Hypervirulent Clostridium difficile ribotypes are CpG depleted

Shengjiang Xiexin decoction mitigates murine Clostridium difficile infection through modulation of the gut microbiota and bile acid metabolism

ETHNOPHARMACOLOGICAL RELEVANCE

The overuse of antibiotics has resulted in Clostridium difficile infection (CDI) as a significant global public health concern. Studies have shown that imbalances in gut microbiota and metabolism play a vital role in the onset of CDI. Shengjiang Xiexin decoction (SJT), a traditional Chinese medicinal formula widely employed in the treatment of gastrointestinal ailments, demonstrates effectiveness in addressing murine CDI. However, the precise mechanistic role of SJT in CDI treatment remains uncertain, particularly regarding its impact on gut microbiota and intestinal metabolism. Thus, further investigation is imperative to shed light on these mechanisms.

AIM OF THE STUDY

This study aims to thoroughly investigate the therapeutic potential of SJT in the treatment of CDI, while also examining its impact on the intricate interplay between gut microbiota and bile acid metabolism. By employing a mouse model, we aspire to uncover novel insights that could pave the way for the development of more effective strategies in combating CDI.

MATERIALS AND METHODS

We developed a mouse model for CDI and assessed SJT's potential as a therapeutic agent through pharmacological analyses. Our study employed high-throughput sequencing of 16S rRNA to identify changes in gut microbiota composition and untargeted metabolomics analysis to evaluate SJT's intervention on intestinal metabolism. We also conducted targeted analysis of bile acid metabolism to examine the specific effects of SJT. Finally, the growth-inhibitory effect of SJT on C. difficile was confirmed through ex vivo cultivation of the pathogen using cecal contents, supporting its potential role in treating CDI by modulating gut microbiota and bile acid metabolism.

RESULTS

In pharmacological studies, SJT was found to effectively reduce the levels of A&B toxins and alleviate colonic inflammation in CDI mice. Mechanistically, SJT demonstrated a mild increase in the abundance and diversity of the gut microbiota. However, its most significant impact was observed in the substantial improvement of the structural composition of the gut microbiota. Specifically, SJT decreased the abundance of gut Polymorphs and Firmicutes while restoring the proportions of family Trichophyton and Bacteroides_S24-7 spp (P < 0.001). Moreover, SJT not only decreased the levels of primary bile acids but also elevated the levels of secondary bile acids. Notably, it enhanced the conversion of taurocholic acid (TCA) to deoxycholic acid (DCA), leading to a balanced bile acid metabolism. Finally, cecal contents of SJT-treated mice showed a significant reduction in the growth of C. difficile, underscoring the therapeutic potential of SJT via modulation of gut microbiota and bile acid metabolism.

CONCLUSION

SJT demonstrates remarkable efficacy in treating CDI in mice by not only effectively combating the infection but also restoring the intricate balance of gut microbiota and bile acid metabolism. Furthermore, promising indications suggest that SJT may have the potential to prevent CDI recurrence. These findings underscore the comprehensive therapeutic value of SJT in managing CDI. Moving forward, we plan to transition from the laboratory to clinical settings to conduct further studies, validating our conclusions on SJT's efficacy.

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.

Bioinformatics-driven discovery of novel Clostridioides difficile lysins and experimental comparison with highly active benchmarks

Clostridioides difficile is the single most deadly bacterial pathogen in the United States, and its global prevalence and outsized health impacts underscore the need for more effective therapeutic options. Towards this goal, a novel group of modified peptidoglycan hydrolases with significant in vitro bactericidal activity have emerged as potential candidates for treating C. difficile infections (CDI). To date, discovery and development efforts directed at these CDI-specific lysins have been limited, and in particular there has been no systematic comparison of known or newly discovered lysin candidates. Here, we detail bioinformatics-driven discovery of six new anti-C. difficile lysins belonging to the amidase-3 family of enzymes, and we describe experimental comparison of their respective catalytic domains (CATs) with highly active CATs from the literature. Our quantitative analyses include metrics for expression level, inherent antibacterial activity, breadth of strain selectivity, killing of germinating spores, and structural and functional measures of thermal stability. Importantly, prior studies have not examined stability as a performance metric, and our results show that the panel of eight enzymes possess widely variable thermal denaturation temperatures and resistance to heat inactivation, including some enzymes that exhibit marginal stability at body temperature. Ultimately, no single enzyme dominated with respect to all performance measures, suggesting the need for a balanced assessment of lysin properties during efforts to find, engineer, and develop candidates with true clinical potential.

Prevalence, Colonization, Epidemiology, and Public Health Significance of Clostridioides difficile in Companion Animals

Clostridioides difficile, previously Clostrdium difficile, is a major cause of antibiotic-associated enteric disease in humans in hospital settings. Increased incidence of C. difficile infection (CDI) in community settings raises concerns over an alternative source of CDI for humans. The detection of genetically similar and toxigenic C. difficile isolates in companion animals, including asymptomatic pets, suggests the potential role of household pets as a source of community-associated CDI. The close association between companion animals and humans, in addition to the use of similar antibiotics in both species, could provide a selective advantage for the emergence of new C. difficile strains and thus increase the incidental transmission of CDI to humans. Therefore, screening household pets for C. difficile is becoming increasingly important from a public health standpoint and may become a part of routine testing in the future, for the benefit of susceptible or infected individuals within a household. In this review, we analyze available information on prevalence, pathophysiology, epidemiology, and molecular genetics of C. difficile infection, focusing on companion animals and evaluate the risk of pet-borne transmission of CDI as an emerging public health concern. Molecular epidemiological characterization of companion animal C. difficile strains could provide further insights into the interspecies transmission of CDI. The mosaic nature of C. difficile genomes and their susceptibility to horizontal gene transfer may facilitate the inter-mixing of genetic material, which could increase the possibility of the emergence of new community-associated CDI strains. However, detailed genome-wide characterization and comparative genome analysis are warranted to confirm this hypothesis.