Candida albicans is abundant in the human gut mycobiota but this species does not colonize the mouse gastrointestinal tract. C. albicans administration in dextran-sulfate solution (DSS) inducedcolitis mouse model (DSS+Candida) might resemble more to human condition, therefore, a DSS colitis model with Candida administration was studied; first, to test the influence of fungi in DSS model and second, to test the efficacy of Lactobacillus rhamnosus L34. We demonstrated serum (1→3)-β-D-glucan (BG) elevation in patients with IBD and endoscopic moderate colitis in clinical remission, supporting the possible influence of gut fungi toward IBD in human. Then, in mouse model, Candida gavage was found to worsen the DSS model indicated by higher mortality rate, more severe colon histology and enhanced gut-leakage (FITC-dextran assay, endotoxemia, serum BG and blood bacterial burdens) but did not affect weight loss and diarrhea. DSS+Candida induced higher pro-inflammatory cytokines both in blood and in intestinal tissue. Worsened systemic pro-inflammatory cytokine responses in DSS+Candida compared with DSS alone was possibly due to the more severe translocation of LPS, BG and bacteria (not fungemia) from gut into systemic circulation. Interestingly, bacteremia from Pseudomonas aeruginosa was more frequently isolated from DSS+Candida than DSS alone. In parallel, P. aeruginosa was also isolated from fecal culture in most of the mice in DSS+Candida group supported by prominent Gammaproteobacteria in fecal microbioata analysis. However, L. rhamnosus L34 attenuated both DSS+Candida and DSS model through the attenuation of gut local inflammation (cytokines and histology), gut-leakage severity, fecal dysbiosis (culture method and microbiome analysis) and systemic inflammation (serum cytokines). In conclusion, gut Candida in DSS model induced fecal bacterial dysbiosis and enhanced leaky-gut induced bacteremia. Probiotic treatment strategy aiming to reduce gut-fungi and fecal dysbiosis could attenuate disease severity. Investigation on gut fungi in patients with IBD is highly interesting.

Gastrointestinal (GI) bacterial translocation in sepsis is well known, but the role of species probiotics is still controversial. We evaluated the therapeutic effects of L34 in a new sepsis model of oral administration of pathogenic bacteria with GI leakage induced by either an antibiotic cocktail (ATB) and/or dextran sulfate sodium (DSS). GI leakage with ATB, DSS, and DSS plus ATB (DSS+ATB) was demonstrated by fluorescein isothiocyanate (FITC)-dextran translocation to the circulation. The administration of pathogenic bacteria, either or serovar Typhimurium, enhanced translocation. Bacteremia was demonstrated within 24 h in 50 to 88% of mice with GI leakage plus the administration of pathogenic bacteria but not with GI leakage induction alone or bacterial gavage alone. bacteremia was found in only 16 to 29% and 0% of mice with and administrations, respectively. bacteremia was demonstrated in 25 to 33% and 10 to 16% of mice with and administrations, respectively. L34 attenuated GI leakage in these models, as shown by the reductions of FITC-dextran gut translocation, serum interleukin-6 (IL-6) levels, bacteremia, and sepsis mortality. The reduction in the amount of fecal bacteria with treatment was demonstrated. In addition, an anti-inflammatory effect of the conditioned medium from L34 was also demonstrated by the attenuation of cytokine production in colonic epithelial cells In conclusion, L34 attenuated the severity of symptoms in a murine sepsis model induced by GI leakage and the administration of pathogenic bacteria.

Gastrointestinal (GI) leakage in Clostridium difficile-associated diarrhea (CDAD) is well known but is not routinely assessed in clinical practice. Serum (1→3)-β-D-glucan (BG), a fungal cell wall component used as a biomarker for invasive fungal disease, was tested in a CDAD mouse model with and without probiotics. Higher serum fluorescein isothiocyanate-dextran (FITC-dextran) and spontaneous gram-negative bacteremia, GI leakage indicators, were frequently found in CDAD mice, which died compared with those which survived. BG, serum macrophage inflammatory protein-2 and FITC-dextran but not quantitative blood bacterial count differentiated the clinical severity. Interestingly, a specific dose of Lactobacillus rhamnosus L34 attenuated CDAD and decreased serum BG and FITC-dextran, but not other parameters. BG also showed a higher area under the receiver operating characteristic curve for 7-day mortality than FITC-dextran. Fifty-five percent of CDAD mice with BG ≥ 60 pg/ml (the human negative cut-off value for invasive fungal disease) at 1 day after C. difficile gavage died within 7 days. In conclusion, S: erum BG was elevated in mice with severe CDAD, an established model of GI leakage with a strong association with mortality rate. BG monitoring in patients with CDAD is of interest as both a potential prognostic tool and a therapeutic efficacy indicator.

Development of an effective therapy to overcome colistin resistance in Klebsiella pneumoniae, a common pathogen causing catheter-related biofilm infections in vascular catheters, has become a serious therapeutic challenge that must be addressed urgently. Although colistin and EDTA have successful roles for eradicating biofilms, no in vitro and in vivo studies have investigated their efficacy in catheter-related biofilm infections of colistin-resistant K. pneumoniae. In this study, colistin resistance was significantly reversed in both planktonic and mature biofilms of colistin-resistant K. pneumoniae by a combination of colistin (0.25–1 µg/ml) with EDTA (12 mg/ml). This novel colistin-EDTA combination was also demonstrated to have potent efficacy in eradicating colistin-resistant K. pneumoniae catheter-related biofilm infections, and eliminating the risk of recurrence in vivo. Furthermore, this study revealed significant therapeutic efficacy of colistin-EDTA combination in reducing bacterial load in internal organs, lowering serum creatinine, and protecting treated mice from mortality. Altered in vivo expression of different virulence genes indicate bacterial adaptive responses to survive in hostile environments under different treatments. According to these data discovered in this study, a novel colistin-EDTA combination provides favorable efficacy and safety for successful eradication of colistin-resistant K. pneumonia catheter-related biofilm infections.