503. Comparison of IMP Carbapenemase-Producing Enterobacteriaceae (CPE) and Non-Carbapenemase-Producing Enterobacteriaceae: A Multicenter Prospective Study of Clinical and Molecular Epidemiology in Japan

BACKGROUND: IMP CPE are the dominant CPE type in Japan. We aimed to compare its epidemiology to that of non-CPE (NCPE). METHODS: Patients with isolation of carbapenem-resistant Enterobacteriaceae (CRE) with meropenem MIC ≥2 mg/L or imipenem MIC ≥2 mg/L and cefmetazole MIC ≥64 mg/L were included from August 2016 to March 2018. Adjusted outcome analyses were conducted using a generalized estimating equation model with weighting based on the inverse probability of propensity scores (PS). RESULTS: Ninety isolates (27 CPE and 63 NCPE) were collected from 88 patients (53 male) in 7 hospitals. CPE included 10 E. cloacae (ENC), 6 K. pneumoniae (KP), 4 E. coli (EC), 3 C. freundii (CF), 2 K. oxytoca, and 1 each of E. aerogenes (EA) and S. marcescens (SM). NCPE included 34 EA, 15 ENC, 4 each of KP, SM, and 2 CF. All CPE were positive for IMP carbapenemase (11 IMP-11, 6 IMP-42, 4 IMP-6, and 3 each of IMP-10 and IMP-1). Most of CPE/NCPE were isolated from sputum (39%), intra-abdomen (21%), and urine (20%). Levofloxacin, gentamicin, and amikacin resistance were found in 6 (22%), 4 (15%), and 1 (4%) CPE, respectively, and 6 (10%), 6 (10%), and 0 NCPE, respectively. Eighteen (67%) bla(IMP) were transferable by conjugation. Cases of CPE involved older patients with more frequent use of devices and carbapenem exposure than those in cases of NCPE (table). The mortality was similar in the 2 groups. Length of hospital stay (LOS) after CPE/NCPE isolation was significantly higher in the CPE group after PS adjustment (P = 0.02). CONCLUSION: CPE had distinct epidemiological characteristics, and CPE isolation was associated with a prolonged hospital stay. Defining the underlying resistance mechanism of CRE is important for appropriate management. [Image: see text] DISCLOSURES: All authors: No reported disclosures.