Clinical and genomic characterization of a cohort of patients with Klebsiella pneumoniae bloodstream infection.

BACKGROUND: The clinical and microbial factors associated with K. pneumoniae bloodstream infections (BSI) are not well characterized. Prior studies have focused on highly resistant or hypervirulent isolates, limiting our understanding of K. pneumoniae strains that commonly cause BSI. We performed a chart review and whole genome sequencing (WGS) to investigate the clinical characteristics, bacterial diversity, AMR determinants, and risk factors for in-hospital mortality in a cohort of patients with K. pneumoniae BSI.

METHODS: We identified 562 patients at Massachusetts General Hospital with K. pneumoniae BSI between 2016 and 2022. We collected data on comorbidities, infection source, clinical outcomes, antibiotic resistance, and performed WGS on 108 sequential BSI isolates from 2021-2022.

RESULTS: Intraabdominal infection was the most common source of infection accounting for 34% of all BSIs. A respiratory source accounted for 6% of BSIs but was associated with a higher in-hospital mortality rate (aOR 5.4, 95% CI 2.2-12.8, P < 0.0001 compared to other sources). Resistance to the first antibiotic prescribed was also associated with a higher risk of death (aOR 5.2, 95% CI 2.2-12.4, P < 0.0001). BSI isolates were genetically diverse, and no clusters of epidemiologically and genetically linked cases were observed. Virulence factors associated with invasiveness were observed at a low prevalence, although an unexpected association between O-antigen type and the source of infection was found.

CONCLUSIONS: These observations demonstrate the versatility of K. pneumoniae as an opportunistic pathogen and highlight the need for new approaches for surveillance and the rapid identification of patients with invasive AMR K. pneumoniae infection.