The Gut Microbiota in Liver Transplantation Recipients During the Perioperative Period

Preoperative Factors Affecting Graft Survival After ABO-incompatible Adult Liver Transplantation

BACKGROUND

Although ABO-incompatible liver transplantation (ABOi LT) has undergone remarkable progress, the prognostic factors are poorly understood. This study aimed to elucidate the preoperative factors affecting graft survival after ABOi LT.

METHODS

Patients who underwent ABOi LT between January 2012 and December 2020 at a single institution in South Korea were retrospectively reviewed. A total of 146 recipients, including 34 patients with graft loss, were analyzed.

RESULTS

In the multivariate Cox proportional hazard model, recipient age (≥55 y; hazard ratio, 2.47; 95% confidence interval, 1.18-5.19; P  = 0.017) and donor ABO type (donor A, hazard ratio, 3.12; 95% confidence interval, 1.33-7.33; P  = 0.009) were significantly associated with an increased risk of graft loss. The most common cause of graft loss was recipient death due to bacterial infection (15/34, 44.1%). Both recipient age and donor ABO type were associated with an increased risk of recipient death due to bacterial infections. The incidence of complications after ABOi LT, including antibody-mediated rejection and diffuse intrahepatic biliary stricture, did not differ according to recipient age or donor ABO type.

CONCLUSIONS

These findings suggest that recipient age and donor ABO type should be considered when preparing for ABOi LT. Careful monitoring and care after transplantation are required for recipients with preoperative risk factors.

Effect of gut microbiota changes on cytokines IL-10 and IL-17 levels in liver transplantation patients

BACKGROUND

Liver transplantation (LT) is a critical intervention for individuals with end-stage liver disease; yet, post-transplant problems, especially infections, graft rejection, and chronic liver disease, are often linked to systemic inflammation. Cytokines, small signaling molecules, significantly influence immune responses during and post-liver transplantation. Nonetheless, the intricate relationships among cytokines, immune responses, and the gut microbiota, especially gut dysbiosis, are still inadequately comprehended. Thus, this study aims to identify the gut microbiota (GM) and determine their relationship to cytokines (IL-17 and IL-10) in LT patients, due to their importance in enhancing the recovery rate.

RESULT

The research included 31 liver transplant (LT) patients from the Gastroenterology Surgical Center at Mansoura University, resulting in the collection of 174 stool and blood samples from all participants. Fourteen bacterial species have been identified in samples collected at three intervals: one week before, one week post, and two weeks post LT. A change in gut microbiota composition was noted, characterized by a rise in potentially pathogenic bacteria such as Enterococci and Enterobacteriaceae (including Escherichia coli and Klebsiella) and a reduction in beneficial bacteria such as Bacteroidetes and Firmicutes. The examination of patient demographic and clinical data revealed no significant correlations between sex, age, or diagnostic categories and gut microbiota composition. The findings of the Multivariate Analysis of Variance (MANOVA) indicated a substantial effect of gut microbiota composition on cytokine levels (IL-10 and IL-17), with all tests producing p-values of 0.001. The assessment of cytokine levels indicated fluctuating variations at several time points following surgery. IL-10 levels in the GM groups exhibited a statistically significant elevation during the second week post-surgery (p = 0.036), suggesting a potential recovery-related anti-inflammatory response. In contrast, IL-17 levels rose in the NI group over time, indicating a transition to a pro-inflammatory condition.

CONCLUSION

This study emphasizes the pivotal role of the gut microbiota in regulating immune responses following transplantation.

Gut Microbial Dysbiosis and Implications in Solid Organ Transplantation

The gut microbiome has been shown to play a significant role in solid organ transplantation, potentially influencing graft function and patient outcomes. Dysbiosis, characterized by reduced microbial diversity and an increase in pathogenic taxa, has been linked to higher incidences of allograft rejection, graft dysfunction, and post-transplant mortality. Several studies suggest that the gut microbiome might be able to serve as both a biomarker and a therapeutic target, potentially guiding personalized immunosuppressive therapies and other interventions to improve outcomes after solid organ transplantation. As summarized in this review, clinical studies have shown that specific microbial shifts correlate with adverse outcomes, including acute rejection and chronic allograft dysfunction. As research surrounding the relationship between the gut microbiome and solid organ transplant progresses, the integration of microbial analysis into clinical practice has the potential to revolutionize post-transplant care, offering new avenues to improve graft survival and patient quality of life. This review aims to provide a comprehensive overview of the relationship between gut microbial dysbiosis and transplantation outcomes, emphasizing the impact on kidney, liver, lung, and heart transplant recipients.

Transplant-Acquired Food Allergy in Children

BACKGROUND

Organ transplantation in children is a vital procedure for those with end-stage organ failure, but it has been linked to the development of post-transplant allergies, especially food allergies. This phenomenon, known as transplant-acquired food allergy (TAFA), is becoming increasingly recognized, though its mechanisms remain under investigation. Pediatric transplant recipients often require lifelong immunosuppressive therapy to prevent graft rejection, which can alter immune function and heighten the risk of allergic reactions. Our review aimed to gather the latest evidence on TAFA.

METHODS

We conducted a PubMed search from 25 June to 5 July 2024, using specific search terms, identifying 143 articles. After screening, 36 studies were included: 24 retrospective studies, 1 prospective study, 2 cross-sectional researches, and 9 case reports/series.

RESULTS

Most studies focused on liver transplants in children. The prevalence of food allergies ranged from 3.3% to 54.3%. Tacrolimus, alongside corticosteroids, was the most commonly used immunosuppressive therapy. In addition to food allergies, some patients developed atopic dermatitis, asthma, and rhinitis. Allergic symptoms typically emerged within a year post-transplant, with common allergens including milk, eggs, fish, nuts, soy, wheat, and shellfish. Both IgE-mediated and non-IgE-mediated reactions were observed, with treatment often involving the removal of offending foods and the use of adrenaline when necessary.

CONCLUSIONS

Consistent immunological monitoring, such as skin prick tests and IgE level assessments, is essential for early detection and management of allergies in these patients. Understanding the link between transplantation and allergy development is crucial for improving long-term outcomes for pediatric transplant recipients.

Identification and comparison of intestinal microbial diversity in patients at different stages of hepatic cystic echinococcosis

There is a significant focus on the role of the host microbiome in different outcomes of human parasitic diseases, including cystic echinococcosis (CE). This study was conducted to identify the intestinal microbiome of patients with CE at different stages of hydatid cyst compared to healthy individuals. Stool samples from CE patients as well as healthy individuals were collected. The samples were divided into three groups representing various stages of hepatic hydatid cyst: active (CE1 and CE2), transitional (CE3), and inactive (CE4 and CE5). One family member from each group was selected to serve as a control. The gut microbiome of patients with different stages of hydatid cysts was investigated using metagenomic next-generation amplicon sequencing of the V3-V4 region of the 16S rRNA gene. In this study, we identified 4862 Operational Taxonomic Units from three stages of hydatid cysts in CE patients and healthy individuals with a combined frequency of 2,955,291. The most abundant genera observed in all the subjects were Blautia, Agathobacter, Faecalibacterium, Bacteroides, Bifidobacterium, and Prevotella. The highest microbial frequency was related to inactive forms of CE, and the lowest frequency was observed in the group with active forms. However, the lowest OTU diversity was found in patients with inactive cysts compared with those with active and transitional cyst stages. The genus Agatobacter had the highest OTU frequency. Pseudomonas, Gemella, and Ligilactobacillus showed significant differences among the patients with different stages of hydatid cysts. Additionally, Anaerostipes and Candidatus showed significantly different reads in CE patients compared to healthy individuals. Our findings indicate that several bacterial genera can play a role in the fate of hydatid cysts in patients at different stages of the disease.

The role of gut barrier dysfunction in postoperative complications in liver transplantation: pathophysiological and therapeutic considerations

PURPOSE

Gut barrier dysfunction is a pivotal pathophysiological alteration in cirrhosis and end-stage liver disease, which is further aggravated during and after the operational procedures for liver transplantation (LT). In this review, we analyze the multifactorial disruption of all major levels of defense of the gut barrier (biological, mechanical, and immunological) and correlate with clinical implications.

METHODS

A narrative review of the literature was performed using PubMed, PubMed Central and Google from inception until November 29th, 2023.

RESULTS

Systemic translocation of indigenous bacteria through this dysfunctional barrier contributes to the early post-LT infectious complications, while endotoxin translocation, through activation of the systemic inflammatory response, is implicated in non-infectious complications including renal dysfunction and graft rejection. Bacterial infections are the main cause of early in-hospital mortality of LT patients and unraveling the pathophysiology of gut barrier failure is of outmost importance.

CONCLUSION

A pathophysiology-based approach to prophylactic or therapeutic interventions may lead to enhancement of gut barrier function eliminating its detrimental consequences and leading to better outcomes for LT patients.

Gut microbiota dynamics in a 1-year follow-up after adult liver transplantation in Northeast China

Background: Liver transplantation (LTx) is the most effective treatment for end-stage liver diseases. Gut microorganisms influence the host physiology. We aim to profile the dynamics of gut microbiota in the perioperative period and a 1-year follow-up of LTx recipients in Northeast China. Methods: A total of 257 fecal samples were longitudinally collected from 85 LTx patients using anal swabs from pre-LTx to 1-year post-LTx. A total of 48 fecal samples from end-stage liver disease patients without LTx served as the control. 16S rRNA sequencing was used to analyze gut microbiota diversity, bacterial genera, phenotype classification, and metabolic pathways. Results: The diversity of gut microbiota decreased significantly after transplantation, accompanied by a profound change in the microbial structure, which is characterized by increased abundance of facultative anaerobic bacteria dominated by g_Enterococcus and reduced anaerobic bacteria composition. Predicted functional analysis also revealed disturbances in the metabolic pathway of the gut microbiota. After LTx, the diversity of microbiota gradually recovered but to a less preoperative level after 1 year of recovery. Compared with pre-transplantation, the microbiome structure was characterized by an increase in Acidaminococcus and Acidithiobacillus after 1 year of transplantation. Conclusion: LTx and perioperative treatment triggered gut microbial dysbiosis. The gut microbiota was restructured after LTx to near to but significantly differed from that of pre-LTx.

Improving liver transplant outcomes with transplant-omics and network biology

PURPOSE OF REVIEW

Molecular omics data is increasingly ubiquitous throughout medicine. In organ transplantation, recent large-scale research efforts are generating the 'transplant-ome' - the entire set of molecular omics data, including the genome, transcriptome, proteome, and metabolome. Importantly, early studies in anesthesiology have demonstrated how perioperative interventions alter molecular profiles in various patient populations. The next step for anesthesiologists and intensivists will be to tailor perioperative care to the transplant-ome of individual liver transplant patients.

RECENT FINDINGS

In liver transplant patients, elements of the transplant-ome predict complications and point to novel interventions. Importantly, molecular profiles of both the donor organ and recipient contribute to this risk, and interventions like normothermic machine perfusion influence these profiles. As we can now measure various omics molecules simultaneously, we can begin to understand how these molecules interact to form molecular networks and emerging technologies offer noninvasive and continuous ways to measure these networks throughout the perioperative period. Molecules that regulate these networks are likely mediators of complications and actionable clinical targets throughout the perioperative period.

SUMMARY

The transplant-ome can be used to tailor perioperative care to the individual liver transplant patient. Monitoring molecular networks continuously and noninvasively would provide new opportunities to optimize perioperative management.

Impact of gut microbiota on liver transplantation

The gut microbiota has been gaining attention due to its interactions with the human body and its role in pathophysiological processes. One of the main interactions is the "gut-liver axis," in which disruption of the gut mucosal barrier seen in portal hypertension and liver disease can influence liver allograft function over time. For example, in patients who are undergoing liver transplantation, preexisting dysbiosis, perioperative antibiotic use, surgical stress, and immunosuppressive use have each been associated with alterations in gut microbiota, potentially impacting overall morbidity and mortality. In this review, studies exploring gut microbiota changes in patients undergoing liver transplantation are reviewed, including both human and experimental animal studies. Common themes include an increase in Enterobacteriaceae and Enterococcaceae species and a decrease in Faecalibacterium prausnitzii and Bacteriodes, while a decrease in the overall diversity of gut microbiota after liver transplantation.

Gut Microbiota and Liver Transplantation: Immune Mechanisms behind the Rejection

Liver transplantation (LT) is the treatment of choice for patients with cirrhosis, decompensated disease, acute liver failure, and hepatocellular carcinoma (HCC). In 3-25% of cases, an alarming problem is acute and chronic cellular rejection after LT, and this event can lead to the need for new transplantation or the death of the patient. On the other hand, gut microbiota is involved in several mechanisms sustaining the model of the "gut-liver axis". These include modulation of the immune response, which is altered in case of gut dysbiosis, possibly resulting in acute graft rejection. Some studies have evaluated the composition of the gut microbiota in cirrhotic patients before and after LT, but few of them have assessed its impact on liver rejection. This review underlines the changes in gut microbiota composition before and after liver transplantation, hypothesizing possible immune mechanisms linking dysbiosis to transplantation rejection. Evaluation of changes in the gut microbiota composition in these patients is therefore essential in order to monitor the success of LT and eventually adopt appropriate preventive measures.

The Role of Microbiota in Liver Transplantation and Liver Transplantation-Related Biliary Complications

Liver transplantation as a treatment option for end-stage liver diseases is associated with a relevant risk for complications. On the one hand, immunological factors and associated chronic graft rejection are major causes of morbidity and carry an increased risk of mortality due to liver graft failure. On the other hand, infectious complications have a major impact on patient outcomes. In addition, abdominal or pulmonary infections, and biliary complications, including cholangitis, are common complications in patients after liver transplantation and can also be associated with a risk for mortality. Thereby, these patients already suffer from gut dysbiosis at the time of liver transplantation due to their severe underlying disease, causing end-stage liver failure. Despite an impaired gut-liver axis, repeated antibiotic therapies can cause major changes in the gut microbiome. Due to repeated biliary interventions, the biliary tract is often colonized by several bacteria with a high risk for multi-drug resistant germs causing local and systemic infections before and after liver transplantation. Growing evidence about the role of gut microbiota in the perioperative course and their impact on patient outcomes in liver transplantation is available. However, data about biliary microbiota and their impact on infectious and biliary complications are still sparse. In this comprehensive review, we compile the current evidence for the role of microbiome research in liver transplantation with a focus on biliary complications and infections due to multi-drug resistant germs.

Global research trends and hotspots of fecal microbiota transplantation: A bibliometric and visualization study

Introduction

Fecal microbiota transplantation (FMT) has gained considerable attention in a variety of clinical research areas, and an increasing number of articles are being published. It is very critical to reveal the global status, future research trends, and hotspots in the FMT research and application.

Methods

We searched the Web of Science Core Collection up to May 10, 2022, and only articles and review articles about FMT were included finally. CiteSpace 5.8.R3, VOSviewer 1.6.18, Scimago Graphica and Microsoft Office Excel 2019 were used for data analysis and visualization. The results included publication characteristics, Co-authorships analysis, Co-cited analysis, Co-occurrence analysis, and burst analysis.

Results

Eleven thousand nine hundred seventy-two records were used for the analysis and visualization finally, these records were published between 1980 and 2022, and the publication about FMT is increasing year by year. Co-authorship analysis shown that the USA played a key role in this field. After data analysis and visualization, a total of 57 hotspots about FMT were produced. We summarized these hotspots and classified them into 7 grades according to the number of evidence sources. The evidence sources included top 25 of Web of Science categories, top 30 most Co-cited references, top 10 clusters of references, top 25 references with the strongest citation bursts, top 25 keywords with the most occurrence frequency, major 15 clusters of keywords, top 25 keywords with the strongest citation bursts, and top 35 disease keywords.

Conclusion

This bibliometric analysis is expected to provide overall perspective for FMT. FMT has gained increasing attention and interest, there are many hotspots in this field, which may help researchers to explore new directions for future research.