Systematic Review on the Influence of Tissue Oxygenation on Gut Microbiota and Anastomotic Healing.

BACKGROUND: Anastomotic leak rates have not improved over several decades despite improvements in surgical techniques and patient care. The gut microbiome has been implicated in the development of leaks. The exact mechanisms by which tissue oxygenation affects gut microbial composition and anastomotic healing physiology are unclear. Also, commonly used carbon dioxide (CO2) is a known vasodilator that improves tissue oxygen tension. We performed a systematic review to determine the influence of hyperoxia, hypoxia, and hypercapnia on the gut microbiome and anastomotic healing. METHODS: A literature search was performed in MEDLINE, EMBASE, and COCHRANE to identify studies investigating the effects of hyperoxia, hypoxia, and hypercapnia on anastomotic healing and gut microbiota published between 1998 and 2018. Two reviewers screened the articles for eligibility and quality. Fifty-three articles underwent full text review, and a narrative synthesis was undertaken. RESULTS: Hyperoxia is associated with better anastomotic healing, increased gastrointestinal oxygen tension, and may reduce gut anaerobes. Hypoxia is associated with poor healing and increased gut anaerobes. However, it is unclear if hypoxia is the most important predictor of anastomotic leaks. Low pressure CO2 pneumoperitoneum and mild systemic hypercapnia are both associated with increased gastrointestinal oxygen tension and may improve anastomotic healing. We found no studies which investigated the effect of hypercapnia on gut microbiota in the context of anastomotic healing. CONCLUSIONS: Tissue oxygenation influences gut anastomotic healing, but little evidence exists to demonstrate the influence on the gut microbiome in the context of healing. Further studies are needed to determine if anastomotic microbiome changes with altered tissue oxygenation and if this affects healing and leak rates. If confirmed, altering tissue oxygenation through hyperoxia or hypercapnia could be feasible means of altering the microbiome such that anastomotic leak rates reduce.

Evidence for Local and Systemic Immune Activation in Functional Dyspepsia and the Irritable Bowel Syndrome: A Systematic Review.

BACKGROUND: Subtle histopathologic features such as eosinophilia and increased mast cells have been observed in functional gastrointestinal disorders (FGIDs), including functional dyspepsia (FD) and the irritable bowel syndrome (IBS). The mechanisms that drive recruitment of these cells to the gastrointestinal tract remain unexplained, largely due to the heterogeneity in phenotypes among patients diagnosed with such conditions. We aimed to systematically review the literature and collate the evidence for immune activation in FD and IBS, and where possible, detail the nature of activation. METHODS: Seven literature databases were searched using the keywords: 'functional gastrointestinal disorder', FGID, 'functional dyspepsia', 'non-ulcer dyspepsia', 'idiopathic dyspepsia', 'irritable bowel syndrome', IBS and 'immun*'. RESULTS: Fifty-one papers reporting discordant immune features met the selection criteria for this review. Changes in lymphocyte populations, including B and T lymphocyte numbers and activation status were reported in IBS and FD, in conjunction with duodenal eosinophilia in FD and increased colonic mast cells in IBS. Increases in circulating α4+ß7+ gut-homing T cells appear to be linked to the pathophysiology of both FD and IBS. Studies in the area are complicated by poor phenotyping of patients into subgroups and the subtle nature of the immune activity involved in FD and IBS. CONCLUSIONS: Alterations in proportions of gut-homing T lymphocytes in both FD and IBS indicate that a loss of mucosal homeostasis may drive the symptoms of FD and IBS. There is indirect evidence that Th17 responses may play a role in FGIDs, however the evidence for a Th2 immune phenotype in FD and IBS is limited. Although immune involvement is evident, large, well-characterised patient cohorts are required to elucidate the immune mechanisms driving the development of FGIDs.

Cell-Free DNA as a Diagnostic Blood-Based Biomarker for Colorectal Cancer: A Systematic Review.

BACKGROUND: Circulating tumour DNA (ctDNA) has emerged as an excellent candidate for the future of liquid biopsies for many cancers. There has been growing interest in blood-based liquid biopsy because of the potential of ctDNA to produce a noninvasive test that can be used for: the diagnosis of colorectal cancer, monitoring therapy response, and providing information on overall prognosis. The aim of this review was to collate and explore the current evidence regarding ctDNA as a screening tool for colorectal cancer (CRC). METHODS: A systematic review of published articles in English over the past 20 y was performed using Medline, Embase, and Cochrane databases on May 23, 2017. After a full-text review, a total of 69 studies were included. Two assessment tools were used to review and compare the methodological quality of these studies. RESULTS: Among the 69 studies included, 17 studies reviewed total cfDNA, whereas six studies looked at the DNA integrity index and 15 focused on ctDNA. There were a total of 40 studies that reviewed methylated cfDNA with 19 of these focussing specifically on SEPT9. CONCLUSIONS: The results of this review indicate that methylated epigenetic ctDNA markers are perhaps the most promising candidates for a blood-based CRC-screening modality using cell-free (cf) DNA. Methylated cfDNA appears to be less specific for CRC compared to ctDNA; however, they have demonstrated good sensitivity for early-stage CRC. Further research is required to determine which methylated cfDNA markers are the most accurate when applied to large cohorts of patients. In addition, reliable comparison of results across multiple studies would benefit from standardization of methodology for DNA extraction and PCR techniques in the future.

Evaluation of a Multi-Gene Methylation Blood-Test for the Detection of Colorectal Cancer.

Circulating tumour DNA biomarkers are an expanding field in oncology research that offer great potential but are currently often limited in value by overall cost. The aim of this study was to evaluate the efficacy of a novel multi-gene methylation blood test for the identification of colorectal cancer and throughout the spectrum of colorectal disease. Participants were recruited either prior to resection for known CRC or prior to screening colonoscopy after a positive faecal immunochemical test. Blood was collected from participants prior to their procedure being performed. The plasma was separated, and multiplex MethylLight droplet digital PCR was used to analyse for the presence of four methylated genes: SDC2, NPY, IKZF1 and SEPT9. A total of 537 participants underwent analysis. The SDC2/NPY genes showed a sensitivity of 33-54% and a specificity of 72-96%, whilst the IKZF1/SEPT9 genes showed a sensitivity of 19-42% and a specificity of 88-96%. Combining the two tests did not significantly increase the test accuracy. The sensitivity for advanced adenoma was 2-15%. There was a significant difference in the frequency of detectable methylation between the participants with CRC and those without CRC. However, neither the sensitivity nor the specificity was superior to current diagnostic screening tests.

A pilot study: intraoperative 16S rRNA sequencing versus culture in predicting colorectal incisional surgical site infection.

BACKGROUND: Surgical Site Infection (SSI) of the abdominal incision is a dreaded complication following colorectal surgery. Identifying the intraoperative surgical site microbes may provide clarity in the pathogenesis of SSIs. Genomic sequencing has revolutionized the ability to identify microbes from clinical samples. Utilization of 16S rRNA amplicon sequencing to characterize the intraoperative surgical site may provide the critical information required to predict and prevent infection in colorectal surgery. METHODS: This is a pilot, prospective observational study of 50 patients undergoing elective colorectal resection. At completion of surgery, prior to skin closure, swabs were taken from the subcutaneous tissue of the abdominal incision to investigate the microbial profile. Dual swabs were taken to compare standard culture technique and 16S rRNA sequencing to establish if a microbial profile was associated with postoperative SSI. RESULTS: 8/50 patients developed an SSI, which was more likely in those undergoing open surgery (5/15 33.3% versus 3/35, 8.6%; P = 0.029). 16S rRNA amplicon sequencing was more sensitive in microbial detection compared to traditional culture. Both culture and 16S rRNA demonstrated contamination of the surgical site, predominantly with anaerobes. Culture was not statistically predictive of infection. 16S rRNA amplicon sequencing was not statistically predictive of infection, however, it demonstrated patients with an SSI had an increased biodiversity (not significant) and a greater relative abundance (not significant) of pathogens such as Bacteroidacaea and Enterobacteriaceae within the intraoperative site. CONCLUSIONS: 16S rRNA amplicon sequencing has demonstrated a potential difference in the intraoperative microbial profile of those that develop an infection. These findings require validation through powered experiments to determine the overall clinical significance.

Does postoperative inflammation or sepsis generate neutrophil extracellular traps that influence colorectal cancer progression? A systematic review.

BACKGROUND: Colorectal cancer is the third most common cancer worldwide. Almost half of those that have a potentially curative resection go on to develop metastatic disease. A recognized risk for recurrence is perioperative systemic inflammation and sepsis. Neutrophil extracellular traps have been implicated as promotors of tumor progression. We aimed to examine the evidence in the literature for an association between neutrophil extracellular traps and postoperative metastasis in colorectal cancer. MATERIALS AND METHODS: Studies published between 2000 and December 2018 that examined the role of neutrophil extracellular traps in sepsis and inflammation in colorectal cancer and in relation to tumor-related outcomes were identified through a database search of Cochrane, CINAHL, and MEDLINE. Quality and bias assessment was carried out by 2 reviewers. RESULTS: Of 8,940 screened and of the 30 studies included, 21 were observational, 5 were in vivo experimental, 1 was in vitro, and 3 used a combination of these approaches. CONCLUSION: There is clear evidence from the literature that presence of a preoperative systemic inflammatory response predicts cancer recurrence following potentially curative resection, but the evidence for association of sepsis and progression is lacking. There is robust experimental evidence in murine models showing that neutrophil extracellular traps are present in sepsis and are associated with cancer progression. Some human observational studies corroborate the prognostic significance of neutrophil extracellular traps in progression of colorectal cancer. Further human studies are needed to translate the experimental evidence and to definitively associate sepsis and neutrophil extracellular traps with poor colorectal cancer-specific outcomes.

Mobility scores as a predictor of length of stay in general surgery: a prospective cohort study.

BACKGROUND: Post-operative length of stay (LOS) is an increasingly important clinical indicator in general surgery. Despite this, no tool has been validated to predict LOS or readiness for discharge in general surgical patients. The de Morton Mobility Index (DEMMI) is a functional mobility assessment tool that has been validated in rehabilitation patient populations. In this prospective cohort study, we aimed to identify if trends in DEMMI scores were associated with discharge within 1 week and overall LOS in general surgical patients. METHODS: A total of 161 patients who underwent elective gastrointestinal resections were included. DEMMI scores were performed preoperatively, on days 1, 2, 3 and 30 post-operative. Statistical analysis was performed to identify any association between DEMMI scores and discharge within 1 week and LOS. RESULTS: Functional recovery (measured by achieving 80% of baseline DEMMI score by post-operative day 1) was significantly associated with discharge within 1 week. Presence of a stoma was associated with longer LOS. The area under the receiver operating characteristic curve using functional recovery on post-operative day 1 as a predictor of discharge within 1 week is 0.772. CONCLUSION: The DEMMI score is a fast, easy and useful tool to, on post-operative day 1, predict discharge within 1 week. The utility of this is to act as an anticipatory trigger for more proactive and efficient discharge planning in the early post-operative period, and there is potential to use the DEMMI as a comparator in clinical trials to assess functional recovery.

Synthesis and antibacterial activity of novel C12 vinyl ketolides.

A novel series of C12 vinyl erythromycin derivatives have been discovered which exhibit in vitro and in vivo potency against key respiratory pathogens. The C12 modification involves replacing the natural C12 methyl group in the erythromycin core with a vinyl group via chemical synthesis. From the C12 vinyl macrolide core, a series of C12 vinyl ketolides was prepared. Several compounds were found to be potent against macrolide-sensitive and -resistant bacteria. The C12 vinyl ketolides 6j and 6k showed a similar antimicrobial spectrum and comparable activity to the commercial ketolide telithromycin. However, the pharmacokinetic profiles of C12 vinyl ketolides 6j and 6k in rats differ from that of telithromycin by having higher lung-to-plasma ratios, larger volumes of distribution, and longer half-lives. These pharmacokinetic differences have a pharmacodynamic effect as both 6j and 6k exhibited better in vivo efficacy than telithromycin in rat lung infection models against Streptococcus pneumoniae and Haemophilus influenzae.

Synthesis and antibacterial activity of C12 des-methyl ketolides.

Synthesis of C(12) des-methyl ketolide is developed featuring an intramolecular epoxide formation/elimination process to establish the C(12) stereocenter. These ketolides are potent against several key respiratory pathogens, including erythromycin resistant erm- and mef-containing strains of Streptococcus pneumoniae.