Phylogenomic analysis of Clostridioides difficile ribotype 106 strains reveals novel genetic islands and emergent phenotypes

Distribution of Clostridioides difficile ribotypes and sequence types across humans, animals and food in 13 European countries

Clostridioides difficile is a One Health pathogen found in humans, animals, and the environment, with food representing a potential transmission route. One Health studies are often limited to a single country or selected reservoirs and ribotypes. This study provides a varied and accessible collection of C. difficile isolates and sequencing data derived from human, animal, and food sources across 13 European countries. A total of 441 strains (human hospital- and community-associated cases n = 280, animal n = 96, food n = 65) were analysed by ribotyping, toxinotyping and whole-genome sequencing (WGS). We detected 83 sequence types (STs), with ST11 (n = 80 isolates) and ST1 (n = 54 isolates) being the most represented. Several STs included strains originating from all source combinations. Further genomic analysis confirmed close genetic relatedness in some of the STs. Additionally, the genomic analysis identified 10 strains from cryptic clades (C-I to C-III) and 4 of them were mono-toxigenic possessing only a variant form of tcdA gene. Amongst 106 ribotypes, 10 were shared between all 3 sources and 68 were source-specific. Some ribotypes were only found at the intersection of human and food source (RT023, RT027), or between human and animal source (RT009, RT045, RT046). C. difficile ribotypes and STs in Europe were diverse. In this collection, some ribotypes showed potential association with food or animal transmission routes. C. difficile strains from divergent clades CI-III, currently emerging in the human population, were rare and mostly food-associated.Trial registration: ClinicalTrials.gov identifier: NCT03503474.

Dogs in Rio de Janeiro as reservoirs of Clostridioides difficile ribotypes causing CDI in humans

INTRODUCTION

In the past decade, the incidence of community-acquired Clostridioides difficile infection (CA-CDI) has increased, suggesting a role for community reservoirs such as animals in its spread.

OBJECTIVE

This study aimed to isolate and characterize C. difficile strains from domestic dogs at veterinary clinics to enhance our understanding of C. difficile epidemiology in Rio de Janeiro.

MATERIAL AND METHODS

For this study 90 stool samples from dogs were collected and cultured in a selective medium (Clostridioides difficile Brucella agar - CDBA) for isolation. Species were identified by MALDI-TOF MS, with confirmation provided by PCR targeting the tpi gene. The antibiotic susceptibility test of the strains was performed using five antibiotics: vancomycin, metronidazole, moxifloxacin, rifampicin, and erythromycin. Strains resistant to metronidazole were further analyzed for the presence of the plasmid pCD-METRO using PCR. The presence of toxin genes (tcdA, tcdB, and cdtB) was investigated, alongside ribotyping and tcdC sequencing analyses. The strains were also tested for biofilm formation and motility.

RESULTS

C. difficile was isolated in 15.5 % (14/90) of the samples. Among the strains analyzed, 87.71 % (12/14) tested positive for both toxin genes tcdA and tcdB and belonged to ribotypes 106 (10/14) and 014/020 (2/14). The remaining 14.3 % (2/14) were non-toxigenic and were identified as ribotype 010. Regarding the antibiotic profile, 42.85 % (6/14) of the strains exhibited resistance to at least one antibiotic, including vancomycin (1/14) and metronidazole (1/14). The metronidazole-resistant strain was also positive for the plasmid pCD-METRO. All strains exhibited both biofilm formation and motility. Among the 12 toxigenic strains sequenced for the tcdC gene, two exhibited a deletion in the same region as the epidemic strain, NAP1 (RT027).

CONCLUSION

Our study found some overlap between C. difficile ribotypes isolated from dogs and from cases of CDI in humans, and the C. difficile prevalence was higher in dogs with diarrhea (p = 0.034).

Investigating the genomic and metabolic abilities of PGPR Pseudomonas fluorescens in promoting plant growth and fire blight management

Pseudomonas fluorescens is commonly found in diverse environments and is well known for its metabolic and antagonistic properties. Despite its remarkable attributes, its potential role in promoting plant growth remains unexplored. This study examines these traits across 14 strains residing in diverse rhizosphere environments through pangenome and comparative genome analysis, alongside molecular docking studies against Erwinia amylovora to combat fire blight. Whole genome analysis revealed circular chromosome (6.01-7.07 Mb) with GC content averaging 59.95-63.39%. Predicted genes included 16S rRNA and protein-coding genes ranging from 4435 to 6393 bp and 1527 to 1541 bp, respectively. Pangenome analysis unveiled an open pangenome, shedding light on genetic factors influencing plant growth promotion and biocontrol, including nitrogen fixation, phosphorus solubilization, siderophore production, stress tolerance, flagella biosynthesis, and induced systemic resistance. Furthermore, pyrrolnitrin, phenazine-1-carboxylic acid, pyoluteorin, lokisin, 2,4-diacetylpholoroglucinol and pseudomonic acid were identified. Molecular docking against key proteins of E. amylovora highlighted the high binding affinities of 2,4-diacetylphloroglucinol, pseudomonic acid, and lokisin. These findings underscore the multifaceted role of P. fluorescens in plant growth promotion and biocontrol, with key biomolecules showing promising applications in plant growth and defense against pathogens.

Virulence factors, antibiotic susceptibility and sequence type distribution of hospital-associated Clostridioides difficile isolates in Israel, 2020-2022

Biofilm formation and toxin production are some of the virulence factors of Clostridioides difficile (C. difficile), which causes hospital-acquired C. difficile infection (HA-CDI). This work investigated the prevalence and distribution of different strains recovered from HA-CDI patients hospitalized in 4 medical centres across Israel, and characterized strains' virulence factors and antibiotic susceptibility. One-hundred and eighty-eight faecal samples were collected. C. difficile 's toxins were detected by the CerTest Clostridium difficile GDH + Toxin A + B combo card test kit. Toxin loci PaLoc and PaCdt were detected by whole-genome sequencing (WGS). Multi-locus sequence typing (MLST) was performed to classify strains. Biofilm production was assessed by crystal violet. Antibiotic susceptibility was determined using Etest. Fidaxomicin susceptibility was tested via agar dilution. Sequence type (ST) 42 was the most (13.8%) common strain. All strains harboured the 2 toxins genes; 6.9% had the binary toxin. Most isolates were susceptible to metronidazole (98.9%) and vancomycin (99.5%). Eleven (5.85%) isolates were fidaxomicin-resistant. Biofilm production capacity was associated with ST (p < 0.001). In conclusion, a broad variety of C. difficile strains circulate in Israel's medical centres. Further studies are needed to explore the differences and their contribution to HA-CDI epidemiology.

Commensal-pathogen dynamics structure disease outcomes during Clostridioides difficile colonization

Gastrointestinal colonization by Clostridioides difficile is common in healthcare settings and ranges in clinical presentation from asymptomatic carriage to lethal C. difficile infection (CDI). We used a systems biology approach to investigate why patients colonized with C. difficile have a range of outcomes. Microbiota-humanization of germ-free mice with fecal samples from toxigenic C. difficile carriers revealed a spectrum of virulence among clade 1 lineages and identified commensal Blautia associated with markers of non-pathogenic colonization. Using gnotobiotic mice engrafted with defined human microbiota, we observed strain-specific CDI severity across clade 1 strains. Yet, mice engrafted with a higher diversity community were protected from severe disease across all strains without suppression of C. difficile colonization. These results indicate that when colonization resistance has been breached without overt infection, commensals can attenuate a diversity of virulent strains without inhibiting pathogen colonization, providing insight into determinants of stable C. difficile carriage.

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.

Prevalence of diagnostically-discrepant Clostridioides difficile clinical specimens: insights from longitudinal surveillance

Background

Clostridioides difficile Infection (CDI) is a healthcare-associated diarrheal disease prevalent worldwide. A common diagnostic algorithm relies on a two-step protocol that employs stool enzyme immunoassays (EIAs) to detect the pathogen, and its toxins, respectively. Active CDI is deemed less likely when the Toxin EIA result is negative, even if the pathogen-specific EIA is positive for C. difficile. We recently reported, however, that low-toxin-producing C. difficile strains recovered from Toxin-negative ('discrepant') clinical stool specimens can be fully pathogenic, and cause lethality in a rodent CDI model. To document frequency of discrepant CDI specimens, and evaluate C. difficile strain diversity, we performed longitudinal surveillance at a Southern Arizona tertiary-care hospital.

Methods

Diarrheic stool specimens from patients with clinical suspicion of CDI were obtained over an eight-year period (2015-2022) from all inpatient and outpatient Units of a > 600-bed Medical Center in Southern Arizona. Clinical laboratory EIA testing identified C. difficile-containing specimens, and classified them as Toxin-positive or Toxin-negative. C. difficile isolates recovered from the stool specimens were DNA fingerprinted using an international phylogenetic lineage assignment system ("ribotyping"). For select isolates, toxin abundance in stationary phase supernatants of pure cultures was quantified via EIA.

Results

Of 8,910 diarrheic specimens that underwent diagnostic testing, 1733 (19.4%) harbored C. difficile. Our major findings were that: (1) C. difficile prevalence and phylogenetic diversity was stable over the 8-year period; (2) toxigenic C. difficile was recovered from 69% of clinically Tox-neg ('discrepant') specimens; (3) the six most prevalent USA ribotypes were recovered in significant proportions (>60%) from Tox-neg specimens; and (4) toxin-producing C. difficile recovered from discrepant specimens produced less toxin than strains of the same ribotype isolated from non-discrepant specimens.

Conclusion

Our study highlights the dominance of Toxin EIA-negative CDI specimens in a clinical setting and the high frequency of known virulent ribotypes in these specimens. Therefore, a careful reevaluation of the clinical relevance of diagnostically-discrepant specimens particularly in the context of missed CDI diagnoses and C. difficile persistence, is warranted.

Prevalence of Clostridioides difficile in dogs (Canis familiaris) with gastrointestinal disorders in Rio de Janeiro

Clostridioides difficile infections (CDI) have a high morbidity and mortality rate and have always been considered a nosocomial disease. Nonetheless, the number of cases of community-acquired CDI is increasing, and new evidence suggests additional C. difficile reservoirs exist. Pathogenic C. difficile strains have been found in livestock, domestic animals, and meat, so a zoonotic transmission has been proposed.

OBJECTIVE

The goal of this study was to isolate C. difficile strains in dogs at a veterinary clinic in Rio de Janeiro, Brazil, and characterize clinical and pathological findings associated with lower gastrointestinal tract disorders.

METHODS

Fifty stool samples and biopsy fragments from dogs were obtained and cultured in the CDBA selective medium. All suggestive C. difficile colonies were confirmed by MALDI-TOF MS and PCR (tpi gene). Vancomycin, metronidazole, moxifloxacin, erythromycin, and rifampicin were tested for antibiotic susceptibility. Biofilm, motility assays, and a PCR for the toxins (tcdA, tcdB, and cdtB), as well as ribotyping, were also performed.

RESULTS

Blood samples and colonic biopsy fragments were examined in C. difficile positive dogs. Ten animals (20%) tested positive for C. difficile by using stool samples, but not from biopsy fragments. Most C. difficile strains were toxigenic: six were A+B+ belonging to RT106; two were A+B+ belonging to RT014/020; and two were A-B- belonging to RT010. All strains were biofilm producers. In the motility test, 40% of strains were as motile as the positive control, CD630 (RT012). In the disc diffusion test, two strains (RT010) were resistant to erythromycin and metronidazole; and another to metronidazole (RT014/020). In terms of C. difficile clinicopathological correlations, no statistically significant morphological changes, such as pseudomembranous and "volcano" lesions, were observed. Regarding hematological data, dogs positive for C. difficile had leucopenia (p = 0.02) and lymphopenia (p = 0.03). There was a significant correlation between senility and the presence of C. difficile in the dogs studied (p = 0,02).

CONCLUSIONS

Although C. difficile has not been linked to canine diarrheal disorders, it appears to be more common in dogs with intestinal dysfunctions. The isolation of ribotypes frequently involved in human CDI outbreaks around the world supports the theory of C. difficile zoonotic transmission.

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.

Clostridioides difficile Toxin B Induced Senescence: A New Pathologic Player for Colorectal Cancer?

Clostridioides difficile (C. difficile) is responsible for a high percentage of gastrointestinal infections and its pathological activity is due to toxins A and B. C. difficile infection (CDI) is increasing worldwide due to the unstoppable spread of C. difficile in the anthropized environment and the progressive human colonization. The ability of C. difficile toxin B to induce senescent cells and the direct correlation between CDI, irritable bowel syndrome (IBS), and inflammatory bowel diseases (IBD) could cause an accumulation of senescent cells with important functional consequences. Furthermore, these senescent cells characterized by long survival could push pre-neoplastic cells originating in the colon towards the complete neoplastic transformation in colorectal cancer (CRC) by the senescence-associated secretory phenotype (SASP). Pre-neoplastic cells could appear as a result of various pro-carcinogenic events, among which, are infections with bacteria that produce genotoxins that generate cells with high genetic instability. Therefore, subjects who develop IBS and/or IBD after CDI should be monitored, especially if they then have further CDI relapses, waiting for the availability of senolytic and anti-SASP therapies to resolve the pro-carcinogenic risk due to accumulation of senescent cells after CDI followed by IBS and/or IBD.

Whole Genome Sequencing Evidences High Rates of Relapse in Clostridioides difficile Infection Caused by the Epidemic Ribotype 106

An increasing prevalence and spread of Clostridioides difficile infection (CDI) caused by DH/NAP11/106/ST-42 has been observed worldwide, probably fostered by its great capacity to produce spores or by the higher resistance rates observed for some strains. Based on the results of our previous study where RT106 showed higher recurrence rates than other relevant ribotypes, a genetic analysis by whole-genome sequencing (WGS) of primary and recurrent RT106 isolates from ten patients was performed to determine whether the higher rate of recurrence associated with RT106 is due to relapses, caused by the same strain, or reinfections, caused by different strains. MLST profiles, resistance mutations, and phylogenetic relatedness were determined by comparative single nucleotide variant (SNV) analysis. All isolates were classified as ST42, and those belonging to the same patient were isogenic, with one exception; strains belonging to different patients were not with two exceptions, pointing to putative transmission events. Phylogenetic analysis also suggested the presence of similar local epidemic lineages associated with moxifloxacin resistance, except for one patient whose isolates clustered with different nonresistant US strains. Our results show that recurrent CDIs caused by RT06/ST42 are mainly due to relapses caused by the primary strains, showing the higher capacity of RT106/ST42 to persist and cause recurrences as compared to other ribotypes.

Molecular epidemiology of Clostridioides difficile in companion animals: Genetic overlap with human strains and public health concerns

Introduction

The changing epidemiology of Clostridioides difficile reflects a well-established and intricate community transmission network. With rising numbers of reported community-acquired infections, recent studies tried to identify the role played by non-human reservoirs in the pathogen's transmission chain. This study aimed at describing the C. difficile strains circulating in canine and feline populations, and to evaluate their genetic overlap with human strains to assess the possibility of interspecies transmission.

Methods

Fecal samples from dogs (n = 335) and cats (n = 140) were collected from two populations (group A and group B) in Portugal. C. difficile isolates were characterized for toxigenic profile and PCR-ribotyping. The presence of genetic determinants of antimicrobial resistance was assessed in all phenotypically resistant isolates. To evaluate the genetic overlap between companion animals and human isolates from Portugal, RT106 (n = 42) and RT014/020 (n = 41) strains from both sources were subjected to whole genome sequencing and integrated with previously sequenced RT106 (n = 43) and RT014/020 (n = 142) genomes from different countries. The genetic overlap was assessed based on core-single nucleotide polymorphism (SNP) using a threshold of 2 SNP.

Results

The overall positivity rate for C. difficile was 26% (76/292) in group A and 18.6% (34/183) in group B. Toxigenic strains accounted for 50% (38/76) and 52.9% (18/34) of animal carriage rates, respectively. The most prevalent ribotypes (RT) were the toxigenic RT106 and RT014/020, and the non-toxigenic RT010 and RT009. Antimicrobial resistance was found for clindamycin (27.9%), metronidazole (17.1%) and moxifloxacin (12.4%), associated with the presence of the ermB gene, the pCD-METRO plasmid and point mutations in the gyrA gene, respectively. Both RT106 and RT014/020 genetic analysis revealed several clusters integrating isolates from animal and human sources, supporting the possibility of clonal interspecies transmission or a shared environmental contamination source.

Discussion

This study shows that companion animals may constitute a source of infection of toxigenic and antimicrobial resistant human associated C. difficile isolates. Additionally, it contributes with important data on the genetic proximity between C. difficile isolates from both sources, adding new information to guide future work on the role of animal reservoirs in the establishment of community associated transmission networks and alerting for potential public health risk.

Assessing the relative performance of fast molecular dating methods for phylogenomic data

Advances in genome sequencing techniques produced a significant growth of phylogenomic datasets. This massive amount of data represents a computational challenge for molecular dating with Bayesian approaches. Rapid molecular dating methods have been proposed over the last few decades to overcome these issues. However, a comparative evaluation of their relative performance on empirical data sets is lacking. We analyzed 23 empirical phylogenomic datasets to investigate the performance of two commonly employed fast dating methodologies: penalized likelihood (PL), implemented in treePL, and the relative rate framework (RRF), implemented in RelTime. They were compared to Bayesian analyses using the closest possible substitution models and calibration settings. We found that RRF was computationally faster and generally provided node age estimates statistically equivalent to Bayesian divergence times. PL time estimates consistently exhibited low levels of uncertainty. Overall, to approximate Bayesian approaches, RelTime is an efficient method with significantly lower computational demand, being more than 100 times faster than treePL. Thus, to alleviate the computational burden of Bayesian divergence time inference in the era of massive genomic data, molecular dating can be facilitated using the RRF, allowing evolutionary hypotheses to be tested more quickly and efficiently.

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.

Characterization of Healthcare-Associated and Community-Associated Clostridioides difficile Infections among Adults, Canada, 2015-2019

We investigated epidemiologic and molecular characteristics of healthcare-associated (HA) and community-associated (CA) Clostridioides difficile infection (CDI) among adult patients in Canadian Nosocomial Infection Surveillance Program hospitals during 2015–2019. The study encompassed 18,455 CDI cases, 13,735 (74.4%) HA and 4,720 (25.6%) CA. During 2015–2019, HA CDI rates decreased by 23.8%, whereas CA decreased by 18.8%. HA CDI was significantly associated with increased 30-day all-cause mortality as compared with CA CDI (p<0.01). Of 2,506 isolates analyzed, the most common ribotypes (RTs) were RT027, RT106, RT014, and RT020. RT027 was more often associated with CDI-attributable death than was non-RT027, regardless of acquisition type. Overall resistance C. difficile rates were similar for all drugs tested except moxifloxacin. Adult HA and CA CDI rates have declined, coinciding with changes in prevalence of RT027 and RT106. Infection prevention and control and continued national surveillance are integral to clarifying CDI epidemiology, investigation, and control.

Genetic Mechanisms of Vancomycin Resistance in Clostridioides difficile: A Systematic Review

Antimicrobial resistance to treatments for Clostridioides difficile infection (CDI) poses a significant threat to global health. C. difficile is widely thought to be susceptible to oral vancomycin, which is increasingly the mainstay of CDI treatment. However, clinical labs do not conduct C. difficile susceptibility testing, presenting a challenge to detecting the emergence and impact of resistance. In this systematic review, we describe gene determinants and associated clinical and laboratory mechanisms of vancomycin resistance in C. difficile, including drug-binding site alterations, efflux pumps, RNA polymerase mutations, and biofilm formation. Additional research is needed to further characterize these mechanisms and understand their clinical impact.

Molecular Epidemiology of Clostridioides difficile Infections in Children

Clostridioides difficile is a prominent cause of health care-related gastrointestinal illness in adults. C. difficile infection (CDI) has been researched for over 40 years; however, research on pediatric CDI specifically has lagged behind for various reasons. Over the past decade, C. difficile has been increasingly reported as a cause of a broad spectrum of gastrointestinal diseases in children, ranging from mild self-limiting diarrhea to severe conditions such as pseudomembranous colitis and toxic megacolon. Recent publications have shown a rise in CDI incidence in children in different parts of the world, especially in patients with particular comorbidities such as hematological malignancies and inflammatory bowel disease. In addition, rising CDI rates have been reported in children in the community without traditional risk factors for CDI. Due to the extensive use of sensitive molecular detection methods to diagnose CDI in many countries, differentiating children who require treatment from those colonized with toxigenic strains remains a problem. Consequently, the molecular epidemiology of pediatric CDI is poorly understood. Even though well-known C. difficile strains causing CDI in children have been described (including hypervirulent strains such as ribotypes 027 and 078), there is a paucity of information about specific C. difficile strains. This mini-review summarizes the information that is currently available on the molecular epidemiology of CDI in children.

Mechanisms of antibiotic resistance of Clostridioides difficile

Clostridioides difficile (CD) is one of the top five urgent antibiotic resistance threats in USA. There is a worldwide increase in MDR of CD, with emergence of novel strains which are often more virulent and MDR. Antibiotic resistance in CD is constantly evolving with acquisition of novel resistance mechanisms, which can be transferred between different species of bacteria and among different CD strains present in the clinical setting, community, and environment. Therefore, understanding the antibiotic resistance mechanisms of CD is important to guide optimal antibiotic stewardship policies and to identify novel therapeutic targets to combat CD as well as other bacteria. Epidemiology of CD is driven by the evolution of antibiotic resistance. Prevalence of different CD strains and their characteristic resistomes show distinct global geographical patterns. Understanding epidemiologically driven and strain-specific characteristics of antibiotic resistance is important for effective epidemiological surveillance of antibiotic resistance and to curb the inter-strain and -species spread of the CD resistome. CD has developed resistance to antibiotics with diverse mechanisms such as drug alteration, modification of the antibiotic target site and extrusion of drugs via efflux pumps. In this review, we summarized the most recent advancements in the understanding of mechanisms of antibiotic resistance in CD and analysed the antibiotic resistance factors present in genomes of a few representative well known, epidemic and MDR CD strains found predominantly in different regions of the world.