497. Changing Molecular Epidemiology of CRE from 2016–2018, Increase in the Unknown

BACKGROUND: Historically, endemic Klebsiella pneumoniae carbapenemase (KPC) has accounted for the majority of carbapenem-resistant Enterobacteriaceae (CRE) in Los Angeles County (LAC). The LAC Department of Public Health (DPH) initiated enhanced CRE surveillance in 2016 to determine CRE prevalence and track emerging non-KPC resistance mechanisms (IMP, NDM, OXA, and VIM) among CRE to describe characteristics and identify local epidemiology for novel multi-drug-resistant organism (N-MDRO) infection and colonization. METHODS: CRE isolates were voluntarily submitted by local clinical laboratories for mechanism detection by LAC Public Health Laboratory via MALDI-TOF and Nanosphere BC-GN. Baseline isolates were collected in 2016. Results are then presented by year through 2018. For N-MDRO cases, LACDPH interviewed healthcare facility (HCF) staff and cases to obtain case characteristics. Data were analyzed via Microsoft Access and SAS. RESULTS: CRE surveillance isolates were voluntarily submitted by 31 labs representing 34% (34/96) LAC hospitals and 1 large regional lab serving 60% of skilled nursing facilities from January 2016 to December 2018. LACDPH tested 1438 CRE isolates during the study period, 1168 (81%) were carbapenemase producing (CP). The proportion of CP CRE and KPC CRE declined over the study period (Table 1). NDM was the most common non-KPC (n = 30) followed by OXA (n = 28). The proportion of CRE with no genotypic marker increased over the course of the study. Case characteristics were obtained from 41 non-KPC CP CRE cases; median age was 66 years (range: 6–94 years); 12 (29%) expired. Among the 41 cases, 20 (49%) had a central line; 11 (27%) had surgery; 14 (34%) had antibiotics in the 6 months prior to culture date. Of the 41 cases, 11 (27%) had international healthcare exposure within 12 months with an invasive procedure and/or antibiotics. CONCLUSION: Surveillance in a large urban setting suggests the molecular epidemiology of CRE is changing, with declining prevalence of KPC, increasing metallo-β-lactamase CP, and large proportion of isolates without resistance markers detected. Given the worrisome trends in non-KPC CRE, more systematic surveillance is warranted, potentially using more robust molecular epidemiology. [Image: see text] DISCLOSURES: All authors: No reported disclosures.