Infection in the compromised host

Acute myocardial infarction caused by coronary mucormycotic embolism

Described here is a rare cardiac complication attributed to mucormycosis in a 63-year-old woman who developed sudden cardiac arrest and pulmonary insufficiency in the course of being treated for acute monocytic leukemia (acute myelogenous leukemia, AML M5a). At autopsy, fresh thrombi were noted in the left pulmonary artery and the left atrium. Postmortem coronary angiography revealed complete occlusion of the circumflex branch of the left coronary artery, and histological examination showed a mucormycotic embolism in the corresponding portion. Multiple small mucormycotic thrombi were also noted in both coronary and pulmonary arteries with hemorrhagic infarction in the corresponding areas.

Gold-silver nanoshells promote wound healing from drug-resistant bacteria infection and enable monitoring via surface-enhanced Raman scattering imaging

Chronic infections, caused by multidrug-resistant (MDR) bacteria, constitute a serious problem yet often underappreciated in clinical practice. The in situ monitoring of the bacteria-infected disease is also necessary to track and verify the therapeutic effect. Herein we present a facile approach to overcome the above challenges through a Raman tag 3,3'-diethylthiatricarbocyanine iodide (DTTC)-conjugated gold-silver nanoshells (AuAgNSs). With a strong responsive of the near-infrared laser due to surface plasmon resonance (SPR) from hybrid metallic nanoshell structure, AuAgNSs exhibits an efficient photothermal effect, and it simultaneously releases silver ions during laser irradiation to bacterial eradicate. Herein, two MDR bacteria strain, methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum β-lactamase Escherichia coli, are chosen as models and studied both in vitro and in vivo. As a result, the AuAgNSs-DTTC substrates enable surface-enhanced Raman scattering imaging to provide a non-invasive and extremely high sensitive detection (down to 300 CFU mL^-1 for MRSA) and prolonged tracking (at least 8 days) of residual bacteria. In a chronic MRSA-infected wound mouse model, the AuAgNSs gel-mediated photothermal therapy/silver-release leads to a synergistic would healing with negligible toxicity or collateral damage to vital organs. These results suggest that AuAgNSs-DTTC is a promising anti-bacterial tool for clinical translation.

Infection after hand surgery

Postoperative infections are uncommon after hand surgery. Infection can delay recovery and contribute to scarring and stiffness. Measures intended to reduce the risk of infection after hand surgery include hand washing, skin preparation, sterile technique, and prophylactic antibiotics. The role of prophylactic antibiotics for small, clean, elective hand surgery procedures lasting less than 2 hours is debated.

Pharmacokinetics of E5564, a Lipopolysaccharide Antagonist, in Patients with Impaired Hepatic Function

E5564 is a structural analog of the Lipid A portion of lipopolysaccharide (LPS). E5564 has been tested in several in vitro and in vivo models and has demonstrated its effectiveness against LPS. It is intended to be an antagonist of LPS to reduce the morbidity and mortality associated with sepsis syndrome. This study assessed the pharmacokinetics (PK) of E5564 in patients with impaired hepatic function. E5564 was administered via intermittent intravenous infusion every 12 hours for six times to 24 hepatic-impaired patients (12 each to Child-Pugh Classifications A and B) and 24 matching healthy volunteers. Plasma samples were analyzed by LC/MS/MS. A one-compartment model resulted in good and comparable fits for all volunteers. Regardless of liver disease state, none of the PK parameters compared (i.e., Cmax (0-12),tmax (0-12),CL,t1/2, Vss, AUC(0-12), AUC(0-last), AUC(0-infinity), C(ss,min), C(ss,max), and C(ss,av)) exhibited any difference between these two groups. This suggested that the exposure of E5564 in volunteers was independent of hepatic function. Thus, no dose adjustment is needed in patients with hepatic impairment classified as Child-Pugh A and B.

Candiduria in renal transplant recipients: incidence, clinical repercussion, and treatment indication

INTRODUCTION

The incidence of candiduria in renal transplant recipients is unknown. In clinical practice, the indications for antifungal therapy are not well established. Furthermore, there is the problem of the choice of the antifungal drug since some of them may select resistant Candida species, or interact with immunosuppressive agents or only be used intravenously.

AIM

We sought to study the incidence, clinical repercussions and effectiveness of antifungal treatment to prevent recurrence of candiduria.

MATERIALS AND METHODS

We examined all episodes of Candida-positive urine cultures (>50,000 cfu/mL) in 996 recipients over 2 years. We considered the Candida species, administered treatment, presence of fever, requirement for hospital admission versus outpatient case, occurrence of simultaneous bacterial urinary tract infection (UTI), antibiotic use during the week before candiduria, and presence of an indwelling urinary catheter.

RESULTS

Among 996 subjects, 34 displayed 83 episodes of candiduria, yielding an accumulated incidence of 3.4% after 2 years. The frequency was higher among women (6.3% vs 1.7%, P<.001). Of the 45 outpatient episodes (54.2%), 17 were treated and one required hospitalization (5.9%). Of the 28 nontreated outpatients, two were hospitalized (7.1%, P=.68 vs treated patients). All cases of hospital admission presented simultaneous bacterial UTI, none developed candidemia, and two patients did not receive any antifungal therapy. With respect to the first episodes of each patient (n=34), 5/11 treated (45.5%) and 4/23 untreated (17.4%) patients developed recurrences (P=.095). Selection of more resistant Candida species was not observed. Fifty cases (60%) were associated with antibiotic therapy and 34 (41%) the presence of a urinary catheter.

CONCLUSIONS

It does not seem necessary to treat candiduria in this setting. Antifungal therapy was not associated with either a reduction in recurrence or the appearance of more resistant species in this study. We observed no important clinical repercussions.

Surgical inflammation: a pathophysiological rainbow

Tetrapyrrole molecules are distributed in virtually all living organisms on Earth. In mammals, tetrapyrrole end products are closely linked to oxygen metabolism. Since increasingly complex trophic functional systems for using oxygen are considered in the post-traumatic inflammatory response, it can be suggested that tetrapyrrole molecules and, particularly their derived pigments, play a key role in modulating inflammation.

In this way, the diverse colorfulness that the inflammatory response triggers during its evolution would reflect the major pathophysiological importance of these pigments in each one of its phases. Therefore, the need of exploiting this color resource could be considered for both the diagnosis and treatment of the inflammation.

The role of prophylactic antibiotics in elective hand surgery

The current literature has poorly defined the role of antibiotic agents in elective hand surgery. The reason for this may be due to a small number of well-designed studies specifically addressing the efficacy of antibiotics in hand surgery. Our purpose is to critically review the current literature in an attempt to more precisely define the role of prophylactic antibiotics in elective hand surgery.

Norepinephrine suppresses wound macrophage phagocytic efficiency through alpha- and beta-adrenoreceptor dependent pathways

BACKGROUND

The systemic response to injury is characterized by massive release of norepinephrine (NE) into the circulation as a result of global sympathetic activation. We have recently demonstrated that NE modulates the recruitment of macrophages to the cutaneous wound. We hypothesized that NE suppresses wound macrophage phagocytic function through canonical adrenergic signaling pathways.

METHODS

Murine wound macrophages were harvested at 5 days after injury and treated with physiologic and pharmacologic dose norepinephrine. Phagocytosis of green fluorescent protein-labeled Escherichia coli was assayed by flow cytometry. The signaling pathways mediating NE modulation of wound macrophage phagocytosis were interrogated by pharmacologic manipulation of alpha- and beta-adrenoreceptors (ARs), intracellular cyclic adenosine monophosphate (cAMP), and protein kinase A (PKA). Tissue specificity was determined by comparison of wound macrophages to splenic macrophages.

RESULTS

Both physiologic and pharmacologic dose NE suppressed wound macrophage phagocytic efficiency. This effect was mediated by alpha- and beta-ARs in a dose-dependent fashion. Direct stimulation of cAMP-suppressed phagocytic efficiency and blockade of PKA signaling prevented NE-mediated suppression of phagocytic efficiency. Splenic macrophage phagocytic efficiency was less than that of wound macrophages and was not altered by NE.

CONCLUSIONS

NE has a profound immunosuppressive effect on wound macrophage function that is tissue specific and appears to be mediated through adrenergic receptors and their canonical downstream signaling pathway. Attenuation of post-injury immunosuppression represents another potential mechanism by which beta-AR blockade may reduce morbidity and mortality after severe injury.

Association between commensal bacteria and opportunistic pathogens in the dental plaque of elderly individuals

Opportunistic infections in the oral cavity of the elderly may increase the incidence of systemic disease. The objective of this study was to investigate the differences in the oral bacterial flora between dependent elderly (inpatients) and independent elderly (community-dwelling residents). After multiple variables were taken into account, inpatients had significantly lower detection rates than community-dwelling residents for alpha-streptococci (p < 0.001) and Neisseria (p 0.004), and higher detection rates for Pseudomonas aeruginosa (p 0.024), methicillin-resistant Staphylococcus aureus (MRSA) (p 0.011) and Actinomyces spp. (p 0.005). Among inpatients, the requirement for a high degree of care was related negatively to detection of alpha-streptococci, but was related significantly to detection of P. aeruginosa (p 0.018) or MRSA (p 0.004). Tube-fed inpatients had a significantly lower detection rate for alpha-streptococci (p 0.041) and a higher detection rate for P. aeruginosa (p 0.004) than those who did not require tube feeding. Inpatients with a history of antibiotic use had a significantly lower detection rate for alpha-streptococci (p 0.049) and a higher detection rate for MRSA (p 0.007) than those without a history of antibiotic use. The detection rates for P. aeruginosa or MRSA in inpatients without alpha-streptococci were higher than in inpatients with alpha-streptococci after controlling for age and gender (P. aeruginosa, p 0.006; MRSA, p 0.001). Overall, detection of alpha-streptococci had an inverse correlation with the detection of P. aeruginosa and MRSA in the oral cavity and is likely to be an indicator of pathogenic bacterial infection.

Effects of octreotide acetate and Saccharomyces boulardii on bacterial translocation in an experimental intestinal loop obstruction model of rats

Intestinal obstruction (IO) induces bacterial translocation (BT) due to mucosal disruption, motility dysfunction, and increased intestinal volume, leading to bacterial overgrowth. This study was conducted to investigate the effects of octreotide acetate (OA) and Saccharomyces boulardii (SB) on the BT and intestinal integrity in an animal model of intestinal loop obstruction (LO). Forty adult male Sprague-Dawley rats (250-300 g) were randomized into 4 groups containing 10 rats each. Complete IO was created in the distal ileum of rats by a single 3-0 silk suture (LO). Group Sham: Sham (Laparotomy only was performed in this group); group LO: LO; group OA: LO plus OA (100 microg/kg, at 0, 12 hours of obstruction); group (SB): LO plus SB (800 mg/kg/day, via orogastric and preoperative for 3 days). After 24 hours, samples of mesenteric lymph nodes (MLN), liver, spleen and blood were obtained and cultured. The terminal ileum specimens were examined histopathologically. There were no BT in group Sham, but BT was noticed totally in 31 (77.5%) cultures in group LO. This rate was reduced to 30% (n = 12), 10% (n = 4) in the groups OA and SB respectively. Bacterial translocations of MLN and the liver in group LO were significantly higher than those of groups OA and SB. Bacterial translocations of the both spleen and blood in group LO were significantly higher than those of groups OA and SB. The mean bacterial counts, colony-forming units per gram tissue (cfu/g), in the MLN, liver and spleen of group LO were found significantly higher than those of groups OA and SB. The mean villus height in group OA was significantly higher than that of group LO and it in the group SB significantly higher than those of groups LO and OA. The present experimental study has demonstrated that OA and SB may have protective effects against BT in mechanical bowel obstruction and additionally SB preserves intestinal mucosal integrity.

Management of urinary tract infections and lymphocele in renal transplant recipients

The most frequent infectious complication after renal transplantation is urinary tract infection. This article deals with antimicrobial prophylaxis, treatment of early and relapsing urinary tract infections, and management of asymptomatic bacteriuria in renal transplant patients. The incidence of lymphocele after renal transplantation varies, and its treatment is still controversial. Management options are discussed.

The relationship between tumor necrosis factor (TNF)-alpha and survival following granulocyte-colony stimulating factor (G-CSF) administration in burn sepsis

Blood levels of tumor necrosis factor (TNF)-alpha were determined in 78 patients with burn sepsis. Of these patients, 51 were managed with additional administration of granulocyte colony-stimulating factor (G-CSF) in addition to routine treatment procedures (group A), while 27 received only routine treatment (group B). G-CSF was administrated for at least nine and at most 14 days; doses were gradually decreased in each 3 day period. On the 1st, 4th, 7th, 10th and 15th days, blood levels of TNF-alpha were determined. We sought to determine whether TNF alpha levels had a prognostic value in the management of burn induced sepsis that was treated with G-CSF. In our study, patients with gradually decreasing TNF-alpha levels in the second 3 day period, were strong candidates for survival, because TNF-alpha levels decreased little in nonsurvivors but decreased greatly in survivors. The survival rate was 42/51 (82.3%) in group A and 9/27 (33.3%) in group B. In conclusion, G-CSF had positive effects on survival, and TNF-alpha was a predictor of prognosis in burn-induced sepsis.

Experimental study of the effects of splenectomy and partial splenectomy on bacterial translocation

BACKGROUND

The aim of this study is to evaluate the effect of splenectomy and partial splenectomy in a burn-induced bacterial translocation model and to study Kupffer cell (KC) morphology and number.

METHODS

Mice were divided into sham-burn and burn groups. Each group was also subdivided to sham-splenectomy, partial-splenectomy, and splenectomy subgroups. At day 0, operations were performed. At the postoperative 10th day, a sham burn or burn injury was made in all animals. Twenty-four hours later, cultures for bacterial translocation were obtained and livers were evaluated for the quantity and morphology of KCs.

RESULTS

Burned-splenectomized animals had significantly decreased bacterial translocation when compared with sham-splenectomized animals (p = 0.031). Interestingly, in both the sham-burned and burned groups, splenectomy subgroups had significantly higher numbers of KCs compared with partial-splenectomy and sham-splenectomy subgroups (p<0.00000). Burn injury caused a significant decrease of KC numbers in all subgroups compared with their correspondent sham-burned subgroups (p<0.05).

CONCLUSION

Results revealed that splenectomy decreases bacterial translocation and also increases the number of KCs.

Prevalence and identity of translocating bacteria in healthy dogs

Bacterial translocation is characterized by the passage of intestinally derived bacteria across the intestinal mucosa to local or regional tissues. This phenomenon is believed to be important in the pathogenesis of gram-negative bacteremia and septicemia; however, the pathway or route of translocation remains unclear. To define the route of translocation better, mesenteric lymph nodes from 50 apparently healthy dogs undergoing elective ovariohysterectomies were cultured aerobically and anaerobically. The aims of this study were to determine the prevalence of bacterial translocation and to quantify and identify types of organisms found in mesenteric lymph nodes. Peripheral blood and portal blood samples were similarly cultured to rule out hematogenous organisms as a source of lymph node contamination. Bacteria were isolated from mesenteric lymph nodes of 26 dogs (52%). The number of bacteria varied from 50 to > 10(5) organisms/g of tissue. Bacteria isolated included Staphylococcus intermedius (n = 3), coagulase-negative Staphylococcus (n = 2), nonhemolytic Streptococcus (n = 4), Bacillus species (n = 5), Escherichia coli (n = 6), Salmonella species (n = 3), Pseudomonas species (n = 2), Enterococcus species (n = 2), Clostridium sordelli (n = 1), Micrococcus species (n = 1), Lactobacillus species (n = 1), and Propionibacterium acnes (n = 1). One of 50 peripheral blood samples yielded an unidentified gram-positive coccus and a coagulase-negative Staphylococcus. No bacteria were isolated from portal blood samples of any dog. Further studies of this type on sick dogs are warranted before clinical recommendations can be made to culture mesenteric lymph nodes routinely.

Effects of alanyl-glutamine on intestinal adaptation and bacterial translocation in rats after 60% intestinal resection

The effects of alanyl-glutamine dipeptide (Ala-Gln)-enriched parenteral nutrition on intestinal mucosa and gut barrier function were investigated. Wistar rats were studied. After moderate surgical stress was induced by 60% resection of the small intestine, the rats were randomized to three groups: the chow group was given standard rat chow; the PN group received standard parenteral nutrition (PN); and the Ala-Gln group received glutamine dipeptide-enriched parenteral nutrition (3% Ala-Gln). Rats were maintained on their respective diets for 8 days. The chow and Ala-Gln groups maintained serum glutamine concentrations, intestinal mucosal thickness and villus height. Bacterial translocation rates in the chow and Ala-Gln groups were 20%, which was significantly less than that in the PN group (70%, P < 0.05). The results indicated that Ala-Gln-enriched parenteral nutrition maintains intestinal adaptation and gut barrier function after massive intestinal resection and parenteral nutrition.

Biliary decompression promotes Kupffer cell recovery in obstructive jaundice

BACKGROUND

Jaundiced patients undergoing surgical procedures have an increased risk of Gram negative sepsis with potential morbidity and mortality. Depressed Kupffer cell clearance capacity (KCCC) predisposes jaundiced patients to endotoxaemia and its sequelae. Biliary decompression remains the main therapeutic strategy in obstructive jaundice.

AIMS

This study investigates the efficacy of internal (ID) and external biliary drainage (ED) on KCCC in an experimental model of extrahepatic biliary obstruction.

METHODS

Adult male Wistar rats (250-300 g) were assigned to one of six groups: sham operated, where the bile duct was mobilised but not divided; bile duct ligation (BDL) for three weeks, and sham operated or BDL for three weeks followed by a second laparotomy and further 21 days of ID or ED, by way of choledochoduodenostomy or choledochovesical fistula respectively. KCCC was measured using an isolated hepatic perfusion technique with FITC labelled latex particles (0.75 mu) as the test probe. Plasma was assayed for bilirubin, endotoxin, and anticore glycolipid antibody (ACGA) concentrations.

RESULTS

Jaundiced rats had reduced KCCC (p < 0.001), increased concentrations of ACGA (p < 0.001), and endotoxin (p < 0.001) compared with controls. Biliary drainage for three weeks produced a recovery in KCCC and normalisation of endotoxin and ACGA concentrations, however, external drainage was less effective than ID (p < 0.01).

CONCLUSIONS

These data support the hypothesis that endotoxaemia and its mediated effects are integral in the pathophysiology of jaundice. Furthermore, a short period of internal biliary drainage is a useful therapeutic strategy in restoring Kupffer cell function and negating systemic endotoxaemia and consequent complications in biliary obstruction.

Survival and therapy of burn patients at the threshold of the twenty-first century: a review

This review summarizes the progress achieved in care of burned patients over the last half century by analyzing the most significant results published between 1949 and 1995. Improved survival has paralleled the development of new antibiotics as well as major advances in resuscitation, nutritional support, immunomodulating agents, surgical techniques and wound care. Today the average burn size associated with a 50% mortality breakpoint is about 70% of the total body surface area--a notable increase over figures from the past.

Effects of perioperative granulocyte colony-stimulating factor on horses with ascending colonic ischemia

Granulocyte colony-stimulating factor (G-CSF) is a glycoprotein that regulates the proliferation and maturation of hematopoietic progenitor cells and modulates the function of mature neutrophils. The responses to administration of G-CSF alone, and in combination with antimicrobials, were studied in an equine model of ascending colon ischemia. Complete segmental colonic ischemia (3.75 hours) with pelvic flexure enterotomy was created in four treatment groups. Group 1 horses received recombinant canine G-CSF (10 micrograms/kg, every 24 hours, intramuscularly), gentamicin sulfate (2.2 mg/kg, every 8 hours, intravenously), and potassium penicillin G (40,000 IU/kg, every 6 hours, intravenously). Group 2 horses were treated with the G-CSF vehicle and antimicrobials as for group 1. Group 3 horses received G-CSF and the antimicrobial drug vehicles, and group 4 horses served as the untreated control receiving G-CSF vehicle and antimicrobial vehicles. The results for 20 horses, five horses in each group, were compared. Treatment with G-CSF was associated with an increased concentration of white blood cells, band neutrophils, neutrophils, lymphocytes, and monocytes in the peripheral blood after surgery. Antimicrobial administration had no detectable effect on cell concentrations after surgery. Administration of G-CSF was associated with an increased concentration of nucleated cells in the peritoneal fluid including neutrophils, small mononuclear cells and large mononuclear cells. Horses that developed incisional infections had lower neutrophil concentrations in the peripheral blood on postoperative day 2 than horses without infected incisions. These results suggested that the prophylactic administration of G-CSF may be useful in the treatment of patients at risk for developing neutropenia after surgery.

Colonic bacteria and bacterial translocation in experimental colitis

The indigenous intestinal flora and an intact mucosa are vital components of body defences against luminal pathogenic bacteria. Disruption of these defences in inflammatory bowel disease may permit bacterial translocation and contribute to disease severity. Support for this hypothesis comes from this study of a hapten-induced rat model of colitis. Induction of colitis was associated with a significantly increased colonic Gram-negative aerobic bacilli count. The results, expressed as log10 [colony-forming units per gram tissue] were: colitic 6.97-8.86 versus control 4.90-6.69 (P < 0.05). Colitis was also associated with a decreased Gram-positive cocci count at 4.00-8.04 versus control 6.45-8.30 (P < 0.05). Bacteria translocated to the mesenteric lymph nodes in five of eight colitic rats (P = 0.01), to the spleen in four (P = 0.04) and to the liver in five (P = 0.01) but to these organs in none of the eight control animals. There was a positive correlation between the severity of colonic inflammation and extent of bacterial translocation in colitic animals (rs = 0.86, P = 0.007).

Endotoxin, TNF-alpha, interleukin-6 and parameters of the cellular immune system in patients with intraabdominal sepsis

The correlation of endotoxin (ET), tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and cellular immune parameters with multiple organ failure and lethal outcome in intraabdominal infections was studied in a group of 18 patients with peritonitis, abscess or pancreatitis. Of these patients, 7 developed respiratory failure and 5 died due to multiple septic organ failure. The peak levels of ET (2.7 +/- 1.3 ng/ml) in the course of the disease were followed by moderate increases of TNF-alpha (mean 147 +/- 41 pg/ml) and IL-6 (170 +/- 61 pg/ml) within 2 days. Analysis of the parameters for the last 12 days prior to death or discharge showed, that the patient group with lethal outcome was characterized by significant lower mean plasma levels of TNF-alpha (less than 75 pg/ml versus greater than 160 pg/ml) and IL-6 (less than 130 pg/ml versus greater than 270 pg/ml), as well as high rates of unstimulated thymidine uptake into peripheral mononuclear blood cells (greater than 44000 cpm/8 x 10(6) PMBC/18 h versus less than 24000 cmp), T-lymphocyte depression (CD3; approximately greater than 40% reduction) with lower T-helper/inducer subset cell numbers (mean CD:CD8 ratio 1.0 +/- 0.55 versus 1.8 +/- 0.2) and lower lectin (PHA) stimulation values (1.9 +/- 1.4 versus 4.1 +/- 1.0). These data demonstrate an anergic immune status with low mediator levels and depressed T-lymphocyte function in patients with poor prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Protein malnutrition alone and in combination with endotoxin impairs systemic and gut-associated immunity

Because protein-malnourished or endotoxemic patients are at an increased risk of developing nosocomial infections, this study was performed to investigate the effects of protein malnutrition and endotoxemia, alone and in combination, on systemic and intestinal immunity. Protein malnutrition was created by feeding the animals a solid diet containing 0.03% protein. Subgroups of these protein-malnourished mice were killed after being challenged with saline or endotoxin on days 0, 7, 14, or 21. At death, the animals were weighed, tissues were harvested for histologic analysis (ileum, mesenteric lymph node [MLN], liver, and spleen), mitogen responsiveness (MLN, Peyer's patches, and spleen), and xanthine oxidase measurements (ileum and cecum). Separate groups were evaluated for survival. Both the saline and endotoxin-challenged mice had lost about 30% of their body weight after 21 days on the low-protein diet. The protein-malnourished mice were more susceptible to endotoxin-induced mortality (70% at 21 days) than the normally nourished mice (0%) (p less than .001). The mitogen responsiveness of the protein-malnourished mice to the T-cell mitogens (PHA and Con-A) progressively decreased the longer the mice were protein malnourished, and this decreased in blastogenic responsiveness was associated with histologic evidence of lymphoid atrophy. In contrast, the blastogenic response to the primarily B-cell mitogen, PWM, was largely preserved. The endotoxin challenge further depressed the immune state of mice tested after 0, 7, or 14 (but not 21) days of protein malnutrition. Thus, both protein malnutrition and endotoxin impaired systemic and gut-associated immune responsiveness to mitogens. However, in the protein-malnourished mice, the degree of immune suppression did not correlate with endotoxin-induced mortality.

Bowel microorganisms--a target for selective antimicrobial control

This article reviews the eight factors that determine the outcome of selective antimicrobial control (SAC) a technique aimed at the clearance of intestinal Gram-negative bacillary carriage by means of lethal faecal anti-microbial concentrations. They are as follows: (i) the carrier state; (ii) compliance; (iii) SAC aiming at prophylaxis vs treatment; (iv) minimum bactericidal concentration (MBC) of the antimicrobial; (v) dosage; (vi) pharmacokinetics; (vii) faecal inactivation; and (viii) microorganisms to be controlled. In the second part, non-absorbable SAC regimens are compared with absorbable trimethoprim/sulphamethoxazole (TMP/SMZ) and the fluoroquinolones in different clinical settings including neutropenia, intensive care, hepatic encephalopathy, liver transplantation and the salmonella carrier state. Ablation of gut carriage and superinfections are the main endpoints reviewed in this article. The newer fluoroquinolones are potent SAC agents to deal with enterobacteria. Pseudomonads are the major gap in their SAC spectrum. TMP/SMZ emerges as a SAC agent of limited value, whilst the newer non-absorbable combination of polymyxin/tobramycin seems to be the most potent SAC programme since it has activity against pseudomonads. In a third part, three current issues--the emergence of resistance, the selectivity and the tissue effect are discussed. Finally, a potent fluoroquinolone combined with oral polymyxin/tobramycin seems to be the most effective SAC programme currently available to control enterobacteria and pseudomonads in patients in whom bacterial translocation is a risk with minimal risk of resistance emerging.

Effect of SDZ MRL 953 on the survival of mice with advanced sepsis that cannot be cured by antibiotics alone

Stimulation of nonspecific immunity as an additional modality for therapy of sepsis that cannot be cured by antibiotics alone was investigated. SDZ MRL 953, a novel monosaccharidic lipid A analog as a prototype immunostimulant, and cefotaxime or gentamicin were administered to normal or myelosuppressed mice in a state of advanced sepsis caused by Escherichia coli or Staphylococcus aureus. In this novel model, antibiotic therapy was initiated when the infected mice appeared moribund. At this stage, neither pretreatment with the immunostimulant nor therapy with high doses of cefotaxime or gentamicin was effective in protecting the animals from fatal sepsis. However, pretreatment with a single dose of SDZ MRL 953 1 day prior to microbial inoculation dramatically improved the curative effects of the antibiotics. Hence, long-term survival was significantly enhanced with increasing doses of the immunostimulant in the combined therapy. Peritoneal macrophages from SDZ MRL 953-pretreated animals were primed for enhanced production of microbicidal reactive oxygen metabolites in vitro. In conclusion, the results of the present study indicate that SDZ MRL 953 is a potential candidate for use in a clinical setting as an adjunct to antimicrobial therapy for infections that cannot be treated successfully with appropriate antibiotics alone.

Bulk prevents bacterial translocation induced by the oral administration of total parenteral nutrition solution

The effects of a fat and glutamine-free orally administered total parenteral nutrition (TPN) solution on intestinal mucosal mass, morphology, barrier function, and cecal bacterial population levels were measured in CD-1 mice. Ileal mucosal protein content decreased by 63% (p less than 0.01) in the oral TPN-fed mice, although they gained weight on this diet. These TPN-fed mice also exhibited changes in mucosal structure and the normal ecology of their cecal microflora was disrupted leading to overgrowth with Gram-negative enteric bacilli. These changes in intestinal mucosal mass, morphology, and gut bacterial ecology were associated with an increased incidence of bacterial translocation (BT) (TPN group 70% BT vs control group 15% BT: p less than 0.01). The administration of cellulose fiber or kaolin (bulk-forming agents), but not of citrus-pectin (a fully-fermentable, nonresidue fiber) reduced the incidence of BT in the TPN-fed mice to control levels. The beneficial effects of these bulk-forming agents appeared to be due to their ability to prevent TPN-induced disruption of the intestinal microflora and alterations in intestinal morphology, even though they did not prevent ileal mucosal protein levels from decreasing. These results suggest that the administration of bulk forming agents will prevent the loss of intestinal barrier function against luminal bacteria that occurs in mice fed an oral TPN solution.

Protein malnutrition predisposes to inflammatory-induced gut-origin septic states

The development of an uncontrolled inflammatory response has been implicated in the pathogenesis of adult respiratory distress syndrome and multiple-organ failure. Because zymosan activates complement and induces a systemic inflammatory response, the effect of zymosan on intestinal structure and barrier function was measured in normally nourished (NN) and protein malnourished (PM) mice. Normally nourished and protein malnourished (up to 21 days) mice challenged intraperitoneally with zymosan (0.1 mg/g body weight) were killed 24 hours after zymosan challenge and their organs cultured for translocating bacteria. Zymosan-induced bacterial translocation was limited to the mesenteric lymph nodes of the NN mice, whereas translocating bacteria spread from the gut to the liver, spleen, and blood stream (p less than 0.05) in the PM mice. Zymosan-induced bacterial translocation appeared to be related primarily to the combination of mucosal injury and a disruption of the gut flora ecology in the PM mice and to mucosal injury in the NN mice. The extent of mucosal injury was greater the longer the mice were protein malnourished before zymosan challenge. The effect of zymosan on survival was measured in separate groups of mice. At a dose of 0.1 mg/g body weight, no deaths occurred in NN mice or in 7-day PM mice. However 20% of the 14-day PM mice and 80% of the 21-day PM mice receiving zymosan died. Thus PM predisposes to mucosal damage and the development of potentially lethal gut origin septic state during periods of systemic inflammation.

Obstructed intestine as a reservoir for systemic infection

Intestinal motility, absorption, and secretion are altered after intestinal obstruction, but at what point the normal bacterial barrier function of the viable gut fails after intestinal obstruction is unclear. Thus, we tested whether after simple intestinal obstruction bacteria would translocate across the viable intestinal wall to cause systemic infection. Within 6 hours of intestinal ligation 1 cm proximal or distal to the ileocecal valve, bacteria had translocated to the mesenteric lymph nodes, and by 24 hours after intestinal obstruction, bacteria had spread to the liver, spleen, and blood stream. Bacterial translocation rarely occurred in the animals undergoing laparotomy and sham intestinal ligation, indicating that bacterial translocation was not due to surgical stress. Based on the results of these studies, bacterial translocation induced by intestinal obstruction appears to be due to disruption of the ecology of the normal gut microflora, leading to intestinal overgrowth with certain enteric bacilli and mucosal damage. Although the exact mechanism(s) by which simple mechanical obstruction injures the intestine is not known, the fact that mucosal injury did not occur in germ-free mice suggests that bacteria may play a role in the pathogenesis of obstruction-induced intestinal injury.

Different lymphocyte compartments respond differently to mitogenic stimulation after thermal injury

Because of the association between the development of an immunocompromised state and an increased risk of infection, increasing attention has been focused on describing and characterizing the immune consequences of thermal injury. Results of human studies are largely based on the in vitro responsiveness of peripheral blood leukocytes, while splenocytes are generally used in the animal studies. Because the response of lymphocytes from different lymphocyte compartments may vary, we compared the responses of murine peripheral blood, splenic, Peyer's patch, and mesenteric lymph node lymphocytes to a battery of mitogens after thermal injury. Burn-induced immunosuppression was maximal in the splenic lymphocyte compartment, where the responses to all three test mitogens were depressed throughout the 28-day postburn study period. Although the PHA-induced mitogen response of lymphocytes from the other three lymphoid compartments remained suppressed throughout the study period, the response to the mitogens Con-A and PWM generally returned to normal or supranormal levels by the seventh postburn day, Therefore it appears that the effect of a thermal injury on lymphocyte function varies according to the lymphocyte compartment examined and the mitogen tested. These results raise the question of whether animal studies using splenic lymphocytes can be correlated with human studies performed on circulating blood lymphocytes.

Obstructive jaundice promotes bacterial translocation from the gut

Experiments were performed to determine if obstructive jaundice promotes the translocation of bacteria from the gastrointestinal tract to visceral organs. Three groups of mice were studied: control (n = 20), sham ligated (n = 28), and bile duct ligated (n = 33). The sham-ligated group underwent laparotomy and manipulation of the portal region, whereas the ligated group had their common bile ducts ligated. Seven days later, the mice were killed, their organs cultured, and the gastrointestinal tract examined histologically. The bilirubin levels of the ligated group (18.7 mg/dL) were elevated compared with the other groups (0.5 mg/dL) (p less than 0.05). The incidence of bacterial translocation was higher in the ligated (33%) than in the control (5%) or sham-ligated (7%) groups (p less than 0.05). Since bile is important in binding endotoxin and maintaining a normal intestinal microflora, cecal bacterial populations were quantitated. The cecal levels of gram-negative, enteric bacilli were 100-fold higher in the bile duct-ligated mice in which bacterial translocation occurred (p less than 0.05), indicating that intestinal bacterial overgrowth was a major factor responsible for bacterial translocation. The mucosal appearance of the intestines from the control and sham-ligated groups was normal. In contrast, subepithelial edema involving the ileal villi was present in the ligated group. In conclusion, the absence of bile within the gastrointestinal tract allows intestinal overgrowth with enteric bacilli and the combination of bacterial overgrowth and mucosal injury appears to promote bacterial translocation.

Inhibition of endotoxin-induced bacterial translocation in mice

The primary functions of the gut are to absorb nutrients and exclude bacteria and their products. However, under certain circumstances the gut may lose its barrier function and serve as a reservoir for systemic microbial infections. These experiments were performed to determine the mechanisms whereby endotoxin causes bacteria to escape (translocate) from the gut. Bacteria translocated from the gut to the mesenteric lymph nodes of mice challenged with nonlethal doses of Escherichia coli 026:B6 or E. coli 0111:B4 endotoxin. Physical disruption of the gut mucosal barrier appears to be the primary mechanism whereby endotoxin promotes bacterial translocation. Mucosal injury and endotoxin-induced bacterial translocation were reduced by inhibition (allopurinol) or inactivation (tung-sten diet) of xanthine oxidase activity (P less than 0.01), but were not affected by the platelet-activation factor antagonists, SRI 63-441 or BN 52021. Because the inhibition or inactivation of xanthine oxidase activity reduced both the extent of mucosal injury and endotoxin-induced bacterial translocation, the effect of endotoxin on the gut appears to be mediated, at least to some degree, by xanthine oxidase-generated, oxygen-free radicals.