P-1529. Antimicrobial resistance and virulence gene profiles of Klebsiella spp. blood isolates misidentified as Klebsiella pneumoniae

Abstract Background Antimicrobial resistance (AMR) continues to pose a significant challenge in modern medicine. Klebsiella pneumoniae (KP) is a major cause of nosocomial infections and is frequently resistant to multiple antibiotics. Current methods in the detection of KP include the use of automated systems like Vitek 2, which rely on general biochemical characteristics of the KP complex, making it difficult to differentiate KP from closely related species like K. variicola and K. quasipneumoniae. These organisms are genetically distinct from KP and may differ in virulence characteristics and clinical features. In this study, we investigated if AMR and virulence genes found in KP are also present in Klebsiella spp. isolates misidentified as KP. Methods We analyzed presumptive KP isolates from blood cultures collected from patients at the Philippine General Hospital between October 2023 and August 2024. Species identification was confirmed using polymerase chain reaction (PCR) and whole genome sequencing (WGS). The species, sequence type (ST), AMR, and virulence genes were identified using the Kleborate software Results Among 60 unique blood isolates initially identified as KP, seven (12%) were reclassified as non-KP Klebsiella spp. These included K. quasipneumoniae (5 isolates), K. variicola (1 isolate), and K. africana (1 isolate). Notably, β-lactamase genes blaNDM-7 and blaCTX-M-123 were identified in two K. quasipneumoniae isolates.None of the isolates exhibited hypermucoid phenotypes or carried hypervirulence-associated genes (iuc, iro, rmp, rmpA2). Despite the absence of these virulence genes, all-cause in-hospital mortality was seen in 4 of 7 patients (57%). Conclusion While hypervirulence-associated genes were absent in non-KP Klebsiella spp., infections caused by these organisms were associated with a high mortality rate. Accurate species identification of the KP complex is essential for understanding epidemiology and guiding appropriate treatment. Disclosures Sohei Harada, MD, PhD, Denka: Honoraria|Eiken Chemical Co., Ltd.: Honoraria|MSD: Honoraria|Pfizer: Advisor/Consultant|Pfizer: Honoraria|Shionogi: Advisor/Consultant|Shionogi: Honoraria|Ushio, Inc.: Honoraria Yohei Doi, MD, PhD, GSK: Advisor/Consultant|Meiji Seika Pharma: Advisor/Consultant|Shionogi: Advisor/Consultant|Shionogi: Honoraria