Colibactin Contributes to the Hypervirulence of pks+ K1 CC23 Klebsiella pneumoniae in Mouse Meningitis Infections

Abstract

Klebsiella pneumoniae is the most common pathogen of community-acquired meningitis in Taiwan. However, the lack of a physiologically relevant meningitis model for K. pneumoniae has impeded research into its pathogenesis mechanism. Based on the core genome MLST analyses, the hypervirulent K1 K. pneumoniae strains, which are etiologically implicated in adult meningitis, mostly belong to a single clonal complex, CC23. Some K1 CC23 K. pneumoniae strains carry a gene cluster responsible for colibactin production. Colibactin is a small genotoxic molecule biosynthesized by an NRPS-PKS complex, which is encoded by genes located on the pks island. Compared to other hypervirulent K. pneumoniae which primarily infect the liver, the colibactin-producing (pks+) K1 CC23 strains had significant tropism toward the brain of BALB/c mice. We aimed in this study to develop a physiologically relevant meningitis model with the use of pks+ K1 CC23 K. pneumoniae. Acute meningitis was successfully induced in adult BALB/c male mice through orogastric, intranasal, and intravenous inoculation of pks+ K1 CC23 K. pneumoniae. Besides the typical symptoms of bacterial meningitis, severe DNA damages, and caspase 3-independent cell death were elicited by the colibactin-producing K1 CC23 K. pneumoniae strain. The deletion of clbA, which abolished the production of colibactin, substantially hindered K. pneumoniae hypervirulence in the key pathogenic steps toward the development of meningitis. Our findings collectively demonstrated that colibactin was necessary but not sufficient for the meningeal tropism of pks+ K1 CC23 K. pneumoniae, and the mouse model established in this study can be applied to identify other virulence factors participating in the development of this life-threatening disease.

Hypervirulent Klebsiella pneumoniae – clinical and molecular perspectives

“…Colibactin damages DNA and disrupts the host cell cycle, but the exact mechanisms by which colibactin contributes to pathogenesis of hvKp are largely unknown. Genetic inactivation of colibactin synthesis in a pks + K1 ST23 isolate reduced the ability of this hvKP strain to colonize the gut and disseminate to other organs in a murine model of systemic infection as well as to induce cell death in the brain during meningitis [138]. Taken together, colibactin appears to support the colonization and pathogenesis of hvKp and may have contributed to the global spread of CG23 [112], of which K1 ST23 strains are prominent.…”

Hypervirulent Klebsiella pneumoniae: a new public health threat

“…The regulators of the mucoid phenotype rmpA and rmpA2, which increase capsule production, also have been shown to increase hvKp virulence, perhaps by impairing phagocytosis and enabling survival within macrophages [9]. Additional hvKp-specific virulence factors identified include colibactin, which contributes to invasion of the central nervous system [10] and the putative metabolite transporter peg-344, which contributes to virulence in pulmonary infection models [11]. The mechanisms responsible for hvKp's relatively unique ability to infect multiple sites and metastatically spread are still poorly defined.…”

Prevalence of pks gene cluster and characteristics of Klebsiella pneumoniae‐induced bloodstream infections

“…Recently, the pks gene cluster was also found in K pneumoniae . It was reported that pks ‐encoding colibactin was related to the K pneumoniae hypervirulence in meningitis model . On the basis of these researches, we speculated that there may be a potential correlation between the pks gene cluster, virulence, and K pneumoniae ‐induced bloodstream infections (BSIs).…”