Prevalence of hypervirulence-associated pathogenicity loci among *Klebsiella pneumoniae * bloodstream isolates at a United States Hospital

Klebsiella pneumoniae is a major threat to human health worldwide. “Classical” K. pneumoniae (cKp) strains commonly cause multidrug-resistant (MDR) infections in debilitated patients residing in hospitals and long-term care facilities.

In contrast, hypervirulent K. pneumoniae (hvKp) strains may cause invasive, community-acquired infections in otherwise healthy individuals. These highly virulent strains were first identified in Taiwan in 1986 and have since disseminated across the globe. The prevalence of hvKp has been well described in Southeast Asia, but is not well understood in the United States.

In this work, 141 consecutive K. pneumoniae blood stream isolates were collected at Northwestern Memorial Hospital from 2015-2017. To screen this collection for hvKp, isolates were tested for the hypermucoviscous phenotype and the presence of aerobactin and salmochelin biosynthesis genes, biomarkers that have been used to distinguish hvKp from cKp. These biomarkers were identified in 12 (8.5%), 6 (4.3%), and 5 (3.5%) isolates, respectively. Whole genome sequencing was performed on the six isolates that contained aerobactin biosynthesis genes and demonstrated that these genes were contained on large plasmids.

Five isolates contained plasmids nearly identical to previously described hvKp virulence plasmids while one was similar to a plasmid from a swine isolate of K. pneumoniae. These findings indicate that several non-clonal hvKp-like strains are present in the U.S.