Clostridium difficile infection: new developments in epidemiology and pathogenesis

Clostridioides difficile infection after appendectomy: An analysis of short-term outcomes from the NSQIP database

BACKGROUND

Clostridioides difficile infection can be a significant complication in surgical patients. The purpose of this study was to describe the incidence and impact on outcomes of Clostridioides difficile infection in adult patients after appendectomy.

METHODS

The American College of Surgeons National Surgical Quality Improvement Program data set was used to identify all patients with the primary procedure code of appendectomy between 2016 and 2018. Patient demographics and clinical characteristics were extracted from the database, and descriptive statistics were performed. A multivariate logistic regression was created to identify predictors of Clostridioides difficile infection following appendectomy.

RESULTS

A total of 135,272 patients who underwent appendectomy were identified, and of those, 469(0.35%) developed Clostridioides difficile infection. Patients with Clostridioides difficile infection were more likely to be older (51.23 vs 40.47 years; P < .0001), female (P = .004), American Society of Anesthesiology score >2 (P < .0001), present with septic shock (P < .0001), or lack functional independence (P < .0001). Patients with Clostridioides difficile infection were more likely to have increased operative time (62.9 vs 50.4 minutes; P < .0001), have perforated appendicitis (48.9% vs 23.5%; P < .0001), and underwent open surgery (7.0% vs 4.0%; P = .0006). Postoperatively, patients with Clostridioides difficile infection required a longer length of stay (4.8 vs 1.8 days; P < .0001), had increased mortality (2.1% vs 0.1%; P < .0001), higher incidences of postoperative abscess (14.9% vs 2.9%; P < .0001), postoperative sepsis (15.1% vs 4.0%; P < .0001), and readmission (30.7% vs 3.4%; all P < .0001). On multivariate analysis, older age (P < .0001), female sex (P = .0043), septic shock (P = .0002), open surgery (P = .037), and dirty wound class (P = .0147) were all independently predictive factors of Clostridioides difficile infection after appendectomy.

CONCLUSION

Clostridioides difficile infection is an uncommon postoperative complication of appendectomy and is associated with worse outcomes and higher mortality. Older patients, female sex, those with sepsis, and those undergoing open surgery are at higher risk for developing Clostridioides difficile infection.

Synergistic Interaction of Low Salinity Stress With Vibrio Infection Causes Mass Mortalities in the Oyster by Inducing Host Microflora Imbalance and Immune Dysregulation

A sudden drop in salinity following extreme precipitation events usually causes mass mortality of oysters exposed to pathogens in ocean environment. While how low salinity stress interacts with pathogens to cause mass mortality remains obscure. In this study, we performed an experiment by low salinity stress and pathogen infection with Vibrio alginolyticus to investigate their synergistic effect on the mortality of the Pacific oyster toward understanding of the interaction among environment, host, and pathogen. We showed that low salinity stress did not significantly affect proliferation and virulence of V. alginolyticus, but significantly altered microbial composition and immune response of infected oysters. Microbial community profiling by 16S rRNA amplicon sequencing revealed disrupted homeostasis of digestive bacterial microbiota with the abundance of several pathogenic bacteria being increased, which may affect the pathogenesis in infected oysters. Transcriptome profiling of infected oysters revealed that a large number of genes associated with apoptosis and inflammation were significantly upregulated under low salinity, suggesting that low salinity stress may have triggered immune dysregulation in infected oysters. Our results suggest that host-pathogen interactions are strongly affected by low salinity stress, which is of great significance for assessing future environmental risk of pathogenic diseases, decoding the interaction among environment, host genetics and commensal microbes, and disease surveillance in the oyster.

Development of a Dual-Fluorescent-Reporter System in Clostridioides difficile Reveals a Division of Labor between Virulence and Transmission Gene Expression

The bacterial pathogen Clostridioides difficile causes gastroenteritis by producing toxins and transmits disease by making resistant spores. Toxin and spore production are energy-expensive processes that are regulated by multiple transcription factors in response to many environmental inputs. While toxin and sporulation genes are both induced in only a subset of C. difficile cells, the relationship between these two subpopulations remains unclear. To address whether C. difficile coordinates the generation of these subpopulations, we developed a dual-transcriptional-reporter system that allows toxin and sporulation gene expression to be simultaneously visualized at the single-cell level using chromosomally encoded mScarlet and mNeonGreen fluorescent transcriptional reporters. We then adapted an automated image analysis pipeline to quantify toxin and sporulation gene expression in thousands of individual cells under different medium conditions and in different genetic backgrounds. These analyses revealed that toxin and sporulation gene expression rarely overlap during growth on agar plates, whereas broth culture increases this overlap. Our results suggest that certain growth conditions promote a “division of labor” between transmission and virulence gene expression, highlighting how environmental inputs influence these subpopulations. Our data further suggest that the RstA transcriptional regulator skews the population to activate sporulation genes rather than toxin genes. Given that recent work has revealed population-wide heterogeneity for numerous cellular processes in C. difficile, we anticipate that our dual-reporter system will be broadly useful for determining the overlap between these subpopulations.

IMPORTANCEClostridioides difficile is an important nosocomial pathogen that causes severe diarrhea by producing toxins and transmits disease by producing spores. While both processes are crucial for C. difficile disease, only a subset of cells express toxins and/or undergo sporulation. Whether C. difficile coordinates the subset of cells inducing these energy-expensive processes remains unknown. To address this question, we developed a dual-fluorescent-reporter system coupled with an automated image analysis pipeline to rapidly compare the expression of two genes of interest across thousands of cells. Using this system, we discovered that certain growth conditions, particularly growth on agar plates, induce a “division of labor” between toxin and sporulation gene expression. Since C. difficile exhibits phenotypic heterogeneity for numerous vital cellular processes, this novel dual-reporter system will enable future studies aimed at understanding how C. difficile coordinates various subpopulations throughout its infectious disease cycle.

Modulation of Lactobacillus rhamnosus GG on the gut microbiota and metabolism in mice with Clostridioides difficile infection

Clostridioides difficile infection (CDI) is a common nosocomial infection and is an urgent threat to public health. Vancomycin is the preferred antibiotic treatment for CDI but is associated with recurrence. Lactobacillus rhamnosus GG is an adjunctive treatment for gastroenteritis and diarrhea and exerts its effects by modulating the immune responses and repairing the intestinal barrier. This study explored the effect of LGG on restoring the intestinal microbiota in mouse models. Primary and recurrent CDI models were constructed, and LGG was administered to C57BL/6 mice. Structural changes in the mouse gut microbiota were determined using 16S rRNA gene analysis based on Illumina sequencing. In the CDI model, 6 days after infection, 33.3% mortality, significant weight loss and colonic injury were observed. LGG can ameliorate these events. In the R-CDI mouse model, vancomycin combined with LGG prevented weight loss, improved the histopathological scores, and effectively reduced the mortality. LGG + vancomycin administration promoted the recovery of the intestinal flora by inhibiting Enterococcus and counteracting the side effects of vancomycin treatment. In both the preventive and therapeutic CDI mouse models, the oral LGG strain showed the ability to protect against primary and recurrent infections, indicating that probiotics have potential for treating intestinal diseases. Overall, these observations suggest that LGG can be applied as a preventive treatment for CDI or in combination with antibiotics to reduce recurrence.

Lactiplantibacillus plantarum E51 protects against Clostridioides difficile-induced damages on Caco-2 intestinal barrier functions

Clostridioides difficile (C. difficile) infection is associated with high morbidity and mortality. This study aimed to evaluate the protective effect of Lactiplantibacillus plantarum E51 (L. plantarum E51) on C. difficile infection using the Caco-2 monolayer in vitro model. Caco-2 cells were infected with C. difficile in the presence/absence of L. plantarum E51 or Lacticaseibacillus rhamnosus GG (LGG). Caco-2 intestinal barrier functions, such as monolayer integrity, IL-8 secretion, and tight junction protein expression, were quantified to investigate the extent to which L. plantarum E51 protected against C. difficile infection in vitro. Furthermore, inhibition of C. difficile adhesion to Caco-2 cells by L. plantarum E51 was explored using competition, exclusion, and displacement assays. The results indicated that L. plantarum E51 inhibited C. difficile growth, ameliorated C. difficile-caused decrease in transepithelial/ transendothelial electrical resistance, attenuated C. difficile-induced IL8 secretion, and upregulated claudin-1 protein expression that was inhibited by C. difficile. Moreover, L. plantarum E51 suppressed C. difficile adhesion to Caco-2 cells. In conclusion, these findings demonstrated that L. plantarum E51 substantially protected against C. difficile-induced damages on intestinal barrier functions in Caco-2 cells. The probiotic potential of L. plantarum E51 against C. difficile infection warrants further investigation.

Systems biology approach to functionally assess the Clostridioides difficile pangenome reveals genetic diversity with discriminatory power

SignificanceClostridioides difficile infections are the most common source of hospital-acquired infections and are responsible for an extensive burden on the health care system. Strains of the C. difficile species comprise diverse lineages and demonstrate genome variability, with advantageous trait acquisition driving the emergence of endemic lineages. Here, we present a systems biology analysis of C. difficile that evaluates strain-specific genotypes and phenotypes to investigate the overall diversity of the species. We develop a strain typing method based on similarity of accessory genomes to identify and contextualize genetic loci capable of discriminating between strain groups.

Destination and Specific Impact of Different Bile Acids in the Intestinal Pathogen Clostridioides difficile

The anaerobic bacterium Clostridioides difficile represents one of the most problematic pathogens, especially in hospitals. Dysbiosis has been proven to largely reduce colonization resistance against this intestinal pathogen. The beneficial effect of the microbiota is closely associated with the metabolic activity of intestinal microbes such as the ability to transform primary bile acids into secondary ones. However, the basis and the molecular action of bile acids (BAs) on the pathogen are not well understood. We stressed the pathogen with the four most abundant human bile acids: cholic acid (CA), chenodeoxycholic acid (CDCA), deoxycholic acid (DCA) and lithocholic acid (LCA). Thin layer chromatography (TLC), confocal laser scanning microscopy (CLSM), and electron microscopy (EM) were employed to track the enrichment and destination of bile acids in the bacterial cell. TLC not only revealed a strong accumulation of LCA in C. difficile, but also indicated changes in the composition of membrane lipids in BA-treated cells. Furthermore, morphological changes induced by BAs were determined, most pronounced in the virtually complete loss of flagella in LCA-stressed cells and a flagella reduction after DCA and CDCA challenge. Quantification of both, protein and RNA of the main flagella component FliC proved the decrease in flagella to originate from a change in gene expression on transcriptional level. Notably, the loss of flagella provoked by LCA did not reduce adhesion ability of C. difficile to Caco-2 cells. Most remarkably, extracellular toxin A levels in the presence of BAs showed a similar pattern as flagella expression. That is, CA did not affect toxin expression, whereas lower secretion of toxin A was determined in cells stressed with LCA, DCA or CDCA. In summary, the various BAs were shown to differentially modify virulence determinants, such as flagella expression, host cell adhesion and toxin synthesis. Our results indicate differences of BAs in cellular localization and impact on membrane composition, which could be a reason of their diverse effects. This study is a starting point in the elucidation of the molecular mechanisms underlying the differences in BA action, which in turn can be vital regarding the outcome of a C. difficile infection.

Clostridioides (Clostridium) difficile in children with diarrhoea in Vietnam

BACKGROUND

Clostridioides (Clostridium) difficile commonly causes hospital-acquired infection which can range from mild diarrhoea to life-threatening toxic megacolon and even death. Reports on C. difficile infection (CDI) in Vietnam are limited, so this study was designed to evaluate the prevalence, molecular epidemiology and antimicrobial susceptibility of C. difficile isolated from children with diarrhoea in Vietnam. Infants are often colonised with C. difficile and it was hypothesised that those colonising strains would represent strains of C. difficile circulating in the hospital/region at the time, however, this was not an attempt to determine if C. difficile was the cause of the diarrhoea.

METHODS

Diarrhoeal stool samples collected at two children's hospitals in northern Vietnam from 1^st October 2020 to 28^th February 2021 were transported to Perth, Western Australia, for culture of C. difficile and further investigations on isolates; PCR ribotyping, toxin gene profiling and antimicrobial susceptibility testing.

RESULTS

From these hospitals, 370 diarrhoeal stool samples were collected, most from children aged 1-15 months (71.9%; 266/370). The overall prevalence of C. difficile in stool samples from children aged ≤16 years was 37.8% (140/370) and the highest prevalence was in the 2-12 months age group (52.9%; 74/140). In total, 151 isolates of C. difficile were recovered; the proportion of toxigenic isolates was 16.6% (25/151). Of the 25 toxigenic C. difficile isolates, the toxin gene profiles A⁺B⁺CDT^- and A^-B⁺CDT^- comprised 72% and 28%, respectively. The four most prevalent C. difficile ribotypes (RTs) were QX 011 (25/151), RT 010 (25/151), QX 107 (12/151) and RT 012 (11/151). All isolates were susceptible to vancomycin, metronidazole and fidaxomicin, while there was significant resistance to clindamycin (90.1%), and some to moxifloxacin (6.6%) and rifaximin (3.3%).

CONCLUSION

The prevalence of C. difficile in children with diarrhoea was high (37.8%) although the proportion of toxigenic strains was comparatively low. The clinical significance of any isolate needs to be determined.

Risk Factors of Patients With Diarrhea for Having Clostridioides (Clostridium) difficile Infection

Nosocomial infections with Clostridioides (Clostridium) difficile have become an emergent health threat. We sought to define risk factors for a C. difficile infection (CDI) beyond the widely known ones, such as antibiotic use and prior hospital stay. We therefore focused on a group of patients with diarrhea in order to identify risk factors for C. difficile infection among this symptomatic cohort. A total of 121 hospitalized patients from Seesen/Germany with diarrhea were included who submitted a stool sample and were interviewed about their socio-demographic background, lifestyle and state of health using a standardized questionnaire. Antibiotic potential of diuretics was examined by agar diffusion test. C. difficile was identified in 29 patients resulting in a prevalence of 24.0%. The infection was hospital-acquired in most cases (p &lt; 0.001, 82.1%; n = 23/28, versus 29/91, 31.9%). The generally accepted risk factor previous antibiotic use was confirmed in this study (p = 0.002, n = 23/28 CDI patients, 82.1%, versus n = 44/91 non-CDI patients, 48.4%). The following additional risk factors were identified: regular consumption of proton pump inhibitors; PPI (p = 0.011, n = 24/29, 82.8% vs. n = 52/92, 56.5%), CDI patients ate less vegetables (p = 0.001, n = 12/29, 41.4% vs. 69/92, 75.0%). The intake of the diuretic agent torasemid in patients with CDI (p = 0.005, n = 18/29, 62.1%) was higher than in patients without (n = 30/92, 32.6%). More patients with CDI had to undergo a surgery in the previous year (p = 0.022, n = 13/29, 44.8% vs. n = 21/92, 22.8%) and held more birds (p = 0.056, n = 4/29, 13.8%) than individuals of the negative group (n = 3/92, 3.3%). In conclusion, although no antibiotic potential was detected in diuretics, especially torasemid seems to have significant influence for the occurrence of a CDI as well as a nutrition poor in vegetables. A diet rich in vegetables represented a fourfold lower risk for a CDI (OR 0.240, CI (0.0720 - 0.796]).

A Case Report and Review of the Literature: Reactive Arthritis Caused by Clostridioides difficile ribotype 027

With an annual incidence of 250-300 per 100,000 inhabitants, reactive arthritis is not uncommon. However, the fact that Clostridioides difficile infection (CDI) can also lead to this complication is largely unknown. We report on a 69-years-old man who developed reactive arthritis of his right knee joint one week after antibiotic-associated diarrhea with evidence of C. difficile of the hypervirulent ribotype 027. His female partner also became infected with C. difficile ribotype 027, but did not develop reactive arthritis. The further investigation showed that the patient - in contrast to his partner - was HLA-B27 positive and had strong antibody levels against C. difficile. The case history together with the review of 45 other cases described so far shows that C. difficile can also lead to reactive arthritis. C. difficile-associated reactive arthritis (CDARA) is characterized by the fact that patients suffer from diarrhea or colitis after taking antibiotics, toxigenic C. difficile or only the toxins are detectable in the stool and there are no other explanations for the arthritis and diarrhea.

Exposure to the mycotoxin deoxynivalenol reduces the transport of conjugated bile acids by intestinal Caco-2 cells

Conjugated bile acids are synthesized in liver and subsequently secreted into the intestinal lumen from which they are actively reabsorbed and transported back to liver. The efficient enterohepatic circulation of conjugated bile acids is important to maintain homeostasis. The mycotoxin deoxynivalenol (DON) is a fungal secondary metabolite that contaminates cereal food. Upon human exposure, it can cause intestinal dysfunction. We explored the effects of DON exposure on the intestinal absorption of conjugated bile acids and the expression of bile acid transporters using an in vitro model based on Caco-2 cell layers grown in transwells. Our study shows that the transport rate of taurocholic acid (TCA) is decreased after 48-h pre-exposure of the Caco-2 cells to 2 µM DON, which is a realistic intestinal DON concentration. Exposure to DON downregulates expression of the genes coding for the apical sodium-dependent bile acid transporter (ASBT), the ileal bile acid-binding protein (IBABP) and the organic solute transporter α (OSTα), and it counteracts the agonist activity of Farnesoid X receptor (FXR) agonist GW4064 on these genes. In addition, the transport of ten taurine or glycine-conjugated bile acids in a physiological relevant mixture by the intestinal Caco-2 cell layers was decreased after pre-exposure of the cells to DON, pointing at a potential for DON-mediated accumulation of the conjugated bile acids at the intestinal luminal side. Together the results reveal that DON inhibits intestinal bile acid reabsorption by reducing the expression of bile acid transporters thereby affecting bile acid intestinal kinetics, leading to bile acid malabsorption in the intestine. Our study provides new insights into the hazards of DON exposure.

Assembly of the exosporium layer in Clostridioides difficile spores

Clostridioides difficile is a Gram-positive, spore-forming obligate anaerobe and a major threat to the healthcare system world-wide. Because of its strict anaerobic requirements, the infectious and transmissible morphotype is the dormant spore. During infection, C. difficile produces spores that can persist in the host and are responsible for disease recurrence and transmission, especially between hospitalized patients. Although the C. difficile spore surface mediates critical interactions with host surfaces, this outermost layer, known as the exosporium, is poorly conserved when compared to members of the Bacillus genus. Notably, the exosporium has been shown to be important for the persistence of C. difficile in the host. In this review, the ultrastructural properties, composition, and morphogenesis of the exosporium will be discussed.

Probiotics Exhibit Strain-Specific Protective Effects in T84 Cells Challenged With Clostridioides difficile-Infected Fecal Water

Clostridioides difficile infection (CDI) is frequently associated with intestinal injury and mucosal barrier dysfunction, leading to an inflammatory response involving neutrophil localization and upregulation of pro-inflammatory cytokines. The severity of clinical manifestations is associated with the extent of the immune response, which requires mitigation for better clinical management. Probiotics could play a protective role in this disorder due to their immunomodulatory ability in gastrointestinal disorders. We assessed five single-strain and three multi-strain probiotics for their ability to modulate CDI fecal water (FW)-induced effects on T84 cells. The CDI-FW significantly (p < 0.05) decreased T84 cell viability. The CDI-FW-exposed cells also exhibited increased pro-inflammatory cytokine production as characterized by interleukin (IL)-8, C-X-C motif chemokine 5, macrophage inhibitory factor (MIF), IL-32, and tumor necrosis factor (TNF) ligand superfamily member 8. Probiotics were associated with strain-specific attenuation of the CDI-FW mediated effects, whereby Saccharomyces boulardii CNCM I-1079 and Lacticaseibacillus rhamnosus R0011 were most effective in reducing pro-inflammatory cytokine production and in increasing T84 cell viability. ProtecFlor™, Lactobacillus helveticus R0052, and Bifidobacterium longum R0175 showed moderate effectiveness, and L. rhamnosus GG R0343 along with the two other multi-strain combinations were the least effective. Overall, the findings showed that probiotic strains possess the capability to modulate the CDI-mediated inflammatory response in the gut lumen.

Clostridium difficile Colonization Before and After Hospitalization in Children

Background:

Beginning in the early 2000s, Clostridium difficile infection has become a major health problem in the United States, Canada, and in most European countries and has not only increased in incidence but also the severity. There are 2 conditions for the development of C. difficile infection: disruption of the normal gastrointestinal flora, and exogenous ingestion of the microorganism. We aimed to study C. difficile colonization in hospitalized children. We identified 2 issues: (1) the relationship between risks before hospital admission and colonization on the first day of hospitalization and (2) the effect of the factors that patients are exposed to during hospitalization on the colonization status at discharge.

Methods:

Patients aged between 2 and 18 years who were hospitalized with various diagnoses were included in this study. C. difficile toxin A/B was investigated in the stool samples taken on the admission and discharge days.

Results:

One hundred six patients were included in the study, of whom 24.5% and 48.1% of hemato-oncology patients were positive for C. difficile toxin A/B. Antibiotic usage within 1 month preceding hospitalization and the presence of underlying disease impact the C. difficile colonization status on the first day of hospitalization.

Conclusion:

Toxigenic C. difficile colonization prevalence is high in hospitalized children, especially in the hemato-oncology patient group.

Motility and the genotype diversity of the flagellin genes fliC and fliD among Clostridioides difficile ribotypes

OBJECTIVE

The motility and genotype of the flagellin fliC and fliD genes were investigated in 82 Clostridioides difficile isolates belonging to the ribotypes (RTs): 027 (n = 41), 176 (n = 17), 023 (n = 8), 017 (n = 6) and 046 (n = 10). The reference C. difficile strains 630 and M120 were included as controls for the motility assay.

METHODS

A Multiple Locus Variable-number Tandem Repeat Analysis (MLVA) was used to exclude the genetic relatedness of C. difficile isolates belonging to the same RT. The variability of the fliC and fliD genes was determined by PCR-restriction fragment length polymorphism (RFLP) analysis and Sanger sequencing. The motility assay was carried out with 0.175% BHI agar tubes and BHI solid media plates with 0.4% agar.

RESULTS

The highest motility was observed in C. difficile RT023 isolates (p < 0.01), followed by RTs 027 and 176. C. difficile isolates of RTs 017 and 046 were less motile than RTs 027, 176 and 023 (p < 0.01). The fliC and fliD genes were present in all clinical isolates irrespective of the motility results. In the fliC gene analysis, four different RFLP groups were identified (I, II, VII, X). The fliC group VII was identified in two RTs (027 and 176), whereas the remaining three groups (I, II and X) belonged to a single RT 046, 017 and 023, respectively. The fliD gene analysis identified four new RFLP groups (a, b, c and d).

CONCLUSIONS

C. difficile RT023 is highly motile and its motility is comparable to the hypervirulent RT027 and its genetic relative RT176.

Cellular adaptation of Clostridioides difficile to high salinity encompasses a compatible solute-responsive change in cell morphology

Infections by the pathogenic gut bacterium Clostridioides difficile cause severe diarrheas up to a toxic megacolon and are currently among the major causes of lethal bacterial infections. Successful bacterial propagation in the gut is strongly associated with the adaptation to changing nutrition-caused environmental conditions; e.g. environmental salt stresses. Concentrations of 350 mM NaCl, the prevailing salinity in the colon, led to significantly reduced growth of C. difficile. Metabolomics of salt- stressed bacteria revealed a major reduction of the central energy generation pathways, including the Stickland-fermentation reactions. No obvious synthesis of compatible solutes was observed up to 24 h of growth. The ensuing limited tolerance to high salinity and absence of compatible solute synthesis might result from an evolutionary adaptation to the exclusive life of C. difficile in the mammalian gut. Addition of the compatible solutes carnitine, glycine-betaine, γ-butyrobetaine, crotonobetaine, homobetaine, proline-betaine and dimethylsulfoniopropionate (DMSP) restored growth (choline and proline failed) under conditions of high salinity. A bioinformatically-identified OpuF-type ABC-transporter imported most of the used compatible solutes. A long-term adaptation after 48 h included a shift of the Stickland fermentation-based energy metabolism from the utilization to the accumulation of L-proline and resulted in restored growth. Surprisingly, salt stress resulted in the formation of coccoid C. difficile cells instead of the typical rod-shaped cells, a process reverted by the addition of several compatible solutes. Hence, compatible solute import via OpuF is the major immediate adaptation strategy of C. difficile to high salinity-incurred cellular stress. This article is protected by copyright. All rights reserved.

Effective Barriers: The Role of NKT Cells and Innate Lymphoid Cells in the Gut

The critical role of commensal microbiota in regulating the host immune response has been established. In addition, it is known that host-microbial interactions are bidirectional, and this interplay is tightly regulated to prevent chronic inflammatory disease. Although many studies have focused on the role of classic T cell subsets, unconventional lymphocytes such as NKT cells and innate lymphoid cells also contribute to the regulation of homeostasis at mucosal surfaces and influence the composition of the intestinal microbiota. In this review, we discuss the mechanisms involved in the cross-regulation between NKT cells, innate lymphoid cells, and the gut microbiota. Moreover, we highlight how disruptions in homeostasis can lead to immune-mediated disorders.

Mechanism of the Gut Microbiota Colonization Resistance and Enteric Pathogen Infection

The mammalian gut microbial community, known as the gut microbiota, comprises trillions of bacteria, which co-evolved with the host and has an important role in a variety of host functions that include nutrient acquisition, metabolism, and immunity development, and more importantly, it plays a critical role in the protection of the host from enteric infections associated with exogenous pathogens or indigenous pathobiont outgrowth that may result from healthy gut microbial community disruption. Microbiota evolves complex mechanisms to restrain pathogen growth, which included nutrient competition, competitive metabolic interactions, niche exclusion, and induction of host immune response, which are collectively termed colonization resistance. On the other hand, pathogens have also developed counterstrategies to expand their population and enhance their virulence to cope with the gut microbiota colonization resistance and cause infection. This review summarizes the available literature on the complex relationship occurring between the intestinal microbiota and enteric pathogens, describing how the gut microbiota can mediate colonization resistance against bacterial enteric infections and how bacterial enteropathogens can overcome this resistance as well as how the understanding of this complex interaction can inform future therapies against infectious diseases.

Host Immune Responses to Clostridioides difficile: Toxins and Beyond

Clostridioides difficile is often resistant to the actions of antibiotics to treat other bacterial infections and the resulting C. difficile infection (CDI) is among the leading causes of nosocomial infectious diarrhea worldwide. The primary virulence mechanism contributing to CDI is the production of toxins. Treatment failures and recurrence of CDI have urged the medical community to search for novel treatment options. Strains that do not produce toxins, so called non-toxigenic C. difficile, have been known to colonize the colon and protect the host against CDI. In this review, a comprehensive description and comparison of the immune responses to toxigenic C. difficile and non-toxigenic adherence, and colonization factors, here called non-toxin proteins, is provided. This revealed a number of similarities between the host immune responses to toxigenic C. difficile and non-toxin proteins, such as the influx of granulocytes and the type of T-cell response. Differences may reflect genuine variation between the responses to toxigenic or non-toxigenic C. difficile or gaps in the current knowledge with respect to the immune response toward non-toxigenic C. difficile. Toxin-based and non-toxin-based immunization studies have been evaluated to further explore the role of B cells and reveal that plasma cells are important in protection against CDI. Since the success of toxin-based interventions in humans to date is limited, it is vital that future research will focus on the immune responses to non-toxin proteins and in particular non-toxigenic strains.

Clostridioides difficile: Current overview and future perspectives

The most common world-wide cause of antibiotic-associated infectious diarrhea and colitis is the toxin producing bacterium, Clostridioides difficile (C. difficile). Here we review the background and characteristics of the bacterium and the toxins produced together with the epidemiology and the complex pathogenesis that leads to a broad clinical spectrum of disease. The review describes the difficulties faced in obtaining a quick and accurate diagnosis despite the range of sensitive and specific diagnostic tools available. We also discuss the problem of disease recurrence and the importance of disease prevention. The high rates of infection recurrence mean that treatment strategies are constantly under review and we outline the diverse treatment options that are currently in use and explore the emerging treatment options of pulsed antibiotic use, microbial replacement therapies and the use of monoclonal antibodies. We summarize the future direction of treatment strategies which include the development of novel antibiotics, the administration of oral polyclonal antibody formulations, the use of vaccines, the administration of competitive non-toxigenic spores and the neutralization of antibiotics at the microbiota level. Future successful treatments will likely involve a combination of therapies to provide the most effective and robust approach to C. difficile management.

Dissemination of antibiotic resistance under antibiotics pressure during anaerobic co-digestion of food waste and sludge: Insights of driving factors, genetic expression, and regulation mechanism

This study revealed the effects and regulation mechanisms on antibiotic resistance genes (ARGs) dissemination during anaerobic co-digestion (AcoD) of food waste and sludge under the exposure of tetracycline, sulfamethoxazole (SMZ) and erythromycin (ERY). Results indicated antibiotics significantly increased the abundance of ARGs, and selectively enriched integron gene, suggesting antibiotics promoted the dissemination of ARGs. Procrustes analysis indicated that bacterial community, integrons and physicochemical properties displayed significant correlations with ARGs, and they respectively contributed 10.61%, 6.94% and 2.97% of explanations on ARGs variation. Especially, the maximum combined contribution (48.6%) of bacterial community and integrons, implying their significances on ARGs alteration. Metatranscriptomic analysis further demonstrated antibiotics upregulated the expressions of total ARGs and virulence factors, raising potential risks. The proposed mechanisms for ARGs dissemination facilitated by antibiotics might be attributed to the changes of ARGs-regulated functions for inducing DNA/cell damage and DNA conjugation during AcoD.

Soluble Non-Starch Polysaccharides From Plantain (Musa x paradisiaca L.) Diminish Epithelial Impact of Clostridioides difficile

Clostridioides difficile infection (CDI) is a leading cause of antibiotic-associated diarrhoea. Adhesion of this Gram-positive pathogen to the intestinal epithelium is a crucial step in CDI, with recurrence and relapse of disease dependent on epithelial interaction of its endospores. Close proximity, or adhesion of, hypervirulent strains to the intestinal mucosa are also likely to be necessary for the release of C. difficile toxins, which when internalized, result in intestinal epithelial cell rounding, damage, inflammation, loss of barrier function and diarrhoea. Interrupting these C. difficile-epithelium interactions could therefore represent a promising therapeutic strategy to prevent and treat CDI. Intake of dietary fibre is widely recognised as being beneficial for intestinal health, and we have previously shown that soluble non-starch polysaccharides (NSP) from plantain banana (Musa spp.), can block epithelial adhesion and invasion of a number of gut pathogens, such as E. coli and Salmonellae. Here, we assessed the action of plantain NSP, and a range of alternative soluble plant fibres, for inhibitory action on epithelial interactions of C. difficile clinical isolates, purified endospore preparations and toxins. We found that plantain NSP possessed ability to disrupt epithelial adhesion of C. difficile vegetative cells and spores, with inhibitory activity against C. difficile found within the acidic (pectin-rich) polysaccharide component, through interaction with the intestinal epithelium. Similar activity was found with NSP purified from broccoli and leek, although seen to be less potent than NSP from plantain. Whilst plantain NSP could not block the interaction and intracellular action of purified C. difficile toxins, it significantly diminished the epithelial impact of C. difficile, reducing both bacteria and toxin induced inflammation, activation of caspase 3/7 and cytotoxicity in human intestinal cell-line and murine intestinal organoid cultures. Dietary supplementation with soluble NSP from plantain may therefore confer a protective effect in CDI patients by preventing adhesion of C. difficile to the mucosa, i.e. a “contrabiotic” effect, and diminishing its epithelial impact. This suggests that plantain soluble dietary fibre may be a therapeutically effective nutritional product for use in the prevention or treatment of CDI and antibiotic-associated diarrhoea.

New ribotype Clostridioides difficile from ST11 group revealed higher pathogenic ability than RT078

Clostridioides difficile is the predominant antibiotic-associated enteropathogen associated with diarrhoea or pseudomembranous colitis in patients worldwide. Previously, we identified C. difficile RT078 isolates (CD21062) from elderly patients in China, including two new ribotype strains (CD10010 and CD12038) belonging to the ST11 group, and their genomic features were also investigated. This study compared sporulation, spore germination, toxin expression, flagellar characteristics, and adhesion among these strains in vitro and analysed their pathogenic ability in vivo using animal models. The results showed sporulation and spore germination did not significantly differ among the three C. difficile strains. CD10010 and CD12038 showed higher transcriptional levels of toxins until 48 h; thereafter, the transcriptional levels of toxins remained constant among RT078, CD10010, and CD12038. RT078 showed a loss of flagellum and its related genes, whereas CD12038 showed the highest motility in vitro. Both CD10010 and CD12038 initially showed flg phase OFF, and the flagellar switch reversed to phase ON after 48 h in swim agar. Flagellar proteins and toxins were both upregulated when flg phase OFF changed to flg phase ON status, enhancing their pathogenic ability. CD12038 showed the highest adhesion to Hep-2 cells. Histopathology and inflammation scores demonstrated that CD12038 caused the most severe tissue damage and infection in vivo. The new ribotype strains, particularly CD12038, exhibit higher pathogenic ability than the typical RT078 strain, both in vitro and in vivo. Therefore, more attention should be paid to this new C. difficile strain in epidemiological research; further studies are warranted.

Nonalcoholic fatty liver disease is associated with worse intestinal complications in patients hospitalized for Clostridioides difficile infection

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) has become the leading cause of chronic liver disease with increasing prevalence worldwide. Clostridioides difficile infection (CDI) remains the most common cause of nosocomial diarrhea in developed countries.

AIM

To assess the impact of NAFLD on the outcomes of hospitalized patients with CDI.

METHODS

This study was a retrospective cohort study. The Nationwide Inpatient Sample database was used to identify a total of 7239 adults admitted as inpatients with a primary diagnosis of CDI and coexisting NAFLD diagnosis from 2010 to 2014 using ICD-9 codes. Patients with CDI and coexisting NAFLD were compared to those with CDI and coexisting alcoholic liver disease (ALD) and viral liver disease (VLD), individually. Primary outcomes included mortality, length of stay, and total hospitalization charges. Secondary outcomes were in-hospital complications. Multivariate regression was used for outcome analysis after adjusting for possible confounders.

RESULTS

CDI with NAFLD was independently associated with lower rates of acute respiratory failure (2.7% vs 4.2%, P < 0.01; 2.7% vs 4.2%, P < 0.05), shorter length of stay (days) (5.75 ± 0.16 vs 6.77 ± 0.15, P < 0.001; 5.75 ± 0.16 vs 6.84 ± 0.23, P <0.001), and lower hospitalization charges (dollars) (38150.34 ± 1757.01 vs 46326.72 ± 1809.82, P < 0.001; 38150.34 ± 1757.01 vs 44641.74 ± 1660.66, P < 0.001) when compared to CDI with VLD and CDI with ALD, respectively. CDI with NAFLD was associated with a lower rate of acute kidney injury (13.0% vs 17.2%, P < 0.01), but a higher rate of intestinal perforation (P < 0.01) when compared to VLD. A lower rate of mortality (0.8% vs 2.7%, P < 0.05) but a higher rate of intestinal obstruction (4.6% vs 2.2%, P = 0.001) was also observed when comparing CDI with NAFLD to ALD.

CONCLUSION

Hospitalized CDI patients with NAFLD had more intestinal complications compared to CDI patients with VLD and ALD. Gut microbiota dysbiosis may contribute to the pathogenesis of intestinal complications.

Reduction in Health Care Facility-Onset Clostridioides difficile Infection: A Quality Improvement Initiative

Objective

To reduce health care facility–onset (HCFO) Clostridioides difficile infection (CDI) incidence by improving diagnostic stewardship and reducing the inappropriate testing of C difficile assays.

Patients and Methods

A multidisciplinary team conducted a quality improvement initiative from January 1, 2020, through March 31, 2021. Clostridioides difficile infection and inappropriate testing were identified via electronic health records using predefined criteria related to stool quantity/caliber, confounding medications, and laboratory data. An intervention bundle was designed including (1) provider education, (2) implementation of an appropriate testing algorithm, (3) expert review of C difficile orders, and (4) batch testing of assays to facilitate review and cancellation if inappropriate.

Results

Compared with a baseline period from January to September 2020, implementation of our intervention bundle from December 2020 to March 2021 resulted in an 83.6% reduction in inappropriate orders tested and a 41.7% reduction in HCFO CDI incidence.

Conclusion

A novel prevention bundle improved C difficile diagnostic stewardship and HCFO CDI incidence by reducing testing of inappropriate orders. Such initiatives targeting HCFO CDI may positively affect patient safety and hospital reimbursement.

Learning from Nature: Bacterial Spores as a Target for Current Technologies in Medicine (Review)

The capability of some representatives of Clostridium spp. and Bacillus spp. genera to form spores in extreme external conditions long ago became a subject of medico-biological investigations. Bacterial spores represent dormant cellular forms of gram-positive bacteria possessing a high potential of stability and the capability to endure extreme conditions of their habitat. Owing to these properties, bacterial spores are recognized as the most stable systems on the planet, and spore-forming microorganisms became widely spread in various ecosystems.

Spore-forming bacteria have been attracted increased interest for years due to their epidemiological danger. Bacterial spores may be in the quiescent state for dozens or hundreds of years but after they appear in the favorable conditions of a human or animal organism, they turn into vegetative forms causing an infectious process. The greatest threat among the pathogenic spore-forming bacteria is posed by the causative agents of anthrax (B. anthracis), food toxicoinfection (B. cereus), pseudomembranous colitis (C. difficile), botulism (C. botulinum), gas gangrene (C. perfringens).

For the effective prevention of severe infectious diseases first of all it is necessary to study the molecular structure of bacterial spores and the biochemical mechanisms of sporulation and to develop innovative methods of detection and disinfection of dormant cells. There is another side of the problem: the necessity to investigate exo- and endospores from the standpoint of obtaining similar artificially synthesized models in order to use them in the latest medical technologies for the development of thermostable vaccines, delivery of biologically active substances to the tissues and intracellular structures. In recent years, bacterial spores have become an interesting object for the exploration from the point of view of a new paradigm of unicellular microbiology in order to study microbial heterogeneity by means of the modern analytical tools.

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.

Clostridium Difficile and COVID-19: General Data, Ribotype, Clinical Form, Treatment-Our Experience from the Largest Infectious Diseases Hospital in Western Romania

Background and Objectives: In Coronavirus Disease 2019 (COVID-19), which is caused by the infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the clinical manifestations are primarily related to the pulmonary system. Under 10% of cases also develop gastrointestinal events such as diarrhea, nausea, vomiting and abdominal pain. Materials and Methods: We conducted an observational, retrospective study in the Infectious Diseases Clinic of "Victor Babes" Hospital, Timis County, in order to assess the incidence, outcome and risk factors for clostridium difficile infection (CDI) in COVID-19 patients. Results: Out of 2065 COVID-19 cases, hospitalized between 1st September 2020 and 30th April 2021, 40 cases of CDI were identified with 32 cases of hospital-onset of CDI and eight cases of community-onset and healthcare-associated CDI. By randomization, polymerase chain reaction ribotyping of Clostridium Difficile was performed in six cases. All the randomized cases tested positive for ribotype 027. The percentage of cases recovered with complications at discharge was higher among COVID-19 patients and CDI (p = 0.001). The in-hospital stay, 36 days versus 28 days, was longer among COVID-19 patients and CDI (p = 0.01). The presence of previous hospitalization (p = 0.004) and administration of antibiotics during the hospital stay, increased the risk of CDI among COVID-19 patients. The mean adjusted CCI at admission was lower among controls (p = 0.01). In two cases, exitus was strictly CDI-related, with one case positive for 027 ribotype. Conclusions: CDI has complicated the outcome of COVID-19 patients, especially for those with comorbidities or previously exposed to the healthcare system. In the face of the COVID-19 pandemic and the widespread, extensive use of antibiotics, clinicians should remain vigilant for possible CDI and SARS-CoV-2 co-infection.

Raw Animal Meats as Potential Sources of Clostridium difficile in Al-Jouf, Saudi Arabia

Clostridium difficile present in feces of food animals may contaminate their meats and act as a potential source of C. difficile infection (CDI) to humans. C. difficile resistance to antibiotics, its production of toxins and spores play major roles in the pathogenesis of CDI. This is the first study to evaluate C. difficile prevalence in retail raw animal meats, its antibiotics susceptibilities and toxigenic activities in Al-Jouf, Saudi Arabia. Totally, 240 meat samples were tested. C. difficile was identified by standard microbiological and biochemical methods. Vitek-2 compact system confirmed C. difficile isolates were 15/240 (6.3%). Toxins A/B were not detected by Xpect C. difficile toxin A/B tests. Although all isolates were susceptible to vancomycin and metronidazole, variable degrees of reduced susceptibilities to moxifloxacin, clindamycin or tetracycline antibiotics were detected by Epsilon tests. C. difficile strains with reduced susceptibility to antibiotics should be investigated. Variability between the worldwide reported C. difficile contamination levels could be due to absence of a gold standard procedure for its isolation. Establishment of a unified testing algorithm for C. difficile detection in food products is definitely essential to evaluate the inter-regional variation in its prevalence on national and international levels. Proper use of antimicrobials during animal husbandry is crucial to control the selective drug pressure on C. difficile strains associated with food animals. Investigating the protective or pathogenic potential of non-toxigenic C. difficile strains and the possibility of gene transfer from certain toxigenic/ antibiotics-resistant to non-toxigenic/antibiotics-sensitive strains, respectively, should be worthy of attention.

Guidelines on Implementing Antimicrobial Stewardship Programs in Korea

These guidelines were developed as a part of the 2021 Academic R&D Service Project of the Korea Disease Control and Prevention Agency in response to requests from healthcare professionals in clinical practice for guidance on developing antimicrobial stewardship programs (ASPs). These guidelines were developed by means of a systematic literature review and a summary of recent literature, in which evidence-based intervention methods were used to address key questions about the appropriate use of antimicrobial agents and ASP expansion. These guidelines also provide evidence of the effectiveness of ASPs and describe intervention methods applicable in Korea.

Defining the black box: a narrative review of factors associated with adverse outcomes from severe Clostridioides difficile infection

In the United States, Clostridioides difficile infection (CDI) is the leading cause of healthcare-associated infection, affecting nearly half a million people and resulting in more than 20,000 in-hospital deaths every year. It is therefore imperative to better characterize the intricate interplay between C. difficile microbial factors, host immunologic signatures, and clinical features that are associated with adverse outcomes of severe CDI. In this narrative review, we discuss the implications of C. difficile genetics and virulence factors in the molecular epidemiology of CDI, and the utility of early biomarkers in predicting the clinical trajectory of patients at risk of developing severe CDI. Furthermore, we identify associations between host immune factors and CDI outcomes in both animal models and human studies. Next, we highlight clinical factors including renal dysfunction, aging, blood biomarkers, level of care, and chronic illnesses that can affect severe CDI diagnosis and outcome. Finally, we present our perspectives on two specific treatments pertinent to patient outcomes: metronidazole administration and surgery. Together, this review explores the various venues of CDI research and highlights the importance of integrating microbial, host, and clinical data to help clinicians make optimal treatment decisions based on accurate prediction of disease progression.

The Case against Antibiotics and for Anti-Virulence Therapeutics

Although antibiotics have been indispensable in the advancement of modern medicine, there are downsides to their use. Growing resistance to broad-spectrum antibiotics is leading to an epidemic of infections untreatable by first-line therapies. Resistance is exacerbated by antibiotics used as growth factors in livestock, over-prescribing by doctors, and poor treatment adherence by patients. This generates populations of resistant bacteria that can then spread resistance genes horizontally to other bacterial species, including commensals. Furthermore, even when antibiotics are used appropriately, they harm commensal bacteria leading to increased secondary infection risk. Effective antibiotic treatment can induce bacterial survival tactics, such as toxin release and increasing resistance gene transfer. These problems highlight the need for new approaches to treating bacterial infection. Current solutions include combination therapies, narrow-spectrum therapeutics, and antibiotic stewardship programs. These mediate the issues but do not address their root cause. One emerging solution to these problems is anti-virulence treatment: preventing bacterial pathogenesis instead of using bactericidal agents. In this review, we discuss select examples of potential anti-virulence targets and strategies that could be developed into bacterial infection treatments: the bacterial type III secretion system, quorum sensing, and liposomes.

High Serum Levels of Toxin A Correlate with Disease Severity in Patients with Clostridioides difficile Infection

Cloistridioides difficile (CD) represents a major public healthcare-associated infection causing significant morbidity and mortality. The pathogenic effects of CD are mainly caused by the release of two exotoxins into the intestine: toxin A (TcdA) and toxin B (TcdB). CD infection (CDI) can also cause toxemia, explaining the systemic complications of life-threatening cases. Currently, there is a lack of sensitive assays to detect exotoxins circulating in the blood. Here, we report a new semi-quantitative diagnostic method to measure CD toxins serum levels. The dot-blot assay was modified to separately detect TcdA and TcdB in human serum with a limit of detection at the pg/mL levels. TcdA and TcdB concentrations in the plasma of 35 CDI patients were measured at the time of CDI diagnosis and at the fourth and tenth day after CDI diagnosis and initiation of anti-CDI treatment. TcdA and TcdB levels were compared to those determined in nine healthy blood donors. Toxemia was detected in the plasma of 33 out of the 35 CDI cases. We also assessed the relationship between TcdA serum levels and CDI severity, reporting that at the time of CDI diagnosis the proportion of severe CDI cases with a TcdA serum level > 60 pg/µL was higher than in mild CDI cases (29.4% versus 66.6%, p = 0.04). In conclusion, data reported here demonstrate for the first time that toxemia is much more frequent than expected in CDI patients, and specifically that high serum levels of TcdA correlate with disease severity in patients with CDI.

Helicobacter pylori Eradication Therapy-associated Diarrhea

Eradication of Helicobacter pylori has contributed to the treatment of peptic ulcers and mucosa-associated lymphoid tissue lymphoma. Moreover, it has possibly decreased the prevalence of gastric cancer. However, eradication therapy is associated with various adverse effects, of which diarrhea is the most common. The incidence of diarrhea after eradication treatment varies from 8% to 48%. In particular, the incidence is higher in patients who receive first-line standard triple therapy compared with those who receive second-line therapy. Both antibiotics and proton pump inhibitors, components of eradication therapy, have short-term and long-term impacts on gut microbiota. The alterations of gut microbiota may not recover until 1 year after eradication therapy. Most cases of diarrhea that occur after eradication therapy are antibiotic-associated diarrhea caused by the destruction of the normal gut microbiota. In some cases, Clostridioides difficile-associated diarrhea occurs after eradication therapy. If bloody diarrhea occurs after eradication therapy and the Clostridioides difficile toxin is not detected, antibiotic-associated hemorrhagic colitis associated with Klebsiella oxytoca infection should be suspected. It is crucial to explain the possibility of diarrhea before initiating eradication therapy to increase compliance. Furthermore, probiotics may be administered to reduce diarrhea. If severe diarrhea or symptoms other than the usual antibiotic-associated diarrhea occur during or after eradication therapy, antibiotics should be discontinued. In addition, appropriate tests to determine the cause of diarrhea should be performed. This review summarizes the alteration of the gut microbiota, the causes of diarrhea after Helicobacter pylori eradication therapy, and its management.

Protospacer-Adjacent Motif Specificity during Clostridioides difficile Type I-B CRISPR-Cas Interference and Adaptation

CRISPR (clustered regularly interspaced short palindromic repeats)-Cas (CRISPR-associated) systems provide prokaryotes with efficient protection against foreign nucleic acid invaders. We have recently demonstrated the defensive interference function of a CRISPR-Cas system from Clostridioides (Clostridium) difficile, a major human enteropathogen, and showed that it could be harnessed for efficient genome editing in this bacterium. However, molecular details are still missing on CRISPR-Cas function for adaptation and sequence requirements for both interference and new spacer acquisition in this pathogen. Despite accumulating knowledge on the individual CRISPR-Cas systems in various prokaryotes, no data are available on the adaptation process in bacterial type I-B CRISPR-Cas systems. Here, we report the first experimental evidence that the C. difficile type I-B CRISPR-Cas system acquires new spacers upon overexpression of its adaptation module. The majority of new spacers are derived from a plasmid expressing Cas proteins required for adaptation or from regions of the C. difficile genome where generation of free DNA termini is expected. Results from protospacer-adjacent motif (PAM) library experiments and plasmid conjugation efficiency assays indicate that C. difficile CRISPR-Cas requires the YCN consensus PAM for efficient interference. We revealed a functional link between the adaptation and interference machineries, since newly adapted spacers are derived from sequences associated with a CCN PAM, which fits the interference consensus. The definition of functional PAMs and establishment of relative activity levels of each of the multiple C. difficile CRISPR arrays in present study are necessary for further CRISPR-based biotechnological and medical applications involving this organism. IMPORTANCE CRISPR-Cas systems provide prokaryotes with adaptive immunity for defense against foreign nucleic acid invaders, such as viruses or phages and plasmids. The CRISPR-Cas systems are highly diverse, and detailed studies of individual CRISPR-Cas subtypes are important for our understanding of various aspects of microbial adaptation strategies and for the potential applications. The significance of our work is in providing the first experimental evidence for type I-B CRISPR-Cas system adaptation in the emerging human enteropathogen Clostridioides difficile. This bacterium needs to survive in phage-rich gut communities, and its active CRISPR-Cas system might provide efficient antiphage defense by acquiring new spacers that constitute memory for further invader elimination. Our study also reveals a functional link between the adaptation and interference CRISPR machineries. The definition of all possible functional trinucleotide motifs upstream protospacers within foreign nucleic acid sequences is important for CRISPR-based genome editing in this pathogen and for developing new drugs against C. difficile infections.

Antibiotic Resistance and Biofilm Production Capacity in Clostridioides difficile

Background

Clostridioides difficile (C. difficile) is one of the primary pathogens responsible for infectious diarrhea. Antibiotic treatment failure, occurring in about 30% of patients, and elevated rates of antibiotic resistance pose a major challenge for therapy. Reinfection often occurs by isolates that produce biofilm, a protective barrier impermeable to antibiotics. We explored the association between antibiotic resistance (in planktonic form) and biofilm-production in 123 C. difficile clinical isolates.

Results

Overall, 66 (53.6%) out of 123 isolates produced a biofilm, with most of them being either a strong (44%) or moderate (34.8%) biofilm producers. When compared to susceptible isolates, a statistically higher percentage of isolates with reduced susceptibility to metronidazole or vancomycin were biofilm producers (p < 0.0001, for both antibiotics). Biofilm production intensity was higher among tolerant isolates; 53.1% of the metronidazole-susceptible isolates were not able to produce biofilms, and only 12.5% were strong biofilm-producers. In contrast, 63% of the isolates with reduced susceptibility had a strong biofilm-production capability, while 22.2% were non-producers. Among the vancomycin-susceptible isolates, 51% were unable to produce biofilms, while all the isolates with reduced vancomycin susceptibility were biofilm-producers. Additionally, strong biofilm production capacity was more common among the isolates with reduced vancomycin susceptibility, compared to susceptible isolates (72.7% vs. 18.8%, respectively). The distribution of biofilm capacity groups was statistically different between different Sequence-types (ST) strains (p =0.001). For example, while most of ST2 (66.7%), ST13 (60%), ST42 (80%) isolates were non-producers, most (75%) ST6 isolates were moderate producers and most of ST104 (57.1%) were strong producers.

Conclusions

Our results suggest an association between reduced antibiotic susceptibility and biofilm production capacity. This finding reinforces the importance of antibiotic susceptibility testing, mainly in recurrence infections that may be induced by a strain that is both antibiotic tolerant and biofilm producer. Better adjustment of treatment in such cases may reduce recurrences rates and complications. The link of biofilm production and ST should be further validated; if ST can indicate on isolate virulence, then in the future, when strain typing methods will be more available to laboratories, ST determination may aid in indecision between supportive vs. aggressive treatment.

Inflammatory Bowel Disease Outcomes Following Fecal Microbiota Transplantation for Recurrent C. difficile Infection

BACKGROUND

Recurrent Clostridioides difficile infection (CDI) in patients with inflammatory bowel disease (IBD) is a clinical challenge. Fecal microbiota transplantation (FMT) has emerged as a recurrent CDI therapy. Anecdotal concerns exist regarding worsening of IBD activity; however, prospective data among IBD patients are limited.

METHODS

Secondary analysis from an open-label, prospective, multicenter cohort study among IBD patients with 2 or more CDI episodes was performed. Participants underwent a single FMT by colonoscopy (250 mL, healthy universal donor). Secondary IBD-related outcomes included rate of de novo IBD flares, worsening IBD, and IBD improvement-all based on Mayo or Harvey-Bradshaw index (HBI) scores. Stool samples were collected for microbiome and targeted metabolomic profiling.

RESULTS

Fifty patients enrolled in the study, among which 15 had Crohn's disease (mean HBI, 5.8 ± 3.4) and 35 had ulcerative colitis (mean partial Mayo score, 4.2 ± 2.1). Overall, 49 patients received treatment. Among the Crohn's disease cohort, 73.3% (11 of 15) had IBD improvement, and 4 (26.6%) had no disease activity change. Among the ulcerative colitis cohort, 62% (22 of 34) had IBD improvement, 29.4% (11 of 34) had no change, and 4% (1 of 34) experienced a de novo flare. Alpha diversity significantly increased post-FMT, and ulcerative colitis patients became more similar to the donor than Crohn's disease patients (P = 0.04).

CONCLUSION

This prospective trial assessing FMT in IBD-CDI patients suggests IBD outcomes are better than reported in retrospective studies.

Invisible steps for a global endemy: molecular strategies adopted by Clostridioides difficile

Clostridioides difficile infection (CDI) is on the rise worldwide and is associated with an increase in deaths and socio-health burden. C. difficile has become ubiquitous in anthropized environments because of the extreme resistance of its spores. Based on the epidemiological data and knowledge of molecular pathogenesis of C. difficile, it is possible to predict its progressive colonization of the human population for the following reasons: first, its global spread is unstoppable; second, the toxins (Tcds) produced by C. difficile, TcdA and TcdB, mainly cause cell death by apoptosis, but the surviving cells acquire a senescence state that favours persistence of C. difficile in the intestine; third, proinflammatory cytokines, tumour necrosis factor-α and interferon-γ, induced during CDI, enhance the cytotoxicity of Tcds and can increase the survival of senescent cells; fourth, Tcds block mobility and induce apoptosis in immune cells recruited at the infection site; and finally, after remission from primary infection or relapse, C. difficile causes functional abnormalities in the enteric glial cell (EGC) network that can result in irritable bowel syndrome, characterized by a latent inflammatory response that contributes to C. difficile survival and enhances the cytotoxic activity of low doses of TcdB, thus favouring further relapses. Since a 'global endemy' of C. difficile seems inevitable, it is necessary to develop an effective vaccine against Tcds for at-risk individuals, and to perform a prophylaxis/selective therapy with bacteriophages highly specific for C. difficile. We must be aware that CDI will become a global health problem in the forthcoming years, and we must be prepared to face this menace.

Impact of nisin on Clostridioides difficile and microbiota composition in a faecal fermentation model of the human colon

AIMS

Nisin is a bacteriocin with a broad spectrum of activity against Gram-positive bacteria. The aims were to assess nisin activity against Clostridioides difficile in a complex microbial environment and determine the minimum inhibitory concentration at which C. difficile growth is suppressed whilst having minimal impact on the faecal microbiota.

METHODS AND RESULTS

Faecal slurries were prepared from fresh faecal samples and spiked with C. difficile (10⁶  CFU per ml). Nisin was added to each fermentation at a range of concentrations from 0 to 500 µM. Following 24 h, 16S rRNA gene sequencing was performed, and the presence of viable C. difficile was assessed. There was no viable C. difficile detected in the presence of 50-500 µM nisin. There was a decrease in the diversity of the microbiota in a nisin dose-dependent manner. Nisin predominantly depleted the relative abundance of the Gram-positive bacteria whilst the relative abundance of Gram-negative bacteria such as Escherichia Shigella and Bacteroides increased.

CONCLUSIONS

Using an ex vivo model of the colon, this study demonstrates the ability of purified nisin to selectively deplete C. difficile in a faecal microbial environment and establishes the minimum concentration at which this occurs whilst having a minimal impact on the composition of the microbiota.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study opens up the potential to use nisin as a therapeutic for clostridial gut infections.

Opportunities for Nanomedicine in Clostridioides difficile Infection

Clostridioides difficile, a spore-forming bacterium, is a nosocomial infectious pathogen which can be found in animals as well. Although various antibiotics and disinfectants were developed, C. difficile infection (CDI) remains a serious health problem. C. difficile spores have complex structures and dormant characteristics that contribute to their resistance to harsh environments, successful transmission and recurrence. C. difficile spores can germinate quickly after being exposed to bile acid and co-germinant in a suitable environment. The vegetative cells produce endospores, and the mature spores are released from the hosts for dissemination of the pathogen. Therefore, concurrent elimination of C. difficile vegetative cells and inhibition of spore germination is essential for effective control of CDI. This review focused on the molecular pathogenesis of CDI and new trends in targeting both spores and vegetative cells of this pathogen, as well as the potential contribution of nanotechnologies for the effective management of CDI.

2'FL and LNnT Exert Antipathogenic Effects against C. difficile ATCC 9689 In Vitro, Coinciding with Increased Levels of Bifidobacteriaceae and/or Secondary Bile Acids

Clostridioides difficile (formerly Clostridium difficile) infection (CDI) is one of the most common hospital-acquired infections, which is often triggered by a dysbiosed indigenous gut microbiota (e.g., upon antibiotic therapy). Symptoms can be as severe as life-threatening colitis. The current study assessed the antipathogenic potential of human milk oligosaccharides (HMOs), i.e., 2'-O-fucosyllactose (2'FL), lacto-N-neotetraose (LNnT), and a combination thereof (MIX), against C. difficile ATCC 9689 using in vitro gut models that allowed the evaluation of both direct and, upon microbiota modulation, indirect effects. During a first 48 h fecal batch study, dysbiosis and CDI were induced by dilution of the fecal inoculum. For each of the three donors tested, C. difficile levels strongly decreased (with >4 log CFU/mL) upon treatment with 2'FL, LNnT and MIX versus untreated blanks, coinciding with increased acetate/Bifidobacteriaceae levels. Interindividual differences among donors at an intermediate time point suggested that the antimicrobial effect was microbiota-mediated rather than being a direct effect of the HMOs. During a subsequent 11 week study with the PathogutTM model (specific application of the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®)), dysbiosis and CDI were induced by clindamycin (CLI) treatment. Vancomycin (VNC) treatment cured CDI, but the further dysbiosis of the indigenous microbiota likely contributed to CDI recurrence. Upon co-supplementation with VNC, both 2'FL and MIX boosted microbial activity (acetate and to lesser extent propionate/butyrate). Moreover, 2'FL avoided CDI recurrence, potentially because of increased secondary bile acid production. Overall, while not elucidating the exact antipathogenic mechanisms-of-action, the current study highlights the potential of HMOs to combat CDI recurrence, help the gut microbial community recover after antibiotic treatment, and hence counteract the adverse effects of antibiotic therapies.

A Guide to the Gut Microbiome and its Relevance to Critical Care

Although it is well-established that particular bacteria may cause gastroenteritis and other infections when present in the gut, it is only recently that scientists have made significant inroads into understanding the huge number of other bacteria and additional microbes that live within the gastrointestinal tract, referred to as the gut microbiome. In particular, it is now recognised that bacteria within the gut microbiome have a wide variety of roles in maintaining different aspects of human health, and that disturbances of these bacteria may potentially cause or contribute to a number of different medical conditions, including particular infections, certain cancers, and chronic conditions, including inflammatory bowel disease. Moreover, there is increasing awareness that these bacteria help determine how the body responds to medication, including antibiotics and chemotherapy. There has been growing interest in different approaches to alter the gut microbiome as a novel approach to medical therapy. This article provides an overview of the importance of the gut microbiome, with a particular focus on critical care.

The Infectious Disease Ontology in the age of COVID-19

BACKGROUND

Effective response to public health emergencies, such as we are now experiencing with COVID-19, requires data sharing across multiple disciplines and data systems. Ontologies offer a powerful data sharing tool, and this holds especially for those ontologies built on the design principles of the Open Biomedical Ontologies Foundry. These principles are exemplified by the Infectious Disease Ontology (IDO), a suite of interoperable ontology modules aiming to provide coverage of all aspects of the infectious disease domain. At its center is IDO Core, a disease- and pathogen-neutral ontology covering just those types of entities and relations that are relevant to infectious diseases generally. IDO Core is extended by disease and pathogen-specific ontology modules.

RESULTS

To assist the integration and analysis of COVID-19 data, and viral infectious disease data more generally, we have recently developed three new IDO extensions: IDO Virus (VIDO); the Coronavirus Infectious Disease Ontology (CIDO); and an extension of CIDO focusing on COVID-19 (IDO-COVID-19). Reflecting the fact that viruses lack cellular parts, we have introduced into IDO Core the term acellular structure to cover viruses and other acellular entities studied by virologists. We now distinguish between infectious agents - organisms with an infectious disposition - and infectious structures - acellular structures with an infectious disposition. This in turn has led to various updates and refinements of IDO Core's content. We believe that our work on VIDO, CIDO, and IDO-COVID-19 can serve as a model for yielding greater conformance with ontology building best practices.

CONCLUSIONS

IDO provides a simple recipe for building new pathogen-specific ontologies in a way that allows data about novel diseases to be easily compared, along multiple dimensions, with data represented by existing disease ontologies. The IDO strategy, moreover, supports ontology coordination, providing a powerful method of data integration and sharing that allows physicians, researchers, and public health organizations to respond rapidly and efficiently to current and future public health crises.

Low-density lipoprotein receptor-related protein 1 is a CROPs-associated receptor for Clostridioides difficile toxin B

As the leading cause of worldwide hospital-acquired infection, Clostridioides difficile (C. difficile) infection has caused heavy economic and hospitalized burden, while its pathogenesis is not fully understood. Toxin B (TcdB) is one of the major virulent factors of C. difficile. Recently, CSPG4 and FZD2 were reported to be the receptors that mediate TcdB cellular entry. However, genetic ablation of genes encoding these receptors failed to completely block TcdB entry, implicating the existence of alternative receptor(s) for this toxin. Here, by employing the CRISPR-Cas9 screen in CSPG4-deficient HeLa cells, we identified LDL receptor-related protein-1 (LRP1) as a novel receptor for TcdB. Knockout of LRP1 in both CSPG4-deficient HeLa cells and colonic epithelium Caco2 cells conferred cells with increased TcdB resistance, while LRP1 overexpression sensitized cells to TcdB at a low concentration. Co-immunoprecipitation assay showed that LRP1 interacts with full-length TcdB. Moreover, CROPs domain, which is dispensable for TcdB's interaction with CSPG4 and FZD2, is sufficient for binding to LRP1. As such, our study provided evidence for a novel mechanism of TcdB entry and suggested potential therapeutic targets for treating C. diff.

Emerging antibody-based products for infectious diseases: Planning for metric ton manufacturing

This review focuses on the emerging monoclonal antibody market for infectious diseases and the metric ton scale manufacturing requirements to meet global demand. Increasing access to existing antibody-based products coupled with the unmet need in infectious disease will likely exceed the current existing global manufacturing capacity. Further, the large numbers of individuals infected during epidemics such as the ongoing COVID-19 pandemic emphasizes the need to plan for metric ton manufacturing of monoclonal antibodies by expanding infrastructure and exploring alternative production systems.

Characterization of Clostridioides difficile DSM 101085 with A-B-CDT+ Phenotype from a Late Recurrent Colonization

During the last decades, hypervirulent strains of Clostridioides difficile with frequent disease recurrence and increased mortality appeared. Clostridioides difficile DSM 101085 was isolated from a patient who suffered from several recurrent infections and colonizations, likely contributing to a fatal outcome. Analysis of the toxin repertoire revealed the presence of a complete binary toxin locus and an atypical pathogenicity locus consisting of only a tcdA pseudogene and a disrupted tcdC gene sequence. The pathogenicity locus shows upstream a transposon and has been subject to homologous recombination or lateral gene transfer events. Matching the results of the genome analysis, neither TcdA nor TcdB production but the expression of cdtA and cdtB was detected. This highlights a potential role of the binary toxin C. difficile toxin in this recurrent colonization and possibly further in a host-dependent virulence. Compared with the C. difficile metabolic model strains DSM 28645 (630Δerm) and DSM 27147 (R20291), strain DSM 101085 showed a specific metabolic profile, featuring changes in the threonine degradation pathways and alterations in the central carbon metabolism. Moreover, products originating from Stickland pathways processing leucine, aromatic amino acids, and methionine were more abundant in strain DSM 101085, indicating a more efficient use of these substrates. The particular characteristics of strain C. difficile DSM 101085 may represent an adaptation to a low-protein diet in a patient with recurrent infections.

Identification and engraftment of new bacterial strains by shotgun metagenomic sequence analysis in patients with recurrent Clostridioides difficile infection before and after fecal microbiota transplantation and in healthy human subjects

BACKGROUND

Recurrent Clostridioides diffícile infection (RCDI) is associated with major bacterial dysbiosis and colitis. Fecal microbiota transplantation (FMT) is a highly effective therapeutic modality for RCDI. While several studies have identified bacterial species associated with resolution of symptoms in patients, characterization of the fecal microbiome at the bacterial strain level in RCDI patients before and after FMT and healthy donors, has been lacking. The aim of this study was to examine the ability of bacterial strains from healthy donors to engraft in the gastrointestinal tract of patients with RCDI following FMT.

METHODS

Fecal samples were collected from 22 patients with RCDI before and after FMT and their corresponding healthy donors. Total DNA was extracted from each sample and analyzed by shotgun metagenomic sequencing. The Cosmos-ID analysis platform was used for taxonomic assignment of sequences and calculation of the relative abundance (RA) of bacterial species and strains. From these data, the total number of bacterial strains (BSI), Shannon diversity index, dysbiosis index (DI), and bacterial engraftment factor, were calculated for each strain.

FINDINGS

A marked reduction (p<0·0001) in the RA of total and specific bacterial strains, especially from phylum Firmicutes, was observed in RCDI patients prior to FMT. This change was associated with an increase in the DI (p<0·0001) and in pathobiont bacterial strains from phylum Proteobacteria, such as Escherichia coli O157:H7 and Klebsiella pneumoniae UCI 34. BSI was significantly lower in this group of patients as compared to healthy donors and correlated with the Shannon Index. (p<0·0001). Identification and engraftment of bacterial strains from healthy donors revealed a greater diversity and higher relative abundance of short-chain fatty acid (SCFA)-producing bacterial strains, including Lachnospiraceae bacterium 5_1_63FAA_u_t, Dorea formicigenerans ATCC 27755, Anaerostipes hadrusand others, in RCDI patients after FMT.

INTERPRETATION

These observations identify a group of SCFA-producing bacterial strains from healthy donors that engraft well in patients with RCDI following FMT and are associated with complete resolution of clinical symptoms and bacterial dysbiosis.