Antimicrobial resistance progression in the United Kingdom: A temporal comparison of Clostridioides difficile antimicrobial susceptibilities

An Investigation into the Prevalence of Clostridioides difficile in Irish Pig Abattoirs and Pork Meat Products as a Potential Source of Human Infection

Clostridioides difficile (C. difficile), once considered a predominantly nosocomial pathogen, is increasingly implicated in community-acquired infections (CA-CDIs). This study investigates the prevalence, ribotypes, and antimicrobial susceptibility of C. difficile in Irish pork products and abattoirs, with a focus on the potential public health implications. A total of 180 retail pork products and 150 pig carcase swabs from three abattoirs were examined, alongside 30 environmental lairage samples. The C. difficile isolates were characterised through ribotyping and tested in terms of antimicrobial susceptibility. No C. difficile was isolated from the retail pork, while the carcase swabs yielded a low recovery rate (0.66%). However, the lairage areas were contaminated with C. difficile (33%), and six different ribotypes were identified, including the clinically relevant RT078. The ribotypes exhibited susceptibility to the antibiotics used to treat C. difficile infection (CDI) (fidaxomicin, vancomycin, and metronidazole) but showed resistance to tetracycline (9%) and ciprofloxacin (100%). These findings align with the international findings on antimicrobial resistance in C. difficile and suggest that strict EU food safety standards could mitigate retail pork contamination risks. Nevertheless, the environmental exposure during slaughtering and handling processes presents potential transmission risks for workers.

Clinical and economic outcomes associated with fidaxomicin in comparison to vancomycin, metronidazole, and FMT: A systematic literature review

BACKGROUND

There are an estimated half a million cases of Clostridioides difficile infection (CDI), in the United States annually. Fidaxomicin, vancomycin, and metronidazole are commonly used for CDI treatment, with fidaxomicin recommended by clinical guidelines as the preferred treatment for initial and recurrent CDI. This systematic literature review aimed to explore clinical and economic outcomes associated with fidaxomicin use with or without comparison to vancomycin, metronidazole, or fecal microbiota transplantation (FMT).

METHODS

The EMBASE, Medline, EconLit, and Evidence Based Medicine Reviews databases were searched from January 1st, 2012 to December 6th, 2022, as fidaxomicin was first approved for adult use in 2011. Identified publications were assessed and extracted by 2 independent reviewers.

RESULTS

Seventy-nine publications were included. Articles reporting at least 50 patients with follow-up ≤90 days were selected to obtain comparable outcome definitions (N = 14). Sustained clinical cure rate at 30- and 60-days follow-up was higher among fidaxomicin-treated patients (70.0-75.1% and 63.2-78.9%; N = 3) than vancomycin (45.1-58.2% and 38.9-50.0%; N = 3). Lower recurrence rates were reported post-fidaxomicin treatment compared to vancomycin, however the ranges overlapped at 30-, 60-, and 90-days follow-up. Limited outcomes for comparators metronidazole and FMT were identified. Healthcare resource use data were limited, with 2 studies reporting direct costs finding that fidaxomicin use-associated savings were driven by reduced hospital admission-related costs. Fidaxomicin was cost-effective in 14 of 21 economic analyses (11 vs vancomycin). Three studies reported vancomycin or FMT as more cost-effective than fidaxomicin. Fidaxomicin was consistently cost-effective or cost-saving among patients receiving concomitant antibiotics, and patients with cancer or renal impairment. Ten publications reported that the higher acquisition cost of fidaxomicin was offset by reduced recurrence and hospital readmission costs.

CONCLUSIONS

Fidaxomicin was clinically effective compared to vancomycin. Fidaxomicin is often reported as cost-effective, consistently within high-risk subpopulations.

Genomic Epidemiology of Clostridioides difficile ST81 in Multiple Hospitals in China

Background

Clostridioides difficile sequence type (ST) 81, mainly associated with ribotype (RT) 369, is a TcdA-negative and TcdB-positive genotype and a common ST found in China. Furthermore, ST81 strains are reported with highest resistance rates to many antimicrobial agents. However, given the potential for C. difficile ST81 transmission, research into the epidemiological characteristics of this type of ST remain limited.

Methods

We conducted a genomic epidemiology study addressing the genetic characteristics of C. difficile ST81 in five tertiary hospitals covering different regions in China between January 2010 and January 2021. Clinical toxigenic C. difficile strains were identified, typed by multi-locus sequence typing (MLST), and phylogenetic analysis, antimicrobial resistant gene (AMR) identification were performed after all these strains were conducted by whole genome sequencing (WGS).

Results

In total, 108 clinical C. difficile strains of ST81 were isolated and successfully analyzed by WGS, which showed that the percentage of isolates with AMRs was common in this type of ST. Furthermore, two types of transposons, Tn916 and Tn6189, were also detected. We found that all C. difficile ST81 genomes were closely related as pairwise core-genomic SNP (cgSNP) distance between the strains was on average 13 cgSNPs (range, 0-425 cgSNPs). Notably, these isolates were split into two sub-lineages (SL I and SL II) by Bayesian analysis, which suggested that both sub-lineages emerged independently. It is noted that some AMRs (such as clbA, dfrF, and cfrB) and Tn916 were only detected in SL I.

Conclusion

C. difficile ST81 is among the common STs in this study. Two independent sub-lineages of C. difficile ST81 strains are found. Furthermore, the presence of a high number of AMR genes and multiple mobile elements indicate a potential risk for transmission of C. difficile ST81. Based on these results, a robust surveillance system is crucial for identifying outbreaks, tracking infection trends, and implementing timely interventions.

Clostridioides difficile infection: history, epidemiology, risk factors, prevention, clinical manifestations, treatment, and future options

SUMMARYClostridioides difficile infection (CDI) is one of the major issues in nosocomial infections. This bacterium is constantly evolving and poses complex challenges for clinicians, often encountered in real-life scenarios. In the face of CDI, we are increasingly equipped with new therapeutic strategies, such as monoclonal antibodies and live biotherapeutic products, which need to be thoroughly understood to fully harness their benefits. Moreover, interesting options are currently under study for the future, including bacteriophages, vaccines, and antibiotic inhibitors. Surveillance and prevention strategies continue to play a pivotal role in limiting the spread of the infection. In this review, we aim to provide the reader with a comprehensive overview of epidemiological aspects, predisposing factors, clinical manifestations, diagnostic tools, and current and future prophylactic and therapeutic options for C. difficile infection.

In Vitro Activity of Dalbavancin and Fourteen Other Antimicrobial Agents Against Toxigenic Clostridioides Difficile Clinical Isolates in a Greek Tertiary-Care Hospital

OBJECTIVE

Clostridioides difficile is a major cause of healthcare-associated diarrhea worldwide. For years, metronidazole and vancomycin were considered the standard treatment for C. difficile infection (CDI). However, they are increasingly being associated with treatment failure and recurrence. In this study we investigated the in vitro activity of dalbavancin and fourteen other antimicrobials against 155 toxigenic C. difficile isolates originating from patients with C. difficile-associated diarrhea.

MATERIALS AND METHODS

Antimicrobial susceptibility was evaluated by the MIC Test Strip and the results were interpreted using both the Clinical and Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial susceptibility Testing (EUCAST) breakpoints.

RESULTS

C. difficile isolates were fully susceptible to metronidazole, vancomycin, amoxicillin/ clavulanate, piperacillin/tazobactam, and tigecycline. All isolates were dalbavancin susceptible by the CLSI breakpoint (≤ 0.25 μg/ml) compared with 97.4% susceptibility by the EUCAST breakpoint (≤ 0.125 μg/ml). Dalbavancin demonstrated significantly lower MIC50 and MIC90 values compared to vancomycin (0.047 vs. 0.38 and 0.125 vs. 0.5, respectively, p < 0.001). Resistance rates to penicillin, ampicilin, cefoxitin, imipenem, meropenem, clindamycin, moxifloxacin, chloramphenicol, and tetracycline were 20%, 14.2% , 100%, 75.5%, 0.6%, 51%, 36.1%, 3.2%, and 14.8%, respectively. Multidrug-resistant (MDR) phenotypes were detected among 41.3% of the isolates.

CONCLUSION

Dalbavancin exhibited potent activity against the isolates tested. As C. difficile is an important healthcare-associated pathogen, continued surveillance is required to monitor for development of resistance.

Advances in Therapeutic Strategies for the Management of Clostridioides difficile Infection

The infection caused by Clostridioides difficile represents one of the bacterial infections with the greatest increase in incidence among nosocomial infections in recent years. C. difficile is a Gram-positive bacterium able to produce toxins and spores. In some cases, infection results in severe diarrhoea and fulminant colitis, which cause prolonged hospitalisation and can be fatal, with repercussions also in terms of health economics. C. difficile is the most common cause of antibiotic-associated diarrhoea in the healthcare setting. The problem of bacterial forms that are increasingly resistant to common antibiotic treatments is also reflected in C. difficile infection (CDI). One of the causes of CDI is intestinal dysmicrobialism induced by prolonged antibiotic therapy. Moreover, in recent years, the emergence of increasingly virulent strains resistant to antibiotic treatment has made the picture even more complex. Evidence on preventive treatments to avoid recurrence is unclear. Current guidelines indicate the following antibiotics for the treatment of CDI: metronidazole, vancomycin, and fidaxomycin. This short narrative review provides an overview of CDI, antibiotic resistance, and emerging treatments.

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.

Clostridioides difficile resistance to antibiotics, including post-COVID-19 data

INTRODUCTION

Updating data on Clostridioides difficile antibiotic resistance is important for treatment improvement of C. difficile infections (CDIs).

AREAS COVERED

Results from 20 countries were included. The mean resistance to 2 mg/l vancomycin, 2 mg/l metronidazole, 4 mg/l moxifloxacin, and 4 mg/l clindamycin was 4.7% (0 to ≥ 26% in two studies), 2.6% (0 to ≥ 40% in 3 studies), 34.9% (6.6->80%), and 61.0% (30->90%), respectively. Resistance to erythromycin (>60-88%), rifampin (>23-55.0%), imipenem (0.6 to > 78% in a clone), tigecycline (0-<5.0%), and fidaxomicin (0-2%) was also found. Resistance to ≥ 5 antibiotics of different classes was reported in some countries. High resistance and multidrug resistance were observed in hypervirulent and epidemic strains. Although only 1% of COVID-19 patients had CDIs, the proportion might be underestimated.

EXPERT OPINION

C. difficile antimicrobial susceptibility varied by country/region, study period, and circulating ribotypes. For CDI treatment, fidaxomicin (preferably) or vancomycin is recommended, while metronidazole is suitable for mild infections. New approaches, including biotherapeutics (Rebyota), strains, antibiotics (ridinilazole and ibezapolstat), and monoclonal antibodies/cocktails merit further evaluation. Because of the resistance rate variations, C. difficile antibiotic susceptibility should be regularly monitored. Post-COVID-19 resistance should be separately presented. Some discrepancies between vancomycin and metronidazole results need to be clarified.

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.

Wolf in Sheep's Clothing: Clostridioides difficile Biofilm as a Reservoir for Recurrent Infections

The microbiota inhabiting the intestinal tract provide several critical functions to its host. Microorganisms found at the mucosal layer form organized three-dimensional structures which are considered to be biofilms. Their development and functions are influenced by host factors, host-microbe interactions, and microbe-microbe interactions. These structures can dictate the health of their host by strengthening the natural defenses of the gut epithelium or cause disease by exacerbating underlying conditions. Biofilm communities can also block the establishment of pathogens and prevent infectious diseases. Although these biofilms are important for colonization resistance, new data provide evidence that gut biofilms can act as a reservoir for pathogens such as Clostridioides difficile. In this review, we will look at the biofilms of the intestinal tract, their contribution to health and disease, and the factors influencing their formation. We will then focus on the factors contributing to biofilm formation in C. difficile, how these biofilms are formed, and their properties. In the last section, we will look at how the gut microbiota and the gut biofilm influence C. difficile biofilm formation, persistence, and transmission.

Broth Microdilution and Gradient Diffusion Strips vs. Reference Agar Dilution Method: First Evaluation for Clostridiales Species Antimicrobial Susceptibility Testing

Antimicrobial susceptibility testing of anaerobes is challenging. Because MIC determination is recommended by both CLSI and EUCAST, commercial broth microdilution and diffusion strip tests have been developed. The reliability of broth microdilution methods has not been assessed yet using the agar dilution reference method. In this work, we evaluated two broth microdilution kits (MICRONAUT-S Anaerobes^® MIC and Sensititre Anaerobe MIC^®) and one gradient diffusion strip method (Liofilchem^®) for antimicrobial susceptibility testing of 47 Clostridiales isolates (Clostridium, Clostridioides and Hungatella species) using the agar dilution method as a reference. The evaluation focused on comparing six antimicrobial molecules available in both microdilution kits. Analytical performances were evaluated according to the Food and Drug Administration (FDA) recommendations. Essential agreements (EA) and categorical agreements (CA) varied greatly according to the molecule and the evaluated method. Vancomycin had values of essential and categorical agreements above 90% for the three methods. The CA fulfilled the FDA criteria for three major molecules in the treatment of Gram-positive anaerobic infections (metronidazole, piperacillin/tazobactam and vancomycin). The highest rate of error was observed for clindamycin. Multicenter studies are needed to further validate these results.