Toxigenic C. difficile induced inflammatory marker expression by human intestinal epithelial cells is asymmetrical

Probiotics Exhibit Strain-Specific Protective Effects in T84 Cells Challenged With Clostridioides difficile-Infected Fecal Water

Clostridioides difficile infection (CDI) is frequently associated with intestinal injury and mucosal barrier dysfunction, leading to an inflammatory response involving neutrophil localization and upregulation of pro-inflammatory cytokines. The severity of clinical manifestations is associated with the extent of the immune response, which requires mitigation for better clinical management. Probiotics could play a protective role in this disorder due to their immunomodulatory ability in gastrointestinal disorders. We assessed five single-strain and three multi-strain probiotics for their ability to modulate CDI fecal water (FW)-induced effects on T84 cells. The CDI-FW significantly (p < 0.05) decreased T84 cell viability. The CDI-FW-exposed cells also exhibited increased pro-inflammatory cytokine production as characterized by interleukin (IL)-8, C-X-C motif chemokine 5, macrophage inhibitory factor (MIF), IL-32, and tumor necrosis factor (TNF) ligand superfamily member 8. Probiotics were associated with strain-specific attenuation of the CDI-FW mediated effects, whereby Saccharomyces boulardii CNCM I-1079 and Lacticaseibacillus rhamnosus R0011 were most effective in reducing pro-inflammatory cytokine production and in increasing T84 cell viability. ProtecFlor™, Lactobacillus helveticus R0052, and Bifidobacterium longum R0175 showed moderate effectiveness, and L. rhamnosus GG R0343 along with the two other multi-strain combinations were the least effective. Overall, the findings showed that probiotic strains possess the capability to modulate the CDI-mediated inflammatory response in the gut lumen.

Clostridium difficile toxin B induces colonic inflammation through the TRIM46/DUSP1/MAPKs and NF-κB signalling pathway

Clostridium difficile (C. difficile) infection results in toxin-induced epithelial injury and marked colonic inflammation. Mitogen-activated protein kinase (MAPK) and NF-κB which regulated by MAP kinase phosphatase (MKP, also known as dual specificity phosphatases, DUSP) are fundamental signalling pathways that mediate multiple cellular processes. However, the regulation of DUSP/MAPKs and NF-κB pathway in C. difficile-induced colonic inflammation remains unclear. Here, we report that TcdB significantly inhibits cell viability and induces production of IL-1β and TNF-α and activation of MAPKs and NF-κB. An E3-ubiquitin ligase, TRIM46, ubiquitinates DUSP1, and its knockdown significantly inhibit TcdB-induced activation of MAPKs and NF-κB and production of IL-1β and TNF-α. Moreover, TRIM46 overexpression induced production of IL-1β and TNF-α also reversed by DUSP1 overexpression. We further found that promoter of TRIM46 also demonstrated binding to NF-κBp65, leading to regulate TRIM46 expression. In addition, the increased colonic inflammation induced by C. difficile administration was inhibited by TRIM46 knockdown in vivo. Taken together, the present study shows that TRIM46, as a new regulator of DUSP1/MAPKs and NF-κB signalling pathway, plays an important role in TcdB-induced colonic inflammation.

Clostridioides difficile associated peritonitis in peritoneal dialysis patients - a case series based review of an under-recognized entity with therapeutic challenges

BACKGROUND

Initial presentation of peritoneal dialysis associated infectious peritonitis can be clinically indistinguishable from Clostridioides difficile infection (CDI) and both may demonstrate a cloudy dialysate. Empiric treatment of the former entails use of 3rd-generation cephalosporins, which could worsen CDI. We present a logical management approach of this clinical scenario providing examples of two cases with CDI associated peritonitis of varying severity where the initial picture was concerning for peritonitis and treatment for CDI resulted in successful cure.

CASE PRESENTATION

A 73-year-old male with ESRD managed with PD presented with fever, abdominal pain, leukocytosis and significant diarrhea. Cell count of the peritoneal dialysis effluent revealed 1050 WBCs/mm3 with 71% neutrophils. C. difficile PCR on the stool was positive. Patient was started on intra-peritoneal (IP) cefepime and vancomycin for treatment of the peritonitis and intravenous (IV) metronidazole and oral vancomycin for treatment of the C. difficile colitis but worsened. PD fluid culture showed no growth. He responded well to IV tigecycline, oral vancomycin and vancomycin enemas. Similarly, a 55-year-old male with ESRD with PD developed acute diarrhea and on the third day noted a cloudy effluent from his dialysis catheter. PD fluid analysis showed 1450 WBCs/mm3 with 49% neutrophils. IP cefepime and vancomycin were initiated. CT of the abdomen showed rectosigmoid colitis. C. difficile PCR on the stool was positive. IP cefepime and vancomycin were promptly discontinued. Treatment with oral vancomycin 125 mg every six hours and IV Tigecycline was initiated. PD fluid culture produced no growth. PD catheter was retained.

CONCLUSIONS

In patients presenting with diarrhea with risk factors for CDI, traditional empiric treatment of PD peritonitis may need to be reexamined as they could have detrimental effects on CDI course and patient outcomes.

Clostridium difficile-derived membrane vesicles induce the expression of pro-inflammatory cytokine genes and cytotoxicity in colonic epithelial cells in vitro

Clostridium difficile is the most common etiological agent of antibiotic-associated diarrhea in hospitalized and non-hospitalized patients. This study investigated the secretion of membrane vesicles (MVs) from C. difficile and determined the expression of pro-inflammatory cytokine genes and cytotoxicity of C. difficile MVs in epithelial cells in vitro. C. difficile ATCC 43255 and two clinical isolates secreted spherical MVs during in vitro culture. Proteomic analysis revealed that MVs of C. difficile ATCC 43255 contained a total of 262 proteins. Translation-associated proteins were the most commonly identified in C. difficile MVs, whereas TcdA and TcdB toxins were not detected. C. difficile ATCC 43255-derived MVs stimulated the expression of pro-inflammatory cytokine genes, including interleukin (IL)-1β, IL-6, IL-8, and monocyte chemoattractant protein-1 in human colorectal epithelial Caco-2 cells. Moreover, these extracellular vesicles induced cytotoxicity in Caco-2 cells. In conclusion, C. difficile MVs are important nanocomplexes that elicit a pro-inflammatory response and induce cytotoxicity in colonic epithelial cells, which may contribute, along with toxins, to intestinal mucosal injury during C. difficile infection.

Beneficial effect of oral tigecycline treatment on Clostridium difficile infection in gnotobiotic piglets

The efficacy of oral tigecycline treatment (2 mg/kg of body weight for 7 days) of Clostridium difficile infection (CDI) was evaluated in the gnotobiotic pig model, and its effect on human gut microflora transplanted into the gnotobiotic pig was determined. Tigecycline oral treatment improved survival, clinical signs, and lesion severity and markedly decreased concentrations of Firmicutes but did not promote CDI. Our data showed that oral tigecycline treatment has a potential beneficial effect on the treatment of CDI.

Induction of cytokines in a macrophage cell line by proteins of Clostridium difficile

Clostridium difficile is a major cause of nosocomial diarrhoea. The toxins produced by C. difficile are responsible for the characteristic pathology observed in C. difficile disease, but several surface-associated proteins of C. difficile are also recognized by the immune system and could modulate the immune response in infection. The aim of this study was to assess the induction of cytokines in a macrophage cell line in response to different antigens prepared from five C. difficile strains: the hypervirulent ribotype 027, ribotypes 001 and 106 and reference strains VPI 10463 and 630 (ribotype 012). PMA-activated THP-1 cells were challenged with surface-layer proteins, flagella, heat-shock proteins induced at 42 and 60 °C and culture supernatants of the five C. difficile strains. The production of the pro-inflammatory cytokines such as TNF-α, IL-1β, IL-6, IL-8 and IL-12p70 was observed in response to the surface-associated proteins, and high levels of TNF-α, IL-1β and IL-8 were detected in response to challenge with culture supernatants. The immune response triggered by the surface-associated proteins was independent of the strain from which the antigens were derived, suggesting that these proteins might not be related to the varying virulence of the hypervirulent ribotype 027 or ribotypes 001 and 106. There was no interstrain difference observed in response to the culture supernatants of the tested C. difficile strains, but this was perhaps due to toxicity induced in the macrophages by large amounts of toxin A and toxin B.

Clostridium difficile toxin-induced inflammation and intestinal injury are mediated by the inflammasome

BACKGROUND & AIMS

Clostridium difficile-associated disease (CDAD) is the leading cause of nosocomial diarrhea in the United States. C difficile toxins TcdA and TcdB breach the intestinal barrier and trigger mucosal inflammation and intestinal damage. The inflammasome is an intracellular danger sensor of the innate immune system. In the present study, we hypothesize that TcdA and TcdB trigger inflammasome-dependent interleukin (IL)-1beta production, which contributes to the pathogenesis of CDAD.

METHODS

Macrophages exposed to TcdA and TcdB were assessed for IL-1beta production, an indication of inflammasome activation. Macrophages deficient in components of the inflammasome were also assessed. Truncated/mutated forms of TcdB were assessed for their ability to activate the inflammasome. The role of inflammasome signaling in vivo was assessed in ASC-deficient and IL-1 receptor antagonist-treated mice.

RESULTS

TcdA and TcdB triggered inflammasome activation and IL-1beta secretion in macrophages and human mucosal biopsy specimens. Deletion of Nlrp3 decreased, whereas deletion of ASC completely abolished, toxin-induced IL-1beta release. TcdB-induced IL-1beta release required recognition of the full-length toxin but not its enzymatic function. In vivo, deletion of ASC significantly reduced toxin-induced inflammation and damage, an effect that was mimicked by pretreatment with the IL-1 receptor antagonist anakinra.

CONCLUSIONS

TcdA and TcdB trigger IL-1beta release by activating an ASC-containing inflammasome, a response that contributes to toxin-induced inflammation and damage in vivo. Pretreating mice with the IL-1 receptor antagonist anakinra afforded the same level of protection that was observed in ASC-/- mice. These data suggest that targeting inflammasome or IL-1beta signaling may represent new therapeutic targets in the treatment of CDAD.

The enterotoxicity of Clostridium difficile toxins

The major virulence factors of Clostridium difficile infection (CDI) are two large exotoxins A (TcdA) and B (TcdB). However, our understanding of the specific roles of these toxins in CDI is still evolving. It is now accepted that both toxins are enterotoxic and proinflammatory in the human intestine. Both purified TcdA and TcdB are capable of inducing the pathophysiology of CDI, although most studies have focused on TcdA. C. difficile toxins exert a wide array of biological activities by acting directly on intestinal epithelial cells. Alternatively, the toxins may target immune cells and neurons once the intestinal epithelial barrier is disrupted. The toxins may also act indirectly by stimulating cells to produce chemokines, proinflammatory cytokines, neuropeptides and other neuroimmune signals. This review considers the mechanisms of TcdA- and TcdB-induced enterotoxicity, and recent developments in this field.

Hypoxia-inducible factor signaling provides protection in Clostridium difficile-induced intestinal injury

BACKGROUND & AIMS

Clostridium difficile is the leading cause of nosocomial infectious diarrhea. Antibiotic resistance and increased virulence of strains have increased the number of C difficile-related deaths worldwide. The innate host response mechanisms to C difficile are not resolved; we propose that hypoxia-inducible factor (HIF-1) has an innate, protective role in C difficile colitis. We studied the impact of C difficile toxins on the regulation of HIF-1 and evaluated the role of HIF-1alpha in C difficile-mediated injury/inflammation.

METHODS

We assessed HIF-1alpha mRNA and protein levels and DNA binding in human mucosal biopsy samples and Caco-2 cells following exposure to C difficile toxins. We used the mouse ileal loop model of C difficile toxin-induced intestinal injury. Mice with targeted deletion of HIF-1alpha in the intestinal epithelium were used to assess the effects of HIF-1alpha signaling in response to C difficile toxin.

RESULTS

Mucosal biopsy specimens and Caco-2 cells exposed to C difficile toxin had a significant increase in HIF-1alpha transcription and protein levels. Toxin-induced DNA binding was also observed in Caco-2 cells. Toxin-induced HIF-1alpha accumulation was attenuated by nitric oxide synthase inhibitors. In vivo deletion of intestinal epithelial HIF-1alpha resulted in more severe, toxin-induced intestinal injury and inflammation. In contrast, stabilization of HIF-1alpha with dimethyloxallyl glycine attenuated toxin-induced injury and inflammation. This was associated with induction of HIF-1-regulated protective factors (such as vascular endothelial growth factor-alpha, CD73, and intestinal trefoil factor) and down-regulation of proinflammatory molecules such as tumor necrosis factor and Cxcl1.

CONCLUSIONS

HIF-1alpha protects the intestinal mucosa from C difficile toxins. The innate protective actions of HIF-1alpha in response to C difficile toxins be developed as therapeutics for C difficile-associated disease.

Piglet models of acute or chronic Clostridium difficile illness

We examined the piglet model of Clostridium difficile illness (CDI) in humans, because swine are naturally susceptible to C. difficile. The piglet is a reproducible model of acute or chronic CDI with characteristic pseudomembranous colitis. Germ-free piglets were consistently and extensively colonized after oral challenge with the human strain 027/BI/NAP1, establishing an infectious dose-age relationship. This allowed a demarcation between acute fatal and chronic models. The clinical manifestations of disease inclusive of gastrointestinal and systemic symptoms and characteristic mucosal lesions of the large bowel (including pseudomembranous colitis) are described. Additionally, we demonstrate the presence of toxins in feces, body fluids, and serum and a significant elevation in interleukin 8 levels in animals with severe disease. We conclude that piglets infected with C. difficile mimic many of the key characteristics observed in humans with CDI and are suitable animals in which to investigate the role played by virulence attributes, drug efficacy, and vaccine candidates.

Human intestinal epithelial response(s) to Clostridium difficile

Clostridium difficile is a gram-positive, spore-forming, toxin-producing anaerobic bacillus that is being increasingly implicated as the leading cause of diarrhea and colitis, particularly in hospitalized, elderly patients. Studies to date suggest that C. difficile toxins A and B play a major role in the observed colonic inflammation and associated disease pathogenesis; however, the role of other potential bacterial factors at present remains unknown. Early effects of C. difficile on host intestinal epithelia include modest induction of innate immune responses with progressive loss of intestinal epithelial cell barrier function and cell death.

Modulation of pathogen-induced CCL20 secretion from HT-29 human intestinal epithelial cells by commensal bacteria

Background

Human intestinal epithelial cells (IECs) secrete the chemokine CCL20 in response to infection by various enteropathogenic bacteria or exposure to bacterial flagellin. CCL20 recruits immature dendritic cells and lymphocytes to target sites. Here we investigated IEC responses to various pathogenic and commensal bacteria as well as the modulatory effects of commensal bacteria on pathogen-induced CCL20 secretion. HT-29 human IECs were incubated with commensal bacteria (Bifidobacterium infantis or Lactobacillus salivarius), or with Salmonella typhimurium, its flagellin, Clostridium difficile, Mycobacterium paratuberculosis, or Mycobacterium smegmatis for varying times. In some studies, HT-29 cells were pre-treated with a commensal strain for 2 hr prior to infection or flagellin stimulation. CCL20 and interleukin (IL)-8 secretion and nuclear factor (NF)-κB activation were measured using enzyme-linked immunosorbent assays.

Results

Compared to untreated cells, S. typhimurium, C. difficile, M. paratuberculosis, and flagellin activated NF-κB and stimulated significant secretion of CCL20 and IL-8 by HT-29 cells. Conversely, B. infantis, L. salivarius or M. smegmatis did not activate NF-κB or augment CCL20 or IL-8 production. Treatment with B. infantis, but not L. salivarius, dose-dependently inhibited the baseline secretion of CCL20. In cells pre-treated with B. infantis, C. difficile-, S. typhimurium-, and flagellin-induced CCL20 were significantly attenuated. B. infantis did not limit M. Paratuberculosis-induced CCL20 secretion.

Conclusion

This study is the first to demonstrate that a commensal strain can attenuate CCL20 secretion in HT-29 IECs. Collectively, the data indicate that M. paratuberculosis may mediate mucosal damage and that B. infantis can exert immunomodulatory effects on IECs that mediate host responses to flagellin and flagellated enteric pathogens.

Peripartum Clostridium difficile infection: case series and review of the literature

Clostridium difficile infection (CDI) in nonhospitalized patients has been reported with increased frequency. An association between CDI and pregnancy has not been stressed. This review will report 4 cases of peripartum CDI with characterization of the infecting strain and a literature review. A PubMed search identified 24 recorded cases of peripartum CDI; information was available for 14 cases. Most patients (91%) received prophylactic antibiotics during delivery or for treatment of bacterial infections (50%). All patients reported diarrhea. Two of our reported cases without known risk factors were found by polymerase chain reaction analysis to be infected with an epidemic and hypervirulent C difficile strain. These cases demonstrate the need for clinicians to consider CDI in patients with severe diarrhea, even if they do not have the traditional risk factors for CDI, such as antibiotic use or concurrent hospitalizations. Further research into the scope and risk factors for peripartum CDI is warranted.

Epidemiology, pathogenesis, and management of Clostridium difficile infection

Clostridium difficile infection is an important health problem worldwide and leads to increased morbidity and mortality, particularly among the elderly population. Antibiotics, especially those with a broad spectrum, often trigger the infection; hence the use of unnecessary antibiotics should be avoided. Mild to moderate cases respond to metronidazole or vancomycin. Severe cases may require bowel resection. Chronic relapsing cases require a prolonged course of antibiotics, immunoglobulin, probiotics, and, occasionally, feces enema. This review provides a comprehensive update on pathogenesis and management of Clostridium difficile infection for health professionals all over the world.

Tumour necrosis factor-α (TNF-α) increases nuclear factor κB (NFκB) activity in and interleukin-8 (IL-8) release from bovine mammary epithelial cells

Epithelia play important immunological roles at a variety of mucosal sites. We examined NFkappaB activity in control and TNF-alpha treated bovine mammary epithelial monolayers (BME-UV cells). A region of the bovine IL-8 (bIL-8) promoter was sequenced and a putative kappaB consensus sequence was identified bioinformatically. We used this sequence to analyse nuclear extracts for IL-8 specific NFkappaB activity. As a surrogate marker of NFkappaB activation, we investigated IL-8 release in two models. Firstly in BME-UV monolayers, IL-8 release in the presence of pro- and anti-inflammatory agents was determined by enzyme-linked immunosorbent assay (ELISA). Secondly, we measured IL-8 secretion from a novel model of intact mucosal sheets of bovine teat sinus. IL-8 release into bathing solutions was assessed following treatment with pro- and anti-inflammatory agents. TNF-alpha enhanced NFkappaB activity in bovine mammary epithelial monolayers. p65 NFkappaB homodimer was identified in both control and TNF-alpha treated cells. Novel sequencing of the bovine IL-8 promoter identified a putative kappaB consensus sequence, which specifically bound TNF-alpha inducible p50/p65 heterodimer. TNF-alpha induced primarily serosal IL-8 release in the cell culture model. Pre-treatment with anti-TNF or dexamethasone inhibited TNF-alpha induced IL-8 release. High dose interleukin-1beta (IL-1beta) induced IL-8 release, however significantly less potently than TNF-alpha. Bovine mammary mucosal tissue released high basal levels of IL-8 which were unaffected by TNF-alpha or IL-1beta but inhibited by both dexamethasone and anti-TNF. These data support a role for TNF-alpha in activation of NFkappaB and release of IL-8 from bovine mammary epithelial cells.