Immune-based treatment and prevention of Clostridium difficile infection

Cell Wall Protein 2 as a Vaccine Candidate Protects Mice Against Clostridioides difficile Infection

BACKGROUND/OBJECTIVES

Clostridioides difficile is a Gram-positive, spore-forming enteric pathogen that causes intestinal disorders, including inflammation and diarrhea, primarily through toxin production. Standard treatment options for C. difficile infection (CDI) involve a limited selection of antibiotics that are not fully effective, leading to high recurrence rates. Vaccination presents a promising strategy for preventing both CDI and its recurrence. Cell wall protein 2 (Cwp2), a highly immunogenic and abundant surface-exposed C. difficile cell wall protein, plays an important role in the bacterium's adherence in vitro. In this study, we aimed to analyze the homology and immunogenicity of Cwp2 and its protection efficacy as a vaccine candidate against CDI in mice.

METHODS

we conducted in silico analyses to assess the homology and immunogenicity of Cwp2, and we evaluated its potential as a vaccine candidate against CDI using a mouse model of immunization and infection.

RESULTS

Our in silico analyses predicted the immunogenic region (functional domain) of Cwp2 and revealed its high homology among various toxinotypes and ribotypes (R.T.s) or sequence types (S.T.s). Immunizations of mice with the Cwp2 functional domain (Cwp2_A) induced potent IgG/A antibody responses against Cwp2_A, protected mice from CDI, and reduced C. difficile spore and toxin levels in feces post-infection. Additionally, anti-Cwp2_A sera inhibited the binding of C. difficile vegetative cells to HCT8 cells.

CONCLUSIONS

Our report demonstrates for the first time the potential of Cwp2_A as an effective vaccine candidate against CDI in mice.

Large Clostridial Toxins: A Brief Review and Insights into Antigen Design for Veterinary Vaccine Development

The group of large clostridial toxins (LCTs) includes toxins A (TcdA) and B (TcdB) from Clostridioides difficile, hemorrhagic and lethal toxins from Paeniclostridium sordellii, alpha toxin from Clostridium novyi (TcnA), and cytotoxin from Clostridium perfringens. These toxins are associated with severe pathologies in livestock, including gas gangrene (P. sordellii and C. novyi), infectious necrotic hepatitis (C. novyi), avian necrotic enteritis (C. perfringens), and enterocolitis (C. difficile). Immunoprophylaxis is crucial for controlling these diseases, but traditional vaccines face production challenges, such as labor-intensive processes, and often exhibit low immunogenicity. This has led to increased interest in recombinant vaccines. While TcdA and TcdB are well-studied for human immunization, other LCTs remain poorly characterized and require further investigation. Therefore, this study emphasizes the importance of understanding lesser-explored toxins and proposes using immunoinformatics to identify their immunodominant regions. By mapping these regions using silico tools and considering their homology with TcdA and TcdB, the study aims to guide future research in veterinary vaccinology. It also explores alternatives to overcome the limitations of conventional and recombinant vaccines, offering guidelines for developing more effective vaccination strategies against severe infections in animals.

Current and Ongoing Developments in Targeting Clostridioides difficile Infection and Recurrence

Clostridioides difficile is a Gram-positive, spore-forming anaerobic bacterial pathogen that causes severe gastrointestinal infection in humans. This review provides background information on C. difficile infection and the pathogenesis and toxigenicity of C. difficile. The risk factors, causes, and the problem of recurrence of disease and current therapeutic treatments are also discussed. Recent therapeutic developments are reviewed including small molecules that inhibit toxin formation, disrupt the cell membrane, inhibit the sporulation process, and activate the host immune system in cells. Other treatments discussed include faecal microbiota treatment, antibody-based immunotherapies, probiotics, vaccines, and violet-blue light disinfection.

Nanoplastics affect the growth of sea urchins (Strongylocentrotus intermedius) and damage gut health

Nanoplastics (NPs) are abundant and widespread throughout the ocean, not only causing severe environmental pollution, but also worsening the aquatic organisms. To elucidate the mechanism of biological toxic effects underlying the responses of marine invertebrates to NPs, Strongylocentrotus intermedius was stressed with three different NPs concentrations (0 particles/L, 10² particles/L and 10⁴ particles/L). Specific growth rates, enzyme activity, gut tissue section observation and structural characteristics of the gut bacterial community were analyzed. After 28 days of exposure, the specific growth rate of S. intermedius decreased significantly with NPs groups. Further, both lysozyme, pepsin, lipase and amylase activities decreased, while the superoxide dismutase activity increased, indicating that NPs negatively affected digestive enzyme and immune enzyme activity. The analysis of gut tissue sections revealed that NPs caused atrophy and cytoplasmic reduction in the epithelial cells of the S. intermedius intestine. Moreover, the structural characterization of the gut bacterial community indicated significant changes in the abundances of members from Campylobacterota, Chlamydiae, and Firmicutes. Members from Arcobacteraceae, Christensenellaceae and Clostridia were endemic to the NPs treatment. The KEGG database analysis demonstrated that the metabolic pathways specific to the NPs treatment group were significantly associated with growth, energy metabolism, and immunity. In summary, NPs have negatively affected on physiological response and altered gut microecological environment.

Oral Immunization with Nontoxigenic Clostridium difficile Strains Expressing Chimeric Fragments of TcdA and TcdB Elicits Protective Immunity against C. difficile Infection in Both Mice and Hamsters

The symptoms of Clostridium difficile infection (CDI) are attributed largely to two C. difficile toxins, TcdA and TcdB. Significant efforts have been devoted to developing vaccines targeting both toxins through parenteral immunization routes. However, C. difficile is an enteric pathogen, and mucosal/oral immunization would be particularly useful to protect the host against CDI, considering that the gut is the main site of disease onset and progression. Moreover, vaccines directed only against toxins do not target the cells and spores that transmit the disease. Previously, we constructed a chimeric vaccine candidate, mTcd138, comprised of the glucosyltransferase and cysteine proteinase domains of TcdB and the receptor binding domain of TcdA. In this study, to develop an oral vaccine that can target both C. difficile toxins and colonization/adhesion factors, we expressed mTcd138 in a nontoxigenic C. difficile (NTCD) strain, resulting in strain NTCD_mTcd138. Oral immunization with spores of NTCD_mTcd138 provided mice full protection against infection with a hypervirulent C. difficile strain, UK6 (ribotype 027). The protective strength and efficacy of NTCD_mTcd138 were further evaluated in the acute CDI hamster model. Oral immunization with spores of NTCD_mTcd138 also provided hamsters significant protection against infection with 2 × 10⁴ UK6 spores, a dose 200-fold higher than the lethal dose of UK6 in hamsters. These results imply that the genetically modified, nontoxigenic C. difficile strain expressing mTcd138 may represent a novel mucosal vaccine candidate against CDI.

Healthcare-associated Clostridium difficile infection: role of correct hand hygiene in cross-infection control

INTRODUCTION

Clostridium difficile (CD) is the most common cause of health-care-associated infectious diarrhea with increasing incidence and severity in recent years. The main cause of hospital's acquired cross infections can be attributed to incorrect hand hygiene. We described the epidemiology of CD infection (CDI) in a teaching hospital in Southern Italy during a two years surveillance period and evaluated the health-care workers compliance to hand hygiene.

METHODS

CDI Incidence rates were calculated as the number of patients with positive C. difficile toxin assay per 10,000 patient-days. Compliance with hand hygiene was the ratio of the number of performed actions to the number of opportunities observed. Approximately 400 Hand Hygiene (HH) opportunities/year /ward were observed. We finally checked out if any correlation could be found.

RESULTS

From January 2015 to December 2016 a total number of 854 CD determinations were performed in patients with clinical symptoms of diarrhea. The search for toxins A and B was positive in 175 cases (21,2%), confirming the diagnosis of CDI. Compliance to hand hygiene was significantly inversely associated with the number of CDIs: the lower the compliance of health-care workers with hand hygiene the higher was the number of cases of CDIs (p = 0.003).

CONCLUSIONS

According to our results proper handwashing of health-care workers appears to be a key intervention in interrupting CD cross infections regardless of age and type of department in which the patient is admitted.

Stimulated enrichment of Clostridium difficile specific IgA in mature cow's milk

Cow milk products enriched with Clostridium difficile (C. diff.) specific IgA are possible alternative therapeutics against C. diff. associated diarrhea. A persistently high level of C. diff. specific IgA in mature milk triggered by continuous immunizations of dairy cows against C. diff. was hypothesized. Nine Brown Swiss cows were repeatedly vaccinated against C. diff. and divided into low responder (LR) and high responder (HR) cows, as measured by their production of anti-C. diff. specific IgA in milk (threshold: 8.0 μg anti-C. diff. specific IgA/mL on average). Total and C. diff. specific IgA were quantified in bovine milk and blood using a sandwich ELISA. Important milk production factors were analyzed per lactation stage. Milk yield, milk fats and proteins were significantly different (P < 0.05) in the early lactation stage when the treated with the untreated cows (n = 30) were compared. In contrast to the "before treatment control" values, the HR's milk anti-C. diff. IgA was approximately 80% higher at any lactation stage, and the HR's total milk IgA increased up to 72% in the late lactation stage. The LR's total milk IgA differed from the baseline by roughly 47% only in the late lactation stage. The total and specific IgA contents in milk were more influenced by the anti-C. diff. immunizations than in blood. The correlations between anti-C. diff. specific IgA, total IgA and the main production factors in milk were classified as weak (I r I < 0.5), except for the close relation of anti-C. diff. specific IgA and total IgA (r = 0.69). To conclude, a sustainable C. diff. specific IgA enrichment in milk can be achieved by continuous immunization of dairy cows, provided a potent and well-formulated anti-C. diff. vaccine is given to dairy cows preselected due to their proven anti-C. diff. receptivity.

Clostridioides difficile Biology: Sporulation, Germination, and Corresponding Therapies for C. difficile Infection

Clostridioides difficile is a Gram-positive, spore-forming, toxin-producing anaerobe, and an important nosocomial pathogen. Due to the strictly anaerobic nature of the vegetative form, spores are the main morphotype of infection and transmission of the disease. Spore formation and their subsequent germination play critical roles in C. difficile infection (CDI) progress. Under suitable conditions, C. difficile spores will germinate and outgrow to produce the pathogenic vegetative form. During CDI, C. difficile produces toxins (TcdA and TcdB) that are required to initiate the disease. Meanwhile, it also produces spores that are responsible for the persistence and recurrence of C. difficile in patients. Recent studies have shed light on the regulatory mechanisms of C. difficile sporulation and germination. This review is to summarize recent advances on the regulation of sporulation/germination in C. difficile and the corresponding therapeutic strategies that are aimed at these important processes.

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.

Bezlotoxumab

Each month, subscribers to The Formulary Monograph Service receive 5 to 6 well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to Pharmacy & Therapeutics Committees. Subscribers also receive monthly 1-page summary monographs on agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation/medication use evaluation (DUE/MUE) is also provided each month. With a subscription, the monographs are available online to subscribers. Monographs can be customized to meet the needs of a facility. Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. For more information about The Formulary Monograph Service, contact Wolters Kluwer customer service at 866-397-3433. The March 2017 monograph topics are crisaborole, insulin degludec/liraglutide, inclusion glargine/lixisenatide, nusimersen, and rucaparib. The MUE is on insulin GLP-1 combo.

Infection prevention and control of Clostridium difficile: a global review of guidelines, strategies, and recommendations

BACKGROUND

Clostridium difficile is the leading cause of health care-associated infections. Given the high incidence of C. difficile infection (CDI) and the lack of primary prevention through immunization, health care professionals should be aware of the most current guidance, as well as strengths and limitations of the evidence base underpinning this guidance.

METHODS

We identified publicly available national or organizational guidelines related to CDI infection and prevention control (IPC) published between 2000 and 2015 and for any health care setting through an internet search using the Google search engine. We reviewed CDI-targeted IPC recommendations and describe the assessment of evidence in available guidelines.

RESULTS

We identified documents from 28 countries/territories, mainly from acute care hospitals in North America, the Western Pacific, and Europe (18 countries). We identified only a few specific recommendations for long-term care facilities (LTCFs) and from countries in South America (Uruguay and Chile), South East Asia (Thailand), and none for Africa or Eastern Mediterranean. Of 10 IPC areas, antimicrobial stewardship was universally recognized as essential and supported by high quality evidence. Five other widely reported "strong" recommendations were: effective environment cleaning (including medical equipment), case isolation, use of personal protective equipment, surveillance, and education. Several unresolved and emerging issues were documented and currently available evidence was classified mainly as of mixed quality.

CONCLUSION

Our review underlines the need for targeted CDI IPC guidelines in several countries and for LTCFs. International harmonisation on the assessment of the evidence for best practices is needed as well as more robust evidence to support targeted recommendations.

Immunogenicity and protective efficacy of recombinant Clostridium difficile flagellar protein FliC

Clostridium difficile is a Gram-positive bacillus and is the leading cause of toxin-mediated nosocomial diarrhea following antibiotic use. C. difficile flagella play a role in colonization, adherence, biofilm formation, and toxin production, which might contribute to the overall virulence of certain strains. Human and animal studies indicate that anti-flagella immune responses may play a role in protection against colonization by C. difficile and subsequent disease outcome. Here we report that recombinant C. difficile flagellin (FliC) is immunogenic and protective in a murine model of C. difficile infection (CDI) against a clinical C. difficile strain, UK1. Passive protection experiments using anti-FliC polyclonal serum in mice suggest this protection to be antibody-mediated. FliC immunization also was able to afford partial protection against CDI and death in hamsters following challenge with C. difficile 630Δerm. Additionally, immunization against FliC does not have an adverse effect on the normal gut flora of vaccinated hamsters as evidenced by comparing the fecal microbiome of vaccinated and control hamsters. Therefore, the use of FliC as a vaccine candidate against CDI warrants further testing.

Gastrointestinal dysbiosis and the use of fecal microbial transplantation in Clostridium difficile infection

The impact of antibiotics on the human gut microbiota is a significant concern. Antibiotic-associated diarrhea has been on the rise for the past few decades with the increasing usage of antibiotics. Clostridium difficile infections (CDI) have become one of the most prominent types of infectious diarrheal disease, with dramatically increased incidence in both the hospital and community setting worldwide. Studies show that variability in the innate host response may in part impact upon CDI severity in patients. That being said, CDI is a disease that shows the most prominent links to alterations to the gut microbiota, in both cause and treatment. With recurrence rates still relatively high, it is important to explore alternative therapies to CDI. Fecal microbiota transplantation (FMT) and other types of bacteriotherapy have become exciting avenues of treatment for CDI. Recent clinical trials have generated excitement for the use of FMT as a therapeutic option for CDI; however, the exact components of the human gut microbiota needed for protection against CDI have remained elusive. Additional investigations on the effects of antibiotics on the human gut microbiota and subsequent CDI will help reduce the socioeconomic burden of CDI and potentially lead to new therapeutic modalities.

Antibiotic therapy and Clostridium difficile infection - primum non nocere - first do no harm

Treatment options for Clostridium difficile infection (CDI) remain limited despite this usually nosocomial infection posing an urgent threat to public health. A major paradox of the management of CDI is the use of antimicrobial agents to treat infection, which runs the risk of prolonged gut microbiota perturbation and so recurrence of infection. Here, we explore alternative CDI treatment and prevention options currently available or in development. Notably, strategies that aim to reduce the negative effects of antibiotics on gut microbiota offer the potential to alter current antimicrobial stewardship approaches to preventing CDI.