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

## TL;DR

This study finds that some Klebsiella species misidentified as Klebsiella pneumoniae have antibiotic resistance genes but lack typical virulence factors, yet still cause high mortality.

## Contribution

The study reveals that non-Klebsiella pneumoniae Klebsiella species can carry resistance genes and cause severe outcomes despite lacking hypervirulence traits.

## Key findings

- Seven of 60 Klebsiella isolates initially identified as K. pneumoniae were reclassified as other Klebsiella species.
- Non-K. pneumoniae isolates carried resistance genes like blaNDM-7 and blaCTX-M-123 but lacked hypervirulence genes.
- High mortality rates were observed in patients infected with non-K. pneumoniae Klebsiella species.

## Abstract

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.

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

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%).

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.

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