Novel approaches to treating Clostridium difficile-associated colitis

Application of recombinant antibodies for treatment of Clostridioides difficile infection: Current status and future perspective

Clostridioides difficile (C. difficile), known as the major cause of antibiotic-associated diarrhea, is regarded as one of the most common healthcare-associated bacterial infections worldwide. Due to the emergence of hypervirulent strains, development of new therapeutic methods for C. difficile infection (CDI) has become crucially important. In this context, antibodies have been introduced as valuable tools in the research and clinical environments, as far as the effectiveness of antibody therapy for CDI was reported in several clinical investigations. Hence, production of high-performance antibodies for treatment of CDI would be precious. Traditional approaches of antibody generation are based on hybridoma technology. Today, application of in vitro technologies for generating recombinant antibodies, like phage display, is considered as an appropriate alternative to hybridoma technology. These techniques can circumvent the limitations of the immune system and they can be exploited for production of antibodies against different types of biomolecules in particular active toxins. Additionally, DNA encoding antibodies is directly accessible in in vitro technologies, which enables the application of antibody engineering in order to increase their sensitivity and specificity. Here, we review the application of antibodies for CDI treatment with an emphasis on recombinant fragment antibodies. Also, this review highlights the current and future prospects of the aforementioned approaches for antibody-mediated therapy of CDI.

Binding and neutralization of C. difficile toxins A and B by purified clinoptilolite-tuff

Clostridioides difficile (C. difficile) infection is a major public health problem worldwide. The current treatment of C. difficile-associated diarrhea relies on the use of antibacterial agents. However, recurrences are frequent. The main virulence factors of C. difficile are two secreted cytotoxic proteins toxin A and toxin B. Alternative research exploring toxin binding by resins found a reduced rate of recurrence by administration of tolevamer. Hence, binding of exotoxins may be useful in preventing a relapse provided that the adsorbent is innocuous. Here, we examined the toxin binding capacity of G-PUR®, a purified version of natural clinoptilolite-tuff. Our observations showed that the purified clinoptilolite-tuff adsorbed clinically relevant amounts of C. difficile toxins A and B in vitro and neutralized their action in a Caco-2 intestinal model. This conclusion is based on four independent sets of findings: G-PUR® abrogated toxin-induced (i) RAC1 glucosylation, (ii) redistribution of occludin, (iii) rarefaction of the brush border as visualized by scanning electron microscopy and (iv) breakdown of the epithelial barrier recorded by transepithelial electrical resistance monitoring. Finally, we confirmed that the epithelial monolayer tolerated G-PUR® over a wide range of particle densities. Our findings justify the further exploration of purified clinoptilolite-tuff as a safe agent in the treatment and/or prevention of C. difficile-associated diarrhea.

Structure and Function of Bovine Whey Derived Oligosaccharides Showing Synbiotic Epithelial Barrier Protective Properties

Commensal gut microbiota and probiotics have numerous effects on the host’s metabolic and protective systems, which occur primarily through the intestinal epithelial cell interface. Prebiotics, like galacto-oligosaccharides (GOS) are widely used to modulate their function and abundance. However, important structure–function relations may exist, requiring a detailed structural characterization. Here, we detailed the structural characterization of bovine whey derived oligosaccharide preparations enriched with GOS or not, dubbed GOS-enriched milk oligosaccharides (GMOS) or MOS, respectively. We explore GMOS’s and MOS’s potential to improve intestinal epithelial barrier function, assessed in a model based on barrier disruptive effects of the Clostridioides difficile toxin A. GMOS and MOS contain mainly GOS species composed of β1-6- and β1-3-linked galactoses, and 3′- and 6′-sialyllactose. Both GMOS and MOS, combined with lactobacilli, like Lactobacillus rhamnosus (LPR, NCC4007), gave synergistic epithelial barrier protection, while no such effect was observed with Bifidobacterium longum (BL NCC3001), Escherichia coli (Nissle) or fructo-oligosaccharides. Mechanistically, for barrier protection with MOS, (i) viable LPR was required, (ii) acidification of growth medium was not enough, (iii) LPR did not directly neutralize toxin A, and (iv) physical proximity of LPR with the intestinal epithelial cells was necessary. This is the first study, highlighting the importance of structure–function specificity and the necessity of the simultaneous presence of prebiotic, probiotic and host cell interactions required for a biological effect.

In Vitro Bactericidal Effects of Photodynamic Therapy Combined with Four Tetracyclines against Clostridioides difficile KCTC5009 in Planktonic Cultures

Surface disinfection in health-care facilities is critical to prevent dissemination of Clostridioides difficile (C. difficile). Tetracyclines (TCs) are broad-spectrum antibiotics that are associated with a low risk of development of C. difficile infection (CDI) and are used as photosensitizers (PS) in photodynamic therapy (PDT). We evaluated whether TCs may be useful environmental cleansing agents. We compared the in vitro ability to kill C. difficile of four TCs (TC, doxycycline, minocycline, and tigecycline) combined with PDT using ultraviolet A (UVA). We included chitosan, a cationic material, as a booster to increase the photodynamic bactericidal efficacy of TCs. PDT-induced bactericidal effects were assessed by the number of viable cells and the degree of DNA damage and membrane integrity. To avoid the intrinsic antibacterial activity of TCs at high concentrations, we used low concentrations of TCs (0.05 and 0.1 mg/mL). The bactericidal effect of treatment with chitosan plus PDT was over 100 times higher than that with PDT alone for each of the four TCs. DNA damage measured by ethidium bromide monoazide and real-time quantitative polymerase chain reaction was also greater for PDT plus chitosan treatment than for PDT alone or under control conditions: the threshold cycle (Ct) values for the control, PDT, and PDT plus chitosan were 14.67 ± 0.22, 20.46 ± 0.12, and 25.54 ± 0.17, respectively. All four TCs caused similar levels of severe cell membrane damage during PDT compared with control conditions. These data suggest that PDT combined with any of the four TCs plus chitosan might be an available tool to kill efficiently planktonic form of C. difficile.

Intraluminal Administration of Resiniferatoxin Protects against Clostridium difficile Toxin A-Induced Colitis

Clostridium difficile toxin A is a colonic inflammatory agent that acts partially by activation of TRPV1 (transient receptor potential vanilloid type 1). Resiniferatoxin (RTX) is an excitotoxin that activates TRPV1 at low concentrations and defunctionalizes TRPV1 at high concentrations. RTX at various doses was injected intraluminally into isolated ileal segments in anesthetized rats. After 3 hours, the treated segments were removed and inflammation was assessed. This acute treatment with RTX resulted in biphasic responses: (1) an increase in inflammation similar to that caused by toxin A and capsaicin at low doses of up to 100 ng RTX and (2) no inflammatory effect of RTX at higher doses (1–100 μg), consistent with a defunctionalizing or neurotoxic effect of RTX at high doses. Separately, anesthetized rats were treated with RTX enemas and one or four weeks later were challenged with toxin A. Toxin A-induced colitis was significantly inhibited one week after an RTX enema, and this effect was RTX dose dependent. When tested four weeks after administration of the RTX enema, protection against toxin A colitis was lost. In conclusion, an RTX enema protects against toxin A-induced colitis in rats for at least one week but less than four weeks.

Influence of diet on the gut microbiome and implications for human health

Recent studies have suggested that the intestinal microbiome plays an important role in modulating risk of several chronic diseases, including inflammatory bowel disease, obesity, type 2 diabetes, cardiovascular disease, and cancer. At the same time, it is now understood that diet plays a significant role in shaping the microbiome, with experiments showing that dietary alterations can induce large, temporary microbial shifts within 24 h. Given this association, there may be significant therapeutic utility in altering microbial composition through diet. This review systematically evaluates current data regarding the effects of several common dietary components on intestinal microbiota. We show that consumption of particular types of food produces predictable shifts in existing host bacterial genera. Furthermore, the identity of these bacteria affects host immune and metabolic parameters, with broad implications for human health. Familiarity with these associations will be of tremendous use to the practitioner as well as the patient.