Enhanced virulence and pro-inflammatory potential of bile-derived Escherichia coli and Klebsiella pneumoniae isolates in primary sclerosing Cholangitis: Implications for disease pathogenesis.

Primary sclerosing cholangitis (PSC) is a chronic liver disease with poorly understood mechanisms, though gut-derived bacterial pathogens have been implicated in its pathogenesis. This study investigated the virulence and inflammatory potential of Escherichia coli and Klebsiella pneumoniae isolates from PSC patients. Bile fluid samples were collected from 15 PSC patients and non-PSC controls, yielding 19 bacterial isolates (9 E. coli, 10 K. pneumoniae). Phylogenetic analysis classified E. coli isolates predominantly into phylogroups D (44.4 %) and B2 (22.2 %), with virulence genes (afaC, clbB, iroN, hcp) frequently detected. K. pneumoniae isolates carried fimH (50 %) and hcp (70 %), with siderophore genes (irp2A, iroN) highly prevalent. PSC-associated E. coli and K. pneumoniae isolates exhibited significantly greater adhesion to Caco-2 cells compared to non-PSC controls (P < 0.05). Internalization capacity was observed in 44.4 % of E. coli and 60 % of K. pneumoniae isolates, though differences were not statistically significant. In HepG2 cells, PSC-associated E. coli isolates induced significantly elevated levels of pro-inflammatory cytokines (IL-1β, IL-6, IL-8; P < 0.01) and upregulated key inflammatory mediators (NF-κB, NOD1, NOD2, STAT3; P < 0.05). In contrast, K. pneumoniae isolates primarily increased IL-8 secretion (P = 0.006), with no significant differences in IL-1β or IL-6. These findings highlight the enhanced virulence and pro-inflammatory potential of PSC-associated bacterial isolates, particularly E. coli, in driving inflammation and contributing to PSC pathogenesis. The study supports the gut leakage theory, suggesting that gut-derived pathogens may play a critical role in initiating and perpetuating the inflammatory cascade in PSC.