New and emerging therapies for Clostridium difficile infection

Probiotics for Prevention and Treatment of Clostridium difficile Infection

Probiotics have been claimed as a valuable tool to restore the balance in the intestinal microbiota following a dysbiosis caused by, among other factors, antibiotic therapy. This perturbed environment could favor the overgrowth of Clostridium difficile, and in fact, the occurrence of C. difficile-associated infections (CDI) is increasing in recent years. In spite of the high number of probiotics able to in vitro inhibit the growth and/or toxicity of this pathogen, its application for treatment or prevention of CDI is still scarce since there are not enough well-defined clinical studies supporting efficacy. Only a few strains, such as Lactobacillus rhamnosus GG and Saccharomyces boulardii, have been studied in more extent. The increasing knowledge about the probiotic mechanisms of action against C. difficile, some of them reviewed here, makes promising the application of these live biotherapeutic agents against CDI. Nevertheless, more effort must be paid to standardize the clinical studies conducted to evaluate probiotic products, in combination with antibiotics, in order to select the best candidate for C. difficile infections.

Curcumin and capsaicin regulate apoptosis and alleviate intestinal inflammation induced by Clostridioides difficile in vitro

Background

The dramatic upsurge of Clostridioides difficile infection (CDI) by hypervirulent isolates along with the paucity of effective conventional treatment call for the development of new alternative medicines against CDI. The inhibitory effects of curcumin (CCM) and capsaicin (CAP) were investigated on the activity of toxigenic cell-free supernatants (Tox-S) of C. difficile RT 001, RT 126 and RT 084, and culture-filtrate of C. difficile ATCC 700057.

Methods

Cell viability of HT-29 cells exposed to varying concentrations of CCM, CAP, C. difficile Tox-S and culture-filtrate was assessed by MTT assay. Anti-inflammatory and anti-apoptotic effects of CCM and CAP were examined by treatment of HT-29 cells with C. difficile Tox-S and culture-filtrate. Expression of BCL-2, SMAD3, NF-κB, TGF-β and TNF-α genes in stimulated HT-29 cells was measured using RT-qPCR.

Results

C. difficile Tox-S significantly (P < 0.05) reduced the cell viability of HT-29 cells in comparison with untreated cells. Both CAP and CCM significantly (P < 0.05) downregulated the gene expression level of BCL-2, SMAD3, NF-κB and TNF-α in Tox-S treated HT-29 cells. Moreover, the gene expression of TGF-β decreased in Tox-S stimulated HT-29 cells by both CAP and CCM, although these reductions were not significantly different (P > 0.05).

Conclusion

The results of the present study highlighted that CCM and CAP can modulate the inflammatory response and apoptotic effects induced by Tox-S from different clinical C. difficile strains in vitro. Further studies are required to accurately explore the anti-toxin activity of natural components, and their probable adverse risks in clinical practice.

Risk Factors, Diagnosis, and Management of Clostridioides difficile Infection in Patients with Inflammatory Bowel Disease

Clostridioides difficile infection (CDI) and inflammatory bowel disease (IBD) are two pathologies that share a bidirectional causal nexus, as CDI is known to have an aggravating effect on IBD and IBD is a known risk factor for CDI. The colonic involvement in IBD not only renders the host more prone to an initial CDI development but also to further recurrences. Furthermore, IBD flares, which are predominantly set off by a CDI, not only create a need for therapy escalation but also prolong hospital stay. For these reasons, adequate and comprehensive management of CDI is of paramount importance in patients with IBD. Microbiological diagnosis, correct evaluation of clinical status, and consideration of different treatment options (from antibiotics and fecal microbiota transplantation to monoclonal antibodies) carry pivotal importance. Thus, the aim of this article is to review the risk factors, diagnosis, and management of CDI in patients with IBD.

Effect of prebiotics on Bacteroides sp. adhesion and biofilm formation and synbiotic effect on Clostridioides difficile

Aim: The objective of this study was to determine the effect of standard and candidate prebiotics on the adhesion and biofilm formation of Bacteroides sp. in monoculture and co-culture with Clostridioides difficile. Materials & methods: The effect of seven prebiotics on the adhesion and biofilm formation of Bacteroides sp. to three human cell lines was determined. The effect of Bacteroides sp. and fructooligosaccharides (FOS) on the adhesion and biofilm formation of C. difficile was tested by the co-incubation assay. Results: Inulin, mannose and raffinose presented the best anti-adhesion properties against Bacteroides sp. Combination of Bacteroides sp. with FOS decreased the adhesion of C. difficile. Conclusion: The study shows the potential role of prebiotics and synbiotics in decreasing the burden of C. difficile infections.

Microbiota-based Therapies Clostridioides difficile infection that is refractory to antibiotic therapy

Clostridioides difficile infection (CDI) has had a devastating impact worldwide with significant rates of mortality, especially among the elderly. Despite effective antibiotics, the incidence of recurrent CDI (rCDI) is increasing and more difficult to treat with antibiotics alone. Fecal Microbiota Transplantation (FMT) has emerged as a consistently effective treatment for rCDI. Mechanisms for FMT are not entirely understood, but remain an area of active investigation. There have been recent safety reports with the use of FMT regarding transmission of pathogens in a few patients that have led to serious illness. With appropriate screening, FMT can be safely administered and continue to have a significant impact on eradication of rCDI and improve the lives of patients suffering from this disease. In this review, we summarize current treatments for CDI with a focus on microbiota-based therapies used for antibiotic refractory disease.

Targeting ectonucleotidases to treat inflammation and halt cancer development in the gut

CD39 and CD73 control cell immunity by hydrolyzing proinflammatory ATP and ADP (CD39) into AMP, subsequently converted into anti-inflammatory adenosine (CD73). By regulating the balance between effector and regulatory cells, these ectonucleotidases promote immune homeostasis in acute and chronic inflammation; while also appearing to limit antitumor effector immunity in gut cancer. This manuscript focuses on the pivotal role of CD39 and CD73 ectonucleotidase function in shaping immune responses in the gut. We focus on those mechanisms deployed by these critical and pivotal ectoenzymes and the regulation in the setting of gastrointestinal tract infections, inflammatory bowel disease and tumors of the gastrointestinal tract. We will highlight translational and clinical implications of the latest and most innovative basic research discoveries of these important players of the purinergic signaling. Immunotherapeutic strategies that have been developed to either boost or control ectonucleotidase expression and activity in important disease settings are also reviewed and the in vivo effects discussed.

Risk Factors for Primary Clostridium difficile Infection; Results From the Observational Study of Risk Factors for Clostridium difficile Infection in Hospitalized Patients With Infective Diarrhea (ORCHID)

Background: There are inconsistent data on the risk factors for Clostridium difficile infection (CDI) in the literature.

Aims: To use two C. difficile infection (CDI) case-control study groups to compare risk factors in hospitalized patients with diarrhea across different countries.

Methods: A multi-center group of CDI cases/controls were identified by standardized testing from seven countries from the prior EUropean, multi-center, prospective bi-annual point prevalence study of CLostridium difficile Infection in hospitalized patients with Diarrhea (EUCLID). A second group of CDI cases/controls was identified from a single center in Germany [parallel study site (PSS)]. Data were extracted from the medical notes to assess CDI risk factors. Univariate analyses and multivariate logistic regression models were used to identify and compare risk factors between the two groups.

Results: There were 253 and 158 cases and 921 and 584 controls in the PSS and EUCLID groups, respectively. Significant variables from univariate analyses in both groups were age ≥65, number of antibiotics (OR 1.2 for each additional antibiotic) and prior hospital admission (all p < 0.001). Congestive heart failure, diabetes, admission from assisted living or Emergency Department, proton pump inhibitors, and chronic renal disease were significant in PSS (all p < 0.05) but not EUCLID. Dementia and admitted with other bacterial diseases were significant in EUCLID (p < 0.05) but not PSS. Following multivariate analyses, age ≥ 65, number of antibiotics and prior hospital admission were consistently identified as CDI risk factors in each individual group and combined datasets.

Conclusion: Our results show that the same CDI risk factors were identified across datasets. These were age ≥ 65 years, antibiotic use and prior hospital admission. Importantly, the odds of developing CDI increases with each extra antibiotic prescribed.

Insights into the Role of Human Gut Microbiota in Clostridioides difficile Infection

Clostridioides difficile infection (CDI) has emerged as a major health problem worldwide. A major risk factor for disease development is prior antibiotic use, which disrupts the normal gut microbiota by altering its composition and the gut’s metabolic functions, leading to the loss of colonization resistance and subsequent CDI. Data from human studies have shown that the presence of C. difficile, either as a colonizer or as a pathogen, is associated with a decreased level of gut microbiota diversity. The investigation of the gut’s microbial communities, in both healthy subjects and patients with CDI, elucidate the role of microbiota and improve the current biotherapeutics for patients with CDI. Fecal microbiota transplantation has a major role in managing CDI, aiming at re-establishing colonization resistance in the host gastrointestinal tract by replenishing the gut microbiota. New techniques, such as post-genomics, proteomics and metabolomics analyses, can possibly determine in the future the way in which C. difficile eradicates colonization resistance, paving the way for the development of new, more successful treatments and prevention. The aim of the present review is to present recent data concerning the human gut microbiota with a focus on its important role in health and disease.

Risk for Clostridiodes difficile Infection among Older Adults with Cancer

To assess whether risk for Clostridiodes difficile infection (CDI) is higher among older adults with cancer, we conducted a retrospective cohort study with a nested case-control analysis using population-based Surveillance, Epidemiology, and End Results-Medicare linked data for 2011. Among 93,566 Medicare beneficiaries, incident CDI and odds for acquiring CDI were higher among patients with than without cancer. Specifically, risk was significantly higher for those who had liquid tumors and higher for those who had recently diagnosed solid tumors and distant metastasis. These findings were independent of prior healthcare-associated exposure. This population-based assessment can be used to identify targets for prevention of CDI.

Multiple-Ascending-Dose Phase 1 Clinical Study of the Safety, Tolerability, and Pharmacokinetics of CRS3123, a Narrow-Spectrum Agent with Minimal Disruption of Normal Gut Microbiota

CRS3123 is a novel small molecule that potently inhibits methionyl-tRNA synthetase of Clostridioides difficile, inhibiting C. difficile toxin production and spore formation. CRS3123 has been evaluated in a multiple-ascending-dose placebo-controlled phase 1 trial. Thirty healthy subjects, ages 18 to 45 years, were randomized into three cohorts of 10 subjects each, receiving either 200, 400, or 600 mg of CRS3123 (8 subjects per cohort) or placebo (2 subjects per cohort) by oral administration twice daily for 10 days. CRS3123 was generally safe and well tolerated, with no serious adverse events (SAEs) or severe treatment-emergent adverse events (TEAEs) reported. All subjects completed their assigned treatment and follow-up visits, and there were no trends in systemic, vital sign, or laboratory TEAEs. There were no QTcF interval changes or any clinically significant changes in other electrocardiogram (ECG) intervals or morphology. CRS3123 showed limited but detectable systemic uptake; although absorption increased with increasing dose, the increase was less than dose proportional. Importantly, the bulk of the oral dose was not absorbed, and fecal concentrations were substantially above the MIC90 value of 1 μg/ml at all dosages tested. Subjects receiving either of the two lower doses of CRS3123 exhibited minimal disruption of normal gut microbiota after 10 days of twice-daily dosing. CRS3123 was inactive against important commensal anaerobes, including Bacteroides, bifidobacteria, and commensal clostridia. Microbiome data showed favorable differentiation compared to other CDI therapeutics. These results support further development of CRS3123 as an oral agent for the treatment of CDI. (This study has been registered at Clinicaltrials.gov under identifier NCT02106338.).

Metagenomic and culturomic analysis of gut microbiota dysbiosis during Clostridium difficile infection

Recently, cocktail of bacteria were proposed in order to treat Clostridium difficile infection (CDI), but these bacteriotherapies were selected more by chance than experimentation. We propose to comprehensively explore the gut microbiota of patients with CDI compared to healthy donors in order to propose a consortium of bacteria for treating C. difficile. We compared stool samples composition from 11 CDI patients and 8 healthy donors using two techniques: metagenomics, 16S V3-V4 region amplification and sequencing and culturomics, high throughout culture using six culture conditions and MALDI-TOF identification. By culturomics, we detected 170 different species in the CDI group and 275 in the control group. Bacteroidetes were significantly underrepresented in the CDI group (p = 0.007). By metagenomics, 452 different operational taxonomic units assigned to the species level were detected in the CDI group compared to 522 in the control group. By these two techniques, we selected 37 bacteria only found in control group in more than 75% of the samples and/or with high relative abundance, 10 of which have already been tested in published bacteriotherapies against CDI, and 3 of which (Bifidobacterium adolescentis, Bifidobacterium longum and Bacteroides ovatus) have been detected by these two techniques. This controlled number of bacteria could be administrated orally in a non-invasive way in order to treat CDI.

Predictors and burden of hospital readmission with recurrent Clostridioides difficile infection: a French nation-wide inception cohort study

To investigate the predictors and burden of hospital readmission with recurrent Clostridioides difficile infection (rCDI) in a large European healthcare system with a low prevalence of hyper-virulent C. difficile clones. We conducted an inception cohort study based on an exhaustive health insurance database and including all survivors of a first hospital stay with CDI over a one-year period (2015) in France. Readmissions with rCDI were defined as a novel hospital stay with CDI within 12 weeks following discharge of the index hospitalization. Risk factors for readmission with rCDI were investigated through multivariate logistic regression analyses. Among the 14,739 survivors of the index hospital stay (females, 57.3%; median age, 74 [58-84] years), 2135 (14.5%) required at least one readmission with rCDI. Independent predictors of readmission were age ≥ 65 years (adjusted odds ratio (aOR), 1.34, 95% confidence interval (CI), 1.21-1.49, P < 0.0001), immunosuppression (aOR, 1.27, 95% CI, 1.15-1.41, P < 0.0001), chronic renal failure (aOR, 1.29, 95% CI, 1.14-1.46, P < 0.0001), and a previous history of CDI (aOR, 2.05, 95% CI, 1.55-2.71, P < 0.0001). The cumulative number of risk factors was independently associated with the hazard of readmission. Mean acute care costs attributable to rCDI were 5619 ± 3594 Euros for readmissions with rCDI as primary diagnosis (mean length of stay, 11.3 ± 10.2 days) and 4851 ± 445 Euros for those with rCDI as secondary diagnosis (mean length of stay, 16.8 ± 18.2 days), for an estimated annual nation-wide cost of 14,946,632 Euros. Hospital readmissions with rCDI are common after an index episode and drive major healthcare expenditures with substantial bed occupancy, strengthening the need for efficient secondary prevention strategies in high-risk patients.

Composition of gut microbiota in patients with toxigenic Clostridioides (Clostridium) difficile: Comparison between subgroups according to clinical criteria and toxin gene load

Data concerning the human microbiota composition during Clostridioides (Clostridium) difficile infection (CDI) using next-generation sequencing are still limited. We aimed to confirm key features indicating tcdB positive patients and compare the microbiota composition between subgroups based on toxin gene load (tcdB gene) and presence of significant diarrhea. Ninety-nine fecal samples from 79 tcdB positive patients and 20 controls were analyzed using 16S rRNA gene sequencing. Chao1 index for alpha diversity were calculated and principal coordinate analysis was performed for beta diversity using Quantitative Insights into Microbial Ecology (QIIME) pipeline. The mean relative abundance in each group was compared at phylum, family, and genus levels. There were significant alterations in alpha and beta diversity in tcdB positive patients (both colonizer and CDI) compared with those in the control. The mean Chao1 index of tcdB positive patients was significantly lower than the control group (P<0.001), whereas there was no significant difference between tcdB groups and between colonizer and CDI. There were significant differences in microbiota compositions between tcdB positive patients and the control at phylum, family, and genus levels. Several genera such as Phascolarctobacterium, Lachnospira, Butyricimonas, Catenibacterium, Paraprevotella, Odoribacter, and Anaerostipes were not detected in most CDI cases. We identified several changes in the microbiota of CDI that could be further evaluated as predictive markers. Microbiota differences between clinical subgroups of CDI need to be further studied in larger controlled studies.

Insights From Analysis of Human Antigen-Specific Memory B Cell Repertoires

Memory B cells that are generated during an infection or following vaccination act as sentinels to guard against future infections. Upon repeat antigen exposure memory B cells differentiate into new antibody-secreting plasma cells to provide rapid and sustained protection. Some pathogens evade or suppress the humoral immune system, or induce memory B cells with a diminished ability to differentiate into new plasma cells. This leaves the host vulnerable to chronic or recurrent infections. Single cell approaches coupled with next generation antibody gene sequencing facilitate a detailed analysis of the pathogen-specific memory B cell repertoire. Monoclonal antibodies that are generated from antibody gene sequences allow a functional analysis of the repertoire. This review discusses what has been learned thus far from analysis of diverse pathogen-specific memory B cell compartments and describes major differences in their repertoires. Such information may illuminate ways to advance the goal of improving vaccine and therapeutic antibody design.

Novel therapies and preventative strategies for primary and recurrent Clostridium difficile infections

Clostridium difficile is the leading infectious cause of antibiotic-associated diarrhea and colitis. C. difficile infection (CDI) places a heavy burden on the healthcare system, with nearly half a million infections yearly and an approximate 20% recurrence risk after successful initial therapy. The high incidence has driven new research on improved prevention such as the emerging use of probiotics, intestinal microbiome manipulation during antibiotic therapies, vaccinations, and newer antibiotics that reduce the disruption of the intestinal microbiome. While the treatment of acute C. difficile is effective in most patients, it can be further optimized by adjuvant therapies that improve the initial treatment success and decrease the risk of subsequent recurrence. Finally, the high risk of recurrence has led to multiple emerging therapies that target toxin activity, recovery of the intestinal microbial community, and elimination of latent C. difficile in the intestine. In summary, CDIs illustrate the complex interaction among host physiology, microbial community, and pathogen that requires specific therapies to address each of the factors leading to primary infection and recurrence.

Clostridioides difficile Infection in Chronic Kidney Disease/End-Stage Renal Disease

Clostridioides difficile infection (CDI) is a major health-care burden and increasingly seen in patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD). Increased antibiotic use, alteration in host defenses, and gastric acid suppression are some of the etiologies for increased risk of CDI in these populations. Patients with CKD/ESRD have a higher risk of initial episode, recurrence, and development of severe CDI than those without CKD or ESRD. Diagnosis and management of CDI in patients with CKD/ESRD are similar to that in the general population. The mortality, length of stay, and health-care costs are higher in patients with CDI and CKD/ESRD. Antimicrobial stewardship with reduction in antibiotic use along with infection-control measures such as contact isolation and hand hygiene with soap and water is essential in the control and prevention of CDI in patients with CKD/ESRD.

The use of faecal microbiota transplant as treatment for recurrent or refractory Clostridium difficile infection and other potential indications: joint British Society of Gastroenterology (BSG) and Healthcare Infection Society (HIS) guidelines

Interest in the therapeutic potential of faecal microbiota transplant (FMT) has been increasing globally in recent years, particularly as a result of randomised studies in which it has been used as an intervention. The main focus of these studies has been the treatment of recurrent or refractory Clostridium difficile infection (CDI), but there is also an emerging evidence base regarding potential applications in non-CDI settings. The key clinical stakeholders for the provision and governance of FMT services in the UK have tended to be in two major specialty areas: gastroenterology and microbiology/infectious diseases. While the National Institute for Health and Care Excellence (NICE) guidance (2014) for use of FMT for recurrent or refractory CDI has become accepted in the UK, clear evidence-based UK guidelines for FMT have been lacking. This resulted in discussions between the British Society of Gastroenterology (BSG) and Healthcare Infection Society (HIS), and a joint BSG/HIS FMT working group was established. This guideline document is the culmination of that joint dialogue.

Probiotics for Prevention and Treatment of Clostridium difficile Infection

Probiotics have been claimed as a valuable tool to restore the balance in the intestinal microbiota following a dysbiosis caused by, among other factors, antibiotic therapy. This perturbed environment could favor the overgrowth of Clostridium difficile and, in fact, the occurrence of C. difficile-associated infections (CDI) is being increasing in recent years. In spite of the high number of probiotics able to in vitro inhibit the growth and/or toxicity of this pathogen, its application for treatment or prevention of CDI is still scarce since there are not enough well-defined clinical studies supporting efficacy. Only a few strains, such as Lactobacillus rhamnosus GG and Saccharomyces boulardii have been studied in more extent. The increasing knowledge about the probiotic mechanisms of action against C. difficile, some of them reviewed here, makes promising the application of these live biotherapeutic agents against CDI. Nevertheless, more effort must be paid to standardize the clinical studied conducted to evaluate probiotic products, in combination with antibiotics, in order to select the best candidate for C. difficile infections.

Treatment of Clostridium difficile Infection with a Small-Molecule Inhibitor of Toxin UDP-Glucose Hydrolysis Activity

Clostridium difficile infection (CDI) is the leading cause of hospital-acquired infectious diarrhea, with significant morbidity, mortality, and associated health care costs. The major risk factor for CDI is antimicrobial therapy, which disrupts the normal gut microbiota and allows C. difficile to flourish. Treatment of CDI with antimicrobials is generally effective in the short term, but recurrent infections are frequent and problematic, indicating that improved treatment options are necessary. Symptoms of disease are largely due to two homologous toxins, TcdA and TcdB, which are glucosyltransferases that inhibit host Rho GTPases. As the normal gut microbiota is an important component of resistance to CDI, our goal was to develop an effective nonantimicrobial therapy. Here, we report a highly potent small-molecule inhibitor (VB-82252) of TcdA and TcdB. This compound inhibits the UDP-glucose hydrolysis activity of TcdB and protects cells from intoxication after challenge with either toxin. Oral dosing of the inhibitor prevented inflammation in a murine intrarectal toxin challenge model. In a murine model of recurrent CDI, the inhibitor reduced weight loss and gut inflammation during acute disease and did not cause the recurrent disease that was observed with vancomycin treatment. Lastly, the inhibitor demonstrated efficacy similar to that of vancomycin in a hamster disease model. Overall, these results demonstrate that small-molecule inhibition of C. difficile toxin UDP-glucose hydrolysis activity is a promising nonantimicrobial approach to the treatment of CDI.

Novel Antimicrobials for the Treatment of Clostridium difficile Infection

The current picture of Clostridium difficile infection (CDI) is alarming with a mortality rate ranging between 3% and 15% and a CDI recurrence rate ranging from 12% to 40%. Despite the great efforts made over the past 10 years to face the CDI burden, there are still gray areas in our knowledge on CDI management. The traditional anti-CDI antimicrobials are not always adequate in addressing the current needs in CDI management. The aim of our review is to give an update on novel antimicrobials for the treatment of CDI, considering the currently available evidences on their efficacy, safety, molecular mechanism of action, and their probability to be successfully introduced into the clinical practice in the near future. We identified, through a PubMed search, 16 novel antimicrobial molecules under study for CDI treatment: cadazolid, surotomycin, ridinilazole, LFF571, ramoplanin, CRS3123, fusidic acid, nitazoxanide, rifampin, rifaximin, tigecycline, auranofin, NVB302, thuricin CD, lacticin 3147, and acyldepsipeptide antimicrobials. In comparison with the traditional anti-CDI antimicrobial treatment, some of the novel antimicrobials reviewed in this study offer several advantages, i.e., the favorable pharmacokinetic and pharmacodynamic profile, the narrow-spectrum activity against CD that implicates a low impact on the gut microbiota composition, the inhibitory activity on CD sporulation and toxins production. Among these novel antimicrobials, the most active compounds in reducing spore production are cadazolid, ridinilazole, CRS3123, ramoplanin and, potentially, the acyldepsipeptide antimicrobials. These antimicrobials may potentially reduce CD environment spread and persistence, thus reducing CDI healthcare-associated acquisition. However, some of them, i.e., surotomycin, fusidic acid, etc., will not be available due to lack of superiority versus standard of treatment. The most CD narrow-spectrum novel antimicrobials that allow to preserve microbiota integrity are cadazolid, ridinilazole, auranofin, and thuricin CD. In conclusion, the novel antimicrobial molecules under development for CDI have promising key features and advancements in comparison to the traditional anti-CDI antimicrobials. In the near future, some of these new molecules might be effective alternatives to fight CDI.

Advances in the diagnosis and treatment of Clostridium difficile infections

Clostridium difficile is a leading cause of antibiotic-associated diarrhea worldwide. The diagnosis of C. difficile infection (CDI) requires both clinical manifestations and a positive laboratory test for C. difficile and/or its toxins. While antibiotic therapy is the treatment of choice for CDI, there are relatively few classes of effective antibiotics currently available. Therefore, the development of novel antibiotics and/or alternative treatment strategies for CDI has received a great deal of attention in recent years. A number of emerging agents such as cadazolid, surotomycin, ridinilazole, and bezlotoxumab have demonstrated activity against C. difficile; some of these have been approved for limited clinical use and some are in clinical trials. In addition, other approaches such as early and accurate diagnosis of CDI as well as disease prevention are important for clinical management. While the toxigenic culture and the cell cytotoxicity neutralization assay are still recognized as the gold standard for the diagnosis of CDI, new diagnostic approaches such as nucleic acid amplification methods have become available. In this review, we will discuss both current and emerging diagnostic and therapeutic modalities for CDI.

Bezlotoxumab: an emerging monoclonal antibody therapy for prevention of recurrent Clostridium difficile infection

Clostridium difficile infection (CDI) is the most common health care-acquired infection associated with high hospital expenditures. The incidence of subsequent recurrent CDI increases with prior episodes of CDI, 15%–35% risk after primary CDI to 35%–65% risk after the first recurrent episode. Recurrent CDI is one of the most challenging and a very difficult to treat infections. Standard guidelines provide recommendations on treatment of primary CDI. However, treatment choices for recurrent CDI are limited. Recent research studies have focused on the discovery of newer alternatives for prevention of recurrent CDI targeting prime virulence factors involved in C. difficile pathogenesis. Bezlotoxumab is a human monoclonal antibody directed against C. difficile toxin B. Multiple in vitro and in vivo animal studies have demonstrated direct binding of bezlotoxumab to C. difficile toxin B preventing intestinal epithelial damage and colitis. Furthermore, this monoclonal antibody mediates early reconstitution of gut microbiota preventing risk of recurrent CDI. Randomized placebo-controlled trials showed concomitant administration of a single intravenous dose of 10 mg/kg of bezlotoxumab, in patients on standard-of-care therapy for CDI, had no substantial effect on clinical cure rates but significantly reduced the incidence of recurrent CDI (~40%). It shows efficacy against multiple strains, including the epidemic BI/NAP1/027 strain. Bezlotoxumab is a US Food and Drug administration-approved, safe and well-tolerated drug with low risk of serious adverse events and drug–drug interactions. Bezlotoxumab has emerged as a novel dynamic adjunctive therapy for prevention of recurrent CDI. Further studies on real-world experience with bezlotoxumab and its impact in reducing rates of recurrent CDI are needed.

Lauric Acid Is an Inhibitor of Clostridium difficile Growth in Vitro and Reduces Inflammation in a Mouse Infection Model

Clostridium difficile is a Gram-positive, spore-forming anaerobic human gastrointestinal pathogen. C. difficile infection (CDI) is a major health concern worldwide, with symptoms ranging from diarrhea to pseudomembranous colitis, toxic megacolon, sepsis, and death. CDI onset and progression are mostly caused by intestinal dysbiosis and exposure to C. difficile spores. Current treatment strategies include antibiotics; however, antibiotic use is often associated with high recurrence rates and an increased risk of antibiotic resistance. Medium-chain fatty acids (MCFAs) have been revealed to inhibit the growth of multiple human bacterial pathogens. Components of coconut oil, which include lauric acid, have been revealed to inhibit C. difficile growth in vitro. In this study, we demonstrated that lauric acid exhibits potent antimicrobial activities against multiple toxigenic C. difficile isolates in vitro. The inhibitory effect of lauric acid is partly due to reactive oxygen species (ROS) generation and cell membrane damage. The administration of lauric acid considerably reduced biofilm formation and preformed biofilms in a dose-dependent manner. Importantly, in a mouse infection model, lauric acid pretreatment reduced CDI symptoms and proinflammatory cytokine production. Our combined results suggest that the naturally occurring MCFA lauric acid is a novel C. difficile inhibitor and is useful in the development of an alternative or adjunctive treatment for CDI.

The role of toxins in Clostridium difficile infection

Clostridium difficile is a bacterial pathogen that is the leading cause of nosocomial antibiotic-associated diarrhea and pseudomembranous colitis worldwide. The incidence, severity, mortality and healthcare costs associated with C. difficile infection (CDI) are rising, making C. difficile a major threat to public health. Traditional treatments for CDI involve use of antibiotics such as metronidazole and vancomycin, but disease recurrence occurs in about 30% of patients, highlighting the need for new therapies. The pathogenesis of C. difficile is primarily mediated by the actions of two large clostridial glucosylating toxins, toxin A (TcdA) and toxin B (TcdB). Some strains produce a third toxin, the binary toxin C. difficile transferase, which can also contribute to C. difficile virulence and disease. These toxins act on the colonic epithelium and immune cells and induce a complex cascade of cellular events that result in fluid secretion, inflammation and tissue damage, which are the hallmark features of the disease. In this review, we summarize our current understanding of the structure and mechanism of action of the C. difficile toxins and their role in disease.

Clostridium difficile infection: new approaches to prevention, non-antimicrobial treatment, and stewardship

INTRODUCTION

Despite the large amount of scientific publications exploring the epidemiology and the clinical management of Clostridium difficile (CD) infection, some issues remain unsolved or need further studies. The aim of this review is to give an update on the hot topics on CD prevention, including stewardship programs, and on the non-microbiological treatment of CD infection. Areas covered: This article will review the importance of minimizing the CD spore shedding in the healthcare environment for potentially reducing CD transmission. Moreover, antimicrobial stewardship programs aimed to reduce CD incidence will be reviewed. Finally, new strategies for reducing CD infection recurrence will be described. Expert commentary: Besides the basic infection control and prevention practices, including hand hygiene, contact isolation and environmental cleaning, in the prevention of CD infection other issues should be addressed including minimizing the spread of CD in the healthcare setting, and implementing the best strategy for reducing CD infection occurrence, including tailored antimicrobial stewardship programs. Regarding new advancements in treatment and management of CDI episodes, non-antimicrobial approaches seem to be promising in reducing and managing recurrent CD infection.

Bezlotoxumab: A Novel Agent for the Prevention of Recurrent Clostridium difficile Infection

During the past decade, the incidence and severity of Clostridium difficile infection (CDI) have significantly increased, leading to a rise in CDI-associated hospitalizations, health care costs, and mortality. Although treatment options exist for CDI, recurrence is frequent following treatment. Furthermore, patients with at least one CDI recurrence are at an increased risk of developing additional recurrences. A novel approach to the prevention of recurrent CDI is the use of monoclonal antibodies directed against the toxins responsible for CDI as an adjunct to antibiotic treatment. Bezlotoxumab, a human monoclonal antibody that binds and neutralizes C. difficile toxin B, is the first therapeutic agent to receive United States Food and Drug Administration approval for the prevention of CDI recurrence. Clinical studies have demonstrated superior efficacy of bezlotoxumab in adults receiving antibiotic therapy for CDI compared with antibiotic therapy alone for the prevention of CDI recurrence. Bezlotoxumab was well tolerated in clinical trials, with the most common adverse effects being nausea, vomiting, fatigue, pyrexia, headache, and diarrhea. The demonstrated efficacy, safety, and characteristics of bezlotoxumab present an advance in prevention of CDI recurrence.

Nonantimicrobial drug targets for Clostridium difficile infections

Clostridium difficile infection (CDI) is a major public health problem worldwide. Treatment has become complicated due to the emergence of strains with increased toxigenicity and sporulation rate, together with rampant antibiotics use that disrupts colonization resistance of the colonic microbiota. As a result, there is a critical need for nonantibiotic treatments. Therapies based on inhibiting the toxins, bacterial structures responsible for colonization, virulence and restoration of the gut microbiota are the most important nonantibiotic targets to combat CDI. This report outlines these targets and how they could become the focus of future therapeutic agents. Inhibiting colonization and virulence factors during CDI will disrupt pathogen persistence and decrease exposure to the inflammatory toxins, allowing the immune system to clear the infection.

Immunization with Recombinant TcdB-Encapsulated Nanocomplex Induces Protection against Clostridium difficile Challenge in a Mouse Model

Clostridium difficile is considered to be one of the major cause of infectious diarrhea in healthcare systems worldwide. Symptoms of C. difficile infection are caused largely by the production of two cytotoxins: toxin A (TcdA) and toxin B (TcdB). Vaccine development is considered desirable as it would decrease the mounting medical costs and mortality associated with C. difficile infections. Biodegradable nanoparticles composed of poly-γ-glutamic acid (γ-PGA) and chitosan have proven to be a safe and effective antigen delivery system for many viral vaccines. However, few studies have used this efficient antigen carrier for bacterial vaccine development. In this study, we eliminated the toxin activity domain of toxin B by constructing a recombinant protein rTcdB consists of residues 1852-2363 of TcdB receptor binding domain. The rTcdB was encapsulated in nanoparticles composed of γ-PGA and chitosan. Three rounds of intraperitoneal vaccination led to high anti-TcdB antibody responses and afforded mice full protection mice from lethal dose of C. difficile spore challenge. Protection was associated with high levels of toxin-neutralizing antibodies, and the rTcdB-encapsulated NPs elicited a longer-lasting antibody titers than antigen with the conventional adjuvant, aluminum hydroxide. Significant reductions in the level of proinflammatory cytokines and chemokines were observed in vaccinated mouse. These results suggested that polymeric nanocomplex-based vaccine design can be useful in developing vaccine against C. difficile infections.

Use of a neutralizing antibody helps identify structural features critical for binding of Clostridium difficile toxin TcdA to the host cell surface

Clostridium difficile is a clinically significant pathogen that causes mild-to-severe (and often recurrent) colon infections. Disease symptoms stem from the activities of two large, multidomain toxins known as TcdA and TcdB. The toxins can bind, enter, and perturb host cell function through a multistep mechanism of receptor binding, endocytosis, pore formation, autoproteolysis, and glucosyltransferase-mediated modification of host substrates. Monoclonal antibodies that neutralize toxin activity provide a survival benefit in preclinical animal models and prevent recurrent infections in human clinical trials. However, the molecular mechanisms involved in these neutralizing activities are unclear. To this end, we performed structural studies on a neutralizing monoclonal antibody, PA50, a humanized mAb with both potent and broad-spectrum neutralizing activity, in complex with TcdA. Electron microscopy imaging and multiangle light-scattering analysis revealed that PA50 binds multiple sites on the TcdA C-terminal combined repetitive oligopeptides (CROPs) domain. A crystal structure of two PA50 Fabs bound to a segment of the TcdA CROPs helped define a conserved epitope that is distinct from previously identified carbohydrate-binding sites. Binding of TcdA to the host cell surface was directly blocked by either PA50 mAb or Fab and suggested that receptor blockade is the mechanism by which PA50 neutralizes TcdA. These findings highlight the importance of the CROPs C terminus in cell-surface binding and a role for neutralizing antibodies in defining structural features critical to a pathogen's mechanism of action. We conclude that PA50 protects host cells by blocking the binding of TcdA to cell surfaces.

Factors associated with Clostridium difficile infection: A nested case-control study in a three year prospective cohort

BACKGROUND

Clostridium difficile infection (CDI) is a serious medical condition that is associated with substantial morbidity and mortality. Identification of risk factors associated with CDI and prompt recognition of patients at risk is key to successfully preventing CDI.

METHODS

A 3-year prospective, observational, cohort study was conducted in a French university hospital and a nested case-control study was performed to identify risk factors for CDI. Inpatients aged 18 years or older, suffering from diarrhea suspected to be related to CDI, were asked to participate.

RESULTS

A total of 945 patients were included, of which 233 cases had a confirmed CDI. CDI infection was more common in men (58.4%) (P = 0.04) compared with patients with diarrhea not related to C. difficile. Previous hospitalization (P < 0.001), prior treatment with antibiotics (P = 0.001) or antiperistaltics (P = 0.002), liver disease (P = 0.003), malnutrition (P < 0.001), and previous CDI (P < 0.001) were significantly more common in patients with CDI. Multivariate logistic regression analysis showed that exposure to antibiotics in the last 60 days (especially third generation cephalosporins and penicillins with β-lactamase inhibitor), chronic renal or liver disease, malnutrition or previous CDI, were associated with an independent high risk of CDI. Age was not related with CDI.

CONCLUSIONS

This study showed that antibiotics and some comorbid conditions were predictors of CDI. Patients at high risk of acquiring CDI at the time of admission may benefit from careful monitoring of antibiotic prescriptions and early attention to infection control issues. In future, these "high-risk" patients may benefit from novel agents being developed to prevent CDI.