Burkholderia pseudomallei as an Enteric Pathogen: Identification of Virulence Factors Mediating Gastrointestinal Infection

Abstract

Burkholderia pseudomallei (Bpm) is a Gram-negative bacterium and the causative agent of melioidosis. Despite advances in our understanding of the disease, Bpm poses a significant health risk, especially in endemic regions, where treatment requires prolonged antibiotic therapy. Even though the respiratory and percutaneous routes are well documented and considered the main ways to acquire the pathogen, the gastrointestinal tract is believed to be an underreported and underrecognized route of infection. In the present study, we describe the development of in vitro and in vivo models to study Bpm gastrointestinal infection. Further, we report that the Type 6 Secretion System (T6SS) and type 1 fimbriae are important virulence factors required for gastrointestinal infection. Using a human intestinal epithelial cell line and mouse primary intestinal epithelial cells (IECs), we demonstrated that Bpm adheres, invades, and forms multinucleated giant cells, ultimately leading to cell toxicity. We demonstrated that mannose-sensitive type 1 fimbria is involved in the initial adherence of Bpm to IECs, although the impact on full virulence was limited. Finally, we also showed that Bpm requires a functional T6SS for full virulence, bacterial dissemination, and for lethality in mice infected by the intragastric route. Overall, we showed that Bpm is an enteric pathogen, that type 1 fimbria is important for Bpm intestinal adherence and identify a new role for T6SS as a key virulence factor in gastrointestinal infection. These studies highlight the importance of gastrointestinal melioidosis as an understudied route of infection and open a new avenue for the pathogenesis of Bpm.

Dual RNA-seq reveals a type 6 secretion system-dependent blockage of TNF-α signaling and BicA as a Burkholderia pseudomallei virulence factor important during gastrointestinal infection

“…Dual RNA-seq has been previously successfully used to profile gene expression simultaneously of an intracellular pathogen and its infected host cell (Westermann and Vogel 2018, Mika-Gospodorz, Giengkam et al 2020, Penaranda, Chumbler et al 2021, López-Agudelo, Baena et al 2022). Therefore, we performed a fully validated dual RNA-seq experiment and then focused our analysis in subsets of bacterial and host proteins differentially expressed during intracellular infection of the Bpm wild type K96243 (Titball, Russell et al 2008) and its Δ hcp1 mutant (Sanchez-Villamil, Tapia et al 2020). Briefly, primary intestinal epithelial cells (IECs) derived from rat were selected as host cells and the bacterial infections were performed using Bpm WT and Bpm Δ hcp1 at an MOI of 10 during 6 and 12 h of growth ( Fig.…”

“…This has been further validated in non-human primates where it was demonstrated that Bpm ingestion serves as the route for disseminated infection (Nelson, Nunez et al 2021). Due to the intracellular nature of this pathogen, it is critical to investigate the molecular mechanisms mediating GI invasion and dissemination to target organs, and we have previously found that the type 1 fimbriae is involved in initial attachment to the intestinal cells, while the type 6 secretion system participates in cell-to-cell spread (Sanchez-Villamil, Tapia et al 2020).…”

“…We have previously demonstrated, using a human intestinal epithelial cell line and mouse primary intestinal epithelial cells (IEC), that Bpm adheres, invades, and forms MNGCs, ultimately leading to cell toxicity (Sanchez-Villamil, Tapia et al 2020). Further, we demonstrated that Bpm requires a functional T6SS for full virulence, bacterial dissemination, and lethality in mice infected by the intragastric route (Sanchez-Villamil, Tapia et al 2020). However, several important questions remain unsolved including the mechanism underlying T6SS activity and its physiological role during infection, particularly during GI cell-to-cell spread.…”

Recent Progress in Shigella and Burkholderia pseudomallei Vaccines

“…B. pseudomallei invasion in non-phagocytic epithelial cells is mediated by adhesins (BoaA, BoaB), type IV pili (PilA), and type I fimbriae (FimA), which is associated with intestinal colonization [1,12,13]. Shigella is a non-flagellated bacillus requiring the help of the host to reach the epithelial surface, and upon contact, it elicits filopodium-mediated motility dependent on the type 3 secretion system (T3SS).…”

Peptidomimetics as Potential Anti-Virulence Drugs Against Resistant Bacterial Pathogens

“…Experimental evidence supports that interference with bacterial secretion systems could be a feasible strategy to affect the virulence of relevant bacterial pathogens. It has been observed that mutant strains in secretion system components are less virulent than the wild-type strains in animal infection models ( Wang et al, 2016 ; Sanchez-Villamil et al, 2020 ; Spencer et al, 2021 ; Taylor et al, 2021 ). Moreover, the inhibition of secretion systems by drugs also attenuated the pathogen’s virulence in vivo ( Sheremet et al, 2018 ; Aburto-Rodríguez et al, 2021 ; Jia et al, 2021 ; Zhang et al, 2021 ; Zigangirova et al, 2021 ).…”