The role of interdigestive small bowel motility in the regulation of gut microflora, bacterial overgrowth, and bacterial translocation in rats.

OBJECTIVE: To clarify the role of the migrating motor complex (MMC) in the regulation of small intestinal microflora and bacterial translocation. SUMMARY BACKGROUND DATA: The intestinal microflora may serve as a source of infectious microorganisms. Failure of regulatory mechanisms of the intestinal flora could therefore play an important role in the pathogenesis of gut-derived infections. METHODS: Rats were fitted with small intestinal myoelectrodes. MMCs were measured on a control day and 3 consecutive days during continuous administration of morphine or placebo. Mesenteric lymph nodes, liver, spleen, peripheral blood, duodenum, and ileum samples were cultured quantitatively. RESULTS: The mean MMC cycle length in placebo-treated animals was 15.1+/-0.5 minutes. MMCs were completely disrupted after morphine treatment. Total bacterial growth in the duodenum was 7.27+/-0.34 10log colony-forming units (CFU)/g with placebo and 8.28+/-0.27 CFU/g with morphine. In placebo-treated animals, the mean MMC cycle length the day before culturing correlated with total bacterial growth in the duodenum. Translocation incidences to the mesenteric lymph nodes, liver, spleen, and blood were 0/8, 1/8, 0/8, and 0/8 with placebo and 7/8, 6/8, 5/8, and 0/8 with morphine. The overall translocation incidence was 1/8 in placebo-treated animals and 8/8 in morphine-treated animals. CONCLUSIONS: The MMC is an important mechanism controlling bacterial growth in the upper small bowel. Its disruption with morphine promotes duodenal bacterial overgrowth and bacterial translocation.     

Effect of intraluminal antibiotics on translocation of Candida albicans in burned guinea-pigs

Guinea-pigs were pretreated orally with various antibiotics and given 3 x 10(10) Candida albicans by gastric lavage followed by a 40 per cent TBSA full skin thickness burn. The mesenteric lymph nodes, liver and spleen were cultured for the presence of viable organisms. Caecal contents were quantitatively cultured for aerobic bacteria and C. albicans. Clindamycin and penicillin G were the greatest promoters of translocation followed by the combination streptomycin/bacitracin. The mechanism for antibiotic-induced translocation is multifactorial centering on intestinal flora, anaerobic spectrum of the antibiotic and host defense as well as microbe virulence. The systemic use of broad-spectrum antibiotics, particularly those with strong anaerobic activity, should not be taken too lightly. A severely immunocompromised patient on this type of therapy may be prone to a severe fungal infection. This study reaffirms the concept that translocation from the gastrointestinal barrier is a potential source of life-threatening nosocomial infection.     

Immunosuppression and intestinal bacterial overgrowth synergistically promote bacterial translocation

Gram-negative, enteric bacilli of the indigenous gastrointestinal tract microflora translocated primarily to the mesenteric lymph nodes in mice given either oral penicillin G sodium or clindamycin hydrochloride. These bacteria also translocated to the mesenteric lymph nodes in mice injected with cyclophosphamide or prednisone. However, in mice treated with the combination of an oral antibiotic plus an immunosuppressive drug, the translocating bacteria spread systemically to the peritoneal cavity. When the treatment with clindamycin and prednisone was extended to 12 days, the mice died of lethal sepsis beginning eight days after treatment. Thus, the combination of intestinal bacterial overgrowth and host immunosuppression synergistically promoted bacterial translocation from the gastrointestinal tract that resulted in lethal sepsis.     

Small bowel transplantation promotes bacterial overgrowth and translocation

Alterations in the symbiotic relationship between immunocompromised hosts and their resident gut microflora may lead to serious complications following small bowel transplantation (SBT). This study examined the effects of SBT and cyclosporine (CsA) immunosuppression on gut bacterial populations and translocation to the mesenteric lymph nodes. Sixty adult male meat-fed Lewis rats were divided into six groups: normal controls, CsA alone (24 mg/kg im qod), CsA carrier vehicle alone, isografts, isografts given CsA, and allografts given CsA. Rats were killed after 3 weeks and segments of small bowel and colon were harvested for quantitative tissue culture. Mesenteric lymph nodes and blood were cultured to identify translocation. Transplantation alone led to an increase in gram-negative aerobes from 2.6 to 4.6 colony forming units/100 mg tissue (P less than 0.05) in the distal ileum (transplanted segment). Eighty-four percent of transplanted animals receiving CsA had bacteria recovered from their mesenteric lymph nodes compared to none in controls (P less than 0.001) and 20% in isografts not receiving CsA (P less than 0.02). Intestinal transplantation alone appears to promote gram-negative overgrowth while the addition of CsA therapy facilitates translocation to the mesenteric lymph nodes and may predispose to gut-associated sepsis following SBT.     

Effect of polymyxin B on intestinal bacterial translocation in Pseudomonas aeruginosa wound-colonized burned mice.

Bacterial translocation (BT) from the gastrointestinal tract has been proposed to play a role in the pathogenesis of septic complications in severely burned patients. In a burn model the effect of a subtherapeutic dose of polymyxin B-sulfate (PB) at BT was examined in Escherichia coli-monoassociated mice with Pseudomonas aeruginosa-inoculated burn wounds. The BT incidence and number of translocating microorganisms to the spleen (p less than 0.01), liver (p less than 0.01), lung (p less than 0.05) and heart (p less than 0.05) were diminished significantly in the PB-treated versus the untreated group. Endotoxin in plasma was detectable in one of the 16 PB-treated versus 6 of the 17 control mice (p less than 0.05). The relation of Pseudomonas burn wound inoculation, BT, endotoxin and the endotoxin-neutralizing properties of PB will be discussed.     

Effect of steroid on mitochondrial oxidative stress enzymes, intestinal microflora, and bacterial translocation in rats subjected to temporary liver inflow occlusion

Protective effects of steroids against ischemia-reperfusion (I/R) injury are well known, but there is little information about the influence of temporary inflow occlusion on intestinal barrier function or bacterial translocation. The aim of this experimental study was to investigate the effects on liver, kidney, spleen, ileal mitochondrial stress enzymes, and bacterial translocation of methylprednisolone (MP) in rats undergoing temporary liver inflow occlusion. Twenty-seven pathogen-free Wistar albino rats were randomized into three groups: group A: I/R (n = 10); group B: I/R + MP (n = 10); and group C: sham (n = 7). Rats in groups A and B were subjected to 20 minutes of portal vein and hepatic artery occlusion with 3 mg/kg MP injected into group B animals intraperitoneally during the occlusion. Twenty-two hours later, all rats were sacrificed to measure mitochondrial oxidative stress enzymes in liver, kidney, spleen, and ileum. We evaluated intestinal bacterial counts, intestinal mucosal histopathology, bacterial translocation to mesenteric lymph nodes (MLN), liver, spleen, and kidney. Decreased levels of malondialdehyde and increased levels of glutathione were observed in all examined tissues of group B compared to those of group A rats. Statistically significant increases in the intestinal counts of Klebsiella spp and Proteus spp and of bacterial translocation to liver, kidney, spleen, and MLN were measured in group B with respect to group A.     

Effect of timing of tracheostomy on changes in bacterial colonisation of the lower respiratory tract in burned children

Objective

The study aims to evaluate the impact of early and late tracheostomy on microbiological changes in the airways in severely burned children.

Materials and methods

Early tracheostomy is sometimes performed within 3 days after the start of mechanical ventilation regular microbiological surveillance of the respiratory tract was done in all patients. From each sputum, tracheobronchial aspirate and bronchoalveolar lavage (BAL), a microscopic slide was made and the material was seeded in a culture medium. The standard culture media used for the growth of respiratory pathogens are blood agar, McConkey agar, VL agar and chocolate agar. The obtained values were statistically analysed.

Results

In the observed period, a total of 68 children underwent mechanical ventilation in our department. A total of 31 (45.59%) children had undergone surgical tracheostomy (18 patients with early tracheostomy and 13 patients with late tracheostomy). The most common bacterium isolated from the lower respiratory tract in patients with early and late tracheostomy was Acinetobacter baumannii (31.53% resp. 44.30% of all bacterial strains).In patients with early tracheostomy, the ratio of G+/G− during the 6–7th day of mechanical ventilation was 1.29:1 and during the 8–10th day, 1:1.43. In patients with late tracheostomy the G+/G− ratio was 1:2.25 and during the 8–10th day, 1:2.25. There was not any statistically significant deviation in the G+/G− ratio in patients with early and late tracheostomy in any of the monitored periods.

Conclusion

The main reasons for performing early tracheostomy are: extent, localisation and depth of the burn. Difficult weaning in an uncooperative patient, failure of extubation with subsequent reintubation and other complications may be an indication for late tracheostomy.The study confirms that the use of appropriately indicated early tracheostomy provides a microbiological benefit for burned children.     

脾切除对肝大部分切除术后细菌移位的影响

目的 观察脾切除对大鼠肝大部分切除术后细菌移位的影响.方法 将SD大鼠随机分为3组:假手术组(SO组),2/3肝切除组(PHx组),肝切除加脾切除组(PHx +Sp组).85只大鼠中30只用于测定门静脉压力,55只用于分析细菌移位、血浆内毒素、血浆D-乳酸、肠组织病理学及免疫功能.结果 PHx组门静脉压力(13.34±0.64) cmH2O(1 cmH2O=0.098 kPa)显著高于SO组(7.64±0.44) cm H2O和PHx+ Sp组(10.30±0.69) cm H2O(P＜0.01).PHx组的细菌移位率高于SO组(65.00％比6.67％;P ＜0.01),也明显高于PHx+ Sp组(25.00％;P ＜0.05).大鼠血浆内毒素中位数SO组为0.00 ng/L,PHx组为4.05 ng/L,PHx +Sp组为1.47 ng/L(P ＜0.01).血浆D-乳酸在SO组和PHx+ Sp组也较PHx组低(分别为1.68、23.36、39.09 g/L,P＜0.01).结论 脾切除能降低肝大部分切除大鼠门静脉压力,增强肠黏膜屏障功能,减少内毒素和细菌移位的发生.     

Effect of starvation, malnutrition, and trauma on the gastrointestinal tract flora and bacterial translocation

We have previously shown, in an animal model, that viable indigenous bacteria will cross the intact gastrointestinal (GI) mucosa and spread systemically, a process termed bacterial translocation, if the normal bacterial ecology of the gut was sufficiently disrupted to allow bacterial overgrowth or if the animals were severely immunosuppressed. Starvation or protein malnutrition disrupts the normal indigenous GI tract microflora and impairs host antibacterial defenses. Consequently, we tested the effect of the combination of starvation or protein malnutrition plus burn trauma in promoting bacterial translocation from the GI tract. Bacterial translocation was measured by quantitatively culturing the mesenteric lymph nodes, spleens, livers, blood, and peritoneal cavities of normal or burned (30% of total body surface area) CD1 mice deprived of food for three days or fed a low-protein (0.03%) diet. The effect of starvation or protein malnutrition on the gut microflora was determined by quantitatively measuring the levels of bacteria present in the ceca. Both starvation and protein malnutrition increased the cecal levels of gram-negative enteric bacilli and decreased the levels of lactobacilli and strict anaerobes. Surprisingly, neither starvation nor protein malnutrition promoted bacterial translocation, even though these animals lost over 20% of their body weight and the ecology of the gut microflora was disrupted. In fact, the protein-malnourished animals exhibited lower incidences of bacterial translocation than normally nourished animals when both groups were monoassociated with Escherichia coli C-25 or monoassociated and burned. Thus, it appears that protein malnutrition does not promote bacterial translocation, even when combined with burn trauma.     

Effect of total parenteral nutrition plus morphine on bacterial translocation in rats.

OBJECTIVE: This study tested the hypothesis that gut stasis induced by parenteral morphine sulfate (MS) leads to enhanced bacterial translocation in rats on total parenteral nutrition (TPN). SUMMARY BACKGROUND DATA: TPN and MS are common adjuncts in the care of critically ill patients. TPN is known to provoke a variable degree of translocation. MS induces gut stasis with an accompanying bacterial overgrowth. The effect of these two treatments in combination on translocation is not known. METHODS: Rats were provided with central and subcutaneous lines for the continuous infusion of nutrients and drugs, respectively. Intestinal transit was assessed by the caudal movement of a fluorescent marker intubated into the proximal duodenum. Quantitative bacteriology was carried out from various segments of the gut and from ileocecal mesenteric lymph nodes (MLN), spleen, liver, and systemic blood obtained by cardia puncture on sacrifice at 96 hours. RESULTS: Transit was unchanged by TPN alone but prolonged when given in combination with MS. Bacterial overgrowth was also enhanced by MS and increased the bacterial translocation to MLN from 50% of animals with TPN, to 100% in those receiving both TPN and MS; the colony-forming units per MLN increased from 33 +/- 14 with TPN alone to 2079 +/- 811 (STD) with TPN plus MS. Furthermore, no bacteria were found at systemic sites with TPN alone, but in 93.3% of animals receiving TPN and MS. In a subgroup of rates provided with glutamine in TPN, the TPN plus MS effects on translocation were not reversed. CONCLUSIONS: These observations demonstrate the important role that morphine plays in promoting translocation, presumably by disrupting fasting motility and enhancing bacterial overgrowth.     

Endotoxin but not malnutrition promotes bacterial translocation of the gut flora in burned mice

Previously we have shown that under certain conditions, bacteria can pass through the intact epithelial mucosa to the mesenteric lymph nodes (MLN), liver, spleen, and bloodstream to cause infection, a process termed bacterial translocation. To extend these studies, we determined the influence of protein malnutrition and endotoxemia on bacterial translocation in burned (25% TBSA) and unburned mice. The results of these experiments documented that protein malnutrition did not promote bacterial translocation from the gut in either burned or unburned animals, although it did disrupt the normal indigenous gut flora. In contrast, a nonlethal dose of endotoxin (IP) promoted bacterial translocation to the mesenteric lymph nodes in burned and unburned mice, but only in burned mice did the bacteria translocate from the gut to other systemic organs (p less than 0.01). Furthermore, the mortality rate of mice receiving only endotoxin or burn was less than 10%, while the combination of endotoxin plus a thermal injury increased the mortality rate to 100% (p less than 0.01). These studies support the concept that bacteria may translocate from the gut to other organs and be a potential source of lethal infections after thermal injury.     

大鼠烧伤休克延迟复苏肠道微血流量的改变及其与细菌移位的关系

目的　探讨烧伤休克期延迟复苏肠道局部微循环改变及其与肠道细菌移位的关系。方法　采用大鼠烧伤休克延迟复苏模型 ,动物分为烧伤休克不复苏组、伤后 8h延迟复苏组、立即复苏组和手术对照组 ,检测肠道细菌移位发生频率、回肠末端肠壁微血流量和体循环平均动脉压变化。　结果　伤后 8h复苏组细菌移位率高达 5 4.2 % ,明显高于立即复苏组 (P <0 .0 1) ,与不复苏组相差不显著 (P >0 .0 5 ) ;延迟复苏后 4h ,肠壁微血流量虽已得到改善 ,但远未达到立即复苏组同时相的微循环血流灌注量 ,而此时外周循环的平均动脉压已恢复至正常范围。　结论　烧伤休克延迟复苏后肠道细菌移位频率居高不下 ,可能与肠壁微血流量改善滞后有关     

消化道重建术后肠道细菌移位的临床研究

目的：探讨消化道重建术后肠黏膜屏障损伤与肠道细菌移位（BT）及BT与术后全身炎症反应综合征（SIRS）的关系。方法：选择60例择期行消化道重建术的患者,于术前和术后1、3、5 d采集外周血,进行血浆二胺氧化酶及全血细菌DNA检测。全血DNA提取后进行PCR扩增,采用的靶基因为大肠杆菌特异性β半乳糖苷酶基因和16SrRNA基因。观察患者至术后10 d以监测SIRS情况。结果：术前PCR检测全血细菌DNA均为阴性,术后共有14例阳性。23例患者术后发生SIRS,其中12例患者PCR阳性。PCR阳性组SIRS发生率为85.7%（12/14）,阴性组为23.9%（11/46）（P〈0.01）。术后出现SIRS的患者PCR阳性率为52.2%（12/23）,无SIRS组为5.4%（2/37）（P〈0.01）。PCR阳性的患者血浆二胺氧化酶浓度较PCR阴性者明显升高（P〈0.01）,有SIRS的患者血浆二胺氧化酶较无SIRS患者明显升高（P〈0.01）。结论：消化道重建术后BT与肠黏膜屏障损伤密切相关,术后SIRS与BT密切相关。PCR技术可早期诊断细菌移位,对术后SIRS有较好的早期预警价值。     

选择性肠道去污染对肝硬化大鼠肝门阻断细菌移位、内毒素血症的影响

目的探讨选择性肠道去污染对肝硬化大鼠肝门阻断后肠道细菌移位、内毒素血症的效果。方法将制成肝硬化模型的60只雄性SD大鼠随机分为假手术组、肝门阻断30rain组（阻断组）及通过选择性肠道去污染预处理组（预处理组）,各20只。在实验术后30min及24h时分别取肠系膜淋巴结、肝、肺及门、腔静脉血作细菌培养,并取门、腔静脉血作内毒素检测。结果阻断组大鼠手术后30min即出现门、腔静脉血内毒素浓度升高（P〈0．01）,在手术24h后升高更明显。并在术后24h肠系膜淋巴结、肝组织及门、腔静脉血细菌培养出现阳性,主要为大肠杆菌。预处理组大鼠无论是手术30min还是24h后,门、腔静脉内毒素水平升高均不明显,较阻断组明显降低（P〈0．01）,肠道外组织及门、腔静脉血细菌培养阳性率也明显降低。结论肝硬化大鼠肝门阻断30min后早期即可出现内毒素血症,并于手术24h后出现明显肠道细菌移位。选择性肠道去污染能减少肝硬化大鼠肝门阻断后肠道细菌移位及内毒素血症的发生。     

Suppression of the human mucosal-related colonic microflora with prophylactic parenteral and/or oral antibiotics

The purpose of this investigation was to assess the effects of preoperative administration of parenteral antibiotics with or without concomitant preoperative administration of oral antibiotics on the colonie mucosal-related microflora. Thirty-one patients were studied in a prospective fashion. Group A patients (n=8) had colonoscopic mucosal biopsies performed after mechanical bowel preparation. Group B patients (n=5) received neomycin and erythromycin (NE), 1 g each following mechanical bowel preparation, at 1,2, and 11 p.m. the evening prior to either elective colon resection (n=2) or prior to colonoscopic biopsy (n=3). Emergent trauma patients who had left colon or sigmoid perforations due to gunshot wounds requiring segmental resection comprised group C (n=7). These patients received cefoxitin or cefotetan 2 g intravenously preoperatively. Individuals in group D (n=11) all had elective left hemicolectomies or sigmoid resections due to nonobstructing malignancies. These patients underwent the same regimen as group B patients in addition to receiving intravenous cefoxitin perioperatively. Quantitative and qualitative bacterial cultures as well as scanning electron microscopy (SEM) were used to study the mucosa-associated flora. Tissue for culture and SEM were obtained from the pathologic specimen immediately after removal. The interval between the dosage of parenteral antibiotics to tissue removal was 3 hours in both groups. Anaerobic and aerobic counts were suppressed the greatest in patients receiving both oral and parenteral antibiotics (p=0.0001). Mean anaerobic counts decreased from 3.4×10⁷ in group A to 1.8×10² (mean cfu/g) in group D patients. Mean aerobic counts in group A decreased from 3.7×10⁶ to 64 (mean cfu/g) in group D. This study documents the effectiveness of oral NE to suppress the mucosa-associated flora when administered preoperatively and suggests that parenteral antibiotics suppress the mucosa-associated bacteria in addition to providing therapeutic serum levels.

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Resumen El propósito de esta investigación fue el de valorar los efectos de la administración preoperatoria de antibióticos parenterales con o sin la administración concomitante de antibióticos orales sobre la microflora de la mucosa colónica. Treinta y un pacientes fueron estudiados en forma prospectiva. Los pacientes del grupo A (n=8) fueron sometidos a biopsias de la mucosa colónica después de la preparación intestinal. Los pacientes del grupo B (n=5) recibieron neomicina y eritromicina, 1 gramo de cada una (NE), después de la preparación mecánica del intestino a la 1, 2, y 11 p.m. del día anterior a la resección electiva del colon (n=2) o antes de la biopsia colonoscópica (n=3). Pacientes traumatizados, operados de urgencia por perforaciones del colon izquierdo o del sigmoide debidas a heridas por arma de fuego y que requirieron resección segmentaria conformaron el grupo C (n=7). Estos pacientes recibieron cefoxitina o cefotetan 2 gm I.V. preoperatoriamente. Los pacientes del grupo D (n=11) fueron sometidos todos a hemicolectomías izquierdas o resecciones del sigmoide por neoplasias malignas no obstructivas. Estos pacientes estuvieron bajo el mismo régimen que los del grupo B además de recibir cefoxitina intravenosa perioperatoriamente. Cultivos cuantitativos y cualitativos, así como la microscopia electrónica de barrido (MEB), fueron utilizados para el estudio de la flora de la mucosa. Tejidos para cultivo y MEB fueron obtenidos a partir de los especímenes inmediatamente después de su remoción. El intervalo entre el dosage de los antibióticos parenterales y la remoción del tejido fue de 3 horas en ambos grupos. Los conteos anaeróbicos y aeróbicos aparecieron en supresión maxima en los pacientes que recibieron antibióticos orales y parenterales (p=0.0001). Los conteos aeróbicos promedio descendieron de 3.4×10⁷ en el grupo A a 1.8×10² (promedio cfu/g) en los pacientes del grupo D. Los conteos aeróbicos promedio en el grupo A descendieron de 3.7×10⁶ a 64 en el grupo D. El presente estudio documenta la efectividad de la NE oral en la supresión de la flora de la mucosa cuando se administran preoperatoriamente y sugiere que los antibióticos parenterales suprimen las bacterias de la mucosa además de proveer nivelés séricos terapéuticos.

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Résumé Les objectifs des cette étude étaient d'évaluer les effets de l'administration préopératoire d'antibiotiques par voie parentérale avec ou sans antibiotiques par voie orale sur la microflore de la muqueuse colique. Trente et un patients ont été étudiés de façon prospective. Dans le groupe A (n=8), on a pratiqué des prélèvements de la muqueuse colique par coloscopie après préparation mécanique. Chaque patient dans le groupe B (n=5) a eu par voie orale après préparation mécanique 1 g de néomycine et 1 g d'érythromycine à 13 h, 14 h, et 23 h, la veille de l'intervention qui était soit une résection colique élective (n=2), soit une colonoscopie avec biopsies (n=3). Dans le groupe C (n=7), nous avons inclus des patients ayant eu une perforation colique par arme à feu nécessitant une résection segmentaire. Ces patients ont reçu soit 2 g de céfoxitine (FOX) soit 2 g de céfotétan, par voie intraveineuse en préopératoire. Les patients dans le groupe D (n=11) ont tous eu une hémicolectomie gauche ou une résection du côlon sigmoïde élective pour des lésions non occlusives. Ces patients ont eu la même préparation orale que ceux du groupe B associée à du FOX en périopératoire. La flore de la muqueuse a été étudiée par des cultures quantitatives et qualitatives ainsi qu'en microscopie électronique. Des tissus ont été prélevés pour mise en culture et examen au microscope électronique à partir des pièces opératoires juste après l'ablation. L'intervalle entre le dosage des antibiotiques parentéraux et le prélèvement tissulaire était de 3 heures dans chaque groupe. Les concentrations d'anaérobies et d'aérobies étaient diminuées surtout chez les patients ayant eu des antibiotiques par voies et orale et parentérale (p=0.0001). La numération moyenne de germes anaérobies a diminué de 3.4×10⁷ dans le groupe A à 1.8×10² (moyenne cfu/g) dans le groupe D. La numération moyenne des germes aérobies dans groupe A a diminué de 3.7×10⁶ à 64 [cfu (unités de formation de colonie) moyenne/G)] dans le groupe D. Cette étude démontre que l'administration préopératoire de la combinaison néomycine-érythromycine par voie orale est efficace pour supprimer la flore de la muqueuse et suggère que les antibiotiques par voie parentérale suppriment les bactéries sur la muqueuse en même temps qu'ils assurent un taux thérapeutique suffisant dans le sang.

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Presented at the Collegium Internationale Chirurgie Digestivae in Toronto, Ontario, Canada, September, 1989.     

Intestinal bacterial translocation in experimentally burned mice with wounds colonized by Pseudomonas aeruginosa.

Translocation of micro-organisms from the gastrointestinal tract may play a role in the pathogenesis of septic complications in severely burned patients. We therefore investigated the influence of burn wound infection with Pseudomonas aeruginosa on translocation in experimentally burned mice. The P. aeruginosa disseminated in 15% of the animals on the second day and in 20% of the animals on the third day postburn in the Pseudomonas-seeded group. Wound colonization with P. aeruginosa, compared with a control group, led to an increased incidence of translocation of Escherichia coli from the GI tract to the spleen (p < 0.005), liver (p < 0.03), lungs (p < 0.005), and peritoneal cavity (p < 0.03) on the second day postburn but not on the third day postburn. On both the second and third days, the number of viable E. coli in the organs in the Pseudomonas-seeded group exceeded that in the organs in the control group. In this model translocation of E. coli from the GI tract played a more important role than did hematogeneous dissemination of P. aeruginosa from the burn wound.