2443. Impact of Antimicrobial Stewardship on the Incidence of Carbapenem-Resistant Pseudomonas aeruginosa: A Nonlinear Time-Series Analysis Approach to Identify Carpapenem Thresholds

BACKGROUND: To estimate the impact of antimicrobials stewardship in the temporary evolution of the Density Incidence of Pseudomonas aeruginosa resistant to carbapenems (DI_PaCRE). METHODS: In Modena Policlinico, a tertiary care hospital, from September 2014, universal rectal screening and antibiotic stewardship (ABS) focusing on carbapenem sparing strategy were introduced. We used the statistical approach already described (A nonlinear time-series analysis approach to identify thresholds in associations between population antibiotic use and rates of resistance. López-Lozano JM, et al. Nat Microbiol. 2019 Apr 8. doi: 10.1038/s41564-019–0410-0) in order to adjust a non-linear model (Multivariate Adaptive Regression Splines) looking for the identification and estimation of thresholds in the influence of the use of Carbapenems on the DI_PaCRE. RESULTS: We identified a threshold at 5.65 DDD/100 bed-days of Carbapenems (CarbUse). Indeed, above this threshold, for every increase of one DDD/100 bed-days, the DI_PaCRE increased by 0.15 new cases by 1000 bed-days. On the basis of our analyses, considering a typical course of 7 days of treatment, an average CarbUse of 6.5 DDD/100 bed-days in 2012 and 2013, for an average of 15000 monthly bed-days, means around 139 treated patients. In order to avoid the emergence of resistance, the threshold was equivalent to a maximum number of 121 patients to be treated. Below this threshold, i.e in 2018, CarbUse including 66 patients treated did not select antimicrobial resistance. CONCLUSION: PaCRE could be controlled by reducing the use of carbapenems below minimum thresholds of 6.5 DDD/100 bed-days. In order to avoid the onset of resistance to carbapenems in Pseudomonas aeruginosa, less than 121 patients per month should receive this class of drug. This finding could provide innovative approach to guide antimicrobial stewardship strategy focused on limit the spread of PaCRE in hospital populations. [Image: see text] DISCLOSURES: All authors: No reported disclosures.