ROLE OF BACTERIAL ADHERENCE AND THE MUCUS BARRIER ON BACTERIAL TRANSLOCATION - EFFECTS OF PROTEIN-MALNUTRITION AND ENDOTOXIN IN RATS

Objective The purpose of the study was to investigate the potential re lations between mucosal bacterial adherence, intestinal mucus and muci n content, and bacterial translocation. Summary Background Data The at tachment of bacteria to mucosal surfaces is the initial event in the p athogenesis of most bacterial infections that originate at mucosal sur faces, such as the gut. The intestinal mucus layer appears to function as a defensive barrier limiting micro-organisms present in the intest inal lumen from colonizing enterocytes. Consequently, studies focusing on the biology of bacterial adherence to the intestinal mucosa likely are to be important in clarifying the pathogenesis of gut origin seps is. Methods To explore the relations between intestinal bacterial adhe rence, mucus bacterial binding, and bacterial translocation, two model s were used. One (protein malnutrition) in which profound alterations in intestinal morphology occurs in the absence of significant transloc ation and one (endotoxin challenge) in which bacterial translocation o ccurs and intestinal morphology is relatively normal. Results Protein malnutrition was not associated with bacterial translocation and measu rement of enteroadherent, mucosally associated bacterial population le vels documented that the total number of gram-negative enteric bacilli adherent to the ileum and cecum was less in the protein-malnourished rats than in the normally nourished animals (p < 0.01). Furthermore, t here was an inverse relation between the duration of protein malnutrit ion and bacterial adherence to the intestinal mucosa (r = 0.62, p < 0. 002). In contrast, after endotoxin challenge, the level of enteroadher ent bacteria was increased and bacterial translocation was observed. T he binding of Escherichia coli to immobilized ileal mucus in vitro was decreased significantly in protein-malnourished rats, whereas E. coli binding to insoluble ileal mucus was increased in the rats receiving endotoxin. Conclusions This study indicates that the adherence of bact eria to the intestinal mucosal surface is an important factor in bacte rial translocation, that intestinal mucus modulates bacterial adherenc e, and that increased levels of mucosally associated bacteria are asso ciated with a loss intestinal barrier function to bacteria.