Pyles T

Oral Glutamine Decreases Bacterial Translocation and Improves Survival in Experimental Gut-Origin Sepsis

BACKGROUND Glutamine has been shown to be an important dietary component for the maintenance of gut metabolism. The purpose of this study was to assess the potential benefit of glutamine-enriched diets on experimental gut-derived sepsis. METHODS BALB/c mice were fed either 2% glutamine-supplemented or 1% glycine-supplemented (near-isonitrogenous control) AIN-76A diets. Control mice received either nonsupplemented AIN-76A or regular Purina Rodent Laboratory Mouse Chow 5001 diets. After 10 days of feeding, the mice were transfused with allogeneic blood (from C3H/HeJ mice), and the feeding protocols were continued for an additional 5 days. The mice then underwent gavage with 10(10) Escherichia coli labeled with either indium-111 oxine or [14C]glucose followed immediately by a 20% burn injury. Some mice were observed 10 days postburn for survival rates. Others were killed 4 hours after burn, and the mesenteric lymph nodes, liver, and spleen were harvested to determine radionuclide and bacterial colony counts. The percentages of viable translocated E coli were also calculated. RESULTS Mice fed glutamine-enriched diets had a lower degree of translocation (as measured by both radionuclide and bacterial counts) to the tissues than did the other groups and had an improvement in the ability to kill translocated E coli (as measured by the percentage of viable bacteria). Survival was significantly higher in the group fed 2% glutamine (81%) compared with the groups fed 1% glycine (36%), AIN-76A (35%), and Purina Rodent Laboratory Mouse Chow 5001 (36%) diets (p < .004). CONCLUSIONS Glutamine-supplemented enteral diets may exert important benefits in preventing gut-origin sepsis after trauma.

Arginine-supplemented diets improve survival in gut-derived sepsis and peritonitis by modulating bacterial clearance. The role of nitric oxide.

ObjectiveThe effect of arginine on survival rates and host defense mechanisms was studied using two clinically relevant models of infection that included transfusion-induced immunosuppression. Summary Background DataDietary arginine will improve resistance to infection but its role in transfusion-induced immunosuppression and bacterial transiocation (gut-derived sepsis) has not been defined. MethodsBalb/c mice were fed for 10 days with either a defined AIN-76A diet, an AIN-76A diet supplemented with 2% arginine, an AIN-76A diet supplemented with 4% glycine, or standard laboratory chow. In most experiments, the mice were then transfused with allogeneic blood and allowed to feed for an additional 5 days before undergoing either cecal Hgation and puncture (CLP) or gavage with 1010 Escherichia coli and a 20% burn injury. Additional animals fed with the arginine supplemented diet were treated with the nitric oxide inhibitor Nw-Nitro-L-arginine (NNA) before gavage and burn. The effect of these diets and NNA on the degree of translocation of 14C-radiolabeled E. coli from the intestine and the ability of the host to kill translocated organisms was also investigated. Mice were fed and received transfusion, gavage, and burn as above. Mesenteric, lymph nodes (MLN), liver and spleen were harvested 4 hours postburn. ResultsSurvival after CLP was 56% in the arginine-supplemented group versus 28% in the AIN-76A group and 20% in the chow group (p < 0.02). After gavage and burn, survival was 100% in the arginine-supplemented group versus 50% in both the glycine-supplemented and chow groups and 35% in the AIN-76A group (p < 0.01). In animals receiving the arginine-supplemented diet, treatment with NNA decreased survival from 95% to 30.5% (p < 0.0001). Greater translocation, as measured by radionuclide counts, was observed to the MLN of the AIN-76A group. However, there was no difference in translocation to the liver and spleen related to dietary group. Quantitative colony counts and the calculated percentage of remaining viable bacteria showed that the ability to kill translocated organisms was significantly enhanced in animals receiving arginine. Treatment with NNA reversed the beneficial effects of arginine on immune defense. ConclusionsThe benefit of arginine appears to be mediated by improved bactericidal mechanisms via the arginine-nitric oxide pathway.

DISTRIBUTION AND SURVIVAL OF ESCHERICHIA COLI TRANSLOCATING FROM THE INTESTINE AFTER THERMAL INJURY

The present investigation was performed to study the kinetics of tissue distribution and deposition of Escherichia coli and endotoxin translocating from the intestine after thermal injury. Escherichia coli was grown in the presence of 14C glucose and both labeled bacteria and endotoxin prepared from the labeled bacteria were used as translocation probes. Escherichia coli (10(8) to 10(10) bacteria) and E. coli endotoxin (100 micrograms per animal) were gavaged into the stomach immediately before a 30% burn injury was inflicted in mice. Animals were killed 1, 4 and 24 hours after burn injury. Translocation occurred extensively within 1 hour after burn injury. Expressed as amount of radioactivity per gram of tissue, translocation was greatest in the mesenteric lymph node (MLN) followed by spleen, lung, and liver. Translocation of endotoxin was similar to translocation of intact bacteria, with the exception that less radioactivity could be found in the peritoneal cavity and more in the liver. Both intact E. coli and endotoxin translocated directly through the intact bowel wall. Killing of bacteria was greatest in the MLN and spleen, approximating 95% to more than 99% of translocating bacteria. Killing efficiency was lowest in the lungs. It is concluded that estimation of translocation by viable bacterial counts in tissues grossly underestimates the extent of translocation of bacteria and ignores the extent of translocation of endotoxin. Translocation of endotoxin may have biologic significance that is independent of and in addition to translocation of intact bacteria.

Identification of the blood component responsible for increased susceptibility to gut-derived infection

It has previously been reported that the transfusion of allogeneic whole blood increases sepsis‐related mortality and decreases the ability of the host to kill bacteria that have translocated from the intestinal tract. To determine which blood component contributes to this adverse effect, the impact of the transfusion of white cells (WBCs), red cells (RBCs), and plasma on microbial translocation, bacteria killing, and mortality rate was studied. Blood from C3H/HeJ mice was separated into WBCs, RBCs, and plasma, and these fractions were transfused to Balb/c mice. Controls received sterile saline. Five days after transfusion, all Balb/c mice underwent a 20‐percent burn and gavage with 1 × 1010 Escherichia coli labeled with 14C‐glucose. Mortality was observed for 10 days. Four additional groups, receiving the same treatment as above, were sacrificed 4 hours after the burn, and mesenteric lymph nodes, liver, kidney, and blood were harvested aseptically. For each tissue, quantitative colony counts, radionuclide counts, and percentage of translocated bacteria that remained alive were calculated. By radionuclide counts, no difference was observed in the degree of 14C E. coli translocation among the groups. In contrast, the percentage of viable bacteria and the mortality rate were significantly higher in the group receiving allogeneic WBCs than in all other groups (p < 0.05). It is concluded that WBCs are the component in transfused blood that has an adverse effect on host resistance to gut‐derived infection.

The degree of bacterial translocation is a determinant factor for mortality after burn injury and is improved by prostaglandin analogs.

Bacterial translocation and related mortality rates were examined in previously transfused BALB/c mice that were gavaged with 14C radioisotope-labeled Escherichia coli before inflicting a 20% full-thickness flame burn. Radionuclide counts were measured in blood obtained by retro-orbital puncture 4 hours postburn, and survival was recorded for 10 days. Radionuclide counts in the blood correlated well with both radionuclide counts and numbers of viable bacterial in the tissues. Survivors had significantly less bacterial translocation as evidenced by blood radionuclide counts compared with nonsurvivors, and there was a significant inverse correlation between the degree of translocation and the length of survival. In the next experiment, the prostaglandin E (PGE) analogs misoprostol, enisoprost, or 16,16-di-methyl PGE2 were administered to transfused animals for 3 days before burn. Prostaglandin E analogs significantly reduced bacterial translocation as measured by blood radionuclide counts 4 hours postburn and improved survival. The data demonstrate that the intensity of bacterial translocation after burn injury is significantly associated with subsequent death. Improvement of survival by PGE analogs is associated with decreased bacterial translocation.

Relationship between extent of burn injury and magnitude of microbial translocation from the intestine

The gut can be a source of sepsis after thermal injury. In the present study the relationship between the extent of burn injury and magnitude of bacterial translocation was investigated. Mice underwent 0%, 10%, 20%, 30%, or 50% total body surface area full-thickness burn and simultaneous gavage with 1 x 10(10) 14C-labeled Escherichia coli. mesenteric lymph nodes, liver, spleen, peritoneal fluid, and burn wound were excised 4 hours after burn injury. Residual radioactivity and bacterial colony counts were measured, and percentages of viable organisms were calculated. Results showed that the rate of translocation of 14C E. coli increased proportionally with the burn size, reaching a maximum at 30%. The cutaneous eschar collected a remarkable amount of labeled bacteria, suggesting enteric microflora as a possible source of contamination of the burn wound via endogenous routes. The percentage of viable organisms in the tissues demonstrated that the ability of mesenteric lymph nodes, liver, and eschar to clear translocated bacteria was directly affected by the severity of the burn injury.

High protein diets are associated with increased bacterial translocation in septic guinea pigs

During sepsis, body protein stores are decreased due to an increase in protein catabolism. The utilization of nutritional support with high-protein diets has been used as a solution to the problem of sepsis-induced protein loss. Work from our laboratory, however, has shown that diets low in protein (5% of total calories) improve survival in septic animals as compared to high protein (20%) diets. The present study investigated the relationship between low-protein diets and improved survival by determining whether septic animals receiving high-protein diets have increased bacterial translocation. Sepsis was induced in guinea pigs by the implantation of an osmotic minipump into the peritoneal cavity containing an equal mixture of Escherichia coli (10(8)) and Staphylococcus aureus (10(8)) or saline. On Day 3 postlaparotomy, the animals were randomized to one of four groups. The groups consisted of septic and nonseptic animals that received a diet with 5 or 20% of total calories as protein. Following 4 days of diet all animals received an instillation of 14C labeled E. coli (10(10)). Four hours later the animals were sacrificed and blood, mesenteric lymph nodes, spleen, lungs, and liver were removed for determination of radionuclide counts. Results indicated that the septic animals that received the high protein diet had more bacterial translocation, as indexed by higher radionuclide counts in the MLN, liver, lung and blood. These findings suggest that a low protein, enterally fed diet may improve survival in septic patients by decreasing the incidence of bacterial translocation.

Translocation and survival of Bacteroides fragilis after thermal injury

B. fragilis and E. coli were labeled with tritiated (3H) thymidine, and 10(10) of each were given separately by gavage in Balb/c mice immediately before a 20% burn injury was inflicted. Control groups received gavage with 3H-B. fragilis or 3H-E. coli without burn. Four hours after burn or gavage was administered, the animals were killed, and the radionuclide and colony counts were determined in the mesenteric lymph nodes, liver, and spleen. Additional groups of mice receiving gavage (B. fragilis or E. coli) and burn were observed for 10 days to study survival. The results showed that 3H-B. fragilis translocated to a greater extent than 3H-E. coli but that fewer B. fragilis than E. coli survived in tissues. Survival was 86% for animals challenged with B. fragilis versus 53% for animals challenged with E. coli. It is concluded that in this model B. fragilis translocates extensively after burn injury and that survival is closely related to the destruction of translocated bacteria.