Abstract
BackgroundExisting animal models provide only indirect information about the pathogenesis of infections caused by indigenous gastrointestinal microflora and the kinetics of bacterial translocation. The aim of this study was to develop a novel animal model to assess bacterial translocation and intestinal barrier function in vivo.MethodsIn anaesthetized male Wistar rats, 0.5 ml of a suspension of green fluorescent protein-transfected E. coli was administered by intraluminal injection in a model of small bowel obstruction. Animals were randomly subjected to non-ischemic or ischemic bowel obstruction. Ischemia was induced by selective clamping of the terminal mesenteric vessels feeding the obstructed bowel loop. Time intervals necessary for translocation of E. coli into the submucosal stroma and the muscularis propria was assessed using intravital microscopy.ResultsBacterial translocation into the submucosa and muscularis propria took a mean of 36 ± 8 min and 80 ± 10 min, respectively, in small bowel obstruction. Intestinal ischemia significantly accelerated bacterial translocation into the submucosa (11 ± 5 min, p < 0.0001) and muscularis (66 ± 7 min; p = 0.004). Green fluorescent protein-transfected E. coli were visible in frozen sections of small bowel, mesentery, liver and spleen taken two hours after E. coli administration.ConclusionsIntravital microscopy of fluorescent bacteria is a novel approach to study bacterial translocation in vivo. We have applied this technique to define minimal bacterial transit time as a functional parameter of intestinal barrier function.
Highlights
Existing animal models provide only indirect information about the pathogenesis of infections caused by indigenous gastrointestinal microflora and the kinetics of bacterial translocation
green fluorescent protein (GFP)-uv E. coli were detected as single fluorescent rods or small clusters of bacteria in the submucosal stroma and, subsequently, in the muscularis propria of the small bowel wall using serosa sided intravital microscopy
Transit time of bacterial translocation During non-ischemic obstruction bacterial translocation into the submucosa and muscularis propria took a mean of 36 ± 8 min and 80 ± 10 min, respectively (Figure 2)
Summary
Existing animal models provide only indirect information about the pathogenesis of infections caused by indigenous gastrointestinal microflora and the kinetics of bacterial translocation. The aim of this study was to develop a novel animal model to assess bacterial translocation and intestinal barrier function in vivo. Bacterial translocation has been defined as the passage of viable bacteria from the gut lumen to extraintestinal organs [1]. Intestinal barrier disorders have been studied in a modified Ussing chamber in vitro [9]. Markers, such as inulin-fluorescein [10] or polyethylene-glycol 4000 [11], fluorescent microspheres [12] or plasmid-labelled bacteria [13] are used to study mucosal permeability in vivo. Gut obstruction and ischemia are severe and often fatal conditions in patients that can result in sepsis and multiple organ failure [14,15]. Obstruction [16,17] and ischemia [18,19] cause mucosal injury with a subsequent increase of mucosal permeability and bacterial translocation
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