Whole genome sequencing reveals potential spread of Clostridium difficile between humans and farm animals in the Netherlands, 2002 to 2011

Genomic epidemiology of Clostridioides difficile sequence type 35 reveals intraspecies and interspecies clonal transmission

Clostridioides difficile sequence type (ST) 35 has been found in humans and animals worldwide. However, its genomic epidemiology and clonal transmission have not been explored in detail. In this study, 176 C. difficile ST35 isolates from six countries were sequenced. Genomic diversity, clonal transmission and epidemiological data were analyzed. Sporulation and virulence capacities were measured. Four ribotypes (RT) were identified including RT046 (97.2%), RT656 (1.1%), RT427 (0.6%), and RT AI-78 (1.1%). Phylogenetic analysis of 176 ST35 genomes, along with 50 publicly available genomes, revealed two distinctive lineages without time-, region-, or source-dependent distribution. However, the distribution of antimicrobial resistance genes differed significantly between the two lineages. Nosocomial and communal transmission occurred in humans with the isolates differed by ≤ two core-genome single-nucleotide polymorphism (cgSNPs) and clonal circulation was found in pigs with the isolates differed by ≤ four cgSNPs. Notably, interspecies clonal transmission was identified among three patients with community acquired C. difficile infection and pigs with epidemiological links, differed by ≤ nine cgSNPs. Toxin B (TcdB) concentrations were significantly higher in human isolates compared to pig isolates, and ST35 isolates exhibited stronger sporulation capacities than other STs. Our study provided new genomic insights and epidemiological evidence of C. difficile ST35 intraspecies and interspecies clonal transmission, which can also be facilitated by its strong sporulation capacity.

Antimicrobial resistance of Clostridioides difficile in veterinary medicine around the world: A scoping review of minimum inhibitory concentrations

Objective

To provide a comprehensive characterization of Clostridioides difficile antimicrobial resistance (AMR) data in veterinary medicine based on the minimum inhibitory concentrations (MICs) of all antimicrobial agents tested in relation to the techniques used.

Methods

A systematic scoping review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for scoping reviews (PRISMA-ScR) and its associated checklist. The objective was to provide a synthesis of the evidence in a summarized and analyzed format.To this end, three scientific databases were consulted: Scopus, PubMed, and Web of Science, up until December 2021. Subsequently, all identified literature was subjected to screening and classification in accordance with the established study criteria, with the objective of subsequent evaluation.

Study selection and data extraction

A comprehensive analysis was conducted on studies regarding Clostridioides difficile antimicrobial resistance (AMR) in veterinary medicine across various animal species and related sources. The analysis included studies that presented data on antimicrobial susceptibility testing using the E-test, agar dilution, or broth microdilution techniques. The extracted data included minimum inhibitory concentration (MIC) values and a comprehensive characterization analysis.

Results

A total of 1582 studies were identified in scientific databases, of which only 80 were subjected to analysis. The research on Clostridioides difficile antimicrobial resistance (AMR) in veterinary medicine is most prolific in Europe and North America. The majority of isolates originate from production animals (55%) and pets (15%), with pigs, horses, and cattle being the most commonly studied species. The tested agents' minimum inhibitory concentrations (MICs) and resulting putative antimicrobial resistance profiles exhibited considerable diversity across animal species and sources of isolation. Additionally, AMR characterization has been conducted at the gene and genomic level in animal strains. The E-test was the most frequently utilized method for antimicrobial susceptibility testing (AST). Furthermore, the breakpoints for interpreting the MICs were found to be highly heterogeneous and frequently observed regardless of the geographical origin of the publication.

Conclusions

Antimicrobial susceptibility testing techniques and results were found to be diverse and heterogeneous. There is no evidence of an exclusive antimicrobial resistance pattern in any animal species. Despite the phenotypic and genomic data collected over the years, further interdisciplinary studies are necessary. Our findings underscore the necessity for international collaboration to establish uniform standards for C. difficile antimicrobial susceptibility testing (AST) methods and reporting. Such collaboration would facilitate a "One Health" approach to surveillance and control, which is of paramount importance.

Molecular Characterization and Potential Host-switching of Swine Farm associated Clostridioides difficile ST11

OBJECTIVE

To conduct molecular prevalence and genetic polymorphism analysis of 24 Swine Farm associated C. difficile ST11 strains, in addition to other representative sequenced ST strains.

METHODS

The collected C. difficile strains underwent whole genome sequencing and bioinformatic analysis using the illumina NovaSeq platform, SPAdes, Prokka, MOB-suite, and FastTree. Virulence and antibiotic resistance genes were identified through NCBI Pathogen Database. Cytotoxicity tests were conducted on HT-29 cells and Vero cells to verify the function of toxin A and toxin B.

RESULTS

The most prevalent resistance genes in ST11 were found to be against β-lactamases, aminoglycosides, and tetracycline. A C. difficile isolate (strain 27) with tcdA deletion and high antibiotic resistance genes was far apart from other swine farm associated ST11 isolates in the phylogenetic branch. The remarkable genetic similarity between animal and human C. difficile strains suggests potential transmission of ST11 strains between animals and humans. The plasmid replicon sequences repUS43 were identified in all ST11 strains except one variant (strain 27), and 91.67% (22/24) of these were assessed by MOB-typer as having mobilizable plasmids.

CONCLUSION

Swine farm associated C. difficile ST11 carried fewer virulence genes than ST11 strains collected from NCBI database. It is critical to monitor the evolution of C. difficile strains to understand their changing characteristics, host-switching, and develop effective control and prevention strategies.

Comparative genome analyses of clinical and non-clinical Clostridioides difficile strains

The pathogenic bacterium Clostridioides difficile is a worldwide health burden with increasing morbidity, mortality and antibiotic resistances. Therefore, extensive research efforts are made to unravel its virulence and dissemination. One crucial aspect for C. difficile is its mobilome, which for instance allows the spread of antibiotic resistance genes (ARG) or influence strain virulence. As a nosocomial pathogen, the majority of strains analyzed originated from clinical environments and infected individuals. Nevertheless, C. difficile can also be present in human intestines without disease development or occur in diverse environmental habitats such as puddle water and soil, from which several strains could already be isolated. We therefore performed comprehensive genome comparisons of closely related clinical and non-clinical strains to identify the effects of the clinical background. Analyses included the prediction of virulence factors, ARGs, mobile genetic elements (MGEs), and detailed examinations of the pan genome. Clinical-related trends were thereby observed. While no significant differences were identified in fundamental C. difficile virulence factors, the clinical strains carried more ARGs and MGEs, and possessed a larger accessory genome. Detailed inspection of accessory genes revealed higher abundance of genes with unknown function, transcription-associated, or recombination-related activity. Accessory genes of these functions were already highlighted in other studies in association with higher strain virulence. This specific trend might allow the strains to react more efficiently on changing environmental conditions in the human host such as emerging stress factors, and potentially increase strain survival, colonization, and strain virulence. These findings indicated an adaptation of the strains to the clinical environment. Further, implementation of the analysis results in pairwise genome comparisons revealed that the majority of these accessory genes were encoded on predicted MGEs, shedding further light on the mobile genome of C. difficile. We therefore encourage the inclusion of non-clinical strains in comparative analyses.

Removal of mobile genetic elements from the genome of Clostridioides difficile and the implications for the organism's biology

Clostridioides difficile is an emerging pathogen of One Health significance. Its highly variable genome contains mobile genetic elements (MGEs) such as transposons and prophages that influence its biology. Systematic deletion of each genetic element is required to determine their precise role in C. difficile biology and contribution to the wider mobilome. Here, Tn5397 (21 kb) and ϕ027 (56 kb) were deleted from C. difficile 630 and R20291, respectively, using allele replacement facilitated by CRISPR-Cas9. The 630 Tn5397 deletant transferred PaLoc at the same frequency (1 × 10-7) as 630 harboring Tn5397, indicating that Tn5397 alone did not mediate conjugative transfer of PaLoc. The R20291 ϕ027 deletant was sensitive to ϕ027 infection, and contained two unexpected features, a 2.7 kb remnant of the mutagenesis plasmid, and a putative catalase gene adjacent to the deleted prophage was also deleted. Growth kinetics of R20291 ϕ027 deletant was similar to wild type (WT) in rich medium but marginally reduced compared with WT in minimal medium. This work indicates the commonly used pMTL8000 plasmid series works well for CRISPR-Cas9-mediated gene deletion, resulting in the largest deleted locus (56.8 kb) described in C. difficile. Removal of MGEs was achieved by targeting conjugative/integrative regions to promote excision and permanent loss. The deletants created will be useful strains for investigating Tn5397 or ϕ027 prophage contribution to host virulence, fitness, and physiology, and a platform for other mutagenesis studies aimed at functional gene analysis without native transposon or phage interference in C. difficile 630 and R20291.

Clostridioides difficile in calves, cattle and humans from Dutch dairy farms: Predominance of PCR ribotype 695 (clade 5, sequence type 11) in cattle

Background

Clostridioides difficile is a leading cause of infectious diarrhea in both humans and livestock. In particular, C. difficile strains belonging to sequence type (ST) 11 are common enteropathogens. The aim of this study was to determine the presence and genetic relatedness of C. difficile types in dairy cattle and calves.

Method

Dutch dairy farms were visited between February and December 2021. Feces was collected from adult dairy cattle and calves of two age categories (<4 weeks and 4 weeks-4 months). Fecal samples were also requested from dairy farmers, family members and employees. Fecal samples were cultured in an enrichment medium for 10-15 days and subcultured on solid media for capillary PCR ribotyping and whole genome sequencing.

Results

C. difficile was detected on 31 out of 157 (19.8%) dairy farms. The highest prevalence was found in calves <4 weeks (17.5%). None of the 99 human samples collected were positive. Thirty-seven cultured isolates belonged to 11 different PCR ribotypes (RT) of which RT695 (56.8%) and RT078/126 (16.2%) were most abundant. In the database of the Netherlands National Expertise Centre for C. difficile infections (CDI, >10.000 patient isolates), RT695 was found in only two patients with hospital-onset CDI, diagnosed in 2020 and 2021. Sequence analysis of 21C. difficile RT695 from cattle revealed that all isolates belonged to clade 5, ST11 and contained genes encoding toxin A, toxin B and binary toxin. RT695 strains carried antimicrobial resistance genes typically found in clade 5C. difficile. Groups of genetically related RT695 isolates were found between dairy farms, whereas identical strains were only present in individual farms.

Conclusions

C. difficile was found in ∼20% of dairy farms with a predominance of the relatively unknown RT695. Isolates of RT695 belonged to the same clade and sequence type as RT078/126, which is recognized as an important zoonotic type.

Gut microbiota-gonadal axis: the impact of gut microbiota on reproductive functions

The influence of gut microbiota on physiological processes is rapidly gaining attention globally. Despite being under-studied, there are available data demonstrating a gut microbiota-gonadal cross-talk, and the importance of this axis in reproduction. This study reviews the impacts of gut microbiota on reproduction. In addition, the possible mechanisms by which gut microbiota modulates male and female reproduction are presented. Databases, including Embase, Google scholar, Pubmed/Medline, Scopus, and Web of Science, were explored using relevant key words. Findings showed that gut microbiota promotes gonadal functions by modulating the circulating levels of steroid sex hormones, insulin sensitivity, immune system, and gonadal microbiota. Gut microbiota also alters ROS generation and the activation of cytokine accumulation. In conclusion, available data demonstrate the existence of a gut microbiota-gonadal axis, and role of this axis on gonadal functions. However, majority of the data were compelling evidences from animal studies with a great dearth of human data. Therefore, human studies validating the reports of experimental studies using animal models are important.

Non-human Clostridioides difficile Reservoirs and Sources: Animals, Food, Environment

Clostridioides difficile is ubiquitous and is found in humans, animals and in variety of environments. The substantial overlap of ribotypes between all three main reservoirs suggests the extensive transmissions. Here we give the overview of European studies investigating farm, companion and wild animals, food and environments including water, soil, sediment, wastewater treatment plants, biogas plants, air, and households. Studies in Europe are more numerous especially in last couple of years, but are still fragmented in terms of countries, animal species, or type of environment covered. Soil seem to be the habitat of divergent unusual lineages of C. difficile. But the most important aspect of animals and environment is their role in C. difficile transmissions and their potential as a source for human infection is discussed.

Burden of Medically Attended Diarrhea and Outpatient Clostridioides difficile Infection Among Persons in 2 Large Integrated Healthcare Settings, 2016-2021

Background

Identification of Clostridioides difficile infection (CDI) in the community setting is increasing. We describe testing for CDI among patients with medically attended diarrhea (MAD) in the outpatient setting, and the incidence of outpatient CDI.

Methods

This was a retrospective cohort study among members ≥18 years of age from Kaiser Permanente Southern California and Kaiser Permanente Northwest from 1 January 2016 through 31 December 2021. MAD was identified by outpatient diarrheal International Classification of Diseases, Tenth Revision diagnosis codes, and CDI through positive laboratory results. Outpatient CDI was defined by no hospitalization ≤7 days after specimen collection. Incidence rates (IRs) of outpatient CDI were stratified by select demographic and clinical variables. Outpatient CDI burden 12 months following index date was measured by CDI-associated healthcare visits, and CDI testing and treatment.

Results

We identified 777 533 MAD episodes; 12.1% (93 964/777 533) were tested for CDI. Of those tested, 10.8% (10 110/93 964) were positive. Outpatient CDI IR was 51.0 (95% confidence interval [CI], 49.8-52.2) per 100 000 person-years, decreasing from 58.2 (95% CI, 55.7-60.7) in 2016 to 45.7 (95% CI, 43.7-47.8) in 2021. Approximately 44% (n = 4200) received an antibiotic 30 days prior to index date and 84.1% (n = 8006) CDIs were "community-associated" (no hospitalizations 12 weeks prior to index date). Of outpatient CDIs, 6.7% (n = 526) had a CDI-associated hospitalization ≤12 months.

Conclusions

There was a high incidence of outpatient CDI despite infrequent CDI testing among patients with MAD. The majority of those with outpatient CDI had no recent antibiotic use and no recent hospitalization. Further studies are needed to understand the source and management of medically attended outpatient CDI.

Comparative Genomics of Clostridioides difficile

Clostridioides difficile, a Gram-positive spore-forming anaerobic bacterium, has rapidly emerged as the leading cause of nosocomial diarrhoea in hospitals. The availability of large numbers of genome sequences, mainly due to the use of next-generation sequencing methods, has undoubtedly shown their immense advantages in the determination of C. difficile population structure. The implementation of fine-scale comparative genomic approaches has paved the way for global transmission and recurrence studies, as well as more targeted studies, such as the PaLoc or CRISPR/Cas systems. In this chapter, we provide an overview of recent and significant findings on C. difficile using comparative genomic studies with implications for epidemiology, infection control and understanding of the evolution of C. difficile.

Antibiotic Resistances of Clostridioides difficile

The rapid evolution of antibiotic resistance in Clostridioides difficile and the consequent effects on prevention and treatment of C. difficile infections (CDIs) are a matter of concern for public health. Antibiotic resistance plays an important role in driving C. difficile epidemiology. Emergence of new types is often associated with the emergence of new resistances, and most of the epidemic C. difficile clinical isolates is currently resistant to multiple antibiotics. In particular, it is to worth to note the recent identification of strains with reduced susceptibility to the first-line antibiotics for CDI treatment and/or for relapsing infections. Antibiotic resistance in C. difficile has a multifactorial nature. Acquisition of genetic elements and alterations of the antibiotic target sites, as well as other factors, such as variations in the metabolic pathways or biofilm production, contribute to the survival of this pathogen in the presence of antibiotics. Different transfer mechanisms facilitate the spread of mobile elements among C. difficile strains and between C. difficile and other species. Furthermore, data indicate that both genetic elements and alterations in the antibiotic targets can be maintained in C. difficile regardless of the burden imposed on fitness, and therefore resistances may persist in C. difficile population in absence of antibiotic selective pressure.

The ESCMID Study Group for Clostridioides difficile: History, Role, and Perspectives

Clostridioides difficile (C. difficile) is a major nosocomial pathogen but is also increasingly recognised as an important diarrhoeal pathogen in the community, not always associated with antibiotics. The European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for C. difficile (ESGCD) is a group of clinicians, scientists, and others from many European countries and further afield, who share a common interest in C. difficile. The aims of the Study Group are centred around raising the profile of  C. difficile infection (CDI) in humans and animals, fostering collaboration amongst centres in different European countries and providing a forum for discussing and disseminating information. One of the principal aims of the Study Group is to raise awareness of C. difficile infections in Europe. ESGCD has a particular interest in the development and dissemination of European guidance on prevention, diagnosis, and treatment of CDI. This chapter will discuss the organisation of ESGCD within the ESCMID Study Group structure, the origins of the Study Group, the aims, and objectives of the group, and will highlight some of the past and present activities of ESGCD in relation to these.

Genomic Analysis of Clostridioides difficile Recovered from Horses in Western Australia

Clostridioides difficile poses an ongoing threat as a cause of gastrointestinal disease in humans and animals. Traditionally considered a human healthcare-related disease, increases in community-associated C. difficile infection (CDI) and growing evidence of inter-species transmission suggest a wider perspective is required for CDI control. In horses, C. difficile is a major cause of diarrhoea and life-threatening colitis. This study aimed to better understand the epidemiology of CDI in Australian horses and provide insights into the relationships between horse, human and environmental strains. A total of 752 faecal samples from 387 Western Australian horses were collected. C. difficile was isolated from 104 (30.9%) horses without gastrointestinal signs and 19 (37.8%) with gastrointestinal signs. Of these, 68 (55.3%) harboured one or more toxigenic strains, including C. difficile PCR ribotypes (RTs) 012 (n = 14), 014/020 (n = 10) and 087 (n = 7), all prominent in human infection. Whole-genome analysis of 45 strains identified a phylogenetic cluster of 10 closely related C. difficile RT 012 strains of equine, human and environmental origin (0-62 SNP differences; average 23), indicating recent shared ancestry. Evidence of possible clonal inter-species transmission or common-source exposure was identified for a subgroup of three horse and one human isolates, highlighting the need for a One Health approach to C. difficile surveillance.

Clostridioides difficile in Pigs and Dairy Cattle in Northern Italy: Prevalence, Characterization and Comparison between Animal and Human Strains

It has been observed that novel strains of Clostridioides difficile can rapidly emerge and move between animal and human hosts. The aim of this study was to investigate the prevalence of C. difficile in pigs and dairy cattle in northern Italy and to characterize and compare C. difficile animal strains with those from patients from the same geographical area. The C. difficile strains were isolated from animals from farms and slaughterhouses (cross-sectional studies) and from neonatal animals with enteric disorders in routine diagnostic investigations (passive surveillance). Samples positive for C. difficile were found in 87% of the pig farms and in 40% of the cattle farms involved in the cross-sectional studies, with a 20% prevalence among suckling piglets and 6.7% prevalence in neonatal calves, with no significant difference between animals with and without diarrheal symptoms. The prevalence of C. difficile in older animal categories was significantly lower. This result suggests that young age is an important risk factor for C. difficile colonization. In cross-sectional studies at slaughterhouses, in both the heavy pigs and dairy cows examined, only 2% of the intestinal content samples were positive for C. difficile and no contamination was found on the surface of the carcasses. Considering passive surveillance, the prevalence rates of positive samples were 29% in piglets and 1.4% in calves. Overall, 267 strains of animal origin and 97 from humans were collected. In total, 39 ribotypes (RTs) were identified, with RT 078 and RT 018 being predominant among animals and humans, respectively. Several RTs overlapped between animals and patients. In particular, RT 569 was identified as an emergent type in our country. Resistance to erythromycin and moxifloxacin was widely diffused among C. difficile strains, regardless of origin. This study supports C. difficile as a pathogen of one-health importance and highlights the need for a collaborative approach between physicians and veterinarians to control and prevent infections that are able to cross species and geographical barriers.

A local-scale One Health genomic surveillance of Clostridioides difficile demonstrates highly related strains from humans, canines, and the environment

Although infections caused by Clostridioides difficile have historically been attributed to hospital acquisition, growing evidence supports the role of community acquisition in C. difficile infection (CDI). Symptoms of CDI can range from mild, self-resolving diarrhoea to toxic megacolon, pseudomembranous colitis, and death. In this study, we sampled C. difficile from clinical, environmental, and canine reservoirs in Flagstaff, Arizona, USA, to understand the distribution and transmission of the pathogen in a One Health framework; Flagstaff is a medium-sized, geographically isolated city with a single hospital system, making it an ideal site to characterize genomic overlap between sequenced C. difficile isolates across reservoirs. An analysis of 562 genomes from Flagstaff isolates identified 65 sequence types (STs), with eight STs being found across all three reservoirs and another nine found across two reservoirs. A screen of toxin genes in the pathogenicity locus identified nine STs where all isolates lost the toxin genes needed for CDI manifestation (tcdB, tcdA), demonstrating the widespread distribution of non-toxigenic C. difficile (NTCD) isolates in all three reservoirs; 15 NTCD genomes were sequenced from symptomatic, clinical samples, including two from mixed infections that contained both tcdB+ and tcdB- isolates. A comparative single nucleotide polymorphism (SNP) analysis of clinically derived isolates identified 78 genomes falling within clusters separated by ≤2 SNPs, indicating that ~19 % of clinical isolates are associated with potential healthcare-associated transmission clusters; only symptomatic cases were sampled in this study, and we did not sample asymptomatic transmission. Using this same SNP threshold, we identified genomic overlap between canine and soil isolates, as well as putative transmission between environmental and human reservoirs. The core genome of isolates sequenced in this study plus a representative set of public C. difficile genomes (n=136), was 2690 coding region sequences, which constitutes ~70 % of an individual C. difficile genome; this number is significantly higher than has been published in some other studies, suggesting that genome data quality is important in understanding the minimal number of genes needed by C. difficile. This study demonstrates the close genomic overlap among isolates sampled across reservoirs, which was facilitated by maximizing the genomic search space used for comprehensive identification of potential transmission events. Understanding the distribution of toxigenic and non-toxigenic C. difficile across reservoirs has implications for surveillance sampling strategies, characterizing routes of infections, and implementing mitigation measures to limit human infection.

Characterization of Food Chain Clostridioides difficile Isolates in Terms of Ribotype and Antimicrobial Resistance

The aim of this study was to characterize C. difficile isolates from the farm, abattoir, and retail outlets in Ireland in terms of ribotype and antibiotic resistance (vancomycin, erythromycin, metronidazole, moxifloxacin, clindamycin, and rifampicin) using PCR and E-test methods, respectively. The most common ribotype in all stages of the food chain (including retail foods) was 078 and a variant (RT078/4). Less commonly reported (014/0, 002/1, 049, and 205) and novel (RT530, 547, and 683) ribotypes were also detected, but at lower frequencies. Approximately 72% (26/36 tested) of the isolates tested were resistant to at least one antibiotic, with the majority of these (65%; 17/26) displaying a multi-drug (three to five antibiotics) resistant phenotype. It was concluded that ribotype 078, a hypervirulent strain commonly associated with C. difficile infection (CDI) in Ireland, was the most frequent ribotype along the food chain, resistance to clinically important antibiotics was common in C. difficile food chain isolates, and there was no relationship between ribotype and antibiotic resistance profile.

Modern Approaches to the Diagnosis and treatment of <i>Clostridioides difficile (C. difficile)</i>-associated Disease in Adults (literature Review and Expert Council Resolution)

Aim: to review the modern approaches to the diagnosis and treatment ofC. difficile-associated disease in adults and present the resolution of the Expert Council held on March 25, 2023 in Moscow.

General provisions.C. difficileis the most important nosocomial pathogen which spores are also commonly found in the environment. Microbiota impairment, primarily due to the use of antibacterial drugs, is a key stage in the development ofC. difficile-associated disease. A search for an infection should be carried out only in patients with diarrhea, and it is advisable to use at least 2 laboratory methods. The drug of choice for first-line treatment is vancomycin. If drug treatment is ineffective or the patient has recurrent clostridial infection, fecal microbiota transplantation should be considered. The probiotic strainSaccharomyces boulardii CNCM I-745has a direct inhibitory effect onC. difficiletoxin A, promotes normalization of the intestinal microbiota composition, and decreases the inflammatory reaction in colonic mucosa colonized with a toxigenic strain ofC. difficile.

Conclusions. Addition of the probiotic strainSaccharomyces boulardii CNCM I-745to antibacterial therapy promotes both primary and secondary prevention ofC. difficile-associated disease.

Global prevalence of Clostridioides difficile in 17,148 food samples from 2009 to 2019: a systematic review and meta-analysis

BACKGROUND

Clostridioides (Clostridium) difficile is an important infectious pathogen, which causes mild-to-severe gastrointestinal infections by creating resistant spores and producing toxins. Spores contaminated foods might be one of the most significant transmission ways of C. difficile-associated infections. This systematic review and meta-analysis study were conducted to investigate the prevalence of C. difficile in food.

METHODS

Articles that published the prevalence of C. difficile in food in PubMed, Web of Science, and Scopus databases were retrieved using selected keywords between January 2009 and December 2019. Finally, 17,148 food samples from 60 studies from 20 countries were evaluated.

RESULTS

The overall prevalence of C. difficile in various foods was 6.3%. The highest and lowest levels of C. difficile contamination were detected to seafood (10.3%) and side dishes (0.8%), respectively. The prevalence of C. difficile was 4% in cooked food, 6.2% in cooked chicken and 10% in cooked seafood.

CONCLUSIONS

There is still little known concerning the food-borne impact of C. difficile, but the reported contamination might pose a public health risk. Therefore, to improve the food safety and prevent contamination with C. difficile spores, it is necessary to observe hygienic issues during foods preparation, cooking and transfer.

Clostridioides difficile, a New “Superbug”

Clostridioides difficile is a Gram-positive, spore-forming, anaerobic bacterium. The clinical features of C. difficile infections (CDIs) can vary, ranging from the asymptomatic carriage and mild self-limiting diarrhoea to severe and sometimes fatal pseudomembranous colitis. C. difficile infections (CDIs) are associated with disruption of the gut microbiota caused by antimicrobial agents. The infections are predominantly hospital-acquired, but in the last decades, the CDI patterns have changed. Their prevalence increased, and the proportion of community-acquired CDIs has also increased. This can be associated with the appearance of hypervirulent epidemic isolates of ribotype 027. The COVID-19 pandemic and the associated antibiotic overuse could additionally change the patterns of infections. Treatment of CDIs is a challenge, with only three appropriate antibiotics for use. The wide distribution of C. difficile spores in hospital environments, chronic persistence in some individuals, especially children, and the recent detection of C. difficile in domestic pets can furthermore worsen the situation. “Superbugs” are microorganisms that are both highly virulent and resistant to antibiotics. The aim of this review article is to characterise C. difficile as a new member of the “superbug” family. Due to its worldwide spread, the lack of many treatment options and the high rates of both recurrence and mortality, C. difficile has emerged as a major concern for the healthcare system.

Clostridial diarrheas in piglets: A review

Clostridium perfringens type C and Clostridioides difficile are the main enteric clostridial pathogens of swine and are both responsible for neonatal diarrhea in this species. The role of Clostridum perfringes type A is under discussion. History, clinical signs, gross lesions and histological findings are the basis for a presumptive diagnosis of C. perfringens type C or C. difficile infection. Confirmation is based upon detection of beta toxin of C. perfringens type C or toxin A/B of C. difficile, respectively, in intestinal contents or feces. Isolation of C. perfringens type C and/or C. difficile is highly suggestive of infection by these microorganisms but it is not enough to confirm a diagnosis as they may be found in the intestine of some healthy individuals. Diagnosis of C. perfringens type A-associated diarrhea is more challenging because the diagnostic criteria have not been well defined and the specific role of alpha toxin (encoded by all strains of this microorganism) and beta 2 toxin (produced by some type A strains) is not clear. The goal of this paper is to describe the main clostridial enteric diseases of piglets, including etiology, epidemiology, pathogenesis, clinical signs, pathology and diagnosis.

Clostridioides difficile in South American Camelids in Germany: First Insights into Molecular and Genetic Characteristics and Antimicrobial Resistance

Little is known about zoonotic pathogens and their antimicrobial resistance in South American camelids (SAC) in Germany including Clostridioides (C.) difficile. The aim of this study was to investigate prevalence, molecular characteristics and antimicrobial resistance of C. difficile in SAC. Composite SAC faecal samples were collected in 43 husbandries in Central Germany and cultured for C. difficile. Toxinotyping and ribotyping was done by PCR. Whole genome sequencing was performed with Illumina^® Miseq™. The genomes were screened for antimicrobial resistance determinants. Genetic relatedness of the isolates was investigated using core genome multi locus sequence typing (cgMLST) and single nucleotide polymorphism analysis. Antimicrobial susceptibility testing was done using the Etest^® method. Eight C. difficile isolates were recovered from seven farms. The isolates belonged to different PCR ribotypes. All isolates were toxinogenic. cgMLST revealed a cluster containing isolates recovered from different farms. Seven isolates showed similar resistance gene patterns. Different phenotypic resistance patterns were found. Agreement between phenotypic and genotypic resistance was identified only in some cases. Consequently, SAC may act as a reservoir for C. difficile. Thus, SAC may pose a risk regarding zoonotic transmission of toxinogenic, potentially human-pathogenic and resistant C. difficile isolates.

Clostridioides difficile in Food-Producing Animals in Romania: First Study on the Prevalence and Antimicrobial Resistance

At present, the epidemiology of the gastrointestinal disease caused by Clostridioides difficile (C. difficile) is starting to be slowly elucidated internationally, although information about the bacteria in the food supply chain is insufficient and, in many countries, even absent. The study was conducted in order to investigate the prevalence of C. difficile isolated from animal feces, as well as to determine the antimicrobial susceptibility of such isolates. The presence of antibiotic resistance determinants has also been evaluated. Overall, a total of 24 (12.5%) C. difficile isolates were recovered (out of the 192 samples collected), the highest percentage of positive isolates being detected in the fecal samples collected from piglets (25%). The majority of the isolates recovered in the current study proved to be toxigenic. Moreover, all C. difficile isolates were susceptible to vancomycin, although a large proportion of the porcine isolates (50%) were resistant to levofloxacin. The tetW and erm(B) genes have also been identified in the porcine isolates. In conclusion, this is the first analysis of the prevalence of C. difficile in food-producing animals in Romania, and it adds further evidence about the possible role of animals as a source of resistant C. difficile strains and a reservoir of antimicrobial resistance determinants.

Characterization of the virulence of three novel clade 2 Clostridioides (Clostridium) difficile strains and a two-year screening in animals and humans in Brazil

Clostridioides (Clostridium) difficile infection (CDI) is an evolving global healthcare problem, and owing to the diverse and dynamic molecular epidemiology of C. difficile, new strains continue to emerge. In Brazil, only two cases of CDI due to the so called hypervirulent PCR ribotype (RT) 027 belonging to clade 2 have ever been reported, whereas incidence of CDI due to another “hypervirulent” RT078 (clade 5) has not yet been reported. In contrast, novel clade 2 strains have been identified in different hospitals. To better understand the epidemiology of CDIs in Brazil, this study aimed to genotypically and phenotypically characterize three novel Brazilian clade 2 strains (RT883, 884, and 885) isolated from patients with confirmed CDI. In addition, to better understand the circulating RTs, a two-year sampling was conducted in patients from the same hospital and in several domestic and wild animal species. The three strains examined showed lower production of A/B toxins than the control RT027, although two of these strains harbored a truncated tcdC gene. All strains showed swimming motility similar to that of RT027, while RT883 showed higher spore production than the reference strain. In the in vivo hamster model, the lethality of all strains was found to be similar to that of RT027. Both cgMLST and cgMLSA analyses revealed a high genetic similarity among the three-novel clade 2 isolates. In the two-year survey in animals and humans, RT883, 884, and 885 were not detected; however, three new RTs (RT988, RT989, and RT990) were isolated, two of which were genetically related to the three previously reported clade 2 strains. RT106 and RT126 were most frequently detected in humans (47.9%) and animals (57.9%), respectively. Furthermore, RT027 and RT078 were not detected in humans. The results of this study suggest that these novel clade 2 strains have virulence potential and that new strains from clade 2 continue to emerge in our setting, indicating the need for long-term local surveillance.

Predominance of Clostridioides difficile PCR ribotype 181 in northern Greece, 2016-2019

OBJECTIVES

The epidemiology of Clostridioides difficile infection (CDI) has undergone many changes since the beginning of this century and continues to evolve based on recent studies. Here, we performed a molecular analysis of C. difficile isolates in northern Greece across 10 health-care facilities, spanning from 2016 to 2019.

METHODS

221 C. difficile isolates were cultured from stool samples of hospitalized patients with diarrhea and screened by PCR for the presence of the toxin A (tcdA), toxin B (tcdB), the binary toxin (cdtA and cdtB) genes and the regulating gene of tcdC. PCR ribotyping of the cultured isolates was performed by a standardized protocol for capillary gel-based PCR ribotyping and an international database with well-documented reference strains.

RESULTS

Thirty-five different PCR ribotypes were identified. The most common RTs identified were: 181 (36%, 80/221), 017 (10%, 21/221), 126 (9%, 19/221), 078 (4%, 9/221) and 012 (4%, 8/221). Notably, the predominant RT181, with toxin profile tcdA⁺tcdB⁺cdtA⁺cdtB⁺, was identified in seven out of ten participating hospitals.

CONCLUSIONS

Multiple C. difficile ribotypes have been circulating in the northern Greece region with RTs 181 (closely related to 027), 017, 126 and 078 being predominant.

Transmission routes of antibiotic resistant bacteria: a systematic review

Background

Quantification of acquisition routes of antibiotic resistant bacteria (ARB) is pivotal for understanding transmission dynamics and designing cost-effective interventions. Different methods have been used to quantify the importance of transmission routes, such as relative risks, odds ratios (OR), genomic comparisons and basic reproduction numbers. We systematically reviewed reported estimates on acquisition routes’ contributions of ARB in humans, animals, water and the environment and assessed the methods used to quantify the importance of transmission routes.

Methods

PubMed and EMBASE were searched, resulting in 6054 articles published up until January 1st, 2019. Full text screening was performed on 525 articles and 277 are included.

Results

We extracted 718 estimates with S. aureus (n = 273), E. coli (n = 157) and Enterobacteriaceae (n = 99) being studied most frequently. Most estimates were derived from statistical methods (n = 560), mainly expressed as risks (n = 246) and ORs (n = 239), followed by genetic comparisons (n = 85), modelling (n = 62) and dosage of ARB ingested (n = 17). Transmission routes analysed most frequently were occupational exposure (n = 157), travelling (n = 110) and contacts with carriers (n = 83). Studies were mostly performed in the United States (n = 142), the Netherlands (n = 87) and Germany (n = 60). Comparison of methods was not possible as studies using different methods to estimate the same route were lacking. Due to study heterogeneity not all estimates by the same method could be pooled.

Conclusion

Despite an abundance of published data the relative importance of transmission routes of ARB has not been accurately quantified. Links between exposure and acquisition are often present, but the frequency of exposure is missing, which disables estimation of transmission routes’ importance. To create effective policies reducing ARB, estimates of transmission should be weighed by the frequency of exposure occurrence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07360-z.

Fate of Clostridia and other spore-forming Firmicute bacteria during feedstock anaerobic digestion and aerobic composting

Pathogenic spore-forming Firmicutes are commonly present in animal and human wastes that are used as fertilizers in crop production. Pre-treatments of organic waste prior to land application offer the potential to abate enteric microorganisms, and therefore reduce the risk of contamination of crops or adjacent water resources with pathogens carried in these materials. The inactivation and reduction of gram-positive spore formers such as Clostridium spp., Clostridioides spp. and Bacillus spp. from animal and human waste can be challenging given the recalcitrance of the spores these bacteria produce. Given the significance of these organisms to human and animal health, information concerning spore-forming bacteria inactivation during anaerobic digestion (AD) and aerobic composting (AC) is required as the basis for recommending safe organic waste management practices. In this review, an assessment of the inactivation of spore-forming Firmicutes during AD and AC was conducted to provide guidance for practical management of organic matrices of animal or human origin. Temperature and pH may be the main factors contributing to the inactivation of spore-forming Firmicutes during batch lab-scale AD (log reduction <0.5-5 log). In continuous digesters, wet AD systems do not effectively inactivate spore-forming Firmicutes even under thermopholic conditions (log reduction -1.09 - 0.98), but dry AD systems could be a feasible management practice to inactivate spore-forming Firmicutes from organic materials with high solid content (log reduction 1.77-3.1). In contrast, composting is an effective treatment to abate spore-forming Firmicutes (log reduction 1.7-6.5) when thermophilic conditions last at least six consecutive days. Temperature, moisture content and composting scale are the key operating conditions influencing the inactivation of spore-forming Firmicutes during composting. Where possible, undertaking AD with subsequent composting to ensure the biosafety of digestate before its downstream processing and recycling is recommended to abate recalcitrant bacteria in digestate.

Assessment of the Transmission Dynamics of Clostridioides difficile in a Farm Environment Reveals the Presence of a New Toxigenic Strain Connected to Swine Production

The recent increase in community-acquired Clostridioides difficile infections discloses the shift in this bacterium epidemiology. This study aimed at establishing a transmission network involving One Health components, as well as assessing the zoonotic potential and genomic features of dominant clones. Samples were collected from different compartments of animal, human and environmental origin, from an animal production unit. C. difficile isolates were characterized for toxigenic profile by multiplex-PCR, while genetic diversity was evaluated by PCR-ribotyping and whole genome-based analysis. The overall C. difficile prevalence was 37.2% (70/188), and included samples from environmental (58.3%, 35/60) and animal (31.5%, 35/111) compartments; human samples (n = 17) taken from healthy workers were negative. A predominant clone from RT033 was found in almost 90% of the positive samples, including samples from all compartments connected to the pig production unit, with core-genome single nucleotide variant (SNV)-based Analysis supporting a clonal transmission between them (mean distance of 0.1 ± 0.1 core-SNVs). The isolates from this clone (herein designated PT RT033) were positive for all C. difficile toxin genes (tcdA, tcdB, cdtA/cdtB). The phyloGenetic positioning of this clone was clearly distinct from the classical RT033 cluster, suggesting a different evolutionary route. This new clone shares genomic features with several RTs from the clade 5 Sequence Type (ST) 11, including a complete pathogenicity locus (PaLoc) that is more similar to the one found in toxigenic strains and contrasting to the less virulent classical RT033 (tcdA-, tcdB-, cdtA + /cdtB +). The presence of a tcdA gene truncated into two ORFs, not previously described, requires further evaluation concerning toxin functionality. We hypothesize that the unique combination of genetic elements found in the PT RT033 clone may contribute to host tropism and environmental dissemination and maintenance. This study constitutes the first report of a toxigenic RT033 clone and adds to the overall knowledge on Clade 5 sequence type 11, considered the C. difficile evolutionary lineage with the highest zoonotic potential. The presence of this clone in all compartments associated with the pig production unit suggests a transmission chain involving these animals and contributes to unveil the role played by animal and environmental reservoirs in this pathogen epidemiology.

Genetic and phenotypic characteristics of Clostridium (Clostridioides) difficile from canine, bovine, and pediatric populations

Objectives:

Carriage of Clostridioides difficile by different species of animals has led to speculation that animals could represent a reservoir of this pathogen for human infections. The objective of this study was to compare C. difficile isolates from humans, dogs, and cattle from a restricted geographic area.

Methods:

C. difficile isolates from 36 dogs and 15 dairy calves underwent whole genome sequencing, and phenotypic assays assessing growth and virulence were performed. Genomes of animal-derived isolates were compared to 29 genomes of isolates from a pediatric population as well as 44 reference genomes.

Results:

Growth rates and relative cytotoxicity of isolates were significantly higher and lower, respectively, in bovine-derived isolates compared to pediatric- and canine-derived isolates. Analysis of core genes showed clustering by host species, though in a few cases, human strains co-clustered with canine or bovine strains, suggesting possible interspecies transmission. Geographic differences (e.g., farm, litter) were small compared to differences between species. In an analysis of accessory genes, the total number of genes in each genome varied between host species, with 6.7% of functional orthologs differentially present/absent between host species and bovine-derived strains having the lowest number of genes. Canine-derived isolates were most likely to be non-toxigenic and more likely to carry phages. A targeted study of episomes identified in local pediatric strains showed sharing of a methicillin-resistance plasmid with dogs, and historic sharing of a wide range of episomes across hosts. Bovine-derived isolates harbored the widest variety of antibiotic-resistance genes, followed by canine

Conclusions:

While C. difficile isolates mostly clustered by host species, occasional co-clustering of canine and pediatric-derived isolates suggests the possibility of interspecies transmission. The presence of a pool of resistance genes in animal-derived isolates with the potential to appear in humans given sufficient pressure from antibiotic use warrants concern.

Comparison of Whole-Genome Sequence-Based Methods and PCR Ribotyping for Subtyping of Clostridioides difficile

Clostridioides difficile is the most common cause of antibiotic-associated gastrointestinal infections. Capillary electrophoresis (CE)-PCR ribotyping is currently the gold standard for C. difficile typing but lacks the discriminatory power to study transmission and outbreaks in detail. New molecular methods have the capacity to differentiate better and provide standardized and interlaboratory exchangeable data. Using a well-characterized collection of diverse strains (N = 630; 100 unique ribotypes [RTs]), we compared the discriminatory power of core genome multilocus sequence typing (cgMLST) (SeqSphere and EnteroBase), whole-genome MLST (wgMLST) (EnteroBase), and single-nucleotide polymorphism (SNP) analysis. A unique cgMLST profile (more than six allele differences) was observed in 82 of 100 RTs, indicating that cgMLST could distinguish most, but not all, RTs. Application of cgMLST in two outbreak settings with RT078 and RT181 (known to have low intra-RT allele differences) showed no distinction between outbreak and nonoutbreak strains in contrast to wgMLST and SNP analysis. We conclude that cgMLST has the potential to be an alternative to CE-PCR ribotyping. The method is reproducible, easy to standardize, and offers higher discrimination. However, adjusted cutoff thresholds and epidemiological data are necessary to recognize outbreaks of some specific RTs. We propose to use an allelic threshold of three alleles to identify outbreaks.

Infection prevention and control insights from a decade of pathogen whole-genome sequencing

Pathogen whole-genome sequencing has become an important tool for understanding the transmission and epidemiology of infectious diseases. It has improved our understanding of sources of infection and transmission routes for important healthcare-associated pathogens, including Clostridioides difficile and Staphylococcus aureus. Transmission from known infected or colonized patients in hospitals may explain fewer cases than previously thought and multiple introductions of these pathogens from the community may play a greater a role. The findings have had important implications for infection prevention and control. Sequencing has identified heterogeneity within pathogen species, with some subtypes transmitting and persisting in hospitals better than others. It has identified sources of infection in healthcare-associated outbreaks of food-borne pathogens, Candida auris and Mycobacterium chimera, as well as individuals or groups involved in transmission and historical sources of infection. SARS-CoV-2 sequencing has been central to tracking variants during the COVID-19 pandemic and has helped understand transmission to and from patients and healthcare workers despite prevention efforts. Metagenomic sequencing is an emerging technology for culture-independent diagnosis of infection and antimicrobial resistance. In future, sequencing is likely to become more accessible and widely available. Real-time use in hospitals may allow infection prevention and control teams to identify transmission and to target interventions. It may also provide surveillance and infection control benchmarking. Attention to ethical and wellbeing issues arising from sequencing identifying individuals involved in transmission is important. Pathogen whole-genome sequencing has provided an incredible new lens to understand the epidemiology of healthcare-associated infection and to better control and prevent these infections.

Clostridioides difficile infection and One Health: An Equine Perspective

Clostridioides (Clostridium) difficile presents a significant health risk to humans and animals. The complexity of the bacterial–host interaction affecting pathogenesis and disease development creates an ongoing challenge for epidemiological studies, control strategies and prevention planning. The recent emergence of human disease caused by strains of C. difficile found in animals adds to mounting evidence that C. difficile infection (CDI) may be a zoonosis. In equine populations, C. difficile is a known cause of diarrhoea and gastrointestinal inflammation, with considerable mortality and morbidity. This has a significant impact on both the well‐being of the animal and, in the case of performance and production animals, it may have an adverse economic impact on relevant industries. While C. difficile is regularly isolated from horses, many questions remain regarding the impact of asymptomatic carriage as well as optimization of diagnosis, testing and treatment. This review provides an overview of our understanding of equine CDI while also identifying knowledge gaps and the need for a holistic One Health approach to a complicated issue.

Clostridioides difficile infection (CDI) during the COVID-19 pandemic

The ongoing coronavirus disease (COVID-19) pandemic has dramatically tested healthcare systems around the world, with serious repercussions on the measures of prevention and control of hospital-acquired infections (HAIs). Among HAIs, Clostridioides difficile infection (CDI) represents one of the most important global public health threats. Although the full impact of the COVID-19 pandemic on CDI remains undetermined, depending on the development of the pandemic in the coming months, in this review literature studies of the last three years have been considered in order to depict the current situation, and make some considerations about possible future developments. If on the one hand, a general reduction in CDI incidence has been reported in several settings, mainly due to the extraordinary reinforcement of infection prevention measures, on the other hand, the critical circumstances experienced in many hospitals have limited the effectiveness of these measures, particularly in the intensive care units (ICUs), increasing the possibility of the occurrence of hospital-acquired CDI (HA-CDI). New concerns have arisen from the decrease in C. difficile testing and the increased use of broad-spectrum antibiotics reported during the pandemic. In particular, overuse of antibiotics and disinfectants may lead to a selection of resistant C. difficile strains not only in hospitals but also in the community. Furthermore, patients infected with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and patients that have survived COVID-19 may represent a new group of frail patients potentially at a higher risk of CDI, a group that could potentially increase in size due to SARS-CoV-2 evolution. In the dramatic COVID-19 era, the multifactorial nature of CDI has emerged more clearly than before, highlighting the necessity of a strong refocus on efforts to improve prevention strategies and to integrate CDI surveillance in a One Health prospective in order to curtail the public health threat posed by this infection in the next future.

Prevention of Infection due to Clostridium (Clostridioides) difficile

Clostridium (Clostridioides) difficile infection (CDI) causes significant morbidity and mortality in the United States every year. Prevention of CDI is difficult because of spore durability and requires implementation of multipronged strategies. Two categories of prevention strategies are infection control and prevention and risk factor reduction. Hand hygiene, contact precautions, patient isolation, and environmental decontamination are cornerstones of infection control and prevention. Risk factor reduction should focus on antibiotic stewardship to reduce unnecessary antibiotic use. If CDI incidence remains higher than the institution's goal despite these measures, then special measures should be considered.

Genetically related Clostridium difficile from water sources and human CDI cases revealed by whole-genome sequencing

Clostridium difficile isolates from the environment are closely related to those from humans, indicating a possible environmental transmission route for C. difficile infection (CDI). In this study, C. difficile was isolated from 47.3% (53/112) of lake/pond, 23.0% (14/61) of river, 20.0% (3/15) of estuary and 0.0% (0/89) of seawater samples. The most common toxigenic strain isolated was C. difficile PCR ribotype (RT) 014/020 (10.5%, 8/76). All water isolates were susceptible to fidaxomicin, metronidazole, rifaximin, amoxicillin/clavulanic acid, moxifloxacin and tetracycline. Resistance to vancomycin, clindamycin, erythromycin and meropenem was detected in 5.3% (4/76), 26.3% (20/76), 1.3% (1/76) and 6.6% (5/76) of isolates, respectively. High-resolution core-genome analysis was performed on RT 014/020 isolates of water origin and 26 clinical RT 014/020 isolates from the same year and geographical location. Notably, both human and water strains were intermixed across three sequence types (STs), 2, 13 and 49. Six closely related groups with ≤10 core-genome single nucleotide polymorphisms were identified, five of which comprised human and water strains. Overall, 19.2% (5/26) of human strains shared a recent genomic relationship with one or more water strains. This study supports the growing hypothesis that environmental contamination by C. difficile plays a role in CDI transmission.

Human and Porcine Transmission of Clostridioides difficile Ribotype 078, Europe

Genomic analysis of a diverse collection of Clostridioides difficile ribotype 078 isolates from Ireland and 9 countries in Europe provided evidence for complex regional and international patterns of dissemination that are not restricted to humans. These isolates are associated with C. difficile colonization and clinical illness in humans and pigs.

Clostridioides difficile infection: an emerging zoonosis?

INTRODUCTION

Clostridioides difficile (C. difficile) infection (CDI) is the most common cause of antibiotic-associated diarrhea and one of the common infections in healthcare facilities. In recent decades, there has been an emerging threat of community-acquired CDI (CA-CDI). Environmental transmission of C. difficile in the community setting has become a major concern, and animals are an important reservoir for C. difficile causing human diseases.

AREAS COVERED

In this article, the molecular epidemiology of C. difficile in animals and recent evidences of zoonotic transfer to humans are reviewed based on an electronic search in the databases of PubMed and Google Scholar.

EXPERT OPINION

C. difficile can be found in stool from diarrheal dogs and cats; therefore, household pets could be a potential source. C. difficile will threaten human health because hypervirulent C. difficile ribotype 078 strains have been found in retail chickens, pig farms, and slaughterhouses. Risk factors for fecal C. difficile carriage in animals include young age, dietary changes, and antibiotic abuse in domestic animals. With the advent of whole genome sequencing techniques, there will be more solid evidence indicating zoonotic transfer of C. difficile from animals to humans.

Clostridioides difficile as a Dynamic Vehicle for the Dissemination of Antimicrobial-Resistance Determinants: Review and In Silico Analysis

The present paper is divided into two parts. The first part focuses on the role of Clostridioides difficile in the accumulation of genes associated with antimicrobial resistance and then the transmission of them to other pathogenic bacteria occupying the same human intestinal niche. The second part describes an in silico analysis of the genomes of C. difficile available in GenBank, with regard to the presence of mobile genetic elements and antimicrobial resistance genes. The diversity of the C. difficile genome is discussed, and the current status of resistance of the organisms to various antimicrobial agents is reviewed. The role of transposons associated with antimicrobial resistance is appraised; the importance of plasmids associated with antimicrobial resistance is discussed, and the significance of bacteriophages as a potential shuttle for antimicrobial resistance genes is presented. In the in silico study, 1101 C. difficile genomes were found to harbor mobile genetic elements; Tn6009, Tn6105, CTn7 and Tn6192, Tn6194 and IS256 were the ones more frequently identified. The genes most commonly harbored therein were: ermB, blaCDD, vanT, vanR, vanG and vanS. Tn6194 was likely associated with resistance to erythromycin, Tn6192 and CTn7 with resistance to the β-lactams and vancomycin, IS256 with resistance to aminoglycoside and Tn6105 to vancomycin.

Epidemiology of community-acquired and recurrent Clostridioides difficile infection

Clostridioides difficile infection is a leading cause of healthcare-associated infections with significant morbidity and mortality. For the past decade, the bulk of infection prevention and epidemiologic surveillance efforts have been directed toward mitigating hospital-acquired C. difficile. However, the incidence of community-associated infection is on the rise. Patients with community-associated C. difficile tend to be younger and have lower mortality rate. Rates of recurrent C. difficile infection overall have decreased in the United States, but future research and public health endeavors are needed to standardize and improve disease detection, stratify risk factors in large-scale population studies, and to identify regional and local variations in strain types, reservoirs and transmission routes to help characterize and combat the changing epidemiology of C. difficile.

The duration of antibiotic treatment is associated with carriage of toxigenic and non-toxigenic strains of Clostridioides difficile in dogs

Clostridioides difficile is a leading cause of human antibiotic-associated diarrhoeal disease globally. Zoonotic reservoirs of infection are increasingly suspected to play a role in the emergence of this disease in the community and dogs are considered as one potential source. Here we use a canine case-control study at a referral veterinary hospital in Scotland to assess: i) the risk factors associated with carriage of C. difficile by dogs, ii) whether carriage of C. difficile is associated with clinical disease in dogs and iii) the similarity of strains isolated from dogs with local human clinical surveillance. The overall prevalence of C. difficile carriage in dogs was 18.7% (95% CI 14.8–23.2%, n = 61/327) of which 34% (n = 21/61) were toxigenic strains. We found risk factors related to prior antibiotic treatment were significantly associated with C. difficile carriage by dogs. However, the presence of toxigenic strains of C. difficile in a canine faecal sample was not associated with diarrhoeal disease in dogs. Active toxin was infrequently detected in canine faecal samples carrying toxigenic strains (2/11 samples). Both dogs in which active toxin was detected had no clinical evidence of gastrointestinal disease. Among the ten toxigenic ribotypes of C. difficile detected in dogs in this study, six of these (012, 014, 020, 026, 078, 106) were ribotypes commonly associated with human clinical disease in Scotland, while nontoxigenic isolates largely belonged to 010 and 039 ribotypes. Whilst C. difficile does not appear commonly associated with diarrhoeal disease in dogs, antibiotic treatment increases carriage of this bacteria including toxigenic strains commonly found in human clinical disease.

Rare variants discovery by extensive whole-genome sequencing of the Han Chinese population in Taiwan: Applications to cardiovascular medicine

Introduction

A population-specific genomic reference is important for research and clinical practice, yet it remains unavailable for Han Chinese (HC) in Taiwan.

Objectives

We report the first whole genome sequencing (WGS) database of HC (1000 Taiwanese genome (1KTW-WGS)) and demonstrate several applications to cardiovascular medicine.

Methods

Whole genomes of 997 HC were sequenced to at least 30X depth. A total of 20,117 relatively healthy HC individuals were genotyped using a customized Axiom GWAS array. We performed a genome-wide genotype imputation technique using IMPUTE2.

Results

We identified 26.7 million single-nucleotide variants (SNVs) and 4.2 million insertions-deletions. Of the SNVs, 16.1% were novel relative to dbSNP (build 152), and 34.2% were novel relative to gnomAD. A total of 18,450 healthy HC individuals were genotyped using a customized Genome-Wide Association Study (GWAS) array. We identified hypertension-associated variants and developed a hypertension prediction model based on the correlation between the WGS data and GWAS data (combined clinical and genetic models, AUC 0.887), and also identified 3 novel hyperlipidemia-associated variants. Each individual carried an average of 16.42 (SD = 3.72) disease-causing variants. Additionally, we established an online SCN5A (an important cardiac gene) database that can be used to explore racial differences. Finally, pharmacogenetics studies identified HC population-specific SNVs in genes (CYP2C9 and VKORC1) involved in drug metabolism and blood clotting.

Conclusion

This research demonstrates the benefits of constructing a population-specific genomic reference database for precision medicine.

Clostridioides difficile on dairy farms and potential risk to dairy farm workers

Clostridioides difficile causes severe colitis in people and is a significant enteric pathogen in many species of animals, including swine, horses, and potentially cattle. C. difficile is shed in feces, and transmission occurs horizontally via the fecal-oral route. Livestock has been suggested as a potential reservoir for C. difficile, and while studies have shown that swine and farm workers can be colonized with identical clones of C. difficile, the zoonotic transmission of C. difficile from livestock to people has not been definitively demonstrated. The goal of this study was to determine whether dairy calves and dairy farm workers harbored genetically similar isolates of C. difficile. First, we validated a glove juice protocol for detecting C. difficile on farm workers' hands. We then visited 23 farms and collected 1) fecal samples from 92 dairy calves, 2) hand rinsates from 38 dairy farm workers, and 3) fecal samples from five of the dairy farm workers who were willing to submit them. All samples underwent anaerobic culture and qPCR to detect C. difficile. C. difficile was detected on 15 of the farms (65.2%, 95% confidence interval (CI) 42.7%-83.6%) and in 28 calves (30.4%, 95% CI 21.2-40.9%) but in none of the hand rinsates or human fecal samples. Thus, the zoonotic transmission of C. difficile on dairy farms could not be demonstrated, and dairy farmers did not appear to be at increased risk of acquiring C. difficile via the fecal-oral route.

Clostridioides difficile in Calves in Central Italy: Prevalence, Molecular Typing, Antimicrobial Susceptibility and Association with Antibiotic Administration

Simple Summary

Clostridioides difficile is a leading cause of nosocomial and community-acquired diarrhoea in men. The infection most commonly occurs in people who have recently been treated with antibiotics. Indistinguishable C. difficile strains have been isolated from livestock and humans, which has shed light on a possible zoonotic origin of this infection. This study aimed to assess the prevalence and risk factors of C. difficile in calves bred in dairy and beef cattle farms of the Umbria, central Italy. We estimated a 19.8% prevalence of farms positive for C. difficile. The C. difficile isolates from calves were potentially toxigenic and resistant to antibiotics, including lincosamides, quinolones, vancomycin and linezolid. Isolates belonging to ribotype RT-126, which is also commonly reported in humans, showed the highest number of resistance to the antimicrobials tested. Furthermore, we observed an almost sixfold increased risk for C. difficile on farms where penicillins had been prescribed. This, together with the detection of toxigenic and antibiotic-resistant isolates, strongly suggests the need for a reduction of antibiotic use in cattle.

Abstract

The emergence of Clostridioides difficile as the main agent of antibiotic-associated diarrhoea has raised concerns about its potential zoonotic role in different animal species. The use of antimicrobials is a major risk factor for C. difficile infection. Here, we provide data on C. difficile infection in dairy and beef calves in Umbria, a region in central Italy. This cross-sectional study focuses on prevalence, risk factors, ribotypes, toxinotypes and antimicrobial resistance profiles of circulating ribotypes. A prevalence of 19.8% (CI95%, 12–27.6%) positive farms was estimated, and the prescription of penicillins on the farms was associated with C. difficile detection (OR = 5.58). Eleven different ribotypes were found, including the ST11 sublineages RT-126 and -078, which are also commonly reported in humans. Thirteen isolates out of 17 showed resistance to at least one of clindamycin, moxifloxacin, linezolid and vancomycin. Among them, multiple-drug resistance was observed in two isolates, belonging to RT-126. Furthermore, RT-126 isolates were positive for tetracycline resistance determinants, confirming that tetracycline resistance is widespread among ST11 isolates from cattle. The administration of penicillins increased the risk of C. difficile in calves: this, together with the recovery of multi-resistant strains, strongly suggests the need for minimising antibiotic misuse on cattle farms.

Editorial for the Special Issue: Clostridium difficile

Clostridium difficile (reclassified as Clostridioides difficile [...].

Randomized Controlled Trial of Oral Vancomycin Treatment in Clostridioides difficile-Colonized Patients

A gold standard diagnostic for Clostridioides difficile infection (CDI) does not exist. An area of controversy is how to manage patients whose stool tests positive by nucleic acid amplification tests but negative by toxin enzyme immunoassay.

Clostridioides difficile infection (CDI) is most commonly diagnosed using nucleic acid amplification tests (NAAT); the low positive predictive value of these assays results in patients colonized with C. difficile unnecessarily receiving CDI treatment antibiotics. The risks and benefits of antibiotic treatment in individuals with such cases are unknown. Fecal samples of NAAT-positive, toxin enzyme immunoassay (EIA)-negative patients were collected before, during, and after randomization to vancomycin (n = 8) or placebo (n = 7). C. difficile and antibiotic-resistant organisms (AROs) were selectively cultured from fecal and environmental samples. Shotgun metagenomics and comparative isolate genomics were used to understand the impact of oral vancomycin on the microbiome and environmental contamination. Overall, 80% of placebo patients and 71% of vancomycin patients were colonized with C. difficile posttreatment. One person randomized to placebo subsequently received treatment for CDI. In the vancomycin-treated group, beta-diversity (P = 0.0059) and macrolide-lincosamide-streptogramin (MLS) resistance genes (P = 0.037) increased after treatment; C. difficile and vancomycin-resistant enterococci (VRE) environmental contamination was found in 53% of patients and 26% of patients, respectively. We found that vancomycin alters the gut microbiota, does not permanently clear C. difficile, and is associated with VRE colonization/environmental contamination. (This study has been registered at ClinicalTrials.gov under registration no. NCT03388268.)

IMPORTANCE A gold standard diagnostic for Clostridioides difficile infection (CDI) does not exist. An area of controversy is how to manage patients whose stool tests positive by nucleic acid amplification tests but negative by toxin enzyme immunoassay. Existing data suggest most of these patients do not have CDI, but most are treated with oral vancomycin. Potential benefits to treatment include a decreased risk for adverse outcomes if the patient does have CDI and the potential to decrease C. difficile shedding/transmission. However, oral vancomycin perturbs the intestinal microbiota and promotes antibiotic-resistant organism colonization/transmission. We conducted a double-blinded randomized controlled trial to assess the risk-benefit of oral vancomycin treatment in this population. Oral vancomycin did not result in long-term clearance of C. difficile, perturbed the microbiota, and was associated with colonization/shedding of vancomycin-resistant enterococci. This work underscores the need to better understand this population of patients in the context of C. difficile/ARO-related outcomes and transmission.

Whole genome sequencing of Clostridioides difficile PCR ribotype 046 suggests transmission between pigs and humans

Background

A zoonotic association has been suggested for several PCR ribotypes (RTs) of Clostridioides difficile. In central parts of Sweden, RT046 was found dominant in neonatal pigs at the same time as a RT046 hospital C. difficile infection (CDI) outbreak occurred in the southern parts of the country.

Objective

To detect possible transmission of RT046 between pig farms and human CDI cases in Sweden and investigate the diversity of RT046 in the pig population using whole genome sequencing (WGS).

Methods

WGS was performed on 47 C. difficile isolates from pigs (n = 22), the farm environment (n = 7) and human cases of CDI (n = 18). Two different core genome multilocus sequencing typing (cgMLST) schemes were used together with a single nucleotide polymorphisms (SNP) analysis and the results were related to time and location of isolation of the isolates.

Results

The pig isolates were closely related (≤6 cgMLST alleles differing in both cgMLST schemes) and conserved over time and were clearly separated from isolates from the human hospital outbreak (≥76 and ≥90 cgMLST alleles differing in the two cgMLST schemes). However, two human isolates were closely related to the pig isolates, suggesting possible transmission. The SNP analysis was not more discriminate than cgMLST.

Conclusion

No general pattern suggesting zoonotic transmission was apparent between pigs and humans, although contrasting results from two isolates still make transmission possible. Our results support the need for high resolution WGS typing when investigating hospital and environmental transmission of C. difficile.

Prevalence and phylogenetic relationship of Clostridioides difficile strains in fresh poultry meat samples processed in different cutting plants

Clostridioides difficile is one of the most frequent causes of nosocomial infections in humans leading to (antibiotic-associated) diarrhea and severe pseudomembranous colitis. With an increasing frequency, C. difficile infections (CDI) are also observed independently of hospitalization and the age of the patients in an ambulant setting. One potential source of so-called community-acquired CDI is a zoonotic transmission to humans based on direct contact with animals or the consumption of food. To estimate the exposure of humans with C. difficile via food, we screened 364 different retail fresh poultry meat products purchased in Berlin and Brandenburg, Germany and further characterized the isolates. None of the 42 turkey or chicken meat samples without skin was contaminated. However, 51 (15.8%) of 322 tested fresh chicken meat samples with skin were C. difficile-positive. The vast majority (84.3%) of all isolates exhibited toxin genes tcdA and tcdB, whereas the binary toxin cdtA/B was absent. Most of the isolates (50/51) were susceptible to all six investigated antimicrobials. However, one non-toxigenic strain was multidrug resistant to the antimicrobials clindamycin and erythromycin. The isolates were mainly represented by PCR-ribotypes (RT) 001, RT002, RT005, and RT014, which were already associated with human CDI cases in Germany and were partially detected in poultry. The relatively high contamination rate of fresh retail chicken meat with skin purchased in Germany indicates chicken meat as a potential source of human infections. Moreover, we identified cutting plants with a higher rate of a C. difficile-contamination (21.4-32.8%). To compare the phylogenetic relationship of the isolated strains from certain cutting plants over several months in 2018 and 2019, we analyzed them using NGS followed by core genome MLST. Interestingly, highly related strains (0-3 alleles distance) of common clinical RT001 and RT002 isolates, as well as of the non-toxigenic RT205 isolates were detectable in same cutting plants over a period of three and 16 months, respectively.The continuous contamination with the same strain could be explained by the longterm persistence of this strain within the cutting plant (e.g., within the scalder), or with a recurring entry e.g. from the same fattening farm.