Effects of starvation and haemorrhage on the large bowel coliform flora with special reference to bacterial mucosal adherence and translocation

Intestinal bacteria translocating to extra-intestinal sites have been suggested to play a role in the etiology of posttraumatic infections and multiple organ failure. In the present study, effects of haemorrhagic stress and /or starvation on the gut flora and bacterial translocation were studied in the rat. Hyperosmotic glucose infusion during haemorrhage in starved rats improved plasma refill but did not reduce bacterial translocation. In this experiment four groups of rats were subjected to haemorrhage. Two groups were given an i.v. infusion of hyperosmotic glucose during moderate (38% blood loss; n=12) or severe (43% blood loss; n=19) haemorrhage without reinfusion. Control groups received an i.v. infusion of saline during moderate (n=12) or severe (n=18) haemorrhage. No difference in bacterial translocation was observed between groups infused with glucose or saline.

Starvation increased the number of coliform bacteria in caecal contents and induced adherence of coliform bacteria to caecal epithelium. Rats in a control group (n=19) were given their regular food. Six rats were starved for 24 hours and another 15 for 48 hours, with free access to water. Six rats underwent non-lethal haemorrhage (mean arterial pressure=55 mm Hg). These animals were only allowed water until sampling 24 hours later. Twenty-four hours starvation increased the number of bacteria in caecal contents 25-fold (p<0.05). 48 hours starvation further increased the number (p<0.001)and induced a marked increase in bacteria adherent to caecal epithelium (p<0.001). In the haemorrhaged group similar changes were observed and bacterial translocation increased (p<0.05) as compared to control rats.

In order to characterise and compare coliform bacteria in caecal contents, on caecal epithelium and in mesenteric Iymph nodes of 57 rats subjected to different degrees of stress a biochemical finger printing method was used. A total of 291 biochemical phenotypes were found in caecal contents of all rats. Out of these, 108 were detected on caecal epithelium and only 19 of these appeared in mesenteric Iymph nodes of the corresponding rat. A total of 36 biochemical phenotypes were found in mesenteric Iymph nodes of all rats. Twenty-one of these belonged to four common phenotypes. The prevalence of these four phenotypes in mesenteric Iymph nodes did not differ significantly, while some of them had a low and some a high prevalence in caecal contents and on caecal epithelium. The phenotypes found in mesenteric Iymph nodes were also, mostly, found adherent to the caecal epithelium of the corresponding rat.

Orally inoculated translocating strains of E. coli were able to colonise the gut. Thus, inoculation increased bacterial translocation in rats lacking these strains in their indigenous gut flora. Two groups of rats were inoculated with two translocating strains of E. coli. One group (n=l l ) was starved for 24 hours and the other (n=20)underwent non-lethal haemorrhage (mean arterial pressure=50 mm Hg) and was starved for 24 hours thereafter. Two non-inoculated groups of similar size, subjected to the same treatments served as controls. In the inoculated groups, bacterial translocation increased both after 24 hours starvation (p<0.05) and haemorrhage (p<0.01)as compared to non-inoculated control rats.

Ingestion of bulking fibre prevented mucosal adherence and translocation of a translocating strain of E. coli. Four groups of rats were inoculated with a translocating strain of E coli. Animals in a control group (n=8) were given their regular food. Eight rats were starved for 48 hours and eight given only bulking fibre for 48 hours. An additional group (n=8) ingested bulking fibre only for 24 hours before and after haemorrhage (mean arterial pressure=50 mm Hg). Bulking fibre for 48 hours reduced both mucosal adherence (p<0.05) and translocation (p<0.001) of the inoculated bacteria as compared to starved rats.

It is concluded that haemorrhagic stress and starvation have marked effects on the gut flora. Glucose infusion given during haemorrhage, previously shown to protect the animal during circulatory shock, cannot prevent bacterial translocation. Brief starvation increases the number of coliform bacteria in caecum and induces bacterial mucosal adherence. Only a limited number of strains of coliform bacteria translocate after stress. Adherence to caecal epithelium was associated with bacterial translocation. Inoculation with translocating strains of E. coli increases bacterial translocation. Bulking fibre prevents bacterial mucosal adherence and translocation. Detailed knowledge of the gut E. coli flora is of great importance when interpreting results of studies on bacterial translocation.