IDEAL Phase 2a Results: Posterior Rectus Sheath Flap for Hiatal Augmentation in Complex Paraesophageal Hernias.

OBJECTIVE: To report the developmental phase results of posterior rectus sheath hiatal flap augmentation (PoRSHA), a promising surgical innovation for large and recurrent paraesophageal hernias. BACKGROUND: Durable hernia repair for large paraesophageal hernias continues to be a surgical challenge. PoRSHA addresses the challenges of current and historical approaches to complex paraesophageal hernias and demonstrates significant promise as a successful alternative approach. METHODS: Using the IDEAL framework, we outline the technical modifications made over the first 27 consecutive cases using PoRSHA. Outcomes measured included hernia recurrence on routine imaging at 6 months and 2 years, development of a postoperative abdominal wall eventration and incidence of solid food dysphagia. RESULTS: Twenty-seven patients at our single institution with type III (n=12), type IV (n=7), or recurrent (n=8) paraesophageal hernias underwent PoRSHA. Surgery was safely and successfully carried out in all cases. Stability of the technique was reached after 16 cases, resulting in 4 main repair types. At an average follow-up of 11 months, we observed no radiologic recurrences, no abdominal eventrations or hernias at the donor site, and 1 patient with occasional solid food dysphagia that resolved with dilation. CONCLUSIONS: PoRSHA can not only be safely added to conventional hiatal hernia repair with appropriate training but also demonstrates excellent short-term outcomes. While the long-term durability with 5-year follow-up is still needed, here we provide cautious optimism that PoRSHA may represent a novel solution to the long-standing high recurrence rates observed with current complex PEH repair.

Western Diet-induced Transcriptional Changes in Anastomotic Tissue Is Associated With Early Local Recurrence in a Mouse Model of Colorectal Surgery.

OBJECTIVE: To determine the timeframe and associated changes in the microenvironment that promote the development of a diet-induced local-regional recurrence in a mouse model of colorectal surgery. BACKGROUND: Postoperative recurrence and metastasis occur in up to 30% of patients undergoing attempted resection for colorectal cancer (CRC). The underlying mechanisms that drive the development of postoperative recurrences are poorly understood. Preclinical studies have demonstrated a diet and microbial-driven pathogenesis of local-regional recurrence, yet the precise mechanisms remain undefined. METHODS: BALB/C mice were fed a western diet (WD) or standard diet (SD), underwent a colon resection and anastomosis, given an Enterococcus faecalis enema on postoperative day (POD) 1, and subjected to a CT26 cancer cell enema (mimicking shed cancer cells) on POD2. Mice were sacrificed between POD3 and POD7 and cancer cell migration was tracked. Dynamic changes in gene expression of anastomotic tissue that were associated with cancer cell migration was assessed. RESULTS: Tumor cells were identified in mice fed either a SD or WD in both anastomotic and lymphatic tissue as early as on POD3. Histology demonstrated that these tumor cells were viable and replicating. In WD-fed mice, the number of tumor cells increased over the early perioperative period and was significantly higher than in mice fed a SD. Microarray analysis of anastomotic tissue found that WD-fed mice had 11 dysregulated genes associated with tumorigenesis. CONCLUSIONS: A WD promotes cancer cells to permeate a healing anastomosis and migrate into anastomotic and lymphatic tissue forming viable tumor nodules. These data offer a novel recurrence pathogenesis by which the intestinal microenvironment promotes a CRC local-regional recurrence.

The role of dietary prehabilitation on anastomotic healing.

PURPOSE OF REVIEW: As the microbiome takes center stage in biomedical research and emerging medical treatments, here we review the scientific basis and role of dietary modulation to prevent anastomotic leakage. RECENT FINDINGS: It is becoming increasingly clear that dietary habits have a profound influence on an individual's microbiome and that the microbiome plays a key and causative role in anastomotic leak etiology and pathogenesis. A review of recent studies indicates that the gut microbiome can become significantly shifted in composition, community structure and function within an extremely short time period of 2 or 3 days simply by changing one's diet. SUMMARY: From a practical standpoint to improve outcome from surgery, these observations, when paired with next generation technology, suggest that it is now possible to manipulate the microbiome of surgical patients to their advantage prior to surgery. This approach will allow surgeons to modulate the gut microbiome with the endpoint of improving the outcome from surgery. Thus a new emerging field termed 'dietary prehabilitation' is now gaining popularity and similar to smoking cessation, weight loss and exercise, may be a practical method to prevent postoperative complications including anastomotic leak.

The Role of the Gut Microbiome on the Development of Surgical Site Infections.

Despite advances in antisepsis techniques, surgical site infection remains the most common and most costly reason for hospital readmission after surgery. Wound infections are conventionally thought to be directly caused by wound contamination. However, despite strict adherence to surgical site infection prevention techniques and bundles, these infections continue to occur at high rates. The contaminant theory of surgical site infection fails to predict and explain most postoperative infections and still remains unproven. In this article we provide evidence that the process of surgical site infection development is far more complex than what can be explained by simple bacterial contamination and hosts' ability to clear the contaminating pathogen. We show a link between the intestinal microbiome and distant surgical site infections, even in the absence of intestinal barrier breach. We discuss the Trojan-horse mechanisms by which surgical wounds may become seeded by pathogens from within one's own body and the contingencies that need to be met for an infection to develop.

A Novel Nonantibiotic Gut-directed Strategy to Prevent Surgical Site Infections.

OBJECTIVE: To determine the efficacy of an orally delivered phosphate-rich polymer, Pi-PEG, to prevent surgical site infection (SSI) in a mouse model of spontaneous wound infection involving gut-derived pathogens. BACKGROUND: Evidence suggests that pathogens originating from the gut microbiota can cause postoperative infection via a process by which they silently travel inside an immune cell and contaminate a remote operative site (Trojan Horse Hypothesis). Here, we hypothesize that Pi-PEG can prevent SSIs in a novel model of postoperative SSIs in mice. METHODS: Mice were fed either a standard chow diet (high fiber/low fat, SD) or a western-type diet (low fiber/high fat, WD), and exposed to antibiotics (oral clindamycin/intraperitoneal cefoxitin). Groups of mice had Pi-PEG added to their drinking water and SSI incidence was determined. Gross clinical infections wound cultures and amplicon sequence variant analysis of the intestinal contents and wound were assessed to determine the incidence and source of the developing SSI. RESULTS: In this model, consumption of a WD and exposure to antibiotics promoted the growth of SSI pathogens in the gut and their subsequent presence in the wound. Mice subjected to this model drinking water spiked with Pi-PEG were protected against SSIs via mechanisms involving modulation of the gut-wound microbiome. CONCLUSIONS: A nonantibiotic phosphate-rich polymer, Pi-PEG, added to the drinking water of mice prevents SSIs and may represent a more sustainable approach in lieu of the current trend of greater sterility and the use of more powerful and broader antibiotic coverage.

Defining Microbiome Readiness for Surgery: Dietary Prehabilitation and Stool Biomarkers as Predictive Tools to Improve Outcome.

OBJECTIVES: Determine whether preoperative dietary prehabilitation with a low-fat, high-fiber diet reverses the impact of Western diet (WD) on the intestinal microbiota and improves postoperative survival. BACKGROUND: We have previously demonstrated that WD fed mice subjected to an otherwise recoverable surgical injury (30% hepatectomy), antibiotics, and a short period of starvation demonstrate reduced survival (29%) compared to mice fed a low-fat, high-fiber standard chow (SD) (100%). METHODS: Mice were subjected to 6 weeks of a WD and underwent dietary pre-habilitation (3 days vs 7 days) with a SD prior to exposure to antibiotics, starvation, and surgery. 16S rRNA gene sequencing was utilized to determine microbiota composition. Mass spectrometry measured short chain fatty acids and functional prediction from 16S gene amplicons were utilized to determine microbiota function. RESULTS: As early as 24 hours, dietary prehabilitation of WD mice resulted in restoration of bacterial composition of the stool microbiota, transitioning from Firmicutes dominant to Bacteroidetes dominant. However, during this early pre-habilitation (ie, 3 days), stool butyrate per microbial biomass remained low and postoperative mortality remained unchanged from WD. Microbiota function demonstrated reduced butyrate contributing taxa as potentially responsible for failed recovery. In contrast, after 7 days of prehabilitation (7DP), there was greater restoration of butyrate producing taxa and survival after surgery improved (29% vs 79% vs 100%: WD vs 7DP vs SD, P < 0.001). CONCLUSIONS: The deleterious effects of WD on the gut microbiota can be restored after 7 days of dietary prehabilitation. Moreover, stool markers may define the readiness of the microbiome to withstand the process of surgery including exposure to antibiotics and short periods of starvation.

Sepsis and the Microbiome: A Vicious Cycle.

Sepsis has been characterized as a dysregulated host response to infection, and the role of the microbiome as a key influencer of this response is emerging. Disruption of the microbiome while treating sepsis with antibiotics can itself result in immune dysregulation. Alterations in the gut microbiome resulting from sepsis and its treatment have been implicated in organ dysfunction typical of sepsis across multiple tissues including the lung, kidney, and brain. Multiple microbiota-directed interventions are currently under investigation in the setting of sepsis, including fecal transplant, the administration of dietary fiber, and the use of antibiotic scavengers that attenuate the effects of antibiotics on the gut microbiota while allowing them to concentrate at the primary sites of infection. The emerging evidence shows that the gut microbiome interacts with various elements of the septic response, and provides yet another reason to consider the judicious use of antibiotics via antibiotic stewardship programs.

Prevention of Anastomotic Leak Via Local Application of Tranexamic Acid to Target Bacterial-mediated Plasminogen Activation: A Practical Solution to a Complex Problem.

OBJECTIVE: To investigate the role of bacterial- mediated plasminogen (PLG) activation in the pathogenesis of anastomotic leak (AL) and its mitigation by tranexamic acid (TXA). BACKGROUND: AL is the most feared complication of colorectal resections. The pathobiology of AL in the setting of a technically optimal procedure involves excessive submucosal collagen degradation by resident microbes. We hypothesized that activation of the host PLG system by pathogens is a central and targetable pathway in AL. METHODS: We employed kinetic analysis of binding and activation of human PLG by microbes known to cause AL, and collagen degradation assays to test the impact of PLG on bacterial collagenolysis. Further, we measured the ability of the antifibrinolytic drug TXA to inhibit this process. Finally, using mouse models of pathogen-induced AL, we locally applied TXA via enema and measured its ability to prevent a clinically relevant AL. RESULTS: PLG is deposited rapidly and specifically at the site of colorectal anastomoses. TXA inhibited PLG activation and downstream collagenolysis by pathogens known to have a causal role in AL. TXA enema reduced collagenolytic bacteria counts and PLG deposition at anastomotic sites. Postoperative PLG inhibition with TXA enema prevented clinically and pathologically apparent pathogen-mediated AL in mice. CONCLUSIONS: Bacterial activation of host PLG is central to collagenolysis and pathogen-mediated AL. TXA inhibits this process both in vitro and in vivo. TXA enema represents a promising method to prevent AL in high-risk sites such as the colorectal anastomoses.

Western Diet Promotes Intestinal Colonization by Collagenolytic Microbes and Promotes Tumor Formation After Colorectal Surgery.

BACKGROUND & AIMS: The Western diet, which is high in fat, is a modifiable risk factor for colorectal recurrence after curative resection. We investigated the mechanisms by which the Western diet promotes tumor recurrence, including changes in the microbiome, in mice that underwent colorectal resection. METHODS: BALB/c male mice were fed either standard chow diet or Western-type diet (characterized by high fat, no fiber, and decreased minerals and vitamins) for 4 weeks; some mice were given antibiotics or ABA-PEG20k-Pi20 (Pi-PEG), which inhibits collagenase production by bacteria, but not bacterial growth, in drinking water. Colorectal resections and anastomoses were then performed. The first day after surgery, mice were given enemas containing a collagenolytic rodent-derived strain of Enterococcus faecalis (strain E2), and on the second day they were given mouse colon carcinoma cells (CT26). Twenty-one days later, distal colons were removed, and colon contents (feces, distal colon, and tumor) were collected. Colon tissues were analyzed by histology for the presence of collagenolytic colonies and by 16S ribosomal RNA sequencing, which determined the anatomic distribution of E faecalis at the site of the anastomosis and within tumors using in situ hybridization. Mouse imaging analyses were used to identify metastases. RESULTS: Colorectal tumors were found in 88% of mice fed the Western diet and given antibiotics, surgery, and E faecalis compared with only 30% of mice fed the standard diet followed by the same procedures. Colon tumor formation correlated with the presence of collagenolytic E faecalis and Proteus mirabilis. Antibiotics eliminated collagenolytic E faecalis and P mirabilis but did not reduce tumor formation. However, antibiotics promoted emergence of Candida parapsilosis, a collagenase-producing microorganism. Administration of a Pi-PEG reduced tumor formation and maintained diversity of the colon microbiome. CONCLUSIONS: We identified a mechanisms by which diet and antibiotic use can promote tumorigenesis by colon cancer cells at the anastomosis after colorectal surgery. Strategies to prevent emergence of these microbe communities or their enzymatic activities might be used to reduce the risk of tumor recurrence in patients undergoing colorectal cancer surgery.

Patient Acceptance of Routine Serial Postoperative Endoscopy Following Low Anterior Resection (LAR) and Its Ability to Detect Biomarkers in Anastomotic Lavage Fluid.

BACKGROUND: Various reports have now established that postoperative endoscopy to examine and intervene in the process of anastomotic healing is both feasible and safe. Here we present our preliminary experience with serial postoperative endoscopy to determine its feasibility, patient acceptance and the ability to obtain and the utility of perianastomotic material for molecular analysis. METHODS: Patients undergoing LAR with ileostomy for rectal cancer were recruited for study to undergo routine serial endoscopic surveillance (SES) at three time points during the course of LAR: intraoperatively, before discharge (postoperative day 3-7) and at follow-up (postoperative day 10-28). At each endoscopy, images were captured, anastomotic tissues were lavaged and lavage fluid was retrieved. Fluid samples were analyzed using proteomics, zymography, ELISA and bacteria via 16S rRNA gene amplicon sequencing and culture of collagenolytic strains. RESULTS: SES is feasible and acceptable to this limited set of patients following LAR. Biologic analysis of perianastomotic fluids was able to detect the presence of proteins, microbiota and inflammatory mediators previously identified at anastomotic sites in animals with pathologic healing. CONCLUSION: SES can be implemented in patients undergoing LAR with a high degree of patient compliance and capture of biologic information and imaging. Application of this approach has the potential to uncover, for the first time, the natural history of normal versus pathologic anastomotic healing in patients undergoing anastomotic surgery.

Influence of the Microbiome on Anastomotic Leak.

Despite advances in surgical technique and the expanded use of antibiotics, anastomotic leak remains a dreaded complication leading to increased hospital length of stay, morbidity, mortality, and cost. Data continues to grow addressing the importance of a functional and diverse colonic microbiome to ensure adequate healing. Individual pathogens, such as Enterococcus faecalis and Pseudomonas aeruginosa , have been implicated in the pathogenesis of anastomotic leak. Yet how these pathogens proliferate remains unclear. It is possible that decreased microbial diversity promotes a shift to a pathologic phenotype among the remaining microbiota which may lead to anastomotic breakdown. As the microbiome is highly influenced by diet, antibiotic use, the stress of surgery, and opioid use, these factors may be modifiable at various phases of the surgical process. A large amount of data remains unknown about the composition and behavior of the "normal" gut microbiome as compared with an altered community. Therefore, targeting the gut microbiome as a modifiable factor in anastomotic healing may represent a novel strategy for the prevention of anastomotic leak.

Can the Cecal Ligation and Puncture Model Be Repurposed To Better Inform Therapy in Human Sepsis?

A recent report by the National Institutes of Health on sepsis research has implied there is a trend to move away from mouse models of sepsis. The most commonly used animal model to study the pathogenesis of human sepsis is cecal ligation and puncture (CLP) in mice. The model has been the mainstay of sepsis research for decades and continues to be considered the gold standard to inform novel pathways of sepsis physiology and its therapeutic direction. As there have been many criticisms of the model, particularly regarding its relevance to human disease, how this model might be repurposed to be more reflective of the human condition begs discussion. In this piece, we compare and contrast the mouse microbiome of the CLP model to the emerging science of the microbiome of human sepsis and discuss the relevance for mice to harbor the specific pathogens present in the human microbiome during sepsis, as well as an underlying disease process to mimic the characteristics of those patients with undesirable outcomes. How to repurpose this model to incorporate these "human factors" is discussed in detail and suggestions offered.

Enterococcus faecalis exploits the human fibrinolytic system to drive excess collagenolysis: implications in gut healing and identification of druggable targets.

Perforations, anastomotic leak, and subsequent intra-abdominal sepsis are among the most common and feared complications of invasive interventions in the colon and remaining intestinal tract. During physiological healing, tissue protease activity is finely orchestrated to maintain the strength and integrity of the submucosa collagen layer in the wound. We (Shogan, BD et al. Sci Trans Med 7: 286ra68, 2015.) have previously demonstrated in both mice and humans that the commensal microbe Enterococcus faecalis selectively colonizes wounded colonic tissues and disrupts the healing process by amplifying collagenolytic matrix-metalloprotease activity toward excessive degradation. Here, we demonstrate for the first time, to our knowledge, a novel collagenolytic virulence mechanism by which E. faecalis is able to bind and locally activate the human fibrinolytic protease plasminogen (PLG), a protein present in high concentrations in healing colonic tissue. E. faecalis-mediated PLG activation leads to supraphysiological collagen degradation; in this study, we demonstrate this concept both in vitro and in vivo. This pathoadaptive response can be mitigated with the PLG inhibitor tranexamic acid (TXA) in a fashion that prevents clinically significant complications in validated murine models of both E. faecalis- and Pseudomonas aeruginosa-mediated colonic perforation. TXA has a proven clinical safety record and is Food and Drug Administration approved for topical application in invasive procedures, albeit for the prevention of bleeding rather than infection. As such, the novel pharmacological effect described in this study may be translatable to clinical trials for the prevention of infectious complications in colonic healing.NEW & NOTEWORTHY This paper presents a novel mechanism for virulence in a commensal gut microbe that exploits the human fibrinolytic system and its principle protease, plasminogen. This mechanism is targetable by safe and effective nonantibiotic small molecules for the prevention of infectious complications in the healing gut.

Surgeon as Basic Bench Scientist: A Play in Three Acts.

There is an ongoing national narrative on the diminishing number of surgeons willing and able to carry out meaningful basic science research as academic surgeons. Various analyses have come to the conclusion that the pressure to be clinically productive has overshadowed individual aspirations to perform bench-level science as a practicing academic surgeon. This review challenges various aspects of this conclusion and offers a path forward to rethink our approach to basic science as performed by practicing surgeons in an academic environment.

Oral Polyphosphate Suppresses Bacterial Collagenase Production and Prevents Anastomotic Leak Due to Serratia marcescens and Pseudomonas aeruginosa.

OBJECTIVE: The objective of this study was to determine the effect of polyphosphate on intestinal bacterial collagenase production and anastomotic leak in mice undergoing colon surgery. BACKGROUND: We have previously shown that anastomotic leak can be caused by intestinal pathogens that produce collagenase. Because bacteria harbor sensory systems to detect the extracellular concentration of phosphate which controls their virulence, we tested whether local phosphate administration in the form of polyphosphate could attenuate pathogen virulence and prevent leak without affecting bacterial growth. METHODS: Groups of mice underwent a colorectal anastomosis which was then exposed to collagenolytic strains of either Serratia marcescens or Pseudomonas aeruginosa via enema. Mice were then randomly assigned to drink water or water supplemented with a 6-mer of polyphosphate (PPi-6). All mice were sacrificed on postoperative day 10 and anastomoses assessed for leakage, the presence of collagenolytic bacteria, and anastomotic PPi-6 concentration. RESULTS: PPi-6 markedly attenuated collagenase and biofilm production, and also swimming and swarming motility in both S. marcescens and P. aeruginosa while supporting their normal growth. Mice drinking PPi-6 demonstrated increased levels of PPi-6 and decreased colonization of S. marcescens and P. aeruginosa, and collagenase activity at anastomotic tissues. PPi-6 prevented anastomotic abscess formation and leak in mice after anastomotic exposure to S. marcescens and P. aeruginosa. CONCLUSIONS: Polyphosphate administration may be an alternative approach to prevent anastomotic leak induced by collagenolytic bacteria with the advantage of preserving the intestinal microbiome and its colonization resistance.

Can Methicillin-resistant Staphylococcus aureus Silently Travel From the Gut to the Wound and Cause Postoperative Infection? Modeling the "Trojan Horse Hypothesis".

OBJECTIVE: To determine whether intestinal colonization with methicillin-resistant Staphylococcus aureus (MRSA) can be the source of surgical site infections (SSIs). BACKGROUND: We hypothesized that gut-derived MRSA may cause SSIs via mechanisms in which circulating immune cells scavenge MRSA from the gut, home to surgical wounds, and cause infection (Trojan Horse Hypothesis). METHODS: MRSA gut colonization was achieved by disrupting the microbiota with antibiotics, imposing a period of starvation and introducing MRSA via gavage. Next, mice were subjected to a surgical injury (30% hepatectomy) and rectus muscle injury and ischemia before skin closure. All wounds were cultured before skin closure. To control for postoperative wound contamination, reiterative experiments were performed in mice in which the closed wound was painted with live MRSA for 2 consecutive postoperative days. To rule out extracellular bacteremia as a cause of wound infection, MRSA was injected intravenously in mice subjected to rectus muscle ischemia and injury. RESULTS: All wound cultures were negative before skin closure, ruling out intraoperative contamination. Out of 40 mice, 4 (10%) developed visible abscesses. Nine mice (22.5%) had MRSA positive cultures of the rectus muscle without visible abscesses. No SSIs were observed in mice injected intravenously with MRSA. Wounds painted with MRSA after closure did not develop infections. Circulating neutrophils from mice captured by flow cytometry demonstrated MRSA in their cytoplasm. CONCLUSIONS: Immune cells as Trojan horses carrying gut-derived MRSA may be a plausible mechanism of SSIs in the absence of direct contamination.