactam (P=0·035) declined post-ertapenem introduction. For Enterobacteriaceae, the mean proportion susceptible to ciprofloxacin (P=0·016) and piperacillin-tazobactam (P=0·038) increased, while the linear trend in susceptibility significantly increased for cefepime (P=0·012) but declined for ceftriaxone (P=0·0032). For Pseudomonas, the mean proportion susceptible to cefepime (P=0·011) and piperacillin-tazobactam (P=0·028) increased, as did the linear trend in susceptibility to ciprofloxacin (P=0·028). Notably, no significant changes in carbapenem susceptibility were observed.

Impact of an Antimicrobial Stewardship Initiative on Ertapenem Use and Carbapenem Susceptibilities at Four Community Hospitals

“…In a long-term study, despite an increasing use of ertapenem over a 9 year period, no association was found between ertapenem and changes in pseudomonal susceptibility to carbapenems [37]. Other studies have reported an increased susceptibility to imipenem among P. aeruginosa after introduction of ertapenem, presumptively due to decrease in group 2 carbapenems [35,36]. While the present study detected an overall decrease in carbapenem non-susceptible Pseudomonas isolates in the postintervention period, whether this is a direct impact of ertapenem or through indirect changes in other antimicrobials is unknown.…”

“…[35][36][37]. In many instances, these investigations reported improved susceptibilities of Enterobacteriaceae and Pseudomonas spp.…”

“…to other broad-spectrum antimicrobial agents, such as cefepime and piperacillin/tazobactam following the introduction of ertapenem to a hospital formulary. However, none have reported significant changes in carbapenem susceptibility following ertapenem usage alone, with many methodological problems cited in these studies [38][39][40][41].…”

Carbapenem stewardship: does ertapenem affect Pseudomonas susceptibility to other carbapenems? A review of the evidence

“…Studies have been conducted in different US centres and around the world to evaluate whether introduction of ertapenem to hospital formularies has had an effect on the susceptibility of Gram-negative bacteria to carbapenems and other antibiotics [6][7][8][9][10][11][12][14][15][16]. The studies typically focused on the number of defined daily doses (DDD) of antibiotic used and changes in the susceptibility of P. aeruginosa and, in some cases, Enterobacteriaceae, before and after ertapenem formulary introduction.…”

“…Multiple single-centre and multicentre ecological studies have recently been conducted that explore whether ertapenem has an impact on hospital ecology [6][7][8][9][10][11][12][13][14][15][16]. Sufficient long-term data are now available to examine whether ertapenem use has resulted in a change in the proportion of carbapenem-susceptible Pseudomonas or in other associated changes in susceptibility to carbapenems.…”