The inhibition mechanism of co-cultured probiotics on biofilm formation of Klebsiella pneumoniae.

Aims Klebsiella pneumoniae , an important opportunistic pathogen of nosocomial inflection, is known for its ability to form biofilm. The purpose of the current study is to assess how co- or mono-cultured probiotics affect K. pneumoniae 's ability to produce biofilms and investigate the potential mechanisms by using a polyester nonwoven chemostat and a Caco-2 cell line. Methods and Results Compared with pure cultures of Lactobacillus rhamnosus and Lactobacillus sake , the formation of K. pneumoniae biofilm was remarkably inhibited by the mixture of L. rhamnosus, L. sake , and Bacillus subtilis at a ratio of 5:5:1 by means of qPCR and FISH assays. In addition, Lactobacillus in combination with B. subtilis could considerably reduce the adherence of K. pneumoniae to Caco-2 cells by using inhibition, competition, and displacement assays. According to the RT-PCR assay, the adsorption of K. pneumoniae to Caco-2 cells was effectively inhibited by the co-cultured probiotics, leading to significant reduction in the expression of proinflammatory cytokines induced by K. pneumoniae. Furthermore, the HPLC and RT-PCR analyses showed that the co-cultured probiotics were able to successfully prevent the expression of the biofilm-related genes of K. pneumoniae by secreting plenty of organic acids as well as the second signal molecule (c-di-GMP), resulting in inhibition on biofilm formation. Conclusion Co-culture of L. sake, L. rhamnosus , and B. subtilis at a ratio of 5:5:1 could exert an antagonistic effect on the colonization of pathogenic K. pneumoniae by down-regulating the expression of biofilm-related genes. At the same time, the co-cultured probiotics could effectively inhibit the adhesion of K. pneumoniae to Caco-2 cells and block the expression of proinflammatory cytokines induced by K. pneumoniae. [ABSTRACT FROM AUTHOR]