Hypermucoviscous carbapenem-resistant Klebsiella pneumoniae ST25 infect human intestinal epithelial cells and induce moderate inflammation

Abstract

Klebsiella pneumoniae is an opportunistic pathogen that can produce moderate and severe infections in 30 immunosuppressed hosts. In recent years, an increase in the isolation of hypermucoviscous carbapenem - 31 resistant K. pneumoniae with sequence type 25 (ST25) in hospitals of Norwest Argentina was observed. This 32 work aimed to study the virulence and inflammatory potential of two K. pneumoniae ST25 strains (LABACER01 33 and LABACER27) in the intestinal mucosa. The human intestinal Caco-2 cells were infected with the K. pneu- 34 moniae ST25 strains and their adhesion and invasion rates as well as changes in the expression of tight junction 35 and inflammatory factors genes were evaluated. ST25 strains were able to adhere and invade Caco-2 cells 36 reducing their viability. Furthermore, both strains reduced the expression of tight junction proteins (occludin, 37 ZO-1, and claudin-5), and increased the expression of inflammatory factors (COX-2, iNOS, MCP-1, IL-6, IL-8, 38 TNF-α) in Caco-2 cells. The inflammatory response induced by LABACER01 and LABACER27 was significant- 39 ly lower than the produced by LPS or other intestinal pathogens including K. pneumoniae NTUH-K2044. No 40 differences in virulence and inflammatory potential were found between LABACER01 and LABACER27. In 41 line with these findings, no major differences between the strains were found when the comparative genomic 42 analysis of virulence factors associated to intestinal infection/colonization was performed. This work is the 43 first in demonstrating that hypermucoviscous carbapenem-resistant K. pneumoniae ST25 infect human intesti- 44 nal epithelial cells and induce moderate inflammation.