2184. Clinical and Molecular Epidemiology of Carbapenem-Resistant Gram-Negative Bacilli in a Los Angeles Tertiary Medical Center

BACKGROUND: Multidrug-resistant gram-negative bacilli are a significant public health threat, associated with 2.2 million deaths worldwide. Of particular importance is the rise of carbapenem-resistant gram-negative bacilli (CRGNB) given the limited options for treatment. The 30-day mortality associated with carbapenem-resistant Pseudomonas aeruginosa, carbapenem-resistant Enterobacterales, and carbapenem-resistant Acinetobacter baumannii ranges from 16 to 24%. In recognition of the substantial danger of these organisms, the World Health Organization has designated three CRGNB as Critical Priority pathogens. METHODS: Based on culture data and antimicrobial susceptibility testing, patients with CRGNB at Cedars-Sinai Medical Center from December 2022 to April 2023 were identified. Clinical data including patient demographics, prior carbapenem use, isolation of additional antibiotic-resistant organisms, subsequent antibiotic therapy, and mortality were compared among CRGNB. RESULTS: Of over 65 isolates, the largest proportion of isolates were cultured from pulmonary sources (44%), followed by urine (34%), skin (12%), blood (6%), and abdominal sources (4%). The most prevalent CRGNB isolated were Pseudomonas aeruginosa (65%), Escherichia coli (13%), and Klebsiella pneumoniae (7%). A majority of patients with CRGNB had prior documented carbapenem use (74%) and 71% of CRGNB were associated with at least one other antibiotic resistant organism. Cefiderocol was used to treat 12% of cases. However, 24% of CRGNB were not treated with antibiotics, often with the rationale that the isolate was likely a colonizing strain. The mortality rate among patients with CRGNB during our observation period was 18%. CONCLUSION: CRGNB are emerging pathogens associated with prior carbapenem use and result in significant mortality. Subsets of organisms from our dataset will be further studied for relatedness using Fourier-Transform infrared spectroscopy and whole genome sequencing. DISCLOSURES: All Authors: No reported disclosures