Klebsiella pneumoniae Translocates across the Intestinal Epithelium via Rho GTPase- and Phosphatidylinositol 3-Kinase/Akt-Dependent Cell Invasion

Abstract

bKlebsiella pneumoniae is an important pathogen that causes hospital-acquired septicemia and is associated with the recent emergence of community-acquired pyogenic liver abscess (PLA). Clinical typing suggests that K. pneumoniae infections originate from the gastrointestinal reservoir. However, the underlying mechanism remains unknown. Here, we have sought to determine how K. pneumoniae penetrates the intestinal barrier. We identified that bacteremia and PLA clinical isolates adhered to and invaded intestinal epithelial cells. Internalization of K. pneumoniae in three different human colonic cell lines was visualized by confocal microscopy and three-dimensional (3D) imaging. Using a Transwell system, we demonstrated that these K. pneumoniae isolates translocated across a polarized Caco-2 monolayer. No disruptions of transepithelial electrical resistance and altered distribution of tight junction protein ZO-1 or occludin were observed. Therefore, K. pneumoniae appeared to penetrate the intestinal epithelium via a transcellular pathway. Using specific inhibitors, we characterized the host signaling pathways involved. Inhibition by cytochalasin D and nocodazole suggested that actin and microtubule cytoskeleton were both important for K. pneumoniae invasion. A Rho inhibitor, ML141, LY294002, and an Akt1/2 inhibitor diminished K. pneumoniae invasion in a dose-dependent manner, indicating that Rho family GTPases and phosphatidylinositol 3-kinase (PI3K)/Akt signaling were required. By a mouse model of gastrointestinal colonization, in vivo invasion of K. pneumoniae into colonic epithelial cells was demonstrated. Our results present evidence to describe a possible mechanism of gastrointestinal translocation for K. pneumoniae. Cell invasion by manipulating host machinery provides a pathway for gut-colonized K. pneumoniae cells to penetrate the intestinal barrier and access extraintestinal locations to cause disease.

TheKlebsiella pneumoniaeYfgL (BamB) lipoprotein contributes to outer membrane protein biogenesis, type-1 fimbriae expression, anti-phagocytosis, andin vivovirulence

“…12,13 Our recent study suggested that transcellular translocation is exploited by K. pneumoniae to migrate from the gut flora into other tissues, resulting in systemic infections. 14 However, the initial stages of K. pneumoniae infection remain unclear.…”

Binding to type I collagen is essential for the infectivity ofVibrio parahaemolyticusto host cells

“…PI3K is an essential downstream factor of the integrin signalling pathway that regulates cytoskeleton organisation and is critical for many pathogens to invade host cells (Banerjee et al, ; Faulstich, Bottcher, Meyer, Fraunholz, & Rudel, ; Hsu et al, ; Lambotin et al, ; Lussier, Basora, Bouatrouss, & Beaulieu, ; Smerling, Tang, Hofmann, & Danker, ). Therefore, we further investigated if PI3K is involved in V .…”

Homology analysis between clinically isolated extraintestinal and enteral Klebsiella pneumoniae among Neonates

“…Furthermore, a study showed that the GI K.pneumoniae could invade and penetrate the intestinal epithelium, which indicated that GI K.pneumoniae could cause extraintestinal infections. This transcellular translocation mechanism is exploited by K. pneumoniae strains from the gut ora to cause systematic infection [27]. Although there was a close relationship between colonization and infections, the homologous relationship between the GI colonized isolates and extraintestinal isolates had not been reported yet.…”