A Phase 2 Extension Study Evaluating the Immunogenicity, Safety, and Tolerability of 3 or 4 Doses of a Clostridioides difficile Vaccine in Healthy US Adults Aged 65 to 85 Years

BACKGROUND

This phase 2 extension explored the long-term antibody persistence of an investigational Clostridioides difficile vaccine and the safety, tolerability, and immunogenicity of dose 4 approximately 12 months post-dose 3.

METHODS

One year post-dose 3, healthy US 65- to 85-year-olds (N = 300) were randomized to dose 4 of vaccine at previously received antigen levels (100 or 200 μg) or placebo. Assessments included safety and percentages of participants achieving neutralizing antibody titers above prespecified thresholds (≥219 and ≥2586 neutralization units/mL for toxins A and B, respectively).

RESULTS

In participants previously given three 200-µg doses and placebo in the extension, toxin A and B neutralizing antibodies were above prevaccination levels 48 months post-dose 3 (36 months after placebo); 24.0% and 26.0% had toxin A and B antibodies at or above prespecified thresholds, respectively. Neutralizing antibodies increased post-dose 4 (12 months post-dose 3) and persisted to 36 months post-dose 4. Thirty days post-dose 4, all participants had toxin A and 86.5% to 100% had toxin B titers at or above prespecified thresholds. Local reactions were more frequent in vaccine recipients. Systemic and adverse event frequencies were similar across groups.

CONCLUSIONS

C difficile vaccine immune responses persisted 48 months post-dose 3. Dose 4 was immunogenic and well tolerated, supporting continued development. Clinical Trials Registration. ClinicalTrials.gov NCT02561195.

The effect of fiber supplementation on the prevention of diarrhea in hospitalized patients receiving enteral nutrition: A meta-analysis of randomized controlled trials with the GRADE assessment

Introduction

Enteral nutrition (EN) in hospitalized patients has several advantages. However, post-feeding diarrhea occurs frequently and has been linked to negative outcomes. The EN formula itself may have an impact on how diarrhea develops, and fiber supplements may theoretically help patients experience less diarrhea. This study aimed to thoroughly evaluate whether adding fiber to EN decreases the likelihood of developing diarrhea and whether different types of fibers pose different effects on diarrhea (PROSPERO CRD 42021279971).

Methods

We conducted a meta-analysis on fiber supplementation in hospitalized adult patients receiving EN. We thoroughly searched PubMed, Medline, Embase, Scopus, Web of Science, CENTRAL, and ClinicalTrials.gov databases from inception to 1 September 2022. Only randomized controlled trials (RCTs) were included. Pooled results on the incidence of diarrhea were calculated using a random-effects model. The Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) approach was applied. Only fiber types from soy polysaccharides (n = 4), psyllium (n = 3), mixed soluble/insoluble fiber (mixed fiber, n = 3), pectin (n = 2), and partially hydrolyzed guar gum (PHGG, n = 2) were examined in the sensitivity analysis.

Results

Among the 4,469 titles found, a total of 16 RCTs were included. Overall, compared to fiber-free formulas, fiber supplementation reduced the occurrence of diarrhea in patients receiving EN by 36% (pooled risk ratio [RR] of 0.64 [95% confidence interval (CI): 0.49-0.82, p = 0.005; I ² = 45%]), with GRADE showing the evidence of moderate certainty. Only mixed fiber and PHGG significantly decreased the incidence of diarrhea according to the sensitivity analyses for fiber types (RR 0.54, 95%CI: 0.39-0.75, I ² = 0% and RR 0.47, 95%CI: 0.27-0.83, I ² = 0%, respectively). The results for the remaining fiber types were unclear.

Conclusion

According to a meta-analysis, fiber supplements help lessen post-feeding diarrhea in hospitalized patients receiving EN. However, not all fiber types produced successful outcomes. Diarrhea was significantly reduced by PHGG and mixed soluble/insoluble fiber.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=279971, identifier: PROSPERO CRD 42021279971.

A Phase 2 Study Evaluating the Safety, Tolerability, and Immunogenicity of Two 3-Dose Regimens of a Clostridium difficile Vaccine in Healthy US Adults Aged 65 to 85 Years

BACKGROUND

Clostridium difficile causes toxin-mediated nosocomial diarrhea and community-acquired infections; no preventive vaccine is licensed. In this phase 2 study, we explored safety, tolerability, and immunogenicity in older US adults of an investigational bivalent C. difficile vaccine that contains equal dosages of genetically and chemically detoxified toxins A and B.

METHODS

Conducted from July 2015 through March 2017, 855 healthy adults aged 65-85 years from 15 US centers were randomized 3:3:1 to receive vaccine (100 or 200 μg) or placebo at 0, 1, and 6 months (month regimen) or 1, 8, and 30 days (day regimen). Serum toxin A- and B-specific neutralizing antibodies were measured. Participant-reported local reactions (LRs) and systemic events (SEs), adverse events (AEs), serious AEs, newly diagnosed chronic medical conditions, and immediate AEs were recorded.

RESULTS

The 200-μg dose level elicited higher immune responses than the 100-µg dose level across regimens. Compared with the day regimen, the month regimen induced stronger and more persistent immune responses that remained elevated 12 months after dose 3. Responses peaked at month 7 (month regimen) and day 37 (day regimen). LRs (primarily injection site pain) were more frequent in vaccine recipients than controls; SE frequency was similar across groups. More related AEs were reported in the day regimen group than the month regimen group.

CONCLUSIONS

The C. difficile vaccine was safe, well tolerated, and immunogenic in healthy US adults aged 65-85 years. Immune responses were particularly robust in the 200-μg month regimen group. These results support continued vaccine development.

CLINICAL TRIALS REGISTRATION

NCT02561195.

Assessing the Risk of Hospital-Acquired Clostridium Difficile Infection With Proton Pump Inhibitor Use: A Meta-Analysis

BACKGROUND Clostridium difficile is the principal infectious cause of antibiotic-associated diarrhea and accounts for 12% of hospital-acquired infections. Recent literature has shown an increased risk of C. difficile infection (CDI) with proton pump inhibitor (PPI) use. OBJECTIVE To conduct a systematic assessment of the risk of hospital-acquired CDI following exposure to PPI. METHODS We searched multiple databases for studies examining the relationship between PPI and hospital-acquired CDI. Pooled odds ratios were generated and assessment for heterogeneity performed. RESULTS We found 23 observational studies involving 186,033 cases that met eligibility criteria. Across studies, 10,307 cases of hospital-acquired CDI were reported. Significant heterogeneity was present; therefore, a random effects model was used. The pooled odds ratio was 1.81 (95% CI, 1.52-2.14), favoring higher risk of CDI with PPI use. Significant heterogeneity was present, likely due to differences in assessment of exposure, study population, and definition of CDI. DISCUSSION This meta-analysis suggests PPIs significantly increase the risk of hospital-acquired CDI. Given the significant health and economic burden of CDI and the risks of PPI, optimization of PPI use should be included in a multifaceted approach to CDI prevention. Infect Control Hosp Epidemiol 2016;1408-1417.

John G. Bartlett: Contributions to the discovery of Clostridium difficile antibiotic-associated diarrhea

In 1975 John Bartlett began trials investigating the problem of antibiotic-associated diarrhea and pseudomembranous colitis. His work led the discovery of Clostridium difficile and he identified it as the leading cause of hospital-associated infections.

Detection of toxins A/B and isolation of Clostridium difficile and Clostridium perfringens from dogs in Minas Gerais, Brazil

The objective of this study was to detect C. difficile A/B toxins and to isolate strains of C. perfringens and C. difficile from diarrheic and non-diarrheic dogs in Brazil. Stool samples were collected from 57 dogs, 35 of which were apparently healthy, and 22 of which were diarrheic. C. difficile A/B toxins were detected by ELISA, and C. perfringens and C. difficile were identified by multiplex PCR. C. difficile A/B toxins were detected in 21 samples (36.8%). Of these, 16 (76.2%) were from diarrheic dogs, and five (23.8%) were from non-diarrheic dogs. Twelve C. difficile strains (21.1%) were isolated, of which ten were A⁺B⁺ and two were A⁻B⁻. All non-toxigenic strains were isolated from non-diarrheic animals. The binary toxin gene cdtB was found in one strain, which was A⁺B⁺ and was derived from a non-diarrheic dog. C. perfringens strains were isolated from 40 samples (70.2%). Of these, 18 (45%) were from the diarrheic group, and 22 (55%) belonged to the non-diarrheic group. All isolates were classified as C. perfringens type A and there was an association between the detection of the cpe gene and the presence of diarrhea. Interestingly, ten strains (25%) were positive for the presence of the cpb2 gene. The high rate of detection of the A/B toxins in non-diarrheic dogs suggests the occurrence of subclinical disease in dogs or carriage of its toxins without disease. More studies are needed to elucidate the epidemiology of C. difficile and C. perfringens in dogs and to better our understanding of C. difficile as a zoonotic agent. This is the first study to report the binary toxin gene in C. difficile strains isolated from dogs in Brazil.