Endogenous Endophthalmitis Caused by ST66-K2 Hypervirulent Klebsiella pneumoniae, United States

Abstract

H ypervirulent Klebsiella pneumoniae (hvKp) strains are mostly community-acquired and can cause invasive infections such as liver abscess with metastatic spread (1,2). The genetic determinants of hypervirulence are found on chromosomal mobile genetic elements, large plasmids, or both. The most common virulence determinants of hvKp include siderophore systems for iron acquisition, increased capsule production, K1 and K2 serotypes, and the colibactin toxin (1). In addition, these hvKp strains demonstrate hypermucoviscosity, as indicated by a positive string test, and are usually susceptible to antimicrobial drugs (1). However, multidrug-resistant hypervirulent strains have emerged in Asia, a region to which hvKp is endemic (1,3). Kp52.145 (laboratory strain B5055), which belongs to sequence type (ST) 66, is one of the most virulent and widely studied K2 strains. The ST66-K2 sublineage contains virulence genes in its chromosome and 2 large plasmids (4,5). ST66-K2 was isolated in Indonesia in 1935; since then, cases have been reported in Australia in 2002 (caused by strain AJ210), Germany in 2017 (caused by strain 18-0005) and France in 2018 (caused by strain SB5881) (6-8).The most common hvKp infection metastatic sites are the eyes, lungs, and central nervous system (1).Endogenous endophthalmitis (EE) caused by hvKp is associated with risk factors such as diabetes mellitus, Asian ancestry, and infection with the K1 serotype (2). Although the prevalence of hvKp is increasing in the United States and Europe (1,2,9), where EE has been documented in patients of Asian and non-Asian descent (9,10), these infections are not well-recognized. Ocular prognoses and clinical outcomes for EE are usually poor and exacerbated by late or missed diagnosis (2). We describe a case of EE caused by a hvKp strain of the ST66-K2 sublineage in the United States.

Genetic and Functional Characterization of a Conjugative KpVP-2-Type Virulence Plasmid From a Clinical Klebsiella pneumoniae Strain

“…This virulence plasmid was demonstrated to contribute to hypervirulence in K. pneumoniae strains (Nassif and Sansonetti, 1986). Since its emergence, ST66-K2 HvKP carrying KpVP-2 has been reported to cause various human infections, including endogenous endophthalmitis, tonsillopharyngitis, acute otitis media, meningitis, bacteraemia, and bacteriuria worldwide (Rodrigues et al, 2020;Kamau et al, 2021;Klaper et al, 2021). These strains exhibited a few SNPs, indicating clonal expansion of this lineage (Rodrigues et al, 2020).…”

“…Even though the prevalence of KpVP-2 is much lower than that of KpVP-1, its influence might be largely underestimated. Since its emergence in or before 1935, ST66-K2 HvKP carrying KpVP-2-type virulence plasmids has been disseminated worldwide, causing serious human infections (Rodrigues et al, 2020;Kamau et al, 2021;Klaper et al, 2021).…”

Hypervirulent Klebsiella pneumoniae

“…8 Genetic elements on chromosomes, large virulence plasmids, or both, are responsible for encoding the determinants of hypervirulence. 9 Clinicians can use these biomarkers to identify hvKP or MDR-hvKP strains. The evolution of hvKP is always triggered by some important factors, such as (1) the enhanced ability to acquire iron and (2) the increased production of capsule or colibactin toxin.…”