Toxin-binding treatment for Clostridium difficile: a review including reports of studies with tolevamer

PhosphoLipidome Alteration Induced by Clostridioides difficile Toxin B in Enteric Glial Cells

Clostridioides difficile (C. difficile) is responsible for a spectrum of nosocomial/antibiotic-associated gastrointestinal diseases that are increasing in global incidence and mortality rates. The C. difficile pathogenesis is due to toxin A and B (TcdA/TcdB), both causing cytopathic and cytotoxic effects and inflammation. Recently, we demonstrated that TcdB induces cytopathic and cytotoxic (apoptosis and necrosis) effects in enteric glial cells (EGCs) in a dose/time-dependent manner and described the underlying signaling. Despite the role played by lipids in host processes activated by pathogens, to counter infection and/or induce cell death, to date no studies have investigated lipid changes induced by TcdB/TcdA. Here, we evaluated the modification of lipid composition in our in vitro model of TcdB infection. Apoptosis, cell cycle, cell viability, and lipidomic profiles were evaluated in EGCs treated for 24 h with two concentrations of TcdB (0.1 ng/mL; 10 ng/mL). In EGCs treated with the highest concentration of TcdB, not only an increased content of total lipids was observed, but also lipidome changes, allowing the separation of TcdB-treated cells and controls into different clusters. The statistical analyses also allowed us to ascertain which lipid classes and lipid molecular species determine the clusterization. Changes in lipid species containing inositol as polar head and plasmalogen phosphatidylethanolamine emerged as key indicators of altered lipid metabolism in TcdB-treated EGCs. These results not only provide a picture of the phospholipid profile changes but also give information regarding the lipid metabolism pathways altered by TcdB, and this might represent an important step for developing strategies against C. difficile infection.

Testing and Diagnosis of Clostridioides difficile Infection in Special Scenarios: A Systematic Review

INTRODUCTION

Clostridioides difficile infection (CDI) is a clinical and laboratory diagnosis. Populations at higher risk of developing disease require a high clinical index of suspicion for laboratory testing to avoid incorrect assumptions of colonization. Common risk factors include recent antibiotic use, elderly (>65 years old), and immunocompromised patients. C. difficile assays should be ordered in an algorithm approach to diagnose an infection rather than colonization. Screening tests are widely available in hospital systems, but novel molecular testing may aid in diagnosis in patients with inconclusive or discordant antigen and toxin test results.  Methods: Data was extracted from PubMed, Scopus, and Cumulative Index of Nursing and Allied Health Literature (CINAHL) databases based on the keywords "clostridioides difficile", "toxin assay", and "toxic megacolon". The data extracted is based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines. A total of 27 reports were included in this systematic review.

RESULTS

Testing patients with a significant gastrointestinal surgical history, hypogammaglobulinemia, inflammatory bowel disease, intensive care unit, and immunocompromised patients for CDI is highly recommended. Diarrhea in these subsets of patients requires correlation of clinical context and an understanding of assay results to avoid over- and under-treating.

CONCLUSION

CDI should be considered in all patients with traditional risk factors. Heightened clinical suspicion of CDI is required in patients with hypogammaglobulinemia, transplant recipients, patients with gastrointestinal surgical history, and inflammatory bowel disease. Testing should be limited to patients with clinical manifestations of CDI to ensure a high pretest probability for test interpretation. Healthcare workers should adhere to testing algorithms to optimize yield in the appropriate clinical context. Diagnostic assays should follow a sequential, stepwise approach to categorize the toxin expression status of the bacteria accurately.

Role of the Alteration in Calcium Homeostasis in Cell Death Induced by Clostridioides difficile Toxin A and Toxin B

Clostridioides difficile (C. difficile), responsible for 15-25% of gastrointestinal infections, causes health problems mainly due to the toxic activity of toxins A and B (Tcds). These are responsible for its clinical manifestations, including diarrhea, pseudomembranous colitis, toxic megacolon and death, with a mortality of 5-30% in primary infection, that increase following relapses. Studies on Tcd-induced cell death have highlighted a key role of caspases, calpains, and cathepsins, with involvement of mitochondria and reactive oxygen species (ROS) in a complex signaling pathway network. The complex response in the execution of various types of cell death (apoptosis, necrosis, pyroptosis and pyknosis) depends on the amount of Tcd, cell types, and Tcd receptors involved, and could have as initial/precocious event the alterations in calcium homeostasis. The entities, peculiarities and cell types involved in these alterations will decide the signaling pathways activated and cell death type. Calcium homeostasis alterations can be caused by calcium influx through calcium channel activation, transient intracellular calcium oscillations, and leakage of calcium from intracellular stores. These increases in cytoplasmic calcium have important effects on all calcium-regulated molecules, which may play a direct role in several cell death types and/or activate other cell death effectors, such as caspases, calpains, ROS and proapoptotic Bcl-2 family members. Furthermore, some support for the possible role of the calcium homeostasis alteration in Tcd-induced cell death originates from the similarity with cytotoxic effects that cause pore-forming toxins, based mainly on calcium influx through plasma membrane pores.

Prevention and Treatment of Clostridium difficile-Associated Diarrhea in Solid Organ Transplant Recipients

Clostridium difficile infection is a significant cause of morbidity and mortality in solid organ transplant recipients. Risk factors in this population include frequent hospitalizations, receipt of immunosuppressive agents, and intestinal dysbiosis triggered by several factors, including exposure to broad-spectrum antimicrobials. The incidence and potential for significant adverse outcomes among solid organ transplant recipients with C difficile infection highlight the evolving need for strategic C difficile infection risk factor modification and novel approaches to disease management in this patient population. This review focuses on current concepts related to the prevention and treatment of C difficile infection in solid organ transplant recipients.

New and emerging therapies in treatment of Clostridium difficile infection

Clostridium difficile infection (CDI) represents one of the most serious nosocomial infections that have grown dramatically over the past decade. Vancomycin and metronidazole are currently used as a standard therapy for CDI. Metronidazole is recommended as a first-line therapy for mild-to-moderate infections and vancomycin is mainly used for severe and/or refractory cases. However, studies have demonstrated that there are quite high CDI relapse rates with both of these medications, which represents a challenge for clinicians. Over the last decade, a number of newer and novel therapeutic options have emerged as promising alternatives to these standard CDI therapies. The following review provides the updated summaries of these newer therapeutic agents and their status in the treatment of CDI.

Clostridioides (Clostridium) difficile infection: current and alternative therapeutic strategies

Clostridioides difficile (C. difficile) has become a pathogen of worldwide importance considering that epidemic strains are disseminated in hospitals of several countries, where community-acquired infections act as a constant source of new C. difficile strains into hospitals. Despite the advances in the treatment of infections, more effective therapies against C. difficile are needed but, at the same time, these therapies should be less harmful to the resident gastrointestinal microbiota. The purpose of this review is to present a description of issues associated to C. difficile infection, a summary of current therapies and those in developmental stage, and a discussion of potential combinations that may lead to an increased efficacy of C. difficile infection treatment.

Identification and initial optimization of inhibitors of Clostridium difficile (C. difficile) toxin B (TcdB)

The discovery, synthesis and preliminary structure-activity relationship (SAR) of a novel class of inhibitors of Clostridium difficile (C. difficile) toxin B (TcdB) is described. A high throughput screening (HTS) campaign resulted in the identification of moderately active screening hits 1-5 the most potent of which was compound 1 (IC₅₀ = 0.77 µM). In silico docking of an early analog offered suggestions for structural modification which resulted in the design and synthesis of highly potent analogs 13j(IC₅₀ = 1 nM) and 13 l(IC₅₀ = 7 nM) which were chosen as leads for further optimization.

A Review of Experimental and Off-Label Therapies for Clostridium difficile Infection

In spite of increased awareness and the efforts taken to optimize Clostridium difficile infection (CDI) management, with the limited number of currently available antibiotics for C. difficile the halt of this increasing epidemic remains out of reach. There are, however, close to 80 alternative treatment methods with controversial anti-clostridial efficacy or in experimental phase today. Indeed, some of these therapies are expected to become acknowledged members of the recommended anti-CDI arsenal within the next few years. None of these alternative treatment methods can respond in itself to all the major challenges of CDI management, which are primary prophylaxis in the susceptible population, clinical cure of severe cases, prevention of recurrences, and forestallment of asymptomatic C. difficile carriage and in-hospital spread. Yet, the greater the variety of treatment choices on hand, the better combination strategies can be developed to reach these goals in the future. The aim of this article is to provide a comprehensive summary of these experimental and currently off-label therapeutic options.

Clostridium difficile Toxins A and B: Insights into Pathogenic Properties and Extraintestinal Effects

Clostridium difficile infection (CDI) has significant clinical impact especially on the elderly and/or immunocompromised patients. The pathogenicity of Clostridium difficile is mainly mediated by two exotoxins: toxin A (TcdA) and toxin B (TcdB). These toxins primarily disrupt the cytoskeletal structure and the tight junctions of target cells causing cell rounding and ultimately cell death. Detectable C. difficile toxemia is strongly associated with fulminant disease. However, besides the well-known intestinal damage, recent animal and in vitro studies have suggested a more far-reaching role for these toxins activity including cardiac, renal, and neurologic impairment. The creation of C. difficile strains with mutations in the genes encoding toxin A and B indicate that toxin B plays a major role in overall CDI pathogenesis. Novel insights, such as the role of a regulator protein (TcdE) on toxin production and binding interactions between albumin and C. difficile toxins, have recently been discovered and will be described. Our review focuses on the toxin-mediated pathogenic processes of CDI with an emphasis on recent studies.

Review article: bile acid diarrhoea - pathogenesis, diagnosis and management

BACKGROUND

Bile acid diarrhoea results from imbalances in the homoeostasis of bile acids in the enterohepatic circulation. It can be a consequence of ileal disease/dysfunction, associated with other GI pathology or can be idiopathic.

AIMS

To summarise the different types of bile acid diarrhoea and discuss the currently available diagnostic methods and treatments.

RESULTS

Bile acid diarrhoea is found in up to 40% of patients diagnosed as having functional diarrhoea/IBS-D, and in up to 80% of patients who have undergone ileal resection. It is likely under-diagnosed and under-treated. In idiopathic disease, errors in regulation feedback of fibroblast growth factor 19 contribute to the development of the condition. Clinical therapeutic trials for bile acid diarrhoea have been used to diagnose it, but the ⁷⁵ SeHCAT test is the primary current method. It is sensitive, specific and widely available, though not in the USA. Other diagnostic methods (such as serum measurement of the bile acid intermediate 7α-hydroxy-4-cholesten-3-one, or C4) have less widespread availability and documentation, and some (such as faecal measurement of bile acids) are significantly more complex and costly. First-line treatment of bile acid diarrhoea is with the bile acid sequestrant cholestyramine, which can be difficult to administer and dose due to gastrointestinal side effects. These side effects are less prominent in newer agents such as colesevelam, which may provide higher efficacy, tolerability and compliance.

CONCLUSION

Bile acid diarrhoea is common, and likely under-diagnosed. Bile acid diarrhoea should be considered relatively early in the differential diagnosis of chronic diarrhoea.

Polymeric drugs: Advances in the development of pharmacologically active polymers

Synthetic polymers play a critical role in pharmaceutical discovery and development. Current research and applications of pharmaceutical polymers are mainly focused on their functions as excipients and inert carriers of other pharmacologically active agents. This review article surveys recent advances in alternative pharmaceutical use of polymers as pharmacologically active agents known as polymeric drugs. Emphasis is placed on the benefits of polymeric drugs that are associated with their macromolecular character and their ability to explore biologically relevant multivalency processes. We discuss the main therapeutic uses of polymeric drugs as sequestrants, antimicrobials, antivirals, and anticancer and anti-inflammatory agents.

Clostridium difficile colitis: review of the therapeutic approach

Clostridium difficile infection (CDI) is the leading cause of antibiotic-associated and nosocomial infectious diarrhea. Presenting as clostridium difficile colitis, it is a significant cause of morbidity and mortality. Metronidazole is regarded as the agent of choice for CDl therapy and also for the first recurrence in most patients with mild to moderate CDI. Vancomycin is recommended as an initial therapy for patients with severe CDI. With recent Food and Drug Administration-approval fidaxomicin is available for clinical use and is as effective as vancomycin with lower relapse rates. Rifaximin and fecal bacteriotherapy are alternative approaches in patients with severe or refractory CDI, before surgical intervention. Antibiotic research is ongoing to add potential new drugs such as teicoplanin, ramoplanin, fusidic acid, nitazoxanide, rifampin, bacitracin to our armamentarium. Role of toxin-binding agents is still questionable. Monoclonal antibody and intravenous immunoglobulin are still investigational therapies that could be promising options. The ongoing challenges in the treatment of CDI include management of recurrence and presence of resistance strains such as NAP1/BI/027, but early recognition of surgical candidates can potentially decrease mortality in CDI.

Recurrent Clostridium difficile infection: From colonization to cure

Clostridium difficile infection (CDI) is increasingly prevalent, dangerous and challenging to prevent and manage. Despite intense national and international attention the incidence of primary and of recurrent CDI (PCDI and RCDI, respectively) have risen rapidly throughout the past decade. Of major concern is the increase in cases of RCDI resulting in substantial morbidity, morality and economic burden. RCDI management remains challenging as there is no uniformly effective therapy, no firm consensus on optimal treatment, and reliable data regarding RCDI-specific treatment options is scant. Novel therapeutic strategies are critically needed to rapidly, accurately, and effectively identify and treat patients with, or at-risk for, RCDI. In this review we consider the factors implicated in the epidemiology, pathogenesis and clinical presentation of RCDI, evaluate current management options for RCDI and explore novel and emerging therapies.

Effective Sequestration of Clostridium difficile Protein Toxins by Calcium Aluminosilicate

Clostridium difficile is a leading cause of antibiotic-associated diarrhea and the etiologic agent responsible for C. difficile infection. Toxin A (TcdA) and toxin B (TcdB) are nearly indispensable virulence factors for Clostridium difficile pathogenesis. Given the toxin-centric mechanism by which C. difficile pathogenesis occurs, the selective sequestration with neutralization of TcdA and TcdB by nonantibiotic agents represents a novel mode of action to prevent or treat C. difficile-associated disease. In this preclinical study, we used quantitative enzyme immunoassays to determine the extent by which a novel drug, calcium aluminosilicate uniform particle size nonswelling M-1 (CAS UPSN M-1), is capable of sequestering TcdA and TcdB in vitro. The following major findings were derived from the present study. First, we show that CAS UPSN M-1 efficiently sequestered both TcdA and TcdB to undetectable levels. Second, we show that CAS UPSN M-1's affinity for TcdA is greater than its affinity for TcdB. Last, we show that CAS UPSN M-1 exhibited limited binding affinity for nontarget proteins. Taken together, these results suggest that ingestion of calcium aluminosilicate might protect gastrointestinal tissues from antibiotic- or chemotherapy-induced C. difficile infection by neutralizing the cytotoxic and proinflammatory effects of luminal TcdA and TcdB.

Clostridium Difficile Infection from a Surgical Perspective

BACKGROUND

The incidence and the severity of Clostridium difficile infection (CDI) have increased significantly over the last decade, especially in high-risk populations such as patients with inflammatory bowel disease (IBD). Surgeons must be able to both identify and minimize the risk of CDI in their own surgical patients and determine which CDI patients will benefit from surgery.

PURPOSE

We sought to define the risk factors, compare the treatment options, define the surgical indications, and identify factors that affect surgical outcomes for CDI based on the currently available literature.

RESULTS

Antibiotic use, exposure to the C. difficile bacteria, IBD, and higher levels of co-morbidity are all risk factors for CDI. The majority of CDI can be treated with antibiotics. Severe or fulminant colitis, however, has a high potential for poor outcome, but experience and some data suggest a lower mortality rate with colectomy rather than with continued medical treatment. Open total abdominal colectomy with end ileostomy is typically the preferred surgical strategy. It is often difficult to determine which patients will fail medical management as some may not manifest clinical signs of severe infection. Surrogate parameters of failure of medical therapy include respiratory and/or renal insufficiency, age greater than 60 years, peripheral vascular disease, congestive heart failure, and coagulopathy, all of which have been associated with worse surgical outcomes. Evidence suggests that in appropriately selected patients, colectomy performed before the development of shock requiring vasopressors, respiratory failure, renal failure, multi-organ dysfunction, and mental status changes may reduce mortality of the most severe forms of colitis. For less severe or recurrent presentations, creation of a loop ileostomy with intra-operative colonic lavage, fecal microbiota transfer, and C. difficile vaccinations are being discussed but have only been studied in small case-controlled series.

CONCLUSIONS

Prevention, containment, and non-surgical treatment are the cornerstone of management for CDI. However, the most severe forms with toxic colitis benefit from involvement of a surgical team. Swift open total abdominal colectomy with end ileostomy in patients with severe or fulminant C. difficile colitis has the best chance to reduce mortality if it is not delayed until shock, end organ damage, vasopressor requirement, mental status changes develop. Less aggressive approaches may be appropriate for milder and refractory forms but require further study before their applicability can be determined.

Clostridium difficile infection: update on diagnosis, epidemiology, and treatment strategies

BACKGROUND

Clostridium difficile infection (CDI) has increased in incidence and severity over the past quarter century, and is now considered a major cause of healthcare-associated infections.

METHODS

Review of the pertinent English-language medical literature.

RESULTS

There has been a substantial change in the management of CDI. The emergence of the NAP1/BI/O27 strain in the early to mid-2000s has been associated with more severe forms of CDI. The pathophysiology, epidemiology, clinical manifestations and diagnosis, as well as new strategies for medical and surgical management are discussed in this review.

CONCLUSIONS

Clostridium difficile infection can range from benign diarrhea to severe disease associated with substantial morbidity and mortality. Treatment modalities vary based on disease severity and timing of onset. The mainstay of medical treatment remains metronidazole and oral/rectal vancomycin. New management strategies are evolving, including adjunctive treatments such as monoclonal antibodies, vaccination, and fecal transplant. In patients with severe disease or clinical deterioration, early surgical consultation for total colectomy or loop ileostomy may be life-saving. Infection control measures are vital to mitigating the spread of CDI.

Randomised clinical trial: colestyramine vs. hydroxypropyl cellulose in patients with functional chronic watery diarrhoea

BACKGROUND

Idiopathic bile acid malabsorption (BAM) has been suggested as a cause of chronic watery diarrhoea, with a response to colestyramine in 70% of patients. However, the efficacy of this drug has never been investigated in placebo-controlled trials.

AIM

To evaluate the efficacy of colestyramine as compared with hydroxypropyl cellulose in the treatment of functional chronic watery diarrhoea.

METHODS

Patients with chronic watery diarrhoea were randomly assigned to groups given colestyramine sachets 4 g twice daily (n = 13) or identical hydroxypropyl cellulose sachets (n = 13) for 8 weeks. The primary end-point was clinical remission defined as a mean of 3 or fewer stools per day during the week before the visit, with less than 1 watery stool per day. A secondary end-point was the reduction in daily watery stool number. SeHCAT test was performed in all patients, but an abnormal test was not a prerequisite to be included.

RESULTS

All included patients had a SeHCAT 7-day retention ≤20%. There were no statistical differences in the percentage of patients in clinical remission at week 8 between colestyramine and hydroxypropyl cellulose with either intention-to-treat (53.8% vs. 38.4%; P = 0.43) or per-protocol (63.6% vs. 38.4%; P = 0.22) analyses. However, the mean per cent decrease in watery stool number was significantly higher with colestyramine than with hydroxypropyl cellulose (-92.4 ± 3.5% vs. -75.8 ± 7.1%; P = 0.048). The rate of adverse events related to study drugs did not differ between groups.

CONCLUSIONS

Colestyramine (4 g twice daily) is effective and safe for short-term treatment of patients with chronic watery diarrhoea presumably secondary to BAM. Clinical Trials Register number EudraCT 2009-011149-14.

Luminal Toxin-Binding Agents for Clostridium difficile Infection

OBJECTIVE

To systematically search the literature for trials evaluating luminal toxin-binding agents (LTBAs) for Clostridium difficile infection (CDI).

METHODS

A systematic search was conducted utilizing PubMed and International Pharmaceutical Abstracts with the following terms: anion-exchange resins, C difficile, cholestyramine, tolevamer, and colestipol. Articles were included if published in the English language and reported clinical outcomes of more than 5 adult humans with CDI treated with LTBAs.

RESULTS

Nearly all clinical trials evaluated LTBA as monotherapy for CDI and LTBAs are inferior to standard therapy. In contemporary practice, LTBAs are employed as adjunctive or sequential therapy for which there is a paucity of data. Some data suggest potential efficacy for recurrent CDI. Current guidelines for CDI assert LTBAs are contraindicated due to drug-drug interactions with vancomycin. However, the impact of this interaction on clinical outcomes has not been evaluated, and it is unknown whether higher doses of vancomycin or separating the administration of LTBAs from vancomycin would mitigate this interaction.

CONCLUSION

LTBA monotherapy is inferior to vancomycin and metronidazole for CDI. Some data indicate possible benefit in reducing recurrent CDI, but outcomes with adjunctive and/or sequential LTBAs are unavailable. Further studies are needed to investigate the role of LTBAs for CDI.

Evaluation of a focused virtual library of heterobifunctional ligands for Clostridium difficile toxins

Higher activity glycopeptoid ligands for two largeClostridium difficiletoxins TcdA and TcdB were discoveredviamodular fragment-based design and virtual screening.

Investigational new treatments for Clostridium difficile infection

Significant progress has been made by industry and academia in the past two years to address the medical threats posed by Clostridium difficile infection. These developments provide an excellent example of how patient need has driven a surge of innovation in drug discovery. Indeed, only two drugs were approved for the infection in the past 30 years but there are 13 treatment candidates in clinical trials today. What makes the latter number even more remarkable is the diversity in the strategies represented (antibiotics, microbiota supplements, vaccines, antibiotic quenchers and passive immunization). In this review, we provide a snapshot of the current stage of these breakthroughs and argue that there is still room for further innovation in treating C. difficile infection.

Microbial bile acid metabolic clusters: the bouncers at the bar

Colonization resistance refers to the ability of the colonic microbiota to prevent invasion by pathogens including Clostridium difficile. In a recent article, Buffie et al. (2014) have demonstrated that a single metabolic cluster present in the normal, colonic microflora is responsible for preventing C. difficile invasion of healthy hosts.

Advances in understanding of bile acid diarrhea

Bile acids (BA) are actively reabsorbed in the terminal ileum by the apical Na(+)-dependent bile salt transporter. This review addresses the epidemiology, pathophysiology, diagnosis and treatment of BA diarrhea (BAD). BAD is typically caused by ileal resection or disease; 25-33% of patients with chronic functional diarrhea or irritable bowel syndrome-diarrhea (IBS-D) have BAD, possibly from deficiency in the ileal hormone, FGF-19, which normally provides feedback inhibition of BA synthesis. Diagnosis of BAD is typically based on reduced BA retention of radiolabeled BA ((75)SeHCAT), increased BA synthesis (serum C4) or increased fecal BA loss. In clinical practice, diagnosis is often based on response to BA sequestrants (e.g., cholestyramine or colesevelam). Diagnostic tests for BA malabsorption (BAM) need to be used more extensively in clinical practice. In the future, farnesoid X receptor agonists that stimulate ileal production of FGF-19 may be alternative treatments of BAD.

Methods for diagnosis of bile acid malabsorption in clinical practice

Altered concentrations of bile acid (BA) in the colon can cause diarrhea or constipation. More than 25% of patients with irritable bowel syndrome with diarrhea or chronic diarrhea in Western countries have BA malabsorption (BAM). As BAM is increasingly recognized, proper diagnostic methods are needed to help direct the most effective course of treatment for the chronic bowel dysfunction. We review the methodologies, advantages, and disadvantages of tools that directly measure BAM: the (14)C-glycocholate breath and stool test, the (75)selenium homotaurocholic acid test (SeHCAT), and measurements of 7 α-hydroxy-4-cholesten-3-one (C4) and fecal BAs. The (14)C-glycocholate test is laborious and no longer widely used. The (75)SeHCAT has been validated but is not available in the United States. Measurement of serum C4 is a simple and accurate method that can be used for most patients but requires further clinical validation. Assays to quantify fecal BA (total and individual levels) are technically cumbersome and not widely available. Regrettably, none of these tests are routinely available in the United States; assessment of the therapeutic effects of a BA binder is used as a surrogate for diagnosis of BAM. Recent data indicate the advantages to studying fecal excretion of individual BAs and their role in BAM; these could support the use of the fecal BA assay, compared with other tests. Measurement of fecal BA levels could become a routine addition to the measurement of fecal fat in patients with unexplained diarrhea. Availability ultimately determines whether the C4, SeHCAT, or fecal BA test is used; more widespread availability of such tests would enhance clinical management of these patients.

Fecal transplantation for the treatment of recurrent clostridium difficile infection

Clostridium difficile infection (CDI) is currently a leading cause of antibiotic and health care-related diarrhea. The incidence and the severity of CDI-related diarrhea have increased dramatically in the USA and Europe in the past few decades. The emergence of multidrug-resistant hypervirulent strains of C. difficile has led to an increase in mortality. Fecal microbiota transplantation (FMT) (also known as fecal bacteriotherapy) has been utilized sporadically since the 1950s; and currently, the interest in using FMT has grown again in the past few years for the treatment of CDI and other chronic gastrointestinal diseases. FMT has shown to be effective, cheap, and has very few side effects. It is believed to manipulate and restore the gut microbiota, and therefore enhances the growth of "healthy" bacteria that break the cycle of recurrent CDI. This article focus on the recent case reports on FMT, and general approach to patients undergoing this therapy. Data were obtained through a literature search via PubMed and Google.

Epidemiology, diagnosis and treatment of Clostridium difficile infection

Clostridium difficile infection (CDI) is considered to be the main cause of bacterial infectious diarrhea in nosocomial settings. Since the beginning of the new century a continuous rise in the incidence of severe CDI has been observed worldwide. Even though some CDI cases are not associated with previous antibiotic exposure, this remains as the principal risk factor for the development of CDI. The rate of recurrences represents perhaps one the most challenging aspect on the management of CDI. There are several microbiological tests available, but glutamate dehydrogenase antigen test can be selected as the first screening step in a diagnostic algorithm, with positive samples then confirmed using a toxin(s) test, to distinguish toxinogenic from nontoxinogenic CDI. Although metronidazole and vancomycin are and have been the mainstay treatment options for CDI, there are some unmet medical and therapeutical needs. Usually oral metronidazole is recommended for initial treatment of nonsevere CDI and vancomycin for treatment of severe disease. Fidaxomicin may be considered in patients who cannot tolerate vancomycin, although more data are needed. For treatment of a nonsevere initial recurrence of CDI, oral metronidazole should be used, but for treatment of subsequent recurrences or more severe cases fidaxomicin may be helpful.

Glutamine and alanyl-glutamine increase RhoA expression and reduce Clostridium difficile toxin-a-induced intestinal epithelial cell damage

Clostridium difficile is a major cause of antibiotic-associated colitis and is associated with significant morbidity and mortality. Glutamine (Gln) is a major fuel for the intestinal cell population. Alanyl-glutamine (Ala-Gln) is a dipeptide that is highly soluble and well tolerated. IEC-6 cells were used in the in vitro experiments. Cell morphology was evaluated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Cell proliferation was assessed by WST-1 and Ki-67 and apoptosis was assessed by TUNEL. Cytoskeleton was evaluated by immunofluorescence for RhoA and F-actin. RhoA was quantified by immunoblotting. TcdA induced cell shrinkage as observed by AFM, SEM, and fluorescent microscopy. Additionally, collapse of the F-actin cytoskeleton was demonstrated by immunofluorescence. TcdA decreased cell volume and area and increased cell height by 79%, 66.2%, and 58.9%, respectively. Following TcdA treatment, Ala-Gln and Gln supplementation, significantly increased RhoA by 65.5% and 89.7%, respectively at 24 h. Ala-Gln supplementation increased cell proliferation by 137.5% at 24 h and decreased cell apoptosis by 61.4% at 24 h following TcdA treatment. In conclusion, TcdA altered intestinal cell morphology and cytoskeleton organization, decreased cell proliferation, and increased cell apoptosis. Ala-Gln and Gln supplementation reduced intestinal epithelial cell damage and increased RhoA expression.

Fidaxomicin inhibits toxin production in Clostridium difficile

OBJECTIVES

Fidaxomicin, which was recently approved for the treatment of Clostridium difficile-associated diarrhoea, demonstrates narrow-spectrum bactericidal activity via inhibition of RNA polymerase. In this study we evaluated its inhibitory activity versus C. difficile toxin gene expression and toxin production by quantifying toxin mRNA and protein.

METHODS

The effects of fidaxomicin, its major metabolite (OP-1118), vancomycin and metronidazole on toxin A and toxin B production were determined by assaying culture supernatants of two C. difficile isolates (ATCC 43255, a high-level toxin-producing strain, and UK-14, a NAP1/027/BI epidemic strain) using a commercial ELISA. The effects of the drugs on toxin gene expression were assessed in stationary-phase cells of C. difficile strain UK-1 (NAP1/027/BI type epidemic strain) and in the closely related non-epidemic strain CD196 by quantitative RT-PCR.

RESULTS

Subinhibitory levels (1/4× MIC) of fidaxomicin or OP-1118 (but not vancomycin or metronidazole) strongly suppressed toxin production in C. difficile (≥ 60%) through at least 1 week of culture. Additionally, transcripts from the pathogenicity loci (tcdR, tcdA and tcdB) were nearly completely inhibited by both fidaxomicin (2× MIC) and OP-1118 (2.5× MIC), but not vancomycin (2.5× MIC).

CONCLUSIONS

Both fidaxomicin and OP-1118 are able to inhibit toxin production in vitro, which may explain prior post-treatment observations of less frequent detectable toxin in fidaxomicin-treated patients (27 subjects) than those treated with vancomycin (8 patients).

Vancomycin treatment's association with delayed intestinal tissue injury, clostridial overgrowth, and recurrence of Clostridium difficile infection in mice

Antibiotic treatment, including vancomycin, for Clostridium difficile infection (CDI) has been associated with recurrence of disease in up to 25% of infected persons. This study investigated the effects of vancomycin on the clinical outcomes, intestinal histopathology, and anaerobic community during and after treatment in a murine model of CDI. C57BL/6 mice were challenged with C. difficile strain VPI 10463 after pretreatment with an antibiotic cocktail. Twenty-four hours after infection, mice were treated daily with vancomycin, nitazoxanide, fidaxomicin, or metronidazaole for 5 days. Mice were monitored for either 6 or 12 days postinfection. Clinical, diarrhea, and histopathology scores were measured. Cecal contents or stool samples were assayed for clostridial or Bacteroides DNA and C. difficile toxins A and B. Vancomycin treatment of infected mice was associated with improved clinical, diarrhea, and histopathology scores and survival during treatment. However, after discontinuation of the drug, clinical scores and histopathology were worse in treated mice than in untreated infected controls. At the end of the study, 62% of the vancomycin-treated mice succumbed to recurrence, with an overall mortality rate equivalent to that of the untreated infected control group. Fidaxomicin-treated mice had outcomes similar to those of vancomycin-treated mice. C. difficile predominated over Bacteroides in cecal contents of vancomycin-treated mice, similar to findings for untreated infected mice. Decreasing the duration of vancomycin treatment from 5 days to 1 day decreased recurrence and deaths. In conclusion, vancomycin improved clinical scores and histopathology acutely but was associated with poor outcome posttreatment in C. difficile-infected mice. Decreasing vancomycin exposure may decrease relapse and improve survival in CDI.

Clostridium difficile: Changing Epidemiology, Treatment and Infection Prevention Measures

Clostridium difficile was first reported as a cause of antibiotic-associated colitis in 1978. In more recent years we have witnessed disturbing trends associated with C. difficile infection (CDI). CDI has become more common, affecting populations previously considered at low risk, more severe with an associated increase in mortality, and more difficult to treat with some patients experiencing multiple relapses and a reduced responsiveness to previously effective antibiotics. These trends have been coincident with the emergence of a new hypervirulent strain responsible for several outbreaks in the last decade. Fortunately, we have also seen promising developments, particularly with regard to testing and treatment. This review discusses recent changes in the epidemiology of CDI and recent developments in the testing, treatment and prevention of CDI.

Efficacy and safety of fidaxomicin compared with oral vancomycin for the treatment of adults with Clostridium difficile-associated diarrhea: data from the OPT-80-003 and OPT-80-004 studies

Clostridium difficile is emerging as one of the most important and devastating pathogens affecting hospitalized populations around the world. The incidence of C. difficile infection is increasing and disease severity is worsening. Thus, an effective alternative to metronidazole and oral vancomycin is urgently needed. Two Phase III trials, OPT-80-003 and OPT-80-004, showed that oral fidaxomicin for 10 days was noninferior compared with treatment with oral vancomycin among adult patients with toxin-positive C. difficile-associated diarrhea (CDAD). Furthermore, fidaxomicin was associated with a lower rate of recurrence of CDAD within 4 weeks of completion of therapy. The safety and tolerability of fidaxomicin was consistent with earlier studies and established that fidaxomicin is an efficacious and well-tolerated treatment option for CDAD. Despite these potential advantages, the cost-effectiveness of this expensive agent remains poorly understood.

Targeting bacterial toxins

Protein toxins constitute the main virulence factors of several species of bacteria and have proven to be attractive targets for drug development. Lead candidates that target bacterial toxins range from small molecules to polymeric binders, and act at each of the multiple steps in the process of toxin-mediated pathogenicity. Despite recent and significant advances in the field, a rationally designed drug that targets toxins has yet to reach the market. This Review presents the state of the art in bacterial toxin targeted drug development with a critical consideration of achieved breakthroughs and withstanding challenges. The discussion focuses on A-B-type protein toxins secreted by four species of bacteria, namely Clostridium difficile (toxins A and B), Vibrio cholerae (cholera toxin), enterohemorrhagic Escherichia coli (Shiga toxin), and Bacillus anthracis (anthrax toxin), which are the causative agents of diseases for which treatments need to be improved.

Systematic review of intestinal microbiota transplantation (fecal bacteriotherapy) for recurrent Clostridium difficile infection

Clostridium difficile infection (CDI) is a gastrointestinal disease believed to be causally related to perturbations to the intestinal microbiota. When standard treatment has failed, intestinal microbiota transplantation (IMT) is an alternative therapy for patients with CDI. IMT involves infusing intestinal microorganisms (in a suspension of healthy donor stool) into the intestine of a sick patient to restore the microbiota. However, protocols and reported efficacy for IMT vary. We conducted a systematic literature review of IMT treatment for recurrent CDI and pseudomembranous colitis. In 317 patients treated across 27 case series and reports, IMT was highly effective, showing disease resolution in 92% of cases. Effectiveness varied by route of instillation, relationship to stool donor, volume of IMT given, and treatment before infusion. Death and adverse events were uncommon. These findings can guide physicians interested in implementing the procedure until better designed studies are conducted to confirm best practices.

Development and evaluation of an ovine antibody-based platform for treatment of Clostridium difficile infection

Treatment of Clostridium difficile is a major problem as a hospital-associated infection which can cause severe, recurrent diarrhea. The currently available antibiotics are not effective in all cases and alternative treatments are required. In the present study, an ovine antibody-based platform for passive immunotherapy of C. difficile infection is described. Antibodies with high toxin-neutralizing titers were generated against C. difficile toxins A and B and were shown to neutralize three sequence variants of these toxins (toxinotypes) which are prevalent in human C. difficile infection. Passive immunization of hamsters with a mixture of toxin A and B antibodies protected them from a challenge with C. difficile spores in a dose-dependent manner. Antibodies to both toxins A and B were required for protection. The administration of toxin A and B antibodies up to 24 h postchallenge was found to reduce significantly the onset of C. difficile infection compared to nonimmunized controls. Protection from infection was also demonstrated with key disease isolates (ribotypes 027 and 078), which are members of the hypervirulent C. difficile clade. The ribotype 027 and 078 strains also have the capacity to produce an active binary toxin and these data suggest that neutralization of this toxin is unnecessary for the management of infection induced by these strains. In summary, the data suggest that ovine toxin A and B antibodies may be effective in the treatment of C. difficile infection; their potential use for the management of severe, fulminant cases is discussed.

The role of toxin A and toxin B in the virulence of Clostridium difficile

During the past decade, there has been a striking increase in Clostridium difficile nosocomial infections worldwide predominantly due to the emergence of epidemic or hypervirulent isolates, leading to an increased research focus on this bacterium. Particular interest has surrounded the two large clostridial toxins encoded by most virulent isolates, known as toxin A and toxin B. Toxin A was thought to be the major virulence factor for many years; however, it is becoming increasingly evident that toxin B plays a much more important role than anticipated. It is clear that further experiments are required to accurately determine the relative roles of each toxin in disease, especially in more clinically relevant current epidemic isolates.

Current Status of Nonantibiotic and Adjunct Therapies for Clostridium difficile Infection

Clostridium difficile infection (CDI) is a leading cause of nosocomial infections and the most important cause of health care-associated diarrhea worldwide. Standard treatment of CDI consists of modifying underlying antibiotic exposure, aggressive supportive measures, and therapy with specific antibiotics, most commonly metronidazole or vancomycin. This general approach to CDI has remained largely unchanged for decades. In an effort to improve outcomes and reduce recurrences of CDI, interest has been renewed in the development of nonantibiotic and adjunct approaches to therapy. In this review, we highlight some of these recent, resurrected, and novel nonantibiotic treatments.

Clostridium difficile: progress and challenges

There is a surge of new interest in C. difficile infection (CDI) reflecting substantial increases in cases and fatalities. The new challenges by this now old pathogen have brought renewed interest in all facets of the disease. Particularly important are the role of fluoroquinolones as inducing agents, the new polymerase chain reaction test to detect toxigenic strains in stools, the important role of the NAP-1 strain, recent evidence favoring oral vancomycin over metronidazole in seriously ill patients, and new guidelines for management.

The ecology and pathobiology of Clostridium difficile infections: an interdisciplinary challenge

Clostridium difficile is a well recognized pathogen of humans and animals. Although C. difficile was first identified over 70 years ago, much remains unknown in regards to the primary source of human acquisition and its pathobiology. These deficits in our knowledge have been intensified by dramatic increases in both the frequency and severity of disease in humans over the last decade. The changes in C. difficile epidemiology might be due to the emergence of a hypervirulent stain of C. difficile, ageing of the population, altered risk of developing infection with newer medications, and/or increased exposure to C. difficile outside of hospitals. In recent years, there have been numerous reports documenting C. difficile contamination of various foods, and reports of similarities between strains that infect animals and strains that infect humans as well. The purposes of this review are to highlight the many challenges to diagnosing, treating, and preventing C. difficile infection in humans, and to stress that collaboration between human and veterinary researchers is needed to control this pathogen.