Intestinal translocation of clinical isolates of vancomycin-resistant Enterococcus faecalis and ESBL-producing Escherichia coli in a rat model of bacterial colonization and liver ischemia/reperfusion injury.

Karin M Van Der Heijden,Flavio H Galvao,Edson Abdala,Camila G Lopes,Luiz A D'Albuquerque,Silvia F Costa,Inneke M Van Der Heijden,Anna S Levin

doi:10.1371/journal.pone.0108453

Abstract

The objectives of this study were to develop a rat model of gastrointestinal colonization with vancomycin-resistant Enterococcus faecalis (VRE) and extended-spectrum beta-lactamase (ESBL)-producing E. coli and to evaluate intestinal translocation to blood and tissues after total and partial hepatic ischemia. Methods - We developed a model of rat colonization with VRE and ESBL-E coli. Then we studied four groups of colonized rats: Group I (with hepatic pedicle occlusion causing complete liver ischemia and intestinal stasis); Group II (with partial liver ischemia without intestinal stasis); Group III (surgical manipulation without hepatic ischemia or intestinal stasis); Group IV (anesthetized without surgical manipulation). After sacrifice, portal and systemic blood, large intestine, small intestine, spleen, liver, lungs, and cervical and mesenteric lymph nodes were cultured. Endotoxin concentrations in portal and systemic blood were determined. Results – The best inocula were: VRE: 2.4×1010 cfu and ESBL-E. coli: 1.12×1010 cfu. The best results occurred 24 hours after inoculation and antibiotic doses of 750 µg/mL of water for vancomycin and 2.1 mg/mL for ceftriaxone. There was a significantly higher proportion of positive cultures for ESBL-E. coli in the lungs in Groups I, II and III when compared with Group IV (67%; 60%; 75% and 13%, respectively; p:0.04). VRE growth was more frequent in mesenteric lymph nodes for Groups I (67%) and III (38%) than for Groups II (13%) and IV (none) (p:0.002). LPS was significantly higher in systemic blood of Group I (9.761±13.804 EU/mL−p:0.01). No differences for endotoxin occurred in portal blood. Conclusion –We developed a model of rats colonized with resistant bacteria useful to study intestinal translocation. Translocation occurred in surgical procedures with and without hepatic ischemia-reperfusion and probably occurred via the bloodstream. Translocation was probably lymphatic in the ischemia-reperfusion groups. Systemic blood endotoxin levels were higher in the group with complete hepatic ischemia.

Highlights

Bacterial translocation is a harmful complication of a large number of gastrointestinal disorders including cirrhosis, liver and intestinal ischemic injury and inflammatory bowel diseases
We identified vancomycin-resistant Enterococcus faecalis (VRE) and extended-spectrum beta-lactamase (ESBL)-E. coli by the profile of resistance
According to the pulsed-field gel electrophoresis (PFGE), VRE and ESBL-E. coli obtained from the stools of the rats were identical to the strains inoculated by gavage

Summary

Introduction

Bacterial translocation is a harmful complication of a large number of gastrointestinal disorders including cirrhosis, liver and intestinal ischemic injury and inflammatory bowel diseases.In several situations, including ischemia and reperfusion lesion, changes in the barrier function of the intestinal epithelium may predispose to increased intestinal permeability, enabling the passage of food, antigens and luminal bacteria [1,2,3,4,5].The ischemia and reperfusion lesion is characterized by a variable period of visceral ischemia with an increase of injury after revascularization [6].Liver ischemia and reperfusion may result in severe impairment of the intestinal microcirculation. Bacterial translocation is a harmful complication of a large number of gastrointestinal disorders including cirrhosis, liver and intestinal ischemic injury and inflammatory bowel diseases. In several situations, including ischemia and reperfusion lesion, changes in the barrier function of the intestinal epithelium may predispose to increased intestinal permeability, enabling the passage of food, antigens and luminal bacteria [1,2,3,4,5]. The ischemia and reperfusion lesion is characterized by a variable period of visceral ischemia with an increase of injury after revascularization [6]. Liver ischemia and reperfusion may result in severe impairment of the intestinal microcirculation. Potential sequelae are: mucosal damage, loss of intestinal barrier function, bacterial translocation, systemic inflammation, multiple organ failure and death [7]. The majority of translocated bacteria are Gram-negative and come from the normal gut flora, suggesting a breakdown of the intestinal barrier function [8,9]

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Conclusion