Clostridium difficile-associated diarrhoea

A Retrospective Budget Impact Analysis of Fidaxomicin Treatment for Clostridioides difficile Infections (CDI) in Germany

BACKGROUND

Clostridioides difficile is the most common cause of healthcare-associated diarrhea. Research suggests that treating C. difficile infections (CDI) with fidaxomicin (FDX) is more effective than vancomycin (VAN), with potential cost savings. The objective was to calculate the budget impact of FDX treatment compared to VAN from a German payer perspective.

RESEARCH DESIGN AND METHODS

The analysis used real-world data of patients discharged from University Hospital Cologne between Jan-01-2018 and Dec-31-2019. We identified recurrent and non-recurrent CDI cases and calculated direct treatment costs based on G-DRG flat rates. To calculate average costs per treatment and the budget impact, recurrence probabilities for VAN and FDX were taken from published evidence (28-day and 90-day scenarios).

RESULTS

Totally, 475 cases were analyzed, thereof 421 non-recurrent, causing mean costs of €32,901 per case (95% CI: 27.752-38.050). Thirty-two patients experienced a recurrence within 28 days, yielding mean costs of €10,952 (95% CI: 5.627-16.277) for their additional hospital stay. The resulting budget impact was €1,303 (95% CI: 670 - 1.937) in favor of FDX, ranging from €148.34 to €2,190.30 in scenario analyses.

CONCLUSION

The analysis indicates FDX treatment can lead to cost savings compared to VAN. Future research should focus on specific patient groups, such as refractory CDI patients.

Revisiting the Intestinal Microbiome and Its Role in Diarrhea and Constipation

The gut microbiota represents a community of microorganisms (bacteria, fungi, archaea, viruses, and protozoa) that colonize the gut and are responsible for gut mucosal structural integrity and immune and metabolic homeostasis. The relationship between the gut microbiome and human health has been intensively researched in the past years. It is now widely recognized that gut microbial composition is highly responsible for the general health of the host. Among the diseases that have been linked to an altered gut microbial population are diarrheal illnesses and functional constipation. The capacity of probiotics to modulate the gut microbiome population, strengthen the intestinal barrier, and modulate the immune system together with their antioxidant properties have encouraged the research of probiotic therapy in many gastrointestinal afflictions. Dietary and lifestyle changes and the use of probiotics seem to play an important role in easing constipation and effectively alleviating diarrhea by suppressing the germs involved. This review aims to describe how probiotic bacteria and the use of specific strains could interfere and bring benefits as an associated treatment for diarrhea and constipation.

Clostridioides difficile infection (CDI): A pan-European multi-center cost and resource utilization study, results from the Combatting Bacterial Resistance in Europe CDI (COMBACTE-CDI)

OBJECTIVES

Clostridioides difficile infection (CDI) is one of the leading nosocomial infections worldwide, resulting in a significantly increasing burden on the healthcare systems. However, Pan-European data about cost and resource utilization of CDI treatment do not exist.

METHODS

A retrospective analysis within the Combatting Bacterial Resistance in Europe CDI project was conducted based on resource costs for inpatient treatment and productivity costs. Country-specific cost values were converted to EURO referred to 1 January, 2019 values. Differences in price levels for healthcare services among the participating countries were adjusted by using an international approach of the Organisation for Economic Co-operation and Development. As the study focused on patients with recurrent CDI, the observed study population was categorized into (a) patients with CDI but without CDI recurrence (case group), (b) patients with CDI recurrence (recurrence group), and (c) patients without CDI (control group).

RESULTS

Overall, 430 hospitalized patients from 12 European countries were included into the analysis between July 2018 and November 2018. Distribution of mean hospital length of stay and mean overall costs per patient between the case group, recurrence group, and control group were as follows: 22 days (95% CI 17-27 days) vs. 55 days (95% CI 17-94 days) vs. 26 days (95% CI 22-31 days; p 0.008) and € 15 242 (95% CI 10 593-19 891) vs. € 52 024 (95% CI 715-103 334) vs. € 21 759 (95% CI 16 484-27 035; p 0.010), respectively. The CDI recurrence rate during the observational period was 18%. Change escalation in CDI medication (OR 3.735) and treatment in an intensive care unit (OR 5.454) were found to be the most important variables associated with increased overall costs of patients with CDI.

CONCLUSIONS

Treatment of patients with recurrent CDI results in a significant burden. Prevention of CDI recurrences should be in focus of daily patient care to identify the most cost-effective treatment strategy.

Infection With Clostridioides difficile Attenuated Collagen-Induced Arthritis in Mice and Involved Mesenteric Treg and Th2 Polarization

Objectives

Rheumatoid arthritis is an autoimmune disease with multifactorial etiopathogenesis. Among the environmental factors, mucosal infections and the inducing pathobionts are gaining increasing attention. We here set out to explore the gut-joint-axis and the impact of Clostridioides difficile infection on subsequent arthritis.

Methods

We combined C. difficile infection in DBA/1J × B10.Q F1 mice with collagen induced arthritis (CIA). Mice were infected via oral gavage and infection was monitored by weight loss, colonic histology, and antibodies against bacteria. Scoring of arthritis was performed macroscopically. Intestinal microbiomes were analyzed and immune responses were monitored via quantification of transcription factor-specific mRNA isolated from the inguinal and mesenteric lymph nodes.

Results

Infection with C. difficile VPI 10463 resulted in significant weight loss and severe colitis yet accelerated the reversal towards the original microbiome after antibiotic treatment. Spontaneous clearance of VPI 10463 infection reduced the incidence of subsequent CIA and led to mesenteric T_reg and T_h2 polarization. However, this attenuating effect was abrogated if VPI 10463 was eradicated via vancomycin followed by fecal microbiota transplantation. Moreover, VPI 10463 infection following the onset of CIA lacked therapeutic potential.

Conclusion

Our results demonstrate that infection with C. difficile VPI10463 induced an inflammation of the gut that protected from subsequent arthritis development in mice. Both, microbial changes to the gut and immune cell mobilization and/or polarization may have contributed to arthritis protection. The prospect of potential therapeutic benefits resulting from C. difficile infections or some byproduct thereof call for further experiments that help elucidate exact mechanisms.

Human C. difficile toxin-specific memory B cell repertoires encode poorly neutralizing antibodies

Clostridioides difficile is a leading cause of nosocomial infection responsible for significant morbidity and mortality with limited options for therapy. Secreted C. difficile toxin B (TcdB) is a major contributor to disease pathology, and select TcdB-specific Abs may protect against disease recurrence. However, the high frequency of recurrence suggests that the memory B cell response, essential for new Ab production following C. difficile reexposure, is insufficient. We therefore isolated TcdB-specific memory B cells from individuals with a history of C. difficile infection and performed single-cell deep sequencing of their Ab genes. Herein, we report that TcdB-specific memory B cell–encoded antibodies showed somatic hypermutation but displayed limited isotype class switch. Memory B cell–encoded mAb generated from the gene sequences revealed low to moderate affinity for TcdB and a limited ability to neutralize TcdB. These findings indicate that memory B cells are an important factor in C. difficile disease recurrence.

The C. difficile toxin-specific human memory B cell repertoire encodes low-affinity, non-neutralizing antibodies.

Clostridium difficile-associated disease and Helicobacter pylori seroprevalence: A case-control study

BACKGROUND

Helicobacter pylori inhabits the stomach and causes persistent inflammation, with changes in gastric acidity. However, it is unclear whether the presence of H pylori plays a role in Clostridium difficile-associated disease (CDAD). The study's aim was to examine relationships of H pylori seroprevalence and serum pepsinogens (PGs), as markers of gastric inflammation, with CDAD.

MATERIALS AND METHODS

A case-control study was conducted among 49 CDAD cases and 54 controls (median age 82 years). Using enzyme-linked immunosorbent assays, sera were tested for H pylori IgG antibody, and PGI and PGII levels. Helicobacter pylori-positive samples were tested for IgG antibody to recombinant cytotoxin-associated gene A (CagA) virulent protein. Logistic regression models were fitted.

RESULTS

Cases and controls were comparable in age (P = .5) and sex distribution (females 62% vs 57%, P = .6). Helicobacter pylori IgG seroprevalence was 47%, of whom 23% were CagA seropositives. Among cases compared to controls, 43% vs 28% were H pylori seropositive but lacking CagA IgG antibody: adjusted odd ratio (OR) 3.43 (95% confidence intervals [CI] 1.29-9.10); 18% vs 4% were positive for CagA phenotype: adjusted OR 9.32 (95% CI 1.61-53.76). This association was not affected by PG levels.

CONCLUSIONS

Helicobacter pylori infection, especially with CagA virulent phenotype, might predispose to C difficile infection in elderly patients.

Developing Gut Microbiota Exerts Colonisation Resistance to Clostridium (syn. Clostridioides) difficile in Piglets

Clostridium (syn. Clostridioides) difficile is considered a pioneer colonizer and may cause gut infection in neonatal piglets. The aim of this study was to explore the microbiota-C. difficile associations in pigs. We used the DNA from the faeces of four sows collected during the periparturient period and from two to three of their piglets (collected weekly until nine weeks of age) for the determination of bacterial community composition (sequencing) and C. difficile concentration (qPCR). Furthermore, C. difficile-negative faeces were enriched in a growth medium, followed by qPCR to verify the presence of this bacterium. Clostridium-sensu-stricto-1 and Lactobacillus spp. predominated the gut microbiota of the sows and their offspring. C. difficile was detected at least once in the faeces of all sows during the entire sampling period, albeit at low concentrations. Suckling piglets harboured C. difficile in high concentrations (up to log₁₀ 9.29 copy number/g faeces), which gradually decreased as the piglets aged. Enrichment revealed the presence of C. difficile in previously C. difficile-negative sow and offspring faeces. In suckling piglets, the C. difficile level was negatively correlated with carbohydrate-fermenting bacteria, and it was positively associated with potential pathogens. Shannon and richness diversity indices were negatively associated with the C. difficile counts in suckling piglets. This study showed that gut microbiota seems to set conditions for colonisation resistance against C. difficile in the offspring. However, this conclusion requires further research to include host-specific factors.

Characterization of Clostridioides difficile ribotypes in domestic dogs in Rio de Janeiro, Brazil

Clostridioides difficile is the major etiologic agent of nosocomial bacterial diarrhoea and pseudomembranous colitis. The pathogenesis of C. difficile infection (CDI)involves two cytotoxic enzymes (TcdA, TcdB) that cause colonic epithelial damage, fluid accumulation and enteritis. CDI has been demonstrated in a variety of animal species and some reports have recently raised the importance of wild animals as a reservoir of this pathogen and possible transmission to humans and domestic animals. The aim of this study was to characterize C. difficile isolates obtained from pet dogs in Rio de Janeiro, Brazil. A total of 50 faecal samples were obtained from healthy and diarrheic dogs. Five of fifty samples (10%) grew C. difficile. Of those, three belonged to the PCR ribotype 106 (ST 42) and were toxigenic (A⁺B⁺). The other two strains belonged to the PCR ribotype 010 (ST 15) and were not toxin producers (A^-B^-). None of the isolates tested positive for the binary toxin genes. Considering the antimicrobial resistance patterns of all isolates using EUCAST breakpoints, all strains were sensitive to metronidazole and vancomycin. However, two strains (ribotype 106 and ribotype 010), were resistant to clindamycin (≤256 μg/mL). All strains were strong biofilm producers. Our study provides evidence that dogs can act as reservoirs for C. difficile epidemic ribotypes.

Differential effects of Clostridium difficile toxins on ion secretion and cell integrity in human intestinal cells

BACKGROUND

Toxin A (TcdA), toxin B (TcdB), and binary toxin (CDT) produced by Clostridium difficile (CD) are thought to play a key role in inducing diarrhea. The aim of this study was to investigate the individual and combined roles of CD toxins in inducing enterotoxic and cytotoxic effect.

METHODS

Ion secretion and epithelial damage were evaluated in the Ussing chambers as measure of enterotoxic or cytotoxic effect, respectively, in human-derived intestinal cells.

RESULTS

When added to the mucosal side of Caco-2 cells, TcdB, but not TcdA, induced ion secretion and its effects increased in the presence of TcdA. CDT also induced ion secretion when added to either the mucosal or serosal compartment. Serosal addition of TcdB induced epithelial damage consistent with its cytotoxic effect. However, mucosal addition of TcdB had similar effects, but only in the presence of TcdA. CDT induced epithelial damage when added to the serosal side of cell monolayers, and this was associated with a late onset but prolonged effect. All data were replicated using human colon biopsies.

CONCLUSIONS

These data indicate that CD, through the combined and direct activity of its three toxins, induces integrated and synergic enterotoxic and cytotoxic effects on the intestinal epithelium.

TPL2 Is a Key Regulator of Intestinal Inflammation in Clostridium difficile Infection

Tumor progression locus 2 (TPL2), a serine/threonine protein kinase, is a major inflammatory mediator in immune cells. The predominant inflammatory actions of TPL2 depend on the activation of mitogen-activated protein kinases (MAPK) and the upregulated production of the cytokines tumor necrosis factor alpha (TNF-α) and interleukin 1β (IL-1β) in macrophages and dendritic cells in response to lipopolysaccharide (LPS). Significant increases in TNF-α, IL-6, IL-β, and IL-8 levels in patients with Clostridium difficile infection (CDI) have been reported. Both TNF-α and IL-6 have been postulated to play key roles in the systemic inflammatory response in CDI, and IL-8 is essential for the development of local intestinal inflammatory responses in CDI. The objective of this study was to elucidate the role of TPL2 in the pathogenesis of CDI. We found that TPL2 was significantly activated in human and mouse intestinal tissues upon C. difficile toxin exposure or CDI. We further demonstrated that TPL2 knockout (TPL2-KO) mice were significantly more resistant to CDI than wild-type mice, with significantly reduced production of TNF-α, IL-6, IL-1β, KC (a mouse homologue of IL-8), and myeloperoxidase (MPO) in the ceca and colons of TPL2-KO mice. Finally, we found that TPL2 inhibition by a specific inhibitor or TPL2 gene ablation significantly reduced TcdB-induced production of TNF-α, IL-6, IL-β, and KC by inhibiting the activation of p38, extracellular signal-regulated kinase (ERK), and c-Jun NH₂-terminal kinase (JNK). Taken together, our data suggest that TPL2 represents a potential therapeutic target for CDI treatment.

The Epidemiology of Community Clostridium difficile Infection: A Five-Year Population-Based Study on the Bailiwick of Jersey, Channel Islands

We studied healthcare-associated and community-associated Clostridium difficile infection (CDI) in Jersey, Channel Islands (2008–2012). The Island’s stable population has reliable denominator data, a clearly defined at-risk population, and healthcare contact that is easily followed. The vast majority of CDI cases had had recent healthcare contact, and true community-associated disease is extremely rare.

Infect Control Hosp Epidemiol 2018;39:603–607

Gene expression profiling in pbMEC - in search of molecular biomarkers to predict immunoglobulin production in bovine milk

Background

Optimization of the immunoglobulin (Ig) yield in bovine milk used as therapeutic immune milk or whey for the prevention of Clostridium difficile-associated diarrhea in humans is of great importance to improve the economic efficiency of production. Individual dairy cows have diverse immune responses upon vaccination, resulting in a variable Ig yield in blood and milk. Therefore, it is advisable to pre-select cows with the best ability to produce and secrete high yields of specific Igs.

Results

The gene expression profile of pbMEC (primary bovine mammary epithelial cells), challenged with the gram-positive, non-mastitis, pathogen Clostridium difficile showed distinct and significant differences in the gene expression of effector molecules of the innate immune system. A number of genes were identified that could possibly serve as molecular biomarkers to differentiate high responder cows from low responder cows. These identified genes play key roles in the promotion of innate immunity.

Conclusion

Using a gene expression profiling approach, we showed that upon others, especially the gene expression of the pro-inflammatory cytokines was altered between the high and low responder cows. Those genes are indicated as potential molecular biomarkers in the pre-selection of cows that are able to secrete high immunoglobulin yields in milk.

Electronic supplementary material

The online version of this article (10.1186/s12917-017-1293-z) contains supplementary material, which is available to authorized users.

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.

Recurrent Clostridium difficile Infection in Children: Patient Risk Factors and Markers of Intestinal Inflammation

BACKGROUND

The management of Clostridium difficile infection (CDI) in children is complicated by recurrence rates of 20%-30%. The identification of risk factors associated with recurrent disease might allow early recognition of those children at highest risk.

METHODS

Pediatric patients with CDI were identified through clinical laboratory records at 2 tertiary-care children's hospitals from March 2013 through May 2014. Subjects were enrolled and followed for 60 days to assess for recurrent CDI (rCDI). Blood samples were obtained at enrollment to evaluate host interleukin (IL)-8 polymorphisms and anti-toxin A antibody levels; stool samples were obtained for inflammatory markers (lactoferrin, calprotectin, IL-8) and C. difficile ribotype 027 strain status. Thirty days post enrollment, another serum sample was obtained to compare antibody responses.

RESULTS

Of the 28 pediatric patients enrolled, 27 completed follow-up and 8 (30%) experienced rCDI. At enrollment, children with malignancy had significantly lower stool calprotectin, lactoferrin and IL-8 than those without malignancy. There was a trend toward increased stool inflammatory markers in those who later developed rCDI. The IL-8 A/A genotype was not associated with recurrent disease. No patients were found to have ribotype 027 or an antibody increase to toxin A.

CONCLUSIONS

The rate of rCDI in our pediatric cohort was 30%. Children with rCDI had a trend toward higher fecal inflammatory markers with the initial infection, and these values were lower in children with malignancy. Fecal lactoferrin, calprotectin and IL-8 should be further studied to determine their value in predicting the risk of rCDI in children.

Diagnosis and outcome of Clostridium difficile infection by toxin enzyme immunoassay and polymerase chain reaction in an island population

BACKGROUND AND AIM

Clostridium difficile infection (CDI) is a potentially life-threatening cause of diarrhea. Correct laboratory diagnosis is essential to differentiate CDI from other causes of diarrhea. A positive fecal C. difficile toxin (CDT) is the best indicator of CDI, but the significance of a positive fecal nucleic acid amplification test (NAAT) remains unclear. Our aim was to elucidate the significance of CDI diagnostics in patients in Jersey.

METHODS

A retrospective, 5-year study was conducted at an island district general hospital of patients who developed CDI. Patients were grouped according to CDT and NAAT status and their association with outcome (indicators of severity and 30-day case-fatality rate) compared.

RESULTS

A total of 207 specimens were toxin positive, 92 NAAT positive and toxin negative, and 39 had a stool sample negative by both toxin and NAAT testing. A positive toxin stool sample was associated with both significantly higher white cell count (14.5 × 10⁹ /L vs 11.3 × 10⁹ /L, P = 0.003) and C-reactive protein (114.7 mg/dL vs 82.9 mg/dL, P = 0.001), but NAAT positivity was not (P = 0.269, 0.728). A positive CDT assay was a significant independent predictor of death (odds ratio [OR]: 1.89 [95% CI: 1.04-3.43], P = 0.046), but a positive NAAT in CDT negative samples was not (OR: 1.02 [95% CI: 0.34-3.12], P = 1.0).

CONCLUSIONS

The findings of this study, derived from evolving clinical practice, provide greater clarity in the interpretation of CDI diagnostics. In CDT-negative disease, a positive NAAT neither predicts disease severity nor mortality. NAAT-positive and toxin-negative patients require instigation of infection control measures, but the need for specific treatment remains unclear.

Clostridium Difficile Infection in Children: A Review

Clostridium difficile is a sporogenic, anaerobic, Gram-positive, emerging enteric pathogen. It represents the most common cause of health care-associated diarrhoea in the United States, with significantly associated morbidity, mortality, and health care costs. Historically regarded as a little more than an innocent coloniser bystander of the gastrointestinal tract of children, C difficile has increasingly demonstrated its behaviour as a true pathogen in the paediatric age groups. This organism may be responsible for a broad spectrum of diseases in children, ranging from self-limiting secretory diarrhoea to life-threatening conditions, such as pseudomembranous colitis, toxic megacolon, intestinal perforation, and septic shock. The incidence and severity of C difficile infection are, however, not completely understood in this population. In particular, although asymptomatic carriage remains high among infants, the clinical significance of detecting C difficile in children aged 1 to 3 years is not fully understood. Moreover, recent epidemiological surveillance has demonstrated a rise in the incidence of C difficile infection, particularly in the community and in low-risk settings. Interestingly, such cases may not show the disease pattern to be associated with typical risk factors, such as recent exposure to antimicrobial drugs or on-going contacts with the health care system.The purpose of the present review is to present the features of C difficile infection that are unique to paediatric patients and to update paediatricians on information and recommendations regarding C difficile infection in children.

High Mobility Group Box1 Protein Is Involved in Endoplasmic Reticulum Stress Induced by Clostridium difficile Toxin A

High Mobility Group Box1 (HMGB1), a damage-associated inflammatory factor, plays an important role in the pathogenesis of numerous chronic inflammatory and autoimmune diseases. In this study, the role of the HMGB1 in TcdA-induced ER stress was identified. Clostridium difficile toxin A is one of the major virulence factors of C. difficile infection (CDI) and has been proved to induce apoptotic cell death through ER stress. Our results showed that HMGB1 might play an important role in the TcdA-induced ER stress and unfolded protein response. HMGB1 activated molecular markers and induced the C/EBP homologous protein upregulation (CHOP). This study may provide the essential information for better understanding of the molecular mechanisms involved in CDI.

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.

A Novel Fic (Filamentation Induced by cAMP) Protein from Clostridium difficile Reveals an Inhibitory Motif-independent Adenylylation/AMPylation Mechanism

Filamentation induced by cAMP (Fic) domain proteins have been shown to catalyze the transfer of the AMP moiety from ATP onto a protein target. This type of post-translational modification was recently shown to play a crucial role in pathogenicity mediated by two bacterial virulence factors. Herein we characterize a novel Fic domain protein that we identified from the human pathogen Clostridium difficile The crystal structure shows that the protein adopts a classical all-helical Fic fold, which belongs to class II of Fic domain proteins characterized by an intrinsic N-terminal autoinhibitory α-helix. A conserved glutamate residue in the inhibitory helix motif was previously shown in other Fic domain proteins to prevent proper binding of the ATP γ-phosphate. However, here we demonstrate that both ATP binding and autoadenylylation activity of the C. difficile Fic domain protein are independent of the inhibitory motif. In support of this, the crystal structure of a mutant of this Fic protein in complex with ATP reveals that the γ-phosphate adopts a conformation unique among Fic domains that seems to override the effect of the inhibitory helix. These results provide important structural insight into the adenylylation reaction mechanism catalyzed by Fic domains. Our findings reveal the presence of a class II Fic domain protein in the human pathogen C. difficile that is not regulated by autoinhibition and challenge the current dogma that all class I-III Fic domain proteins are inhibited by the inhibitory α-helix.

Clostridium difficile infection in the pediatric transplant patient

CDIs are on the rise in both hospital and community settings in adults and children. Children with cancer or a history of HSCT or SOT appear to be at higher risk for primary disease, recurrent disease, and severe outcomes when compared to children with other comorbidities. The reasons for this are not clear and no studies to date have analyzed risk factors for CDI in pediatric transplant patients. Colonization rates in children with cancer and a transplant history are also high. Determining which children are colonized with Clostridium difficile and symptomatic from another source vs. symptomatic from CDI is difficult and a clinical conundrum for the transplant physician. The use of fecal transplantation for severe or rCDI is likely safe and effective in the immunosuppressed pediatric cancer or transplant patient, but this will need to be more thoroughly studied in this patient population.

Defective mutations within the translocation domain of Clostridium difficile toxin B impair disease pathogenesis

The Clostridium difficile toxin B is one of the main virulence factors and plays an important role in the pathogenesis of C. difficile infection (CDI). We recently revealed crucial residues in the translocation domain of TcdB for the pore formation and toxin translocation. In this study, we investigated the effects of mutating a critical site involved in pore formation, Leu-1106, to residues that differ in size and polarity (Phe, Ala, Cys, Asp). We observed a broad range of effects on TcdB function in vitro consistent with the role of this site in pore formation and translocation. We show that mice challenged systemically with a lethal dose (LD100) of the most defective mutant (L1106K) showed no symptoms of disease highlighting the importance of this residue and the translocation domain in disease pathogenesis. These findings offer insights into the structure function of the toxin translocation pore, and inform novel therapeutic strategies against CDI.

Immune-based treatment and prevention of Clostridium difficile infection

Clostridium difficile (C. difficile) causes over 500,000 infections per year in the US, with an estimated 15,000 deaths and an estimated cost of $1-3 billion. Moreover, a continual rise in the incidence of severe C. difficile infection (CDI) has been observed worldwide. Currently, standard treatment for CDI is the administration of antibiotics. While effective, these treatments do not prevent and may contribute to a disease recurrence rate of 15-35%. Prevention of recurrence is one of the most challenging aspects in the field. A better knowledge of the molecular mechanisms of the disease, the host immune response and identification of key virulence factors of C. difficilenow permits the development of immune-based therapies. Antibodies specific for C. difficile toxins have been shown to effectively treat CDI and prevent disease relapse in animal models and in humans. Vaccination has been recognized as the most cost-effective treatment/prevention for CDI. This review will summarize CDI transmission, epidemiology, major virulent factors and highlights the rational and the development of immune-based approaches against this remerging threat.

The non-toxigenic Clostridium difficile CD37 protects mice against infection with a BI/NAP1/027 type of C. difficile strain

Clostridium difficile CD37, a clinical isolate from the USA, does not produce toxin A, B or binary toxin. The aim of this study was to determine whether strain CD37 can protect mice against infection from a challenge with a toxigenic C. difficile strain. Three groups of mice (n = 10) were pretreated with a antibiotics cocktail for 5 days, switched to sterile water for 2 days, and given one dose of clindamycin (10 mg/kg) one day (day-1) before challenge (day 0) with a toxigenic C. difficile strain. Group 1 (CD37 + UK6) was given 10(7)C. difficile CD37 vegetative cells by gavage twice a day on days -1 and -2, followed by challenge with 10(6) spores of the toxigenic C. difficile UK6 (BI/NAPI/027) on day 0; Group 2 (UK6) was infected with 10(6)C. difficile UK6 spores on day 0; Group 3 (CD37) was challenged with 10(6) CD37 vegetative cells on day 0. Our data show that pre-inoculation of strain CD37 provided mice significant protection (survival, p < 0.001 between groups CD37 + UK6 and UK6) against subsequent infection with the strain UK6, while mice infected with CD37 only did not develop any symptoms of C. difficile infection (CDI). Our results highlight the potential use of CD37 as a therapeutic strain for the prevention of primary and recurrent CDI in humans.

Community-acquired Clostridium difficile infection in children: A retrospective study

BACKGROUND

Community acquired-Clostridium difficile infection (CDI) has increased also in children in the last years.

AIMS

To determine the incidence of community-acquired CDI and to understand whether Clostridium difficile could be considered a symptom-triggering pathogen in infants.

METHODS

A five-year retrospective analysis (January 2007-December 2011) of faecal specimens from 124 children hospitalized in the Niguarda Ca' Granda Hospital for prolonged or muco-haemorrhagic diarrhoea was carried out. Stool samples were evaluated for common infective causes of diarrhoea and for Clostridium difficile toxins. Patients with and without CDI were compared for clinical characteristics and known risk factors for infection.

RESULTS

Twenty-two children with CDI were identified in 5 years. An increased incidence of community-acquired CDI was observed, ranging from 0.75 per 1000 hospitalizations in 2007 to 9.8 per 1000 hospitalizations in 2011. Antimicrobial treatment was successful in all 19 children in whom it was administered; 8/22 CDI-positive children were younger than 2 years. No statistically significant differences in clinical presentation were observed between patients with and without CDI, nor in patients with and without risk factors for CDI.

CONCLUSIONS

Our study shows that Clostridium difficile infection is increasing and suggests a possible pathogenic role in the first 2 years of life.

Using a Novel Lysin To Help Control Clostridium difficile Infections

As a consequence of excessive antibiotic therapies in hospitalized patients, Clostridium difficile, a Gram-positive anaerobic spore-forming intestinal pathogen, is the leading cause of hospital-acquired diarrhea and colitis. Drug treatments for these diseases are often complicated by antibiotic-resistant strains and a high frequency of treatment failures and relapse; therefore, novel nonantibiotic approaches may prove to be more effective. In this study, we recombinantly expressed a prophage lysin identified from a C. difficile strain, CD630, which we named PlyCD. PlyCD was found to have lytic activity against specific C. difficile strains. However, the recombinantly expressed catalytic domain of this protein, PlyCD1-174, displayed significantly greater lytic activity (>4-log kill) and a broader lytic spectrum against C. difficile strains while still retaining a high degree of specificity toward C. difficile versus commensal clostridia and other bacterial species. Our data also indicated that noneffective doses of vancomycin and PlyCD1-174 when combined in vitro could be significantly more bactericidal against C. difficile. In an ex vivo treatment model of mouse colon infection, we found that PlyCD1-174 functioned in the presence of intestinal contents, significantly decreasing colonizing C. difficile compared to controls. Together, these data suggest that PlyCD1-174 has potential as a novel therapeutic for clinical application against C. difficile infection, either alone or in combination with other preexisting treatments to improve their efficacy.

Risk Factors for In-Hospital Mortality among a Cohort of Children with Clostridium difficile Infection

OBJECTIVE

The incidence of Clostridium difficile infection (CDI) has increased and has been associated with poor outcomes among hospitalized children, including increased risk of death. The purpose of this study was to identify risk factors for all-cause in-hospital mortality among children with CDI.

METHODS

A multicenter cohort of children with CDI, aged 1–18 years, was established among children hospitalized at 41 freestanding children’s hospitals between January 1, 2006 and August 31, 2011. Children with CDI were identified using a validated case-finding tool (ICD-9-CM code for CDI plus C. difficile test charge). Only the first CDI-related hospitalization during the study period was used. Risk factors for all-cause in-hospital mortality within 30 days of C. difficile test were evaluated using a multivariable logistic regression model.

RESULTS

We identified 7,318 children with CDI during the study period. The median age of this cohort was 6 years [interquartile range (IQR): 2–13]; the mortality rate was 1.5% (n=109); and the median number of days between C. difficile testing and death was 12 (IQR, 7–20). Independent risk factors for death included older age [adjusted odds ratio (OR, 95% confidence interval), 2.29 (1.40–3.77)], underlying malignancy [3.57 (2.36–5.40)], cardiovascular disease [2.06 (1.28–3.30)], hematologic/immunologic condition [1.89 (1.05–3.39)], gastric acid suppression [2.70 (1.43–5.08)], and presence of >1 severity of illness marker [3.88 (2.44–6.19)].

CONCLUSION

Patients with select chronic conditions and more severe disease are at increased risk of death. Identifying risk factors for in-hospital mortality can help detect subpopulations of children that may benefit from targeted CDI prevention and treatment strategies.

Infect Control Hosp Epidemiol 2015;36(10):1183–1189

First report of Clostridium difficile NAP1/027 in a Mexican hospital

Background and Objective

Clostridium difficile NAP1/ribotype 027 is associated with severe disease and high mortality rates. Our aim was to determine the prevalence of NAP1/ribotype 027 among C. difficile isolates in a tertiary care hospital, and review the main clinical data.

Methods

We included 106 stool samples from 106 patients. Samples were tested for A&B toxins and were cultured on CCFA agar. The genes tcdA, tcdB, tcdC, cdtA, and cdtB were amplified using PCR in clinical isolates. The tcdA 3’-end deletion analysis, PCR-ribotyping, and pulsed-field gel electrophoresis (PFGE) were also performed. Stool samples that were positive for culture were tested by the GeneXpert C. difficile assay. Clinical data were collected.

Results

Thirty-six patients tested positive for A&B toxins; and 22 patients had positive culture for C. difficile, 14 of which tested positive for the A&B toxins and all 22 patients tested positive by the GeneXpert C. difficile assay. Risk factors included an average hospital stay of 16.1 days prior to toxin detection, average antibiotic use for 16.2 days, and a median of 3 antibiotics used. The 30-day crude mortality rate was 8.4%. Six of the 22 patients died, and 3 of those deaths were directly attributed to C. difficile infection. The majority of isolates, 90.9% (20/22), carried genes tcdB, tcdA, cdtA, and cdtB; and these strains carried the corresponding downregulator gene tcdC, with an 18-bp deletion. PFGE was performed on 17 isolates, and one main pattern was observed. Analysis of the ribotyping data showed similar results.

Conclusion

The above findings represent the clonal spread of C. difficile in our institution, which mainly includes the NAP1/027 strain. This is the first report of C. difficile ribotype NAP1/027 in Mexico.

Clostridium difficile toxin B intoxicated mouse colonic epithelial CT26 cells stimulate the activation of dendritic cells

Clostridium difficile causes antibiotic-associated diarrhea and pseudomembranous colitis mainly through two exotoxins TcdA and TcdB that target intestinal epithelial cells. Dendritic cells (DCs) play an important role in regulating intestinal inflammatory responses. In the current study, we explored the interaction of TcdB-intoxicated epithelial cells with mouse bone marrow-derived DCs. TcdB induced cell death and heat shock protein translocation in mouse intestinal epithelial CT26 cells. The intoxicated epithelial cells promoted the phagocytosis and the TNF-α secretion by DCs. Incubation with TcdB-intoxicated CT26 cells stimulated DC maturation. Moreover, TcdB-treated CT26 cells induced DC immigration when they were injected into mice subcutaneously. Taken together, these data demonstrate that TcdB-intoxicated intestinal epithelial cells are able to stimulate DC activation in vitro and attract DCs in vivo, indicating that epithelial cells may be able to regulate DC activation under the exposure of TcdB during C. difficile infection.

New perspectives in Clostridium difficile disease pathogenesis

Clostridium difficile is associated with a spectrum of clinical manifestations ranging from asymptomatic carriage to severe life-threatening pseudomembranous colitis. Current perspectives indicate that C difficile pathogenesis is a multifactorial disease process dictated by pathogenic toxin production, gut microbial dysbiosis, and altered host inflammatory responses. This article summarizes recent findings underpinning the cellular and molecular mechanisms regulating bacterial virulence and sheds new light on the critical roles of the host immune response, intestinal microbiota, and metabolome in mediating disease pathogenesis.

Novel risk factors for recurrent Clostridium difficile infection in children

OBJECTIVES

Clostridium difficile, a common cause of antibiotic-associated diarrhea, has been reported to recur in high rates in adults. The rates and risk factors for recurrent C difficile infection (rCDI) in children have not been well established.

METHODS

We conducted a retrospective cohort study of 186 pediatric patients seen at a tertiary care referral center for a 5-year period diagnosed as having a primary C difficile infection. Children with recurrent disease, defined as return of symptoms of C difficile infection and positive testing ≤60 days after the completion of therapy, were compared with children who did not experience an episode of recurrence.

RESULTS

Of the 186 pediatric patients included in this study, 41 (22%) experienced rCDI. On univariable analysis, factors significantly associated with rCDI included malignancy, recent hospitalization, recent surgery, antibiotic use, number of antibiotic exposures by class, acid blocker use, immunosuppressant use, and hospital-acquired disease. On multivariable analysis, malignancy (odds ratio [OR] 3.39, 95% confidence interval [CI] 1.52-7.85), recent surgery (OR 2.40, 95% CI 1.05-5.52), and the number of antibiotic exposures by class (OR 1.33, 95% CI 1.01-1.75) were significantly associated with recurrent disease in children.

CONCLUSIONS

The rate of rCDI in children was 22%. Recurrence was significantly associated with the risk factors of malignancy, recent surgery, and the number of antibiotic exposures by class.

The roles of host and pathogen factors and the innate immune response in the pathogenesis of Clostridium difficile infection

Clostridium difficile (C. difficile) is the most common cause of nosocomial antibiotic-associated diarrhea and the etiologic agent of pseudomembranous colitis. The clinical manifestation of C. difficile infection (CDI) is highly variable, from asymptomatic carriage, to mild self-limiting diarrhea, to the more severe pseudomembranous colitis. Furthermore, in extreme cases, colonic inflammation and tissue damage can lead to toxic megacolon, a condition requiring surgical intervention. C. difficile expresses two key virulence factors; the exotoxins, toxin A (TcdA) and toxin B (TcdB), which are glucosyltransferases that target host-cell monomeric GTPases. In addition, some hypervirulent strains produce a third toxin, binary toxin or C. difficile transferase (CDT), which may contribute to the pathogenesis of CDI. More recently, other factors such as surface layer proteins (SLPs) and flagellin have also been linked to the inflammatory responses observed in CDI. Although the adaptive immune response can influence the severity of CDI, the innate immune responses to C. difficile and its toxins play crucial roles in CDI onset, progression, and overall prognosis. Despite this, the innate immune responses in CDI have drawn relatively little attention from clinical researchers. Targeting these responses may prove useful clinically as adjuvant therapies, especially in refractory and/or recurrent CDI. This review will focus on recent advances in our understanding of how C. difficile and its toxins modulate innate immune responses that contribute to CDI pathogenesis.

Controversies Surrounding Clostridium difficile Infection in Infants and Young Children

Clostridium difficile is a frequent cause of antibiotic-associated diarrhea in adults and older children. However, as many as 80% of infants can be asymptomatically colonized. The reasons for this have not been well established but are believed to be due to differences in toxin receptors or toxin internalization. Determining which children who test positive for C. difficile warrant treatment is exceedingly difficult, especially in the setting of increased rates of detection and the rising risk of disease in children lacking classic risk factors for C. difficile.

Epidemiology of Clostridium difficile infection in two tertiary-care hospitals in Perth, Western Australia: a cross-sectional study

The epidemiology of Clostridium difficile infection (CDI) has changed over time and between countries. It is therefore essential to monitor the characteristics of patients at risk of infection and the circulating strains to recognize local and global trends, and improve patient management. From December 2011 to May 2012 we conducted a prospective, observational epidemiological study of patients with laboratory-confirmed CDI at two tertiary teaching hospitals in Perth, Western Australia to determine CDI incidence and risk factors in an Australian setting. The incidence of CDI varied from 5.2 to 8.1 cases/10 000 occupied bed days (OBDs) at one hospital and from 3.9 to 16.3/10 000 OBDs at the second hospital. In total, 80 patients with laboratory-confirmed CDI met eligibility criteria and consented to be in the study. More than half (53.8%) had hospital-onset disease, 28.8% had community-onset and healthcare facility-associated disease and 7.5% were community-associated infections according to the definitions used. Severe CDI was observed in 40.0% of these cases but the 30-day mortality rate for all cases was only 2.5%. Besides a shorter length of stay among cases of community-onset CDI, no characteristics were identified that were significantly associated with community-onset or severe CDI. From 70 isolates, 34 different ribotypes were identified. The predominant ribotypes were 014 (24.3%), 020 (5.7%), 056 (5.7%) and 070 (5.7%). Whereas this study suggests that the characteristics of CDI cases in Australia are not markedly different from those in other developed countries, the increase in CDI rate observed emphasizes the importance of surveillance.

Clostridium difficile Infection: Epidemiology, Pathogenesis, Risk Factors, and Therapeutic Options

The incidence and mortality rate of Clostridium difficile infection have increased remarkably in both hospital and community settings during the last two decades. The growth of infection may be caused by multiple factors including inappropriate antibiotic usage, poor standards of environmental cleanliness, changes in infection control practices, large outbreaks of C. difficile infection in hospitals, alteration of circulating strains of C. difficile, and spread of hypervirulent strains. Detection of high-risk populations could be helpful for prompt diagnosis and consequent treatment of patients suffering from C. difficile infection. Metronidazole and oral vancomycin are recommended antibiotics for the treatment of initial infection. Current treatments for C. difficile infection consist of supportive care, discontinuing the unnecessary antibiotic, and specific antimicrobial therapy. Moreover, novel approaches include fidaxomicin therapy, monoclonal antibodies, and fecal microbiota transplantation mediated therapy. Fecal microbiota transplantation has shown relevant efficacy to overcome C. difficile infection and reduce its recurrence.

Clostridium difficile infection in children hospitalized due to diarrhea

The frequency of Clostridium difficile infection (CDI)-related hospitalizations is increasing. The aim of this study was to determine the extent of CDI among children hospitalized with diarrhea, risk factors or predictors for severe CDI, the prevalence of NAP1, and to compare the course of CDI depending on bacteria toxicity profile. A retrospective analysis of case records of 64 children (age range 3 months–16 years, median age 2.12 years) with CDI as defined by diarrheal disease and positive polymerase chain reaction (PCR) test (Xpert C. difficile) was conducted. Modified national adult guidelines were used to assess the severity of CDI. CDIs represented 2.7 % of patients with diarrhea (13.5 cases per 1,000 admissions). Thirty-three CDIs (52 %) were community-associated. Antibacterial use preceded CDI in 61 patients (95 %). Seventeen cases (27 %) were binary toxin-positive (CDT+), 13 of which were NAP1 (20.5 %). Over 75 % of CDIs with NAP1 was hospital-acquired, and more often proceeded with generalized infection (p < 0.05). Risk factors for severe CDI (34 %) included NAP1 [odds ratio (OR), 4.85; 95 % confidence interval (Cl), 1.23, 21.86) and co-morbidities (OR, 4.25; 95 % Cl, 1.34, 14.38). Diarrhea ≥10 stools daily was associated with severe CDI (p = 0.01). Recurrence occurred in three patients (4.5 %). There was no mortality. C. difficile is an important factor of antibiotic-associated diarrhea in children. Co-morbidities and NAP1 predispose to severe CDI.

Effects of Clostridium difficile toxin A and B on human T lymphocyte migration

Bacterial products such as toxins can interfere with a variety of cellular processes, leading to severe human diseases. Clostridium difficile toxins, TcdA and TcdB are the primary contributing factors to the pathogenesis of C. difficile-associated diseases (CDAD). While the mechanisms for TcdA and TcdB mediated cellular responses are complex, it has been shown that these toxins can alter chemotactic responses of neutrophils and intestinal epithelial cells leading to innate immune responses and tissue damages. The effects of C. difficile toxins on the migration and trafficking of other leukocyte subsets, such as T lymphocytes, are not clear and may have potential implications for adaptive immunity. We investigated here the direct and indirect effects of TcdA and TcdB on the migration of human blood T cells using conventional cell migration assays and microfluidic devices. It has been found that, although both toxins decrease T cell motility, only TcdA but not TcdB decreases T cell chemotaxis. Similar effects are observed in T cell migration toward the TcdA- or TcdB-treated human epithelial cells. Our study demonstrated the primary role of TcdA (compared to TcdB) in altering T cell migration and chemotaxis, suggesting possible implications for C. difficile toxin mediated adaptive immune responses in CDAD.

Structural insight into the Clostridium difficile ethanolamine utilisation microcompartment

Bacterial microcompartments form a protective proteinaceous barrier around metabolic enzymes that process unstable or toxic chemical intermediates. The genome of the virulent, multidrug-resistant Clostridium difficile 630 strain contains an operon, eut, encoding a bacterial microcompartment with genes for the breakdown of ethanolamine and its utilisation as a source of reduced nitrogen and carbon. The C. difficile eut operon displays regulatory genetic elements and protein encoding regions in common with homologous loci found in the genomes of other bacteria, including the enteric pathogens Salmonella enterica and Enterococcus faecalis. The crystal structures of two microcompartment shell proteins, CD1908 and CD1918, and an uncharacterised protein with potential enzymatic activity, CD1925, were determined by X-ray crystallography. CD1908 and CD1918 display the same protein fold, though the order of secondary structure elements is permuted in CD1908 and this protein displays an N-terminal β-strand extension. These proteins form hexamers with molecules related by crystallographic and non-crystallographic symmetry. The structure of CD1925 has a cupin β-barrel fold and a putative active site that is distinct from the metal-ion dependent catalytic cupins. Thin-section transmission electron microscopy of Escherichia coli over-expressing eut proteins indicates that CD1918 is capable of self-association into arrays, suggesting an organisational role for CD1918 in the formation of this microcompartment. The work presented provides the basis for further study of the architecture and function of the C. difficile eut microcompartment, its role in metabolism and the wider consequences of intestinal colonisation and virulence in this pathogen.

Toxigenic Clostridium difficile PCR ribotypes from wastewater treatment plants in southern Switzerland

The occurrence of Clostridium difficile in nine wastewater treatment plants in the Ticino Canton (southern Switzerland) was investigated. The samples were collected from raw sewage influents and from treated effluents. Forty-seven out of 55 characterized C. difficile strains belonged to 13 different reference PCR ribotypes (009, 010, 014, 015, 039, 052, 053, 066, 070, 078, 101, 106, and 117), whereas 8 strains did not match any of those available in our libraries. The most frequently isolated ribotype (40%) was 078, isolated from six wastewater treatment plants, whereas ribotype 066, a toxigenic emerging ribotype isolated from patients admitted to hospitals in Europe and Switzerland, was isolated from the outgoing effluent of one plant. The majority of the isolates (85%) were toxigenic. Forty-nine percent of them produced toxin A, toxin B, and the binary toxin (toxigenic profile A(+) B(+) CDT(+)), whereas 51% showed the profile A(+) B(+) CDT(-). Interestingly, eight ribotypes (010, 014, 015, 039, 066, 078, 101, and 106) were among the riboprofiles isolated from symptomatic patients admitted to the hospitals of the Ticino Canton in 2010. Despite the limitation of sampling, this study highlights that toxigenic ribotypes of C. difficile involved in human infections may occur in both incoming and outgoing biological wastewater treatment plants. Such a finding raises concern about the possible contamination of water bodies that receive wastewater treatment plant effluents and about the safe reuse of treated wastewater.

Risk factors and outcomes associated with severe clostridium difficile infection in children

BACKGROUND

The incidence and severity of Clostridium difficile infection (CDI) is increasing among adults; however, little is known about the epidemiology of CDI among children.

METHODS

We conducted a nested case-control study to identify the risk factors for and a prospective cohort study to determine the outcomes associated with severe CDI at 2 children's hospitals. Severe CDI was defined as CDI and at least 1 complication or ≥2 laboratory or clinical indicators consistent with severe disease. Studied outcomes included relapse, treatment failure, and CDI-related complications. Isolates were tested to determine North American pulsed-field gel electrophoresis type 1 lineage.

RESULTS

We analyzed 82 patients with CDI, of whom 48 had severe disease. Median age in years was 5.93 (1.78-12.16) and 1.83 (0.67-8.1) in subjects with severe and nonsevere CDI, respectively (P = 0.012). All patients with malignancy and CDI had severe disease. Nine subjects (11%) had North American pulsed-field gel electrophoresis type 1 isolates. Risk factors for severe disease included age (adjusted odds ratio [95% confidence interval]: 1.12 [1.02, 1.24]) and receipt of 3 antibiotic classes in the 30 days before infection (3.95 [1.19, 13.11]). If infants less than 1 year of age were excluded, only receipt of 3 antibiotic classes remained significantly associated with severe disease. Neither the rate of relapse nor treatment failure differed significantly between patients with severe and nonsevere CDI. There was 1 death.

CONCLUSIONS

Increasing age and exposure to multiple antibiotic classes were risk factors for severe CDI. Although most patients studied had severe disease, complications were infrequent. Relapse rates were similar to those reported in adults.

Systemic dissemination of Clostridium difficile toxins A and B is associated with severe, fatal disease in animal models

BACKGROUND

Clostridium difficile infection (CDI) can cause a wide range of disease, from mild diarrhea to fulminant systemic disease. The incidence of systemic CDI with fatal consequence has increased rapidly in recent years.

METHODS

Using an ultrasensitive cytotoxicity assay, we measured C. difficile toxin A (TcdA) and C. difficile toxin B (TcdB) in sera and body fluids of piglets and mice exposed to C. difficile to investigate the relationship between the presence of toxins in body fluids and systemic manifestations of CDI.

RESULTS

We found that both TcdA and TcdB disseminate systemically, with toxins present in the sera and body fluids of infected animals, and toxemia is significantly correlated with the development of systemic CDI. The systemic administration of neutralizing antibodies against both toxins blocked the development of systemic disease in mice. We measured cytokine concentrations in the sera of mice and piglets with systemic and nonsystemic CDI and found that proinflammatory mediators were considerably elevated in animals with systemic CDI.

CONCLUSION

Our study demonstrates the existence of a strong correlation between toxemia and the occurrence of systemic disease, supporting the hypothesis that systemic CDI is most likely due to the toxicity of TcdA and TcdB and the induction of proinflammatory cytokines by the toxins.

Novel one-step method for detection and isolation of active-toxin-producing Clostridium difficile strains directly from stool samples

The alarming emergence of hypervirulent strains of Clostridium difficile with increased toxin production, severity of disease, morbidity, and mortality emphasizes the need for a culture method that permits simultaneous isolation and detection of virulent strains. The C. difficile toxins A and B are critical virulence factors, and strains can either be toxin-producing (virulent) or non-toxin-producing (nonvirulent). Strains that are isolated from human infections generally produce either toxin A or toxin B or both. The methods currently available for culturing C. difficile do not differentiate strains that produce active toxins from strains that do not produce toxins or produce inactive toxins. As a result, the identification and isolation of toxin-producing strains from stool is currently a two-step process. First, the stool is plated on a selective medium, and then suspected colonies are analyzed for toxin production or the presence of the toxin genes. We describe here a novel selective and differential culture method, the Cdifftox plate assay, which combines in a single step the specific isolation of C. difficile strains and the detection of active toxin. This assay was developed based on our recent finding that the A and B toxins of C. difficile cleave chromogenic substrates that have stereochemical characteristics similar to their natural substrate, UDP-glucose. The Cdifftox plate assay is shown here to be extremely accurate (99.8% effective) in detecting toxin-producing strains through the analysis of 528 C. difficile isolates selected from 50 tissue culture cytotoxicity assay-positive clinical stool samples. The Cdifftox plate assay advances and improves the culture approach such that only C. difficile strains will grow on this agar, and virulent strains producing active toxins can be differentiated from nonvirulent strains, which do not produce active toxins. This new method reduces the time and effort required to isolate and confirm toxin-producing C. difficile strains.

Development of an algorithm for assessing the risk to food safety posed by a new animal disease

An algorithm was developed as a tool to rapidly assess the potential for a new or emerging disease of livestock to adversely affect humans via consumption or handling of meat product, so that the risks and uncertainties can be understood and appropriate risk management and communication implemented. An algorithm describing the sequence of events from occurrence of the disease in livestock, release of the causative agent from an infected animal, contamination of fresh meat and then possible adverse effects in humans following meat handling and consumption was created. A list of questions complements the algorithm to help the assessors address the issues of concern at each step of the decision pathway. The algorithm was refined and validated through consultation with a panel of experts and a review group of animal health and food safety policy advisors via five case studies of potential emerging diseases of cattle. Tasks for model validation included describing the path taken in the algorithm and stating an outcome. Twenty-nine per cent of the 62 experts commented on the model, and one-third of those responding also completed the tasks required for model validation. The feedback from the panel of experts and the review group was used to further develop the tool and remove redundancies and ambiguities. There was agreement in the pathways and assessments for diseases in which the causative agent was well understood (for example, bovine pneumonia due to Mycoplasma bovis). The stated pathways and assessments of other diseases (for example, bovine Johne's disease) were not as consistent. The framework helps to promote objectivity by requiring questions to be answered sequentially and providing the opportunity to record consensus or differences of opinion. Areas for discussion and future investigation are highlighted by the points of diversion on the pathway taken by different assessors.