Brad A. Feltis

Clostridium difficile toxins A and B can alter epithelial permeability and promote bacterial paracellular migration through HT-29 enterocytes.

Clostridium difficile toxins A and B are the widely recognized etiologic agents of antibiotic-associated diseases ranging from diarrhea to pseudomembranous colitis. We hypothesized that C. difficile toxins may alter intestinal epithelial permeability and facilitate bacterial penetration of the intestinal epithelial barrier. Experiments were designed to clarify the effects of C. difficile toxins A and B on the flux of inert particles across HT-29 enterocyte monolayers, and to correlate these results with bacteria-enterocyte interactions. In all experiments, mature, confluent HT-29 cultures were preincubated 16 h with toxin A or B (1-100 ng/mL). To study alterations in epithelial permeability, toxin-treated enterocytes were incubated with 5 pM solutions of 10- and 40-kD inert dextran particles. Toxin A, but not toxin B, was associated with increased dextran flux through enterocyte monolayers. To study bacteria-enterocyte interactions, toxin-treated enterocytes were incubated with 10(8) Salmonella typhimurium, Proteus mirabilis, or Escherichia coli. Although numbers of internalized bacteria were generally unaffected, both toxins were associated with increased bacterial adherence, as well as increased bacterial transmigration through enterocyte monolayers. Bacterial transmigration was significantly greater using toxin A- compared to toxin B-treated enterocytes, consistent with the observation that dextran flux was significantly greater using toxin A- compared to toxin B-treated enterocytes. Thus intestinal colonization with toxigenic C. difficile may facilitate bacterial penetration of the intestinal epithelium by a mechanism involving increased permeability of the intestinal epithelial barrier.

Does microbial translocation play a role in critical illness

Available data document that translocation of enteric microbes is a normal process, occurring at low background levels in normal humans and in laboratory animals, and increasing in certain clinical conditions. There is likely no one common mechanism facilitating systemic infection with enteric flora; rather, systemic infection depends on the extent to which the host experiences enteric overgrowth, increased intestinal permeability, and/or immunosuppression. Thus, systemic infection results from these three factors, acting alone or in concert, to overwhelm the host’s ability to eliminate translocating microbes. Although the existence of microbial translocation is well documented in humans and experimental animals, the clinical significance of this phenomenon has been the subject of intense debate. Data from recent clinical studies support the hypothesis that the translocation of enteric flora is clinically significant and predisposes to infectious complications, possibly including multiple organ failure.

Attenuated Salmonella typhimurium prevents the establishment of unresectable hepatic metastases and improves survival in a murine model

PURPOSE The authors investigated the utility of attenuated Salmonella typhimurium for preventing the establishment of hepatic metastases in a murine model. METHODS A single, oral 10(8) cfu dose of attenuated S typhimurium was given 8 days before the establishment of a model of unresectable hepatic metastases. Animals were assessed for hepatic tumor number and volume, hepatic lymphocyte population analysis, and survival. RESULTS Pretreatment with Salmonella provided a 10-fold reduction in hepatic tumor burden compared with saline-treated controls. The antitumor effect is associated with markedly elevated natural killer (NK), CD8+ and CD4+ hepatic lymphocytes. Pretreatment with Salmonella provided a 90-day survival rate of 30%, whereas control animals were dead by 30 days. All long-term survivors were devoid of hepatic tumor. CONCLUSIONS Attenuated S typhimurium effectively prevents the establishment of hepatic metastases in a murine model, providing a clear survival benefit. Thus, it may represent a novel form of in vivo immunotherapy for the prevention of hepatic metastases for patients with locally advanced colorectal cancer.

Cyclooxygenase-2 Inhibition Augments the Hepatic Antitumor Effect of Oral Salmonella Typhimurium in a Model of Mouse Metastatic Colon Cancer

AbstractINTRODUCTION: Oral inoculation with a nontoxic, attenuated strain of Salmonella typhimurium reduces tumor burden and improves survival in a mouse model of metastatic colon cancer. These effects are likely mediated by S. typhimurium-induced increases in hepatic natural killer leukocytes. Cyclooxygenase-2 inhibitors may mediate antitumor effects through antiangiogenic, immune, or proapoptotic pathways. We hypothesized that cyclooxygenase-2 inhibitors would act synergistically with S. typhimurium, resulting in additional antitumor effects. METHODS: Four groups of mice were studied: control, S. typhimurium alone, cyclooxygenase-2 inhibitor alone, and S. typhimurium plus cyclooxygenase-2 inhibitor. Mice were given normal drinking water (control, S. typhimurium alone) or water with 1,600 parts per million cyclooxygenase-2 inhibitor (cyclooxygenase-2 inhibitor alone, and S. typhimurium plus cyclooxygenase-2 inhibitor) and orally inoculated with saline (control, cyclooxygenase-2 inhibitor alone) or 109 S. typhimurium (S. typhimurium alone, S. typhimurium plus cyclooxygenase-2 inhibitor). Twenty-four hours later, all mice underwent laparotomy, and 5 × 104 MCA38 murine adenocarcinoma cells were injected into the spleen. On Day 14, hepatic tumor number and tumor volume was quantitated and hepatic leukocytes were analyzed by flow cytometry. RESULTS: Compared with control mice orally inoculated with saline, S. typhimurium-treated mice had fewer and smaller tumors; mice treated with cyclooxygenase-2 inhibitor alone had tumor burden similar to control mice, and mice treated with S. typhimurium plus cyclooxygenase-2 inhibitor had fewer and smaller tumors compared with all other groups. Increased liver natural killer cells and decreased CD4+ and CD8+ T cells were observed in both S. typhimurium-treated groups. No alterations in hepatic leukocyte phenotype were observed in mice receiving cyclooxygenase-2 inhibitor alone. CONCLUSION: Oral cyclooxygenase-2 inhibitor appeared to act synergistically with S. typhimurium to reduce tumor burden. This combination therapy may have clinical application in the treatment or prevention of hepatic metastases associated with colorectal cancer.

Bacterial translocation and lipopolysaccharide-induced mortality in genetically macrophage-deficient op/op mice.

Genetically macrophage-deficient op/op mice have a total absence of macrophage colony-stimulating factor (also known as colony-stimulating factor 1 or CSF−1), and therefore an absence of a population of macrophages dependent on CSF−1. op/op mice also have profound secondary deficiencies in certain cytokines secreted by this macrophage population, such as tumor necrosis factor, interleukin−1, and granulocyte colony-stimulating factor. In the present study, op/op mice were used to clarify the role of the macrophage in two clinical processes: (a) bacterial translocation in response to antibiotic-induced intestinal overgrowth, and (b) endotoxin-induced bacterial translocation, morbidity, and mortality. The results were unexpected, in that bacterial translocation and endotoxin-induced morbidity and mortality were similar in op/op mice and their functionally normal littermates. These data indicated either that a specific macrophage population and its cytokines (including tumor necrosis factor and interleukin 1) might not play pivotal roles in the pathogenesis of bacterial translocation and endotoxin-induced septic shock, or alternatively, as yet unknown redundancies in vivo might compensate for the genetic deficiencies associated with the op/op mutation.

Mycotic aneurysm of the descending thoracic aorta caused by Pseudomonas aeruginosa in a solid organ transplant recipient: case report and review.

BACKGROUND Pseudomonas aeruginosa is a rare cause of aortic mycotic aneurysms. Optimal treatment, including reconstructive graft material and appropriate length of antibiotic therapy, is being debated. METHODS We describe a 26-year-old kidney-pancreas recipient who developed an aneurysm of the descending thoracic aorta caused by P. aeruginosa. RESULTS After surgical debridement and cryopreserved allograft reconstruction, parenteral antibiotics were continued for 12 months, at which time the patient was converted to oral antibiotic therapy. Within 6 months, he redeveloped a thoracic aortic aneurysm, necessitating reoperation and lifelong parenteral antibiotic therapy. CONCLUSION Herein we review and discuss the relevant literature concerning surgical and antibiotic treatment of mycotic thoracic aneurysms.

Transanal wading pool suction-drain injury resulting in complete evisceration of the small intestine: case report and review of the literature

Suction evisceration from a pool drain is a rare injury. This child presented with what appeared to be isolated perineal trauma. Ultimately, the patient was found to have complete transanal small bowel evisceration. Reported herein are the specifics of this case, along with a review of the relevant literature relating to this case.