786. Facility Reported vs. CLSI MIC Breakpoint Comparison of Carbapenem Non-susceptible (Carb-NS) Pseudomonas aeruginosa (PSA) From 2016-2019: A Multicenter Evaluation

BACKGROUND: CLSI lowered Pseudomonas aeruginosa (PSA) Carbapenem (Carb) interpretive breakpoint minimum inhibitory concentrations (MICs) in 2012. It often takes several years for commercial test manufacturers and microbiology labs to incorporate revised breakpoints. We compare facility-reported rates of Carb-NS PSA to the 2012 CLSI MIC breakpoints, using a large nationwide database for isolates tested in 2016-2020 at United States (US) facilities. Table. Imipenem (IPM)/meropenem (MEM)/doripenem (DOR) interpretation (evaluable isolates) results for PSA. [Image: see text] METHODS: All adults with a positive non-contaminant PSA culture (first isolate per 30-day period from blood, respiratory, urine, skin/wound, intra-abdominal, or other) in ambulatory and inpatient settings from 298 US hospitals from Q1 2016-Q4 2020 were evaluated (BD Insights Research Database, Becton, Dickinson & Company). Facility-reported Carb-non susceptible (NS) was defined as lab information system feed designations of susceptible (S), intermediate (I) or resistant (R) to imipenem (IPM), meropenem (MEM) and/or doripenem (DOR) per commercial panels. Where available, MICs were interpreted using CLSI 2012 Carb breakpoints (µg/ml) of ≤2 (S), 4 (I), ≥8 (R) for IPM/MEM/DOR. For evaluable PSA isolates we compared susceptibility results as reported by the facility to those using CLSI MIC breakpoints. RESULTS: Overall, 86.9% (255,844/294,426) of non-duplicate PSA isolates with facility-reported IPM/MEM/DOR susceptibility interpretations also had interpretable MIC results. S rates were 84.9% and 83.3% as reported by facilities and determined by CLSI criteria, respectively (Table). Facilities under-reported Carb-NS by 9.8%, using CLSI criteria as the standard (10.4% and 7.7% of R and I isolates, respectively, were missed by facility reporting). CONCLUSION: Systematic application of CLSI breakpoints in 2016-20 would have had minimal impact on PSA S rates in the US. However, facility reporting failed to identify ~10% of Carb-NS isolates. The clinical implications of this observation are unknown. Facilities should know their local epidemiology, decide if under-reporting might be an issue, and assess if there is any impact on their patients. DISCLOSURES: Vikas Gupta, PharmD, BCPS, Becton, Dickinson and Company (Employee, Shareholder) Kalvin Yu, MD, BD (Employee) Jason M Pogue, PharmD, BCPS, BCIDP, Merck (Consultant)QPex (Consultant)Shionogi (Consultant)Utility Therapeutics (Consultant)VenatoRX (Consultant) Janet Weeks, PhD, Becton, Dickinson and Company (Employee) Cornelius J. Clancy, MD, Merck (Grant/Research Support)