Polydextrose reduces the infection of Klebsiella pneumoniae in mice by downregulating the expression of TamA.

Abstract

Polydextrose (PDX), as a prebiotic, is an extensively branched glucose polymer that can promote the growth of beneficial bacteria in the gut. Recent research indicates that PDX regulates intestinal function and supports immune balance, which helps to protect the gut from pathogenic bacteria. However, scarce research has been found that PDX prevents the host infection through the direct effects on the pathogen. In this study, we developed a mouse model infected with Klebsiella pneumoniae by pretreating with PDX, assessed the effect of PDX on K. pneumoniae acute infection in mice, and explored its potential mechanisms. We developed a mouse model that is infected with K. pneumoniae by pretreating with PDX. Colony counting quantified the K. pneumoniae bacterial load in the parenchymal organs of mice. A scanning electron microscope was used to investigate the morphological characteristics of K. pneumoniae. The expression level of TamA (translocation and assembly module A) was detected by reverse transcription-polymerase chain reaction (RT-PCR) and western blotting. The CRISPR-Cas9 technique was applied to construct the tamA mutant strains (ΔtamA) and the tamA complement strain (C-ΔtamA). The biofilm formation capacity was evaluated by the crystal violet assay. The capsule production was quantified by measuring uronic acid content. In the PDX pretreated model, PDX did not alter the growth characteristics and morphological structure of K. pneumoniae. However, it significantly reduces the load of K. pneumoniae in the lung, liver, spleen, and intestinal tract of mice, which is related to inhibiting the expression of the outer membrane TamA protein by PDX. In an in vitro study, the results indicated that deletion of tamA significantly inhibited capsule production and biofilm formation of K. pneumoniae, weakened interspecific and intraspecific competitive abilities with other members of the Enterobacteriaceae family, and reduced the adhesion ability to Caco-2 and murine lung epithelial (MLE) cells. Compared with the wild strain, PDX treatment and the deletion of tamA inhibit the expression of adhesion factors (including FimH, FimC, FimD, and MrkD) and the capsule synthesis genes (including galF, wzi, and manC) in K. pneumoniae. PDX can prevent the infection of K. pneumoniae in mice. The potential mechanism may involve downregulating TamA expression and inhibiting adhesion-related molecules. Therefore, PDX can serve as a potential prebiotic to reduce K. pneumoniae infections in both humans and animals.IMPORTANCEOur findings revealed that polydextrose (PDX) could significantly reduce the load of Klebsiella pneumoniae in the lung, liver, spleen, and intestinal tract of mice. The potential mechanism is related to inhibiting the expression of the outer membrane TamA protein by PDX. The deletion of tamA significantly inhibited the capsule production and biofilm formation of K. pneumoniae, weakened the interspecific and intraspecific competitiveness ability with other members of the Enterobacteriaceae family, and reduced the adhesion ability to Caco-2 and MLE cells. Our data suggest that PDX may act as a prebiotic to reduce K. pneumoniae infections in humans and animals.