Host Immune Markers Distinguish Clostridioides difficile Infection From Asymptomatic Carriage and Non-C. difficile Diarrhea

An ultrasensitive genosensor for detection of toxigenic and non-toxigenic Clostridioides difficile based on a conserved sequence in surface layer protein coding gene

Clostridioides difficile (C. difficile) is the most common agent of antibiotic-associated diarrhea, leading to intestinal infection through the secretion of two major toxins. Not all strains of this bacterium are toxigenic, but some of them cause infection via their accessory virulence factors, such as surface layer protein (SlpA). SlpA is conserved in both toxigenic and non-toxigenic strains of C. difficile. In the present work, an amplification-free electrochemical genosensor was designed for the detection of the slpA gene. A glassy carbon electrode coated with gold nanoparticle-reduced graphene oxide nanocomposite was used as the working electrode, and its surface was modified using a simple thiolated linear oligonucleotide as the bioreceptor. Moreover, the hexaferrocenium tri[hexa(isothiocyanato) iron(III)] trihydroxonium (HxFc) complex was used as an intercalator, and its redox signal was recorded using differential pulse voltammetry. Scan rate studies indicated a quasi-reversible adsorption-controlled process for the HxFc complex. This genosensor showed high sensitivity with a limit of detection of 0.2 fM, a linear response range of 0.46-1900 fM, and a satisfactory specificity toward the synthetic slpA target gene. Also, the genosensor indicated responses in the mentioned linear range toward the genome extracted from either toxigenic or non-toxigenic strains of C. difficile.

Diagnostic Guidance for C. difficile Infections

Diagnosis of Clostridioides difficile infection (CDI) can be challenging. First of all, there has been debate on which of the two reference assays, cell cytotoxicity neutralization assay (CCNA) or toxigenic culture (TC), should be considered the gold standard for CDI detection. Although the CCNA suffers most from suboptimal storage conditions and subsequent toxin degradation, TC is reported to falsely increase CDI detection rates as it cannot differentiate CDI patients from patients asymptomatically colonised by toxigenic C. difficile. Several rapid assays are available for CDI detection and fall into three broad categories: (1) enzyme immunoassays for glutamate dehydrogenase, (2) enzyme immunoassays or single-molecule array assays for toxins A/B and (3) nucleic acid amplification tests detecting toxin genes. All three categories have their own limitations, being suboptimal specificity and/or sensitivity or the inability to discern colonised patients from CDI patients. In light of these limitations, multi-step algorithmic testing has been advocated by international guidelines (IDSA/SHEA and ESCMID) in order to optimize diagnostic accuracy. As a result, a survey performed in 2018-2019 in Europe revealed that most of all hospital sites reported using more than one test to diagnose CDI. CDI incidence rates are also influenced by sample selection criteria, as several studies have shown that if not all unformed stool samples are tested for CDI, many cases may be missed due to an absence of clinical suspicion. Since methods for diagnosing CDI remain imperfect, there has been a growing interest in alternative testing strategies like faecal microbiota biomarkers, immune modulating interleukins, cytokines and imaging methods. At the moment, these alternative methods might play an adjunctive role, but they are not suitable to replace conventional CDI testing strategies.

C. difficile intoxicates neurons and pericytes to drive neurogenic inflammation

Clostridioides difficile infection (CDI) is a major cause of healthcare-associated gastrointestinal infections1,2. The exaggerated colonic inflammation caused by C. difficile toxins such as toxin B (TcdB) damages tissues and promotes C. difficile colonization3-6, but how TcdB causes inflammation is unclear. Here we report that TcdB induces neurogenic inflammation by targeting gut-innervating afferent neurons and pericytes through receptors, including the Frizzled receptors (FZD1, FZD2 and FZD7) in neurons and chondroitin sulfate proteoglycan 4 (CSPG4) in pericytes. TcdB stimulates the secretion of the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) from neurons and pro-inflammatory cytokines from pericytes. Targeted delivery of the TcdB enzymatic domain, through fusion with a detoxified diphtheria toxin, into peptidergic sensory neurons that express exogeneous diphtheria toxin receptor (an approach we term toxogenetics) is sufficient to induce neurogenic inflammation and recapitulates major colonic histopathology associated with CDI. Conversely, mice lacking SP, CGRP or the SP receptor (neurokinin 1 receptor) show reduced pathology in both models of caecal TcdB injection and CDI. Blocking SP or CGRP signalling reduces tissue damage and C. difficile burden in mice infected with a standard C. difficile strain or with hypervirulent strains expressing the TcdB2 variant. Thus, targeting neurogenic inflammation provides a host-oriented therapeutic approach for treating CDI.

Baseline stool toxin concentration is associated with risk of recurrence in children with Clostridioides difficile infection

BACKGROUND

In adults with Clostridioides difficile infection (CDI), higher stool concentrations of toxins A and B are associated with severe baseline disease, CDI-attributable severe outcomes, and recurrence. We evaluated whether toxin concentration predicts these presentations in children with CDI.

METHODS

We conducted a prospective cohort study of inpatients aged 2-17 years with CDI who received treatment. Patients were followed for 40 days after diagnosis for severe outcomes (intensive care unit admission, colectomy, or death, categorized as CDI primarily attributable, CDI contributed, or CDI not contributing) and recurrence. Baseline stool toxin A and B concentrations were measured using ultrasensitive single-molecule array assay, and 12 plasma cytokines were measured when blood was available.

RESULTS

We enrolled 187 pediatric patients (median age, 9.6 years). Patients with severe baseline disease by IDSA-SHEA criteria (n = 34) had nonsignificantly higher median stool toxin A+B concentration than those without severe disease (n = 122; 3,217.2 vs 473.3 pg/mL; P = .08). Median toxin A+B concentration was nonsignificantly higher in children with a primarily attributed severe outcome (n = 4) versus no severe outcome (n = 148; 19,472.6 vs 429.1 pg/mL; P = .301). Recurrence occurred in 17 (9.4%) of 180 patients. Baseline toxin A+B concentration was significantly higher in patients with versus without recurrence: 4,398.8 versus 280.8 pg/mL (P = .024). Plasma granulocyte colony-stimulating factor concentration was significantly higher in CDI patients versus non-CDI diarrhea controls: 165.5 versus 28.5 pg/mL (P < .001).

CONCLUSIONS

Higher baseline stool toxin concentrations are present in children with CDI recurrence. Toxin quantification should be included in CDI treatment trials to evaluate its use in severity assessment and outcome prediction.

Stool Interleukin-1β Differentiates Clostridioides difficile Infection (CDI) From Asymptomatic Carriage and Non-CDI Diarrhea

BACKGROUND

Despite advances in the understanding and diagnosis of Clostridioides difficile infection (CDI), clinical distinction within the colonization-infection continuum remains an unmet need.

METHODS

By measuring stool cytokines and antitoxin antibodies in well-characterized cohorts of CDI (diarrhea, nucleic acid amplification test [NAAT] positive), non-CDI diarrhea (NCD; diarrhea, NAAT negative), asymptomatic carriers (ASC; no diarrhea, NAAT positive) and hospital controls (CON; no diarrhea, NAAT negative), we aim to discover novel biological markers to distinguish between these cohorts. We also explore the relationship of these stool cytokines and antitoxin antibody with stool toxin concentrations and disease severity.

RESULTS

Stool interleukin (IL) 1β, stool immunoglobulin A (IgA), and immunoglobulin G (IgG) anti-toxin A had higher (P < .0001) concentrations in CDI (n = 120) vs ASC (n = 43), whereas toxins A, B, and fecal calprotectin did not. Areas under the receiver operating characteristic curve (ROC-AUCs) for IL-1β, IgA, and IgG anti-toxin A were 0.88, 0.83, and 0.83, respectively. A multipredictor model including IL-1β and IgA anti-toxin A achieved an ROC-AUC of 0.93. Stool IL-1β concentrations were higher in CDI compared to NCD (n = 75) (P < .0001) and NCD + ASC+ CON (CON, n = 75) (P < .0001), with ROC-AUCs of 0.83 and 0.86, respectively. Stool IL-1β had positive correlations with toxins A (ρA = +0.55) and B (ρB = +0.49) in CDI (P < .0001) but not in ASC (P > .05).

CONCLUSIONS

Stool concentrations of the inflammasome pathway, proinflammatory cytokine IL-1β, can accurately differentiate CDI from asymptomatic carriage and NCD, making it a promising biomarker for CDI diagnosis. Significant positive correlations exist between stool toxins and stool IL-1β in CDI but not in asymptomatic carriers.

Characterization of the gut microbiome of patients with Clostridioides difficile infection, patients with non-C. difficile diarrhea, and C. difficile-colonized patients

Introduction

Clostridioides difficile infection (CDI) is the main cause of nosocomial diarrhea in developed countries. A key challenge in CDI is the lack of objective methods to ensure more accurate diagnosis, especially when differentiating between true infection and colonization/diarrhea of other causes. The main objective of this study was to explore the role of the microbiome as a predictive biomarker of CDI.

Methods

Between 2018 and 2021, we prospectively included patients with CDI, recurrent CDI (R-CDI), non-CDI diarrhea (NO-CDI), colonization by C. difficile, and healthy individuals. Clinical data and fecal samples were collected. The microbiome was analyzed by sequencing the hypervariable V4 region of the 16S rRNA gene on an Illumina Miseq platform. The mothur bioinformatic pipeline was followed for pre-processing of raw data, and mothur and R were used for data analysis.

Results

During the study period, 753 samples from 657 patients were analyzed. Of these, 247 were from patients with CDI, 43 were from patients colonized with C. difficile, 63 were from healthy individuals, 324 were from NOCDI, and 76 were from R-CDI. We found significant differences across the groups in alpha and beta diversity and in taxonomic abundance. We identified various genera as the most significant biomarkers for CDI (Bacteroides, Proteus, Paraprevotella, Robinsoniella), R-CDI (Veillonella, Fusobacterium, Lactobacillus, Clostridium sensu stricto I), and colonization by C. difficile (Parabacteroides, Faecalicoccus, Flavonifractor, Clostridium XVIII).

Discussion

We observed differences in microbiome patterns between healthy individuals, colonized patients, CDI, R-CDI, and NOCDI diarrhea. We identified possible microbiome biomarkers that could prove useful in the diagnosis of true CDI infections. Further studies are warranted.

Higher In Vivo Fecal Concentrations of Clostridioides difficile Toxins A and B in Patients With North American Pulsed-Field Gel Electrophoresis Type 1/Ribotype 027 Strain Infection

Ultrasensitive, quantitative Clostridioides difficile stool toxin measurement demonstrated significantly higher concentrations of toxins A and B in patients infected with the North American pulsed-field gel electrophoresis type 1/ribotype 027 (NAP-1/027) strain compared with other strains, providing in vivo confirmation of the in vitro association between NAP-1/027 and elevated toxin production.

Clostridioides Difficile Infection before and during Coronavirus Disease 2019 Pandemic-Similarities and Differences

The aim of this study was to investigate the differences of Clostridioides difficile infection (CDI) during the COVID-19 pandemic compared to the pre-COVID-19 era. CDI patients treated at the Clinic for Infectious Diseases, Clinical Center of Vojvodina, Serbia during 2017-2019 (n = 304) were compared with COVID-19/CDI patients treated in period September 2021-September 2022 (n = 387). Groups were compared by age, gender, comorbidities, previous medications, laboratory findings, and outcome within 30 days. In the CDI/COVID-19 group, we found: greater percentage of males 59.8% vs. 42.6% (p ≤ 0.001), older age 72.8 ± 9.4 vs. 65.6 ± 11.7 (p ≤ 0.001), higher Charlson comorbidity score (CCS) (3.06 ± 1.54 vs. 2.33 ± 1.34 (p ≤ 0.001), greater percentage of chronic renal failure (33.9% vs. 23.4% (p = 0.003), malignances (24.3% vs. 13.5% (p ≤ 0.001), chronic obstructive pulmonary disease (22.7% vs. 15.5% (p = 0.017), higher usage of macrolide (38.5% vs. 8.6% (p ≤ 0.001), greater percentage of patients with hypoalbuminemia ≤25 g/L (19.6% vs. 12.2% (p ≤ 0.001), lower percentage of patients with elevated creatinine (≥200 mmol/L) (31.5% vs. 43.8%) (p = 0.002), and greater percentage of lethal outcome 29.5% vs. 6.6% (p ≤ 0.001). In the prediction of lethal outcome multivariate regression analysis extracted as an independent predictor, only higher CRP values in the non-COVID-19 group and in the COVID-19 group: older age (p ≤ 0.001), CCS (p = 0.019) and CRP (p = 0.015). COVID-19 changes the disease course of CDI and should be taken into consideration when managing those patients.

Clinical Presentations, Predictive Factors, and Outcomes of Clostridioides difficile Infection among COVID-19 Hospitalized Patients—A Single Center Experience from the COVID Hospital of the University Clinical Center of Vojvodina, Serbia

Background: This study aimed to investigate the clinical form, risk factors, and outcomes of patients with COVID-19 and Clostridioides difficile co-infections. Methods: This retrospective study (2 September 2021-1 April 2022) included all patients with Clostridioides difficile infection (CDI) and COVID-19 infection who were admitted to the Covid Hospital of the University Clinical Center of Vojvodina. Results: A total of 5124 COVID-19 patients were admitted to the Covid Hospital, and 326 of them (6.36%) developed hospital-onset CDI. Of those, 326 of the CDI patients (88.65%) were older than 65 years. The median time of CDI onset was 12.88 days. Previous hospitalizations showed 69.93% of CDI patients compared to 38.81% in the non-CDI group (p = 0.029). The concomitant antibiotics exposure was higher among the CDI group versus the non-CDI group (88.65% vs. 68.42%, p = 0.037). Albumin levels were ≤ 25 g/L among 39.57% of the CDI patients and 21.71% in the non-CDI patients (p = 0.021). The clinical manifestations of CDI ranged from mild diarrhea (26.9%) to severe diarrhea (63.49%) and a complicated form of colitis (9.81%). Regarding outcomes, 79.14% of the CDI patients recovered and 20.86% had fatal outcomes in-hospital. Although a minority of the patients were in the non-CDI group, the difference in mortality rate between the CDI and non-CDI group was not statistically significant (20.86% vs. 15.13%, p = 0.097). Conclusions: Elderly patients on concomitant antibiotic treatments with hypoalbuminemia and with previous healthcare exposures were the most affected by COVID-19 and CD co-infections.

Analysis of Intestinal Mycobiota of Patients with Clostridioides difficile Infection among a Prospective Inpatient Cohort

Clostridioides difficile infection (CDI) is a burden to health care systems worldwide. Gut microbiota dysbiosis associated with CDI has been well accepted. However, contribution of fungal mycobiota to CDI has recently gained research interest. Here, we report the gut mycobiota composition of 149 uniquely well characterized participants from a prospective clinical cohort and evaluate the discriminating ability of gut mycobiota to classify CDI and non-CDI patients. Fecal samples were divided into two groups: (i) CDI (inpatients who had clinically significant diarrhea and positive nucleic acid amplification testing [NAAT] and received subsequent CDI therapy, n = 58) and (ii) non-CDI, which can be further divided into three subgroups: (a) carrier (inpatients with positive stool NAAT but without diarrhea; n = 28); (b) diarrhea (inpatients with negative stool NAAT; n = 31); and (c) control (inpatients with negative stool NAAT and without diarrhea; n = 32). Fecal mycobiota composition was analyzed by internal transcribed spacer 2 (ITS2) sequencing. In comparison to non-CDI patients, CDI patients tend to have gut mycobiota with lower biodiversity, weaker fungi correlations, and weaker correlations between fungi and host immune factors. Notably, 11 genera (Saccharomyces, Penicillium, Aspergillus, Cystobasidium, Cladosporium, and so on) were significantly enriched in non-CDI patients, and Pichia and Suhomyces were enriched in patients with CDI, while 1 two genera, Cystobasidium and Exophiala, had higher abundance in patients with diarrhea compared with CDI (linear discriminant analysis [LDA] > 3.0; P < 0.05). Ascomycota and Basidiomycota (or Candida and Saccharomyces) exhibited a strong negative correlation (r ≤ -0.714 or r ≤ -0.387; P < 0.05), and the ratios of Ascomycota to Basidiomycota or genera Candida to Saccharomyces were dramatically higher in CDI patients than in non-CDI patients (P < 0.05). A disease-specific pattern with much weaker fungal abundance correlations was observed in the CDI group compared to that in the non-CDI and diarrhea groups, suggesting that these correlations may contribute to the development of CDI. Our findings provided specific markers of stool fungi that distinguish CDI from all non-CDI hospitalized patients. This study's potential clinical utility for better CDI diagnosis warrants further investigation. IMPORTANCE Clostridioides difficile is an opportunistic bacterial pathogen that causes a serious and potentially life-threatening infection of the human gut. It remains an existing challenge to distinguish active infection of CDI from diarrhea with non-CDI causes. A few large prospective studies from recent years suggest that there is no single optimal test for the diagnosis of CDI. Previous research has concentrated on the relationship between bacteria and CDI, while the roles of fungi, as a significant proportion of the gut microbial ecosystem, remain understudied. In this study, we report a series of fungal markers that may add diagnostic values for the development of a more systematic approach to accurate CDI diagnosis. These results help open the door for better understanding of the relationship between host immune factors and the fungal community in the context of CDI pathogenesis.

The value of fecal calprotectin in Clostridioides difficile infection: A systematic review

As a marker of inflammation, calprotectin has potential application value in a variety of inflammatory diseases, such as arthritis and bacterial infections. Clostridioides difficile infection (CDI) is an infectious disease that causes intestinal damage and inflammation. This systematic review aims to determine whether fecal calprotectin has application value in CDI. Nine databases were searched from inception to 6 June 2022, and 17 studies were included. These studies were divided into four groups according to their content. Generally speaking, fecal calprotectin is not an ideal indicator for the diagnosis and prognosis prediction of CDI but may serve as a potential indicator for assessing disease severity and as a readily detectable marker for CDI screening. In addition, patients in need of treatment or with detectable toxins in stool may tend to have higher levels of fecal calprotectin. In summary, fecal calprotectin has some potential application value in CDI. However, further studies are needed to verify these findings and determine the reliability of calprotectin as a biomarker for CDI.

Validation of Clinical Risk Models for Clostridioides difficile-Attributable Outcomes

Clostridioides difficile is the leading health care-associated pathogen, leading to substantial morbidity and mortality; however, there is no widely accepted model to predict C. difficile infection severity. Most currently available models perform poorly or were calibrated to predict outcomes that are not clinically relevant. We sought to validate six of the leading risk models (Age Treatment Leukocyte Albumin Serum Creatinine (ATLAS), C. difficile Disease (CDD), Zar, Hensgens, Shivashankar, and C. difficile Severity Score (CDSS)), guideline severity criteria, and PCR cycle threshold for predicting C. difficile-attributable severe outcomes (inpatient mortality, colectomy/ileostomy, or intensive care due to sepsis). Models were calculated using electronic data available within ±48 h of diagnosis (unavailable laboratory measurements assigned zero points), calibrated using a large retrospective cohort of 3,327 inpatient infections spanning 10 years, and compared using receiver operating characteristic (ROC) and precision-recall curves. ATLAS achieved the highest area under the ROC curve (AuROC) of 0.781, significantly better than the next best performing model (Zar 0.745; 95% confidence interval of AuROC difference 0.0094–0.6222; P = 0.008), and highest area under the precision-recall curve of 0.232. Current IDSA/SHEA severity criteria demonstrated moderate performance (AuROC 0.738) and PCR cycle threshold performed the worst (0.531). The overall predictive value for all models was low, with a maximum positive predictive value of 37.9% (ATLAS cutoff ≥9). No clinical model performed well on external validation, but ATLAS did outperform other models for predicting clinically relevant C. difficile-attributable outcomes at diagnosis. Novel markers should be pursued to augment or replace underperforming clinical-only models.

Future Applications of Metagenomic Next-Generation Sequencing for Infectious Diseases Diagnostics

Metagenomic next-generation sequencing (mNGS) has the theoretical capacity to detect any microbe present in a host. mNGS also has the potential to infer a pathogen's phenotypic characteristics, including the ability to colonize humans, cause disease, and resist treatment. Concurrent host nucleic acid sequencing can assess the infected individual's physiological state, including characterization and appropriateness of the immune response. When the pathogen cannot be identified, host RNA sequencing may help infer the organism's nature. While the full promise of mNGS remains far from realization, the potential ability to identify all microbes in a complex clinical sample, assess each organism's virulence and antibiotic susceptibility traits, and simultaneously characterize the host's response to infection provide opportunities for mNGS to supplant existing technologies and become the primary method of infectious diseases diagnostics.

Integrating gut microbiome and host immune markers to understand the pathogenesis of Clostridioides difficile infection

Clostridioides difficile (C.difficile) infection is the most common cause of healthcare-associated infection and an important cause of morbidity and mortality among hospitalized patients. A comprehensive understanding of C.difficile infection (CDI) pathogenesis is crucial for disease diagnosis, treatment, and prevention. Here, we characterized gut microbial compositions and a broad panel of innate and adaptive immunological markers in 243 well-characterized human subjects (including 187 subjects with both microbiota and immune marker data), who were divided into four phenotype groups: CDI, Asymptomatic Carriage, Non-CDI Diarrhea, and Control. We found that the interactions between gut microbiota and host immune markers are very sensitive to the status of C.difficile colonization and infection. We demonstrated that incorporating both gut microbiome and host immune marker data into classification models can better distinguish CDI from other groups than can either type of data alone. Our classification models display robust diagnostic performance to differentiate CDI from Asymptomatic carriage (AUC~0.916), Non-CDI Diarrhea (AUC~0.917), or Non-CDI that combines all other three groups (AUC~0.929). Finally, we performed symbolic classification using selected features to derive simple mathematic formulas that explicitly quantify the interactions between the gut microbiome and host immune markers. These findings support the potential roles of gut microbiota and host immune markers in the pathogenesis of CDI. Our study provides new insights for a microbiome-immune marker-derived signature to diagnose CDI and design therapeutic strategies for CDI.

Pediatric Clostridioides difficile Infection: Diagnosis and Diagnostic Stewardship

Although the pathogenesis of Clostridioides difficile infection (CDI) is complex and incompletely understood, it is believed that the elaboration of C. difficile toxins is necessary for disease. There are a variety of tests available for the detection of both the C. difficile organism and its toxins; however, each has limitations and the best application of these tests to the diagnosis of CDI in children remains uncertain. Nucleic acid amplification tests are unable to reliably discriminate between CDI and C. difficile colonization, while commercially available enzyme immunoassays for toxin detection lack sensitivity. An understanding of preanalytic factors, relevant patient features, and test performance characteristics is essential to the accurate diagnosis of CDI in children. Specific diagnostic stewardship strategies can also increase the likelihood that positive tests reflect disease rather than colonization. Ultimately, CDI remains a clinical diagnosis and clinical judgment is essential when interpreting test results, regardless of the methods used.

Absence of Toxemia in Clostridioides difficile Infection: Results from Ultrasensitive Toxin Assay of Serum

Clostridioides difficile infection (CDI) is caused by Toxins A and B, secreted from pathogenic strains of C. difficle. This infection can vary greatly in symptom severity and in clinical presentation. Current assays used to diagnose CDI may lack the required sensitivity to detect the exotoxins circulating in blood. The ultrasensitive single molecule array (Simoa) assay was modified to separately detect toxin A and toxin B in serum with a limit of detection at the low picogram level. When applied to a diverse cohort, Simoa was unable to detect toxins A or B in serum from patients with CDI, including many classified as having severe disease. The detection of toxin may be limited by the inference of antitoxin antibodies circulating in serum. This result does not support the hypothesis that toxemia occurs in C. difficile infection, conflicting with the findings of other published reports.

The future of Clostridioides difficile diagnostics

PURPOSE OF REVIEW

Although the epidemiology of Clostridioides difficile has changed, this organism continues to cause significant morbidity and mortality. This review addresses current and future approaches to the diagnosis of C. difficile disease.

RECENT FINDINGS

Over the last several years, large prospective studies have confirmed that there is no single optimal test for the diagnosis of C. difficile disease. The pendulum has swung from a focus on rapid molecular diagnosis during the years of the ribotype 027 epidemic, to a call for use of algorithmic approaches that include a test for toxin detection. In addition, diagnostic stewardship has been shown to improve test utilization, especially with molecular methods. Advances in testing include development of ultrasensitive toxin tests and an expansion of biomarkers that may be more C. difficile specific. Microbiome research may be leveraged to inform novel diagnostic approaches based on measurements of volatile and nonvolatile organic compounds in stool.

SUMMARY

As rates of C. difficile infection decline, emphasis is now on improving test utilization and a quest for improved diagnostic approaches. These approaches may involve implementation of technologies that improve toxin testing, predict patients likely to have disease and/or a severe outcome, and harnessing research on changes in the microbiome to advance metabolomics.

Recent advances in Clostridioides difficile infection epidemiology, diagnosis and treatment in children

PURPOSE OF REVIEW

The US Centers for Disease Control and Prevention (CDC) classified Clostridioides difficile as an 'urgent' public health threat that requires 'urgent and aggressive action'. This call to action has led to new discoveries that have advanced C. difficile infection (CDI) epidemiology, diagnosis and treatment, albeit predominantly in adults. In 2017, the Infectious Diseases Society of America and Society for Healthcare Epidemiology of America published clinical practice guidelines for both adults and children. At that time, recommendations in children were generally limited to relatively low-quality evidence.

RECENT FINDINGS

Since publication of this guidance, there have been many advancements in the understanding of CDI in children. These include better understanding of healthcare settings as uncommon sources of C. difficile acquisition in children; risk factors for recurrent and community-associated CDI; performance of diagnostic tests in children and strategies for optimizing their use; and a more rigorous evidence base for CDI treatment in children, including the first-ever randomized controlled trial of CDI treatment in children and the largest study of fecal microbiota transplantation in children.

SUMMARY

This review highlights the most recent salient advancements in paediatric CDI knowledge and practice that supplement published clinical guidance provided prior to these advancements.

Ultrasensitive and quantitative toxin measurement correlates with baseline severity, severe outcomes, and recurrence among hospitalized patients with Clostridioides difficile infection

BACKGROUND

Stool toxin concentrations may impact Clostridioides difficile infection (CDI) severity and outcomes. We correlated fecal C. difficile toxin concentrations, measured by an ultrasensitive and quantitative assay, with CDI baseline severity, attributable outcomes, and recurrence.

METHODS

We enrolled 615 hospitalized adults (≥ 18y) with CDI (acute diarrhea, positive stool NAAT, and decision to treat). Baseline stool toxin A and B concentrations were measured by Single Molecule Array. Subjects were classified by baseline CDI severity (four scoring methods) and outcomes within 40 days (death, ICU stay, colectomy, and recurrence).

RESULTS

Among 615 patients (median 68.0 years), in all scoring systems, subjects with severe baseline disease had higher stool toxin A+B concentrations than those without (P<0.01). Nineteen subjects (3.1%) had a severe outcome primarily-attributed to CDI (group 1). This group had higher median toxin A+B [14,303 pg/mL (IQR 416.0, 141,967)] than subjects in whom CDI only contributed to the outcome [group 2, 163.2 pg/mL(0.0, 8423.3)], subjects with severe outcome unrelated to CDI [group 3, 158.6 pg/mL (0.0, 1795.2)], or no severe outcome [group 4, 209.5 pg/mL (0.0, 8566.3)](P=0.003). Group 1 was more likely to have detectable toxin (94.7%) than groups 2-4 (60.5-66.1%)(P=0.02). Individuals with recurrence had higher toxin A+B [2266.8 pg/mL(188.8, 29411)] than those without [154.0 pg/mL(0.0, 5864.3)](P<0.001) and higher rates of detectable toxin (85.7% versus 64.0%, P=0.004).

CONCLUSIONS

In CDI patients, ultrasensitive stool toxin detection and concentration correlated with severe baseline disease, severe CDI-attributable outcomes, and recurrence, confirming the contribution of toxin quantity to disease presentation and clinical course.

Fecal Mycobiota Combined With Host Immune Factors Distinguish Clostridioides difficile Infection From Asymptomatic Carriage

BACKGROUND & AIMS

Although the role of gut microbiota in Clostridioides difficile infection (CDI) has been well established, little is known about the role of mycobiota in CDI. Here, we performed mycobiome data analysis in a well-characterized human cohort to evaluate the potential of using gut mycobiota features for CDI diagnosis.

METHODS

Stool samples were collected from 118 hospital patients, divided into 3 groups: CDI (n = 58), asymptomatic carriers (Carrier, n = 28), and Control (n = 32). The nuclear ribosomal DNA internal transcribed spacer 2 was sequenced using the Illumina HiSeq platform to assess the fungal composition. Downstream statistical analyses (including Alpha diversity analysis, ordination analysis, differential abundance analysis, fungal correlation network analysis, and classification analysis) were then performed.

RESULTS

Significant differences were observed in alpha and beta diversity between patients with CDI and Carrier (P < .05). Differential abundance analysis identified 2 genera (Cladosporium and Aspergillus) enriched in Carrier. The ratio of Ascomycota to Basidiomycota was dramatically higher in patients with CDI than in Carrier and Control (P < .05). Correlations between host immune factors and mycobiota features were weaker in patients with CDI than in Carrier. Using 4 fungal operational taxonomic units combined with 6 host immune markers in the random forest classifier can achieve very high performance (area under the curve ∼92.38%) in distinguishing patients with CDI from Carrier.

CONCLUSIONS

Our study provides specific markers of stool fungi combined with host immune factors to distinguish patients with CDI from Carrier. It highlights the importance of gut mycobiome in CDI, which may have been underestimated. Further studies on the diagnostic applications and therapeutic potentials of these findings are warranted.

Humoral Immune Response to Clostridioides difficile Toxins A and B in Hospitalized Immunocompromised Patients With C difficile Infection

Background

The humoral immune response to Clostridioides difficile toxins in C difficile infection (CDI) is incompletely characterized in immunocompromised hosts (ICHs).

Methods

We conducted a prospective study of hospitalized adults with CDI, with and without immunosuppression (hematologic malignancy, active solid tumor, solid organ or stem cell transplant, inflammatory bowel disease, autoimmune disease, congenital or acquired immunodeficiency, asplenia, chronic receipt of high-dose steroids, or receipt of immunosuppressing medications within 12 months). Serum and stool antibody concentrations of immunoglobulin (Ig)M, IgG, and IgA to C difficile toxins A and B at treatment days 0, 3, and 10–14 were compared.

Results

Ninety-eight subjects (47 ICH; 51 non-ICH) were enrolled. Baseline serum antitoxin A and B antibody levels were similar. At day 3, ICHs demonstrated lower serum levels of antitoxin A IgG, antitoxin A IgA, and antitoxin B IgA (all P < .05). At day 10–14, lower antitoxin A IgG concentrations were observed in ICHs (ICH, 21 enzyme-linked immunosorbent assay [ELISA] units; interquartile range [IQR], 16.4–44.6) compared with non-ICH subjects (49.0 ELISA units; IQR, 21.5–103; P = .045). In stool, we observed lower concentrations of antitoxin B IgA antibodies at baseline and at day 3 for ICH subjects, with a notable difference in concentrations of antitoxin B IgA at day 3 (ICH, 6.7 ELISA units [IQR, 1.9–13.9] compared with non-ICH, 18.1 ELISA units [IQR, 4.9–31.7]; P = .003).

Conclusions

The ICHs with CDI demonstrated lower levels of C difficile antitoxin antibodies in serum and stool during early CDI therapy compared with non-ICHs. These data provide insight into the humoral response to CDI in ICHs.

Detection of Free Toxin B in the Stool of Asymptomatic Clostridioides difficile Carriers by the Cell Cytotoxicity Neutralization Assay

Cell cytotoxicity neutralization assay (CCNA) is considered to be a gold standard to diagnose Clostridioides difficile infections. We performed CCNA on 77 consecutive admission screening rectal swabs from asymptomatic toxigenic C. difficile carriers. Thirty-nine percent of specimens from asymptomatic carriers were positive. Thus, CCNA specificity may be lower than previously thought.

Usefulness of Fecal Calprotectin in the Management of Patients with Toxigenic Clostridioides difficile

The availability of highly sensitive molecular tests for the detection of Clostridioides difficile in feces leads to overtreatment of patients who are probably only colonized. In this prospective study, the usefulness of fecal calprotectin (fCP) is evaluated in a cohort of patients with detection of toxigenic C. difficile in feces. Patients were classified by an infectious diseases consultant blinded to fCP results into three groups-group I, presumed Clostridioides difficile infection (CDI); group II, doubtful but treated CDI; and group III, presumed C. difficile colonization or self-limited CDI not needing treatment. One hundred and thirty-four patients were included. The median fCP concentrations were 410 (138-815) μg/g in group I, 188 (57-524) μg/g in group II, and 51 (26-97) μg/g in group III (26 cases); p < 0.05 for all comparisons. In forty-five out of 134 cases (33.5%), the fCP concentrations were below 100 µg/g. In conclusion, fCP is low in most patients who do not need treatment against C. difficile, and should be investigated as a potentially useful test in the management of patients with detected toxigenic C. difficile.

Advances and required improvements in methods to diagnosing Clostridioides difficile infections in the healthcare setting

INTRODUCTION

Clostrididioides difficile is associated with adverse clinical outcomes and increased morbidity, mortality, length of hospital stay, and health-care costs.Areas Covered: We searched relevant papers in PubMed for the last 10 years. In major papers, we scanned the bibliographies to ensure that important articles were included. This review addresses the evolving epidemiology of Clostridioides difficile infection (CDI) and discusses novel methods/approaches for improving the diagnosis of this important disease.

EXPERT OPINION

No single diagnostic test to date has demonstrated optimum sensitivity and specificity for detection of CDI. Many institutions have developed multi-step algorithms consistent with guidelines established by various professional societies. Some institutions have successfully tried to improve the pretest probability of molecular assays by implementing appropriate sample rejection criteria and establishing best practice alerts at the time of electronic order entry. Others have established PCR cycle threshold cutoffs to attempt to differentiate symptomatic patients from asymptomatic carriers or to make predictions about severity of disease with variable success. As research advances our understanding of C. difficile pathogenesis and pathophysiology, more information on CDI specific biomarkers is emerging. Finally, assessments of the microbiome and metabolome may expand the diagnostic armamentarium with advances in mass spectrometry and sequencing technologies.

Two-step Testing for Clostridioides Difficile is Inadequate in Differentiating Infection From Colonization in Children

OBJECTIVES

Recent Infectious Disease Society of America guidelines recommend multistep testing algorithms to diagnose Clostridioides difficile infection (CDI), including a combination of nucleic acid amplification-based testing (NAAT) and toxin enzyme immunoassay (EIA). The use of these algorithms in children, including the ability to differentiate between C. difficile colonization and CDI, however, has not been evaluated.

METHODS

We prospectively enrolled asymptomatic pediatric patients with cancer, cystic fibrosis (CF), or inflammatory bowel disease (IBD) and obtained a stool sample for NAAT testing. If positive by NAAT (colonized), EIA was performed. In addition, children with symptomatic CDI who tested positive by NAAT via the clinical laboratory were enrolled, and EIA was performed on residual stool. A functional cell cytotoxicity neutralization assay (CCNA) was also applied to stool samples from both the colonized and symptomatic cohorts.

RESULTS

Of the 225 asymptomatic children enrolled in the study, 47 (21%) were colonized with C. difficile including 9/59 (15.5%) with cancer, 30/92 (32.6%) with CF, and 8/74 (10.8%) with IBD. An additional 41 children with symptomatic CDI were enrolled. When symptomatic and colonized children were compared, neither EIA positivity (44% vs 26%, P = 0.07) nor CCNA positivity (49% vs 45%, P = 0.70) differed significantly or were able to predict disease severity in the symptomatic cohort.

CONCLUSIONS

Use of a multistep testing algorithm with NAAT followed by EIA failed to differentiate symptomatic CDI from asymptomatic colonization in our pediatric cohort. As multistep algorithms are moved into clinical care, the pediatric provider will need to be aware of their limitations.

Systems approaches for the clinical diagnosis of Clostridioides difficile infection

Clostridioides difficile infection (CDI) is an urgent threat to global public health. Patient susceptibility to C. difficile is highly dependent on host immune status and gut dysbiosis resulting in loss of protective microbiota consortia that prevent spore germination, pathogen colonization, and disease pathogenesis. Recent clinical studies highlight the problems of differentiating symptomatic CDI from asymptomatic C. difficile carriage in patients with diarrhea. In this review, we consider how integration of microbiome and host immune systems biology data may aid in the clinical diagnosis of CDI when validated against gold standard testing and combined with standard microbiology laboratory assays.