Clinical and Genomic Characteristics of Carbapenem-Resistant Klebsiella pneumoniae Bloodstream Infections in Older Adults: A Single-Center Study from Changsha, China.

Background: Bloodstream infections (BSIs) caused by carbapenem-resistant Klebsiella pneumoniae (CRKP) pose a huge threat to global public health. The mortality rates are particularly high among older adults. However, few studies have focused on CRKP BSIs in older adults. This study aims to investigate the clinical and genomic characteristics of CRKP-BSIs in older adults. Methods: This study collected all eligible older patients (age ≥65 years) with CRKP-BSIs from a national regional medical center in Changsha, China from 2020 to 2023. The identification of CRKP strains was performed using MALDI-TOF mass. The antimicrobial susceptibility testing was evaluated by VITEK 2 Compact system. Clinical data of the patients were collected and a binary logistic regression model was used to analyze the risk factors associated with 30-day mortality. The genomic characteristics of CRKP were characterized by whole-genome sequencing (WGS). Results: A total of 77 older adults with CRKP-BSIs were ultimately included in this study, with an all-cause mortality rate as high as 64.9% (50/77). Mechanical ventilation (OR=8.851; 95% CI 1.503-52.127; p=0.016) is a risk factor for 30-day mortality. 97.4% (75/77) of the strains carried carbapenemase genes, with blaKPC-2  alone (92.2%, 71/77) being the most common, followed by blaKPC-2 + blaNDM-1 (2.6%, 2/77). Up to 72.7% (56/77) of the isolates were identified as hypervirulent CRKP (Hv-CRKP). MLST revealed ST11 (96.1%,74/77) dominated absolutely. Five different capsular serotypes were detected, with KL64 (81.8%, 63/77) being the most common. Through phylogenetic relationship analysis, we speculated that there might have been 10 clonal transmission events of CRKP within the hospital. Conclusion: CRKP-BSIs in older adults are primarily driven by a limited genetic lineage, ST11, in Changsha, China. Therefore, it is urgently necessary to strengthen the active screening and continuous monitoring of high-risk clone ST11 CRKP among older adults.