Low-fat/high-fibre diet prehabilitation improves anastomotic healing via the microbiome: an experimental model.

BACKGROUND: Both obesity and the presence of collagenolytic bacterial strains (Enterococcus faecalis) can increase the risk of anastomotic leak. The aim of this study was to determine whether mice chronically fed a high-fat Western-type diet (WD) develop anastomotic leak in association with altered microbiota, and whether this can be mitigated by a short course of standard chow diet (SD; low fat/high fibre) before surgery. METHODS: Male C57BL/6 mice were assigned to either SD or an obesogenic WD for 6 weeks followed by preoperative antibiotics and colonic anastomosis. Microbiota were analysed longitudinally after operation and correlated with healing using an established anastomotic healing score. In reiterative experiments, mice fed a WD for 6 weeks were exposed to a SD for 2, 4 and 6 days before colonic surgery, and anastomotic healing and colonic microbiota analysed. RESULTS: Compared with SD-fed mice, WD-fed mice demonstrated an increased risk of anastomotic leak, with a bloom in the abundance of Enterococcus in lumen and expelled stool (65-90 per cent for WD versus 4-15 per cent for SD; P = 0·010 for lumen, P = 0·013 for stool). Microbiota of SD-fed mice, but not those fed WD, were restored to their preoperative composition after surgery. Anastomotic healing was significantly improved when WD-fed mice were exposed to a SD diet for 2 days before antibiotics and surgery (P < 0·001). CONCLUSION: The adverse effects of chronic feeding of a WD on the microbiota and anastomotic healing can be prevented by a short course of SD in mice. Surgical relevance Worldwide, enhanced recovery programmes have developed into standards of care that reduce major complications after surgery, such as surgical-site infections and anastomotic leak. A complementary effort termed prehabilitation includes preoperative approaches such as smoking cessation, exercise and dietary modification. This study investigated whether a short course of dietary prehabilitation in the form of a low-fat/high-fibre composition can reverse the adverse effect of a high-fat Western-type diet on anastomotic healing in mice. Intake of a Western-type diet had a major adverse effect on both the intestinal microbiome and anastomotic healing following colonic anastomosis in mice. This could be reversed when mice received a low-fat/high-fibre diet before operation. Taken together, these data suggest that dietary modifications before major surgery can improve surgical outcomes via their effects on the intestinal microbiome.

ANTECEDENTES: Tanto la obesidad como la presencia de cepas bacterianas colagenolíticas (Enterococcus faecalis) pueden aumentar el riesgo de fuga anastomótica. El objetivo de este estudio fue determinar si los ratones alimentados durante un tiempo prolongado con una dieta de tipo occidental con alto contenido en grasas (western type diet, WD) desarrollaban una fuga anastomótica en asociación con una microbiota alterada, así como determinar si una dieta estándar preoperatoria de corta duración baja en grasa/alta en fibra (standard diet, SD) podía mitigar la aparición de fuga. MÉTODOS: Ratones machos C57BL/6 obtenidos de Charles River fueron asignados aleatoriamente a una dieta chow estándar (SD) o a una dieta de tipo occidental obesogénica (WD) durante 6 semanas, seguida de la administración preoperatoria de antibióticos y la realización de una anastomosis en el colon. La microbiota se analizó longitudinalmente después de la operación y se correlacionó con la curación utilizando una puntuación de cicatrización anastomótica ya establecida. En experimentos repetidos, los ratones con una WD durante 6 semanas fueron expuestos a una SD durante 2, 4 y 6 días antes de la cirugía de colon, analizándose la cicatrización de la anastomosis y la microbiota del colon. RESULTADOS: Los ratones alimentados con WD en comparación con los alimentados con SD presentaron un mayor riesgo de fuga anastomótica con un rápido incremento en la abundancia de Enterococcus (65-90% para WD versus 4-15% para SD, P < 0,01). La microbiota de ratones alimentados con SD, pero no con WD, se restableció a su composición preoperatoria después de la operación. La cicatrización anastomótica mejoró significativamente cuando los ratones alimentados con WD fueron expuestos a una dieta SD durante 2 días antes del tratamiento antibiótico y de la cirugía (P < 0,01). CONCLUSIÓN: En ratones, los efectos adversos de una alimentación crónica con una WD sobre la microbiota y la cicatrización anastomótica se pueden prevenir mediante una SD de corta duración.

Novel de novo synthesized phosphate carrier compound ABA-PEG20k-Pi20 suppresses collagenase production in Enterococcus faecalis and prevents colonic anastomotic leak in an experimental model.

BACKGROUND: Previous work has demonstrated that anastomotic leak can be caused by collagenolytic bacteria such as Enterococcus faecalis via an effect on wound collagen. In humans, E. faecalis is the organism cultured most commonly from a leaking anastomosis, and is not routinely eliminated by standard oral or intravenous antibiotics. Novel strategies are needed to contain the virulence of this pathogen when present on anastomotic tissues. METHODS: Polyphosphorylated polymer ABA-PEG20k-Pi20 was tested in mice for its ability to prevent anastomotic leak caused by collagenolytic E. faecalis. The study design included a distal colonic resection and anastomosis followed by introduction of E. faecalis to anastomotic tissues via enema. Mice were assigned randomly to receive either ABA-PEG20-Pi20 or its unphosphorylated precursor ABA-PEG20k in their drinking water. The development of anastomotic leak was determined after the animals had been killed. RESULTS: Overnight incubation of two different E. faecalis collagenolytic strains with 2 mmol/l of ABA-PEG20k-Pi20 led to near complete inhibition of collagenase production (from 21 000 to 1000 and from 68 000 to 5000 units; P < 0·001; 6 samples per group) without suppressing bacterial growth. In mice drinking 1 per cent ABA-PEG20k-Pi20, the phosphate concentration in the distal colonic mucosa increased twofold and leak rates decreased from eight of 15 to three of 15 animals (P < 0·001). In mice drinking ABA-PEG20k-Pi20, the percentage of collagenolytic colonies among E. faecalis populations present at anastomotic tissue sites was decreased by 6-4800-fold (P = 0·008; 5 animals). CONCLUSION: These data indicate that oral intake of ABA-PEG20k-Pi20 may be an effective agent to contain the virulence of E. faecalis and may prevent anastomotic leak caused by this organism. Clinical relevance Progress in understanding the pathogenesis of anastomotic leak continues to point to intestinal bacteria as key causative agents. The presence of pathogens such as Enterococcus faecalis that predominate on anastomotic tissues despite antibiotic use, coupled with their ability to produce collagenase, appears to alter the process of healing that leads to leakage. Further antibiotic administration may seem logical, but carries the unwanted risk of eliminating the normal microbiome, which functions competitively to exclude and suppress the virulence of pathogens such as E. faecalis. Therefore, non-antibiotic strategies that can suppress the production of collagenase by E. faecalis without affecting its growth, or potentially normal beneficial microbiota, may have unique advantages. The findings of this study demonstrate that drinking a phosphate-based polymer can achieve the goal of preventing anastomotic leak by suppressing collagenase production in E. faecalis without affecting its growth.

Lack of evidence for tissue hypoxia as a contributing factor in anastomotic leak following colon anastomosis and segmental devascularization in rats.

PURPOSE: Current surgical dogma dictates that tissue ischemia and hypoxia are major contributing factors in anastomotic leak despite scant evidence. The aim of this study was to determine if tissue hypoxia is a feature of anastomotic leakage in rats following colon resection and segmental devascularization. METHODS: Rats were randomly assigned to undergo sham operation, segmental colon devascularization alone, colectomy alone, or segmental devascularization plus colectomy. Tissue hypoxia present at the colon anastomosis site across the various treatment groups was determined at sacrifice on postoperative day 6. Pimonidazole HCl was injected 30 min prior to sacrifice. Anastomotic tissues were examined and scored for healing versus leakage using an anastomotic healing score (AHS). Collagen content, hypoxia, enteric smooth muscle and periendothelial stromal patterning, and apoptosis were evaluated histologically. RESULTS: No differences in tissue hypoxia were noted in the 16% of anastomotic tissues with poor healing compared to the remaining 84% of rats whose anastomoses healed well. No significant changes were found in cell death in the submucosa of any group. Consistent with previous findings, poor healing was associated with lower collagen content. Submucosal thickness correlated with increased arteriole diameter (R 2 = 0.25, p < 0.005). CONCLUSIONS: These results demonstrate that tissue hypoxia is not a distinctive feature of anastomotic tissues that fail to heal and leak, even when their blood supply is interrupted. These findings suggest that compensatory factors may mitigate the effects of ischemia and hypoxia during healing of anastomotic tissues and that the process of leakage involves factors beyond their acute effects.