Gram-negative Bacterial Overgrowth Research Articles

Intestinal Colonization with Enterococcus faecium Does Not Influence Pulmonary Defense against Pseudomonas aeruginosa in Mice

BackgroundEnterococci, and especially multiresistant Enterococcus faecium, are increasingly found colonizing hospitalized patients. This increased prevalence of colonization is not only associated with an increased prevalence of infections caused by enterococci, but also by infections with other nosocomial pathogens. In this study we investigated the causality of this observed relationship, by determining the influence of intestinal colonization with E. faecium on pulmonary defense against Pseudomonas aeruginosa.Methodology/Principal FindingsThree groups of mice were tested; 2 groups of mice were pre-treated with vancomycin, of which one group was subsequently treated by oral gavage of vancomycin-resistant E. faecium (VRE). The third group did not receive any pre-treatment. P. aeruginosa pneumonia was induced in all mice. Vancomycin treatment resulted in intestinal gram-negative bacterial overgrowth and VRE treatment resulted in colonization throughout the intestines. All 3 groups of mice were able to clear P. aeruginosa from the lungs and circulation, with comparable lung cytokine responses and lung damage. Mice treated with vancomycin without VRE colonization displayed modestly increased plasma levels of TNF-α and IL-10.ConclusionOvergrowth of E. faecium and/or gram-negative bacteria does not impact importantly on pulmonary defense against P. aeruginosa pneumonia.

Relationship between sepsis intensity, Gram-negative bacterial overgrowth and bacterial translocation in rats

Relationship between sepsis intensity, Gram-negative bacterial overgrowth and bacterial translocation in rats

Serial Transverse Enteroplasty Enhances Intestinal Function in a Model of Short Bowel Syndrome

OBJECTIVE/SUMMARY BACKGROUND DATA: Serial transverse enteroplasty (STEP) is a new intestinal lengthening procedure that has been shown to clinically increase bowel length. This study examined the impact of the STEP procedure upon intestinal function in a model of short bowel syndrome. Young pigs (n=10) had a reversed segment of bowel interposed to induce bowel dilatation. Five pigs underwent a 90% bowel resection with a STEP procedure on the remaining dilated bowel while 5 served as controls and had a 90% bowel resection without a STEP procedure. Determinations of nutritional status, absorptive capacity, and bacterial overgrowth were conducted 6 weeks after resection. Statistical comparisons were made by 2-sample t test (significance at P<0.05). The STEP procedure lengthened the bowel from 105.2+/-7.7 cm to 152.2+/-8.3 cm (P<0.01). The STEP animals showed improved weight retention compared with controls (mean, -0.5%+/-1.8% body weight versus -17.6%+/-1.5%, P<0.001). Intestinal carbohydrate absorption, as measured by d-Xylose absorption and fat absorptive capacity as measured by serum vitamin D and triglyceride levels, were increased in the STEP group versus controls. Serum citrulline, a marker of intestinal mucosal mass, was significantly elevated in the STEP pigs compared with controls. None of the STEP animals but 4 of 5 control animals were noted to have gram-negative bacterial overgrowth in the proximal bowel. STEP improves weight retention, nutritional status, intestinal absorptive capacity, and serum citrulline levels in a porcine short bowel model. A salutary effect upon bacterial overgrowth was also noted. These data support the use of this operation in short bowel syndrome.

Gut Decontamination Prevents Bronchoscopy-Induced Bacterial Translocation

Background: Selective gut decontamination is suggested to suppress the gram-negative bacterial overgrowth in the intestine and consequently to reduce bacterial translocation. Objective: The purpose of the present study is to examine the effects of gut decontamination on bronchoscopy-induced bacterial translocation, and intestinal mucosal injury. Methods: Forty-five rats were assigned into three groups. Group 1 served as control (n = 15). Group 2 (n = 15) and group 3 (n = 15) underwent bronchoscopy. In addition, group 3 underwent gut decontamination. Gut decontamination was performed two days prior to bronchoscopy with erythromycin and neomycin. Twenty-four hours after bronchoscopy, blood, mesenteric lymph nodes, spleen, liver, ileum and cecum were harvested for bacterial determination. The ileum was also assessed and graded histologically according to Chiu’s injury scale. Results: In the bronchoscopy group, bacterial translocation to the mesenteric lymph nodes was found in 7/15 rats (46.7%), compared to none of the controls (p = 0.01). These rats also showed significant evidence of intestinal injury, compared to the controls (mean ranks, 32.7 or 8.5, p < 0.0001). On the other hand, gut decontamination prevented bacterial translocation, compared to the bronchoscopy group (p = 0.011). However, gut decontamination provided no beneficial effect on the intestinal mucosal injury, compared to the bronchoscopy group. These animals also revealed significant intestinal injury, compared to the controls (mean ranks, 27.8 or 8.5, p < 0.0001). Conclusions: Our data shows that despite no amelioration in bronchoscopy-induced intestinal mucosal injury, gut decontamination has a preventive role for bronchoscopy-induced bacterial translocation.

Role of acid suppressants in intensive care medicine

Bleeding from stress-induced mucosal lesions continues to be a potential problem in critically ill patients, although its incidence has decreased dramatically over the past decade. Patients considered to be at risk are those with respiratory failure, coagulopathy, severe burns or tetraplegia. The most important cause of stress ulcer bleeding is tissue hypoxia. Provided that appropriate dosage regimens are administered, all agents approved for stress ulcer prophylaxis may reduce the incidence of overt as well as clinically important bleeding. However, the efficacy of stress ulcer prophylaxis does not correlate with the efficacy of gastric acid inhibition. Although numerous studies have demonstrated that an alkaline gastric juice is associated with gastric Gram-negative bacterial overgrowth, controversy remains over whether the pharmacological suppression of gastric acid in critically ill patients facilitates nosocomial pneumonia. The reasons for these divergent results are discussed, as is a possible association between gastric acid suppression and other systemic infections. Finally, several cost-effectiveness analyses performed over recent years have demonstrated that, in properly selected critically ill patients, stress ulcer prophylaxis is cost-effective.

Pentoxifylline and thalidomide fail to reduce hepatic steatosis during total parenteral nutrition and bowel rest in the rat.

We suggested that the continuous translocation of endotoxin from Gram-negative bacterial overgrowth during bowel rest and total parenteral nutrition (TPN) causes the release of tumor necrosis factor (TNF), resulting in liver damage and hepatic dysfunction. Because TPN-induced hepatic steatosis was significantly reduced by the monoclonal antibodies against TNF, we attempted a more clinically applicable approach using pentoxifylline and thalidomide. A control group (group I) fed rat chow and four groups of rats receiving TPN were studied. Group II received TPN only; group III, TPN and 100 mg/kg/d pentoxifylline; group IV, TPN and 200 mg/kg/d pentoxifylline; and group V, TPN and 5 mg/kg/d thalidomide. On day 7, total liver fat was determined. Bowel rest and TPN resulted in a significant (p < .0005) increase in liver fat content that was unaltered by either pentoxifylline or thalidomide. Our results show no role for pentoxifylline or thalidomide in reducing TPN-associated hepatic steatosis.

Comparison of the immediate, residual, and cumulative antibacterial effects of Novaderm R, Novascrub R, Betadine Surgical Scrub, Hibiclens, and liquid soap

Background: Triclosan (Irgasan), an antibacterial active against staphylococci and coliform bacteria, has been formulated for use as a handwash. There has been only one previous report of the use of the glove juice test to determine the immediate, residual, and cumulative effects of a 1% triclosan-based handwash product. There have been no previous studies on the use of 1% triclosan combined with povidone-iodine (PI) in a handwash product. Methods: The glove juice technique was used to document and compare the immediate, 3-hour residual, and 5-day cumulative effects on the mean log 10 bacterial counts of 1% triclosan—based handwash product and 1% triclosan with 5% PI. A standardized surgical handwashing technique was used before sample collection. These results and the identity and type of the aerobic bacteria cultured from the samples were compared with the results of standardized washing and glove juice sampling with 4% weight/volume chlorhexidine gluconate (CHG), 7.5% PI, and a nonantimicrobial liquid soap. Results: All five tested products showed significant log 10 reduction from baseline on day 1, hour 0 ( p < 0.05). There was no significant difference between the mean log 10 bacterial count when 7.5% PI, 4% CHG, and 1% triclosan with 5% PI were compared with each other immediately after washing ( p > 0.05). There was a significant difference between 1% triclosan and the liquid soap when they were each compared with 4% CHG, 7.5% PI, and 1% triclosan with 5% PI. There was no statistically significant difference between the 1% triclosan product and the liquid soap ( p > 0.20). All products were effective at reducing the immediate bacterial count from the baseline level. All formulations except the liquid soap showed significant cumulative effect ( p < 0.05) after multiple washes, with no significant difference between the cumulative effects of the liquid soap and 1% triclosan ( p > 0.05). Both products differed significantly ( p < 0.05) from the CHG, PI, and triclosan with PI. CHG, PI, and triclosan with PI showed effects significantly different from each other ( p < 0.05). Conclusions: Triclosan combined with PI resulted in the prevention of bacterial regrowth at 3 hours such as occurred when PI alone was used. Triclosan-containing products have a small cumulative effect, although not as great as that produced by CHG. The triclosan-based products did not appear to select for gram-negative bacterial overgrowth, although the study period may have been too short to detect such an effect.

Antitumor necrosis factor antibodies reduce hepatic steatosis during total parenteral nutrition and bowel rest in the rat.

In previous studies, we demonstrated the overgrowth of gram-negative bacteria in the gut and an enhanced release of tumor necrosis factor (TNF) by peritoneal macrophages, suggesting that endotoxin, TNF, or both, may act as hepatotoxins to produce hepatic steatosis during total parenteral nutrition (TPN) and bowel rest. The present study attempts to better define the role of each of these two mediators. The first part examines the LD50 for various doses of endotoxin in TPN-treated rats compared with free-feeding and free-feeding saline-infused rats. In the second part we repeatedly administered anti-TNF monoclonal antibodies to rats subjected to TPN and bowel rest. In the first set of experiments, 87 male Sabra rats were randomized into three groups: free-feeding, infused with normal saline, and infused with TPN. On day 7 of the experiment, all rats received an IV injection of endotoxin at various doses (1.5, 2.5, 5.0, 7.5, and 10 mg/kg). The LD50 in the three groups and at the various doses of lipopolysaccharide tested was determined at 24 hours postinjection. In the second set of experiments, 38 male Sabra rats were randomized into three groups: infused with normal saline and fed rat food ad libitum, infused with TPN, and infused with TPN but also receiving monoclonal antibodies against TNF. Lower endotoxin doses were required to achieve LD50 in the two IV-infused groups (2.5 to 5.0 mg/kg) compared with the free-feeding group (7.5 mg/kg) (p < .03). These findings suggest a moderate increase in susceptibility to the lethal effect of endotoxin in IV-treated rats. The total hepatic fat and triglyceride levels, which were markedly increased in TPN rats, were significantly reduced by using anti-TNF antibodies. Enhanced TNF production by peritoneal macrophages during TPN was completely eliminated by anti-TNF antibodies, probably the result of suppressed TNF production. The continuous translocation of endotoxin from gram-negative bacterial overgrowth in the gut during TPN and bowel rest results in enhanced release of TNF by macrophages. TNF causes hepatic dysfunction, portrayed in the present experimental model as hepatic steatosis. TPN-induced hepatic steatosis was significantly reduced by the administration of monoclonal antibodies against TNF-alpha.

Critical Care Pharmacotherapy

During recent years, research in critical care medicine has focused on the role of the gastrointestinal tract in the pathogenesis of multiple organ failure and nosocomial infection, and on preventive measures. Gram-negative bacterial overgrowth of the oropharynx and stomach has been proved to be a cause of nosocomial pneumonia. Topical application of antibiotics into the oropharynx and stomach, and preservation of gastric acidity have been shown to be effective prophylaxis in ventilated patients. Recent studies have demonstrated that gastric alkalinisation is no longer necessary for the prevention of stress ulcer bleeding in critically ill patients. Tissue hypoxaemia, not gastric acidity, is the underlying pathomechanism of stress ulcer bleeding. In experimental investigations, pirenzepine and sucralfate improved gastric mucosal oxygen supply. Both compounds effectively prevent bleeding without increasing gastric pH. In mechanically ventilated patients, significantly lower rates of pneumonia occur with both of these drugs compared with antacids or histamine H2-receptor antagonists. Topical antibiotics (selective digestive decontamination) are most effective in patients with alkaline gastric juice, but of only marginal clinical relevance in those with acidic gastric contents. Isoflurane, propofol and clonidine have been recently investigated for sedation of ventilated patients. Isoflurane may lead to fluoride accumulation after more than 1 day. Propofol dosage has to be increased more often after 4 to 7 days, leading to fat overload and significantly increased costs. Clonidine was highly effective in patients with 'sympathetic overshoot', e.g. those experiencing alcohol or opioid withdrawal. Wound infections are an important problem in burn patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Intestinal gram-negative bacterial overgrowth in vivo augments the in vitro response of Kupffer cells to endotoxin.

A number of disease states and therapeutic maneuvers common to surgical patients can result in changes in the intestinal flora, permitting bacterial overgrowth and translocation of bacteria to gut lymphoid tissue. It is possible that these changes in gut flora increase portal levels of several factors that are capable of altering macrophage activation state, including endotoxin, lymphokines, and eicosanoids. Since Kupffer cells are directly exposed to gut factors via the portal circulation, changes in intestinal flora may influence Kupffer cell responses. Using germfree rats, it has previously been shown that the presence of gut bacterial flora is important in inducing Kupffer cells to respond to endotoxin, and that an overgrowth of gram-negative bacteria can further augment Kupffer cell responses, supporting the above-mentioned hypothesis. The current set of experiments examines how intestinal gram-negative bacterial overgrowth in normal adult rats effects the response of Kupffer cells to septic stimuli. Kupffer cells were obtained from conventional rats with induced intestinal overgrowth with Escherichia coli C25 for 2 or 7 days. After 2 days of overgrowth, Kupffer cells were only slightly less responsive to lipopolysaccharide (LPS) than control Kupffer cells. However, after 7 days of overgrowth, when placed in coculture with normal hepatocytes, Kupffer cells were significantly more responsive to LPS (p less than 0.001), inducing a greater degree of suppression in hepatocyte protein synthesis at lower LPS concentrations. When cultured alone, Kupffer cells from these animals also produced more interleukin-1 (p less than 0.002) and prostaglandin E2 (PGE2) (p less than 0.009) in response to LPS. These results show that intestinal gram-negative bacterial overgrowth in conventional rats can have direct influences on the response of hepatic macrophages to septic stimuli, and provides further support to the hypothesis that imbalances in the intestinal flora can effect the responses of immune cells in other sites of the body.

Athlete's foot caused by pseudomonas aeruginosa

An enzymatically active pigment-producing clinical isolate of Pseudomonas aeruginosa was found to produce a diffusible antifungal product that was shown to be inhibitory to the growth of several dermatophytes, specifically, Trichophyton rubrum, Trichophyton mentagrophytes, Microsporum gypseum, and Microsporum audouini. In this study, Trichophyton rubrum was used as the test organism. The antifungal product was partially purified by Sephadex column chromatography and was found to be stable at 5°, 25°, and 37° C. Several investigators have alluded to the fact that as asymptomatic cases of dermatophytosis simplex progress to symptomatic dermatophytosis complex, the bacterial profile changes from a gram-positive bacterial ecosystem to a gram-negative bacterial overgrowth. The primary event in the pathogenesis of interdigital athlete's foot is the invasion of the horny layer by dermatophytes. This presents as a mild to moderate scaly lesion and is asymptomatic. As a result of predisposing factors, such as hyperhidrosis, occlusion by tight shoes, minute abrasions due to friction, and fungal-infected skin surfaces, dynamic overgrowth of opportunistic gram-negative bacilli prevails. As the gram-negative population increases, the recovery of dermatophytes dramatically diminishes, until a point is reached when no dermatophytes can be recovered from clinically symptomatic tinea pedis. Pseudomonas aeruginosa is inhibiting its fungal competitor Trichophyton rubrum by producing a diffusible antifungal agent into the infectious environment of the intertriginous foot lesion. Clinically, the patient is diagnosed as having tinea pedis; laboratory culture for fungus and KOH are negative, and what was a paradox just a few years ago can currently be identified and treated appropriately as gram-negative athlete's foot.