Carbapenem-resistant Enterobacteriaceae and the correlation between carbapenem and fluoroquinolone usage and resistance in the US military health system

•In the health care system, carbapenem and quinolone use increased.•Incidences of carbapenem resistant Enterobacteriaceae increased and then decreased.•Inpatient consumption of fluoroquinolones correlated with carbapenem resistance.•Incidences of resistance and drug consumption may be too low for correlation.•This is the largest such use/resistance correlation study in the United States to date.

Whether carbapenem or fluoroquinolone usage is correlated with carbapenem-resistant Enterobacteriaceae (CRE) has not been investigated at the level of an entire US nationwide managed health care system. We analyzed 75 million person-years of surveillance and 1,969,315 cultures from all 266 hospitals in the geographically dispersed US military health system. Incidences of CRE remained under 1 case per 100,000 person-years. Incidences of CRE increased relative to 2005 baseline levels in 3 of 7 subsequent years, then decreased in 2012 (P < 0.05). Incident proportions of carbapenem resistance (CR) differed significantly among years, geographical regions, and bacterial species. Although use and resistance strongly correlated (R > 0.80) for several “drug-bug” combinations, none were significant at the national or facility level. One exception was that inpatient consumption of fluoroquinolones was significantly correlated (P = 0.0007) with CR in Escherichia coli when data from the major referral centers of the Southern and Northern regions were combined.