1452. Molecular Profile of β-Lactamase Genes and Siderophore-Dependent Iron Transporter Genes of Cefiderocol High MIC Isolates from SIDERO-WT Studies

BACKGROUND: Cefiderocol (CFDC) is a novel siderophore cephalosporin with efficacy against Gram-negative (GN) bacteria, including carbapenem-resistant Enterobacterales and non-glucose-fermenters such as Pseudomonas aeruginosa and Acinetobacter baumannii. In consecutive multinational surveillance (SIDERO-WT) studies (2014–2017), CFDC demonstrated activity with minimum inhibitory concentrations (MICs) of ≤4 mg/mL against 99.4% of 28,629 GN clinical isolates. We conducted molecular characterization of 161 isolates with CFDC MICs >4 mg/mL from the SIDERO-WT studies. METHODS: A total of 161 isolates underwent whole genome sequencing by Illumina Hiseq. Analyses were done using the CLC genomics workbench (Qiagen) for possible resistance-related genes (e.g. β-lactamases, porin channels or penicillin-binding protein genes) and some TonB-dependent siderophore uptake receptor genes (fiu, cir, piu, pir). Fiu and Cir in Escherichia coli and Piu in P. aeruginosa are the iron transporters involved in CFDC transport. RESULTS: Of 161 isolates with CFDC MIC >4 mg/mL, 128 were A. baumannii, 22 Enterobacterales, 7 Burkholderia multivorans, 2 P. aeruginosa, and 2 Stenotrophomonas maltophilia. Genes encoding PER/VEB extended-spectrum β-lactamases and NDM-type metallo-β-lactamases were detected in some isolates, but other β-lactamase genes (bla) were not shown to be linked to high CFDC MICs. bla(PER)/bla(VEB) were found only in A. baumannii and bla(NDM) was found in A. baumannii and Klebsiella pneumoniae. In 128 A. baumannii isolates, 103 harbored PER or VEB, including PER positive isolates from Russia (n=87) and Turkey (n=6) and 4 VEB positive isolates from USA. Nine NDM-positive isolates (7 K. pneumoniae, 2 A. baumannii) were found. Disruption of iron transport genes was also detected in some isolates, including piuA (11 A. baumannii, 1 P. aeruginosa), pirA (2 A. baumannii), and fiuA (4 B. multivorans, 1 Proteus mirabilis). No cir homologs were found in 2 B. multivorans. CONCLUSION: PER and NDM could reduce susceptibility to CFDC, as such isolates have been seen in some countries. Iron transporter disruption was also observed in some isolates with high CFDC MICs; the contribution of these deficiencies in A. baumannii and B. multivorans requires further study. DISCLOSURES: Yoshinori Yamano, PhD, Shionogi & Co., Ltd. (Employee) Miki Takemura, MSc, Shionogi & Co., Ltd. (Employee) Krystyna Kazmierczak, PhD, Shionogi & Co., Ltd. (Independent Contractor) Mark G G. Wise, PhD, Shionogi & Co., Ltd. (Independent Contractor) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Consultant)Shionogi & Co., Ltd. (Independent Contractor) Roger Echols, MD, Shionogi Inc. (Consultant)