Clinical gram-positive sepsis: does it fundamentally differ from gram-negative bacterial sepsis?

Acute infections and venous thromboembolism

BACKGROUND

Data on the association between acute infections and venous thromboembolism (VTE) are sparse. We examined whether various hospital-diagnosed infections or infections treated in the community increase the risk of VTE.

METHODS

We conducted this population-based case-control study in Northern Denmark (population 1.8 million) using medical databases. We identified all patients with a first hospital-diagnosed VTE during the period 1999-2009 (n = 15 009). For each case, we selected 10 controls from the general population matched for age, gender and county of residence (n = 150 074). We identified all hospital-diagnosed infections and community prescriptions for antibiotics 1 year predating VTE. We used odds ratios from a conditional logistic regression model to estimate incidence rate ratios (IRRs) of VTE within different time intervals of the first year after infection, controlling for confounding.

RESULTS

Respiratory tract, urinary tract, skin, intra-abdominal and bacteraemic infections diagnosed in hospital or treated in the community were associated with a greater than equal to twofold increased VTE risk. The association was strongest within the first 2 weeks after infection onset, gradually declining thereafter. Compared with individuals without infection during the year before VTE, the IRR for VTE within the first 3 months after infection was 12.5 (95% confidence interval (CI): 11.3-13.9) for patients with hospital-diagnosed infection and 4.0 (95% CI: 3.8-4.1) for patients treated with antibiotics in the community. Adjustment for VTE risk factors reduced these IRRs to 3.3 (95% CI: 2.9-3.8) and 2.6 (95% CI: 2.5-2.8), respectively. Similar associations were found for unprovoked VTE and for deep venous thrombosis and pulmonary embolism individually.

CONCLUSIONS

Infections are a risk factor for VTE.

The use of sequential organ failure assessment parameters in an awake porcine model of severe Staphylococcus aureus sepsis

The human sequential organ failure assessment (SOFA) scoring system is used worldwide in intensive care units for assessing the extent of organ dysfunction/failure in patients with severe sepsis. An increasing number of septic cases are caused by Gram-positive bacteria as Staphylococcus aureus. The aim of the current study was to apply the human SOFA parameters in an awake, porcine model of severe S. aureus sepsis. Five pigs were inoculated intravenously with S. aureus and two control animals were sham-inoculated. Extensive clinical monitoring and sequential blood sampling was obtained and analysed for SOFA parameters. Dysfunction/failure was observed in the respiratory, haemostatic and hepatic system of all infected animals, together with initial cardiovascular dysfunction. The pulmonary system was the first to fail clinically, which corresponds with similar human findings, whereas the liver was affected earlier in pigs compared to humans. The use of human SOFA parameters was valuable in identifying dysfunctional/failing organs and showed consistency between this porcine model and human severe sepsis. Applying SOFA parameters in this model increased the relevance for comparison to clinical methods of evaluating human severe sepsis. Changes in SOFA parameters may in future porcine studies serve as a target for monitoring the effect of therapeutic intervention.

Macrophages are important mediators of either tumor- or inflammation-induced lymphangiogenesis

The lymphatic system provides important functions for tissue fluid homeostasis and immune response. Lymphangiogenesis, the formation of new lymphatics, comprises a series of complex cellular events in vitro or in vivo, e.g., proliferation, differentiation, and sprouting. Recent evidence has implied that macrophages act as a direct structural contributor to lymphatic endothelial walls or secret VEGF-C/-D and VEGF-A to initiate lymphangiogenesis in inflamed or tumor tissues. Bone marrow-derived macrophages are versatile cells that express different functional programs in response to exposure to microenvironmental signals, and can be identified by specific expression of a number of proteins, F4/80, CD11b, and CD68. Several causative factors, e.g., NF-κB, IL-1β, TNF-α, SDF-1, M-CSF, especially TonEBP/VEGF-C signaling, may be actively involved in macrophage-induced lymphangiogenesis. Alteration of macrophage phenotype and function has a profound effect on the development and progression of inflammation and malignancy, and macrophage depletion for controlling lymphangiogenesis may provide a novel approach for prevention and treatment of lymphatic-associated diseases.

A myeloid hypoxia-inducible factor 1α-Krüppel-like factor 2 pathway regulates gram-positive endotoxin-mediated sepsis

Although gram-positive infections account for the majority of cases of sepsis, the molecular mechanisms underlying their effects remains poorly understood. We investigated how cell wall components of gram-positive bacteria contribute to the development of sepsis. Experimental observations derived from cultured primary macrophages and the cell line indicate that gram-positive bacterial endotoxins induce hypoxia-inducible factor 1α (HIF-1α) mRNA and protein expression. Inoculation of live or heat-inactivated gram-positive bacteria with macrophages induced HIF-1 transcriptional activity in macrophages. Concordant with these results, myeloid deficiency of HIF-1α attenuated gram-positive bacterial endotoxin-induced cellular motility and proinflammatory gene expression in macrophages. Conversely, gram-positive bacteria and their endotoxins reduced expression of the myeloid anti-inflammatory transcription factor Krüppel-like transcription factor 2 (KLF2). Sustained expression of KLF2 reduced and deficiency of KLF2 enhanced gram-positive endotoxins induced HIF-1α mRNA and protein expression in macrophages. More importantly, KLF2 attenuated gram-positive endotoxins induced cellular motility and proinflammatory gene expression in myeloid cells. Consistent with these results, mice deficient in myeloid HIF-1α were protected from gram-positive endotoxin-induced sepsis mortality and clinical symptomatology. By contrast, myeloid KLF2-deficient mice were susceptible to gram-positive sepsis induced mortality and clinical symptoms. Collectively, these observations identify HIF-1α and KLF2 as critical regulators of gram-positive endotoxin-mediated sepsis.

Impact of molecular mimicry on the clinical course and outcome of sepsis syndrome

We investigated the impact of molecular mimicry between pathogenic microbes and their antigenic surrounding on the clinical course and outcome of pneumonia induced sepsis. Using mathematical prediction, we estimated the mimicry tendency of the identified pathogenic flora of patients with the human proteome as well as intestinal microbes. Since gut bacteria become invasive and hostile in critical illness, mimicry between these organisms and the infectious flora is expected to be rather hyperinflammatory type, in contrast to the expectedly tolerogenic self versus pathogen cross-reactions. Differential effects of these two kinds of cross-reactions were studied. The predicted similarity of the identified pathogenic flora and intestinal microbes was higher in non-survivor patients compared to survivors (P=0.019). Higher values of "pathogen versus intestinal flora/pathogen versus human proteome" mimicry ratios (inflammatory quotients) were associated with mortality at a higher extent of significance (P<0.01), and correlated with admission APACHE II disease severity scores (R=0.311; P=0.017). We also found a correlation between the previously reported sepsis mortality rates by causative agent and the corresponding inflammatory quotients of these pathogens (R=0.738; P<0.05). Gram negative species showed higher similarity to intestinal bacteria and reached higher inflammatory quotients compared to Gram positives (P=0.01 and P<0.01, respectively). The disadvantageous effect of "pathogen versus intestinal flora" mimicry - presumably due to the extension of inflammation from the infectious focus to the already injured gut - is in accordance with the gut-lymph hypothesis, assessing that the destruction of the intestinal symbiosis culminates in the formation of damageous gut origin lymph. Our results raise the idea that molecular mimicry between pathogenic microbes and their antigenic surrounding might be a contributing factor behind the clinically and experimentally observed differences in microbiologically distinct forms of sepsis syndrome.

Sepsis in the pediatric cardiac intensive care unit

The survival rate for children with congenital heart disease (CHD) has increased significantly coincident with improved techniques in cardiothoracic surgery, cardiopulmonary bypass and myocardial protection, and perioperative care. Cardiopulmonary bypass, likely in combination with ischemia-reperfusion injury, hypothermia, and surgical trauma, elicits a complex, systemic inflammatory response that is characterized by activation of the complement cascade, release of endotoxin, activation of leukocytes and the vascular endothelium, and release of proinflammatory cytokines. This complex inflammatory state causes a transient immunosuppressed state, which may increase the risk of hospital-acquired infection in these children. Postoperative sepsis occurs in nearly 3% of children undergoing cardiac surgery and has been associated with longer length of stay and mortality risks in the pediatric cardiac intensive care unit. Herein, we review the epidemiology, pathobiology, and management of sepsis in the pediatric cardiac intensive care unit.

Fatal group A Streptococcus purpura fulminans in a child receiving TNF-α blocker

Inhibition of tumor necrosis factor alpha (TNF-α) is effective in the treatment of many pediatric autoimmune diseases and inflammatory conditions. Commonly available biologic agents blocking TNF-α are infliximab, etanercept, and adalimumab. These agents have changed the management of rheumatic diseases in the adult population and are being used more and more in pediatric patients as safety and efficacy have been demonstrated. Infections have been the most commonly reported adverse effects of TNF-α inhibition. Granulomatous infections such as tuberculosis are well-known complications, but serious bacterial infections are also reported. We describe a fatal case of purpura fulminans caused by group A Streptococcus in an 8-year-old child with systemic juvenile idiopathic arthritis treated with etanercept. This case highlights the clinical association of severe bacterial infection and TNF-α inhibition in children. Pediatricians should educate their patients who are treated with TNF-α blockers regarding early warning symptoms and should also have a lower threshold for initiating antibiotic therapy in case of fever.

Laminar inflammatory gene expression in the carbohydrate overload model of equine laminitis

REASONS FOR PERFORMING STUDY

There is a need to assess the laminar inflammatory response in a laminitis model that more closely resembles clinical cases of sepsis-related laminitis than the black walnut extract (BWE) model.

OBJECTIVES

To determine if a similar pattern of laminar inflammation, characterised by proinflammatory cytokine expression, occurs in the CHO model of laminitis as has been previously reported for the BWE model.

METHODS

Sixteen horses administered 17.6 g of starch (85% corn starch/15% wood flour)/kg bwt via nasogastric (NG) tube were anaesthetised either after developing a temperature>38.9°C (DEV group, n=8) or at onset of Obel grade 1 lameness (OG1 group, n=8). Control horses (CON group, n=8) were anaesthetised 24 h after NG administration of 6 l of deionised water. Laminar tissue was collected from horses while under anaesthesia, followed by humane euthanasia. Real time-quantitative PCR was used to assess laminar mRNA concentrations of genes involved in inflammatory signalling.

RESULTS

Increased mRNA concentrations (P<0.05) for IL-1β, IL-6, IL-12p35, COX-2, E-selectin and ICAM-1 were present in laminae from horses with OG1 lameness but not at the DEV time, when compared to the CON horses. No differences between the groups were found for IL-2, IL-4, IL-10, TNF-α, IFN-γ or COX-1 at either the DEV or OG1 time points.

CONCLUSIONS

There was a notable difference in the temporal pattern of inflammatory events between the BWE and CHO models, with the majority of laminar inflammatory events appearing to occur at or near the onset of lameness in the CHO model, whereas many of these events peak earlier in the developmental stages in the BWE model. This suggests that, in addition to circulating inflammatory molecules, there may be a local phenomenon in the CHO model resulting in the simultaneous onset of multiple laminar events including endothelial activation, leucocyte emigration and proinflammatory cytokine expression.

POTENTIAL RELEVANCE

The similar (although somewhat delayed) inflammatory response in the CHO model of laminitis indicates that inflammatory signalling is a consistent entity in the pathophysiology of laminitis.

Peptide-based treatment of sepsis

Sepsis (blood poisoning) is a severe infectious disease with high mortality, and no effective therapy is actually known. In the case of Gram-negative bacteria, endotoxins (lipopolysaccharides) are known to be responsible for the strong inflammation reaction leading to the systemic infection. Peptides based on endotoxin-binding domains of human or animal proteins represent a promising approach in sepsis research. Although so far no medicament is available, the progress in recent years might lead to a breakthrough in this field. In this review, recent investigations are summarised, which may lead to an understanding of the mechanisms of action of peptides to suppress the inflammation reaction in vitro and in vivo (animal models) and thus may allow the development of effective anti-septic drugs.

Effects of the TLR2 agonists MALP-2 and Pam3Cys in isolated mouse lungs

Background

Gram-positive and Gram-negative bacteria are main causes of pneumonia or acute lung injury. They are recognized by the innate immune system via toll-like receptor-2 (TLR2) or TLR4, respectively. Among all organs, the lungs have the highest expression of TLR2 receptors, but little is known about the pulmonary consequences of their activation. Here we studied the effects of the TLR2/6 agonist MALP-2, the TLR2/1 agonist Pam₃Cys and the TLR4 agonist lipopolysaccharide (LPS) on pro-inflammatory responses in isolated lungs.

Methodology/Principal Findings

Isolated perfused mouse lungs were perfused for 60 min or 180 min with MALP-2 (25 ng/mL), Pam₃Cys (160 ng/mL) or LPS (1 µg/mL). We studied mediator release by enzyme linked immunosorbent assay (ELISA), the activation of mitogen activated protein kinase (MAPK) and AKT/protein kinase B by immunoblotting, and gene induction by quantitative polymerase chain reaction. All agonists activated the MAPK ERK1/2 and p38, but neither JNK or AKT kinase. The TLR ligands upregulated the inflammation related genes Tnf, Il1β, Il6, Il10, Il12, Ifng, Cxcl2 (MIP-2α) and Ptgs2. MALP-2 was more potent than Pam₃Cys in inducing Slpi, Cxcl10 (IP10) and Parg. Remarkable was the strong induction of Tnc by MALP2, which was not seen with Pam₃Cys or LPS. The growth factor related genes Areg and Hbegf were not affected. In addition, all three TLR agonists stimulated the release of IL-6, TNF, CXCL2 and CXCL10 protein from the lungs.

Conclusions/Significance

TLR2 and TLR4 activation leads to similar reactions in the lungs regarding MAPK activation, gene induction and mediator release. Several genes studied here have not yet been appreciated as targets of TLR2-activation in the lungs before, i.e., Slpi, tenascin C, Parg and Traf1. In addition, the MALP-2 dependent induction of Tnc may indicate the existence of TLR2/6-specific pathways.

Lipoteichoic acid-induced TNF-α and IL-6 gene expressions and oxidative stress production in macrophages are suppressed by ketamine through downregulating Toll-like receptor 2-mediated activation oF ERK1/2 and NFκB

Lipoteichoic acid (LTA), a gram-positive bacterial outer membrane component, can cause septic shock. Our previous studies showed that ketamine has anti-inflammatory and antioxidant effects on gram-negative LPS-induced macrophage activation. In this study, we further evaluated the effects of ketamine on the regulation of LTA-induced TNF-alpha and IL-6 gene expressions and oxidative stress production in macrophages and its possible mechanisms. Exposure of macrophages to a therapeutic concentration of ketamine (100 microM) inhibited LTA-induced TNF-alpha and IL-6 expressions at protein or mRNA levels. In parallel, ketamine at 100 microM reduced LTA-stimulated phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). Sequentially, ketamine reduced the LTA-triggered translocation of nuclear factor-kappaB (NFkappaB) from the cytoplasm to nuclei and its transactivation activity. Pretreatment with PD98059, an inhibitor of ERK, decreased LTA-enhanced NFkappaB activation and TNF-alpha and IL-6 mRNA syntheses. Cotreatment with ketamine and PD98059 synergistically suppressed the LTA-induced translocation and transactivation of NFkappaB and biosyntheses of TNF-alpha and IL-6 mRNA. Application of Toll-like receptor 2 (TLR2) small interfering RNA (si)RNA into macrophages decreased the levels of this receptor, and simultaneously ameliorated LTA-augmented NFkappaB transactivation and consequent production of TNF-alpha and IL-6 mRNA. Cotreatment with ketamine and TLR2 siRNA synergistically lowered TNF-alpha and IL-6 mRNA syntheses in LTA-activated macrophages. Ketamine and TLR2 siRNA could reduce the LTA-induced increases in production of nitrite and intracellular reactive oxygen species in macrophages, and their combination had better effects than a single exposure. Thus, this study shows that one possible mechanism involved in ketamine-induced inhibition of LTA-induced TNF-alpha and IL-6 gene expressions and oxidative stress production is through downregulating TLR2-mediated phosphorylation of ERK1/2 and the subsequent translocation and transactivation of NFkappaB.

A randomized, double-blind, placebo-controlled trial of TAK-242 for the treatment of severe sepsis

OBJECTIVE

To evaluate whether TAK-242, a small-molecule inhibitor of Toll-like receptor-4-mediated signaling, suppresses cytokine levels and improves 28-day all-cause mortality rates in patients with severe sepsis.

DESIGN

Randomized, double-blind, placebo-controlled trial.

SETTING

A total of 93 intensive care units worldwide.

PATIENTS

A total of 274 patients with severe sepsis and shock or respiratory failure.

INTERVENTIONS

Patients were randomly assigned to receive a 30-min loading dose followed by 96-hr infusions of placebo, TAK-242 1.2 mg/kg/day, or TAK-242 2.4 mg/kg/day.

MEASUREMENTS AND MAIN RESULTS

The primary pharmacodynamic end point was change in serum interleukin-6 levels relative to baseline, with 28-day all-cause mortality rate the primary clinical end point. The trial was terminated because of a lack of effect of TAK-242 in suppressing serum interleukin-6 levels. A total of 274 subjects were randomly assigned and treated. Clinical parameters at baseline were balanced across the three groups. TAK-242 did not suppress interleukin-6 as measured by 0- to 96.5-hr area under the interleukin-6 concentration curve at either dose. Specifically, the area under the effect curve increased by 9% and 26.9% in the TAK-242 1.2 and 2.4 mg/kg/day groups, respectively, which was not statistically different from placebo (p = .63 and .15, respectively). The 28-day mortality rate was 24% in the placebo, 22% in the low-dose, and 17% in the high-dose group (p = .26 for placebo vs. high dose). A nonsignificant reduction in mortality rate was observed in a subset of patients with both shock and respiratory failure (placebo [n = 51], 33%, vs. high dose [n = 52], 19%, p = .10). Transient, dose-related increases in methemoglobin levels were observed with TAK-242 treatment in 30.1% of the patients.

CONCLUSIONS

TAK-242 failed to suppress cytokine levels in patients with sepsis and shock or respiratory failure. Treatment with TAK-242 resulted in mild increases in serum methemoglobin levels but was otherwise well tolerated. Although observed mortality rates in patients with both shock and respiratory failure were lower with the 2.4 mg/kg/day dose, differences were not significant.

Sepsis redefined: the search for surrogate markers

Sepsis is a common and severe medical condition with substantial associated morbidity, mortality and cost. Furthermore, the incidence of sepsis has been rising annually over the past three decades, and morbidity and mortality remain high. The management of sepsis is further complicated by its very heterogeneous nature. This extends not only to the offending pathogens, but also to the nature and severity of the host response as well as its clinical manifestations. Efforts to identify surrogate markers for sepsis have therefore been an ongoing struggle. In this article we present some insights into various sepsis markers through history, presenting advantages and caveats associated with their use and interpretation. We also discuss the state of functional genomics, a relatively recent technological advancement that has already begun to change our understanding of sepsis pathophysiology, and offer new directions in the development of a more sensitive and specific sepsis biomarker.

The response of the host microcirculation to bacterial sepsis: does the pathogen matter?

Sepsis results from the interaction between a host and an invading pathogen. The microcirculatory dysfunction is now considered central in the development of the often deadly multiple organ dysfunction syndrome in septic shock patients. The microcirculatory flow shutdown and flow shunting leading to oxygen demand and supply mismatch at the cellular level and the local activation of inflammatory pathways resulting from the leukocyte–endothelium interactions are both features of the sepsis-induced microcirculatory dysfunction. Although the host response through the inflammatory and immunologic response appears to be critical, there are also evidences that Gram-positive and Gram-negative bacteria can exert different effects at the microcirculatory level. In this review we discuss available data on the potential bacterial-specific microcirculatory alterations observed during sepsis.

Procalcitonin in sepsis and systemic inflammation: a harmful biomarker and a therapeutic target

The worldwide yearly mortality from sepsis is substantial, greater than that of cancer of the lung and breast combined. Moreover, its incidence is increasing, and its response to therapy has not appreciably improved. In this condition, the secretion of procalcitonin (ProCT), the prohormone of calcitonin, is augmented greatly, attaining levels up to thousands of fold of normal. This hypersecretion emanates from multiple tissues throughout the body that are not traditionally viewed as being endocrine. The serum values of ProCT correlate with the severity of sepsis; they recede with its improvement and worsen with exacerbation. Accordingly, as highlighted in this review, serum ProCT has become useful as a biomarker to assist in the diagnosis of sepsis, as well as related infectious or inflammatory conditions. It is also a useful monitor of the clinical course and prognosis, and sensitive and specific assays have been developed for its measurement. Moreover, it has been demonstrated that the administration of ProCT to septic animals greatly increases mortality, and several toxic effects of ProCT have been elucidated by in vitro experimental studies. Antibodies have been developed that neutralize the harmful effects of ProCT, and their use markedly decreases the symptomatology and mortality of animals that harbour a highly virulent sepsis analogous to that occurring in humans. This therapy is facilitated by the long duration of serum ProCT elevation, which allows for a broad window of therapeutic opportunity. An experimental groundwork has been established that suggests a potential applicability of such therapy in septic humans.

Artesunate protects sepsis model mice challenged with Staphylococcus aureus by decreasing TNF-alpha release via inhibition TLR2 and Nod2 mRNA expressions and transcription factor NF-kappaB activation

Gram-positive bacteria have become the most common organisms responsible for the development of sepsis. Staphylococcus aureus (S. aureus) is the major gram-positive pathogen in both community-acquired and nosocomial infections. The Mortality associated with nosocomial infections caused by S. aureus may vary but are generally high. In the present study, we found that artesunate (AS) could protect mice against a lethal challenge with heat-killed S. aureus in a dose-dependent manner, and AS in combination with ampicillin sodium-sulbactam sodium (AMPS) could further increase survival of mice challenged with live S. aureus than AMPS alone. This protection was associated with reductions of serum at TNF-alpha level. In in vitro experiments, AS-pretreatment strongly inhibited TNF-alpha release from murine peritoneal macrophage induced by heat-killed S. aureus or peptidoglycan in a dose-dependent manner. AS reduced the Toll like receptor 2 (TLR2) and nucleotide-binding oligomerization domain containing 2 (Nod2) mRNA expressions up-regulated by heat-killed S. aureus and inhibited NF-kappaB activation induced by heat-killed S. aureus. In conclusion, our results demonstrated that AS-mediated protection on septic mice challenged with S. aureus was associated with its reduction on TNF-alpha release via inhibition of TLR2 and Nod2 mRNA expressions and transcription factor NF-kappaB activation.

Recombinant human growth hormone improves survival and protects against acute lung injury in murine Staphylococcus aureus sepsis

OBJECTIVE

To investigate whether recombinant human growth hormone (rhGH) reduces mortality and protects against Staphylococcus aureus sepsis-induced acute lung injury.

METHODS

The bacteria-positive rate of blood smears and bacteria colony counts in bacteria plate culture, TNFalpha and IL-10 plasma levels, lung injury score, expression of intercellular adhesion molecule-1 (ICAM-1) as well as activation of nuclear factor-kappa B (NF-kappaB) in the lungs were determined 6, 12 and 24 h after 140 KM mice were injected with physiologic saline (i.p. group C, n = 20); S. aureus E311122 (1.75 x 10(12) cfu/L, 40 ml/kg, i.p. group S, n = 60); or S. aureus (as group S) with a subsequent treatment of rhGH (1.0 U kg(-1) day(-1)), i.m. group T, n = 60). The cumulative survival rate of an additional 15 mice from each group was followed for 7 days post S. aureus injection.

RESULTS

rhGH treatment significantly increased IL-10 plasma levels and the 7-day cumulative survival rate, whereas the bacteria-positive rate of blood smears, bacteria colony counts in bacteria plate cultures, lung injury score, ICAM-1 and NF-kappaB expression in the lungs were significantly reduced. In addition, rhGH treatment significantly suppressed the S. aureus sepsis-induced elevation of TNFalpha plasma levels.

CONCLUSIONS

These results indicate an ability of rhGH to prevent S. aureus sepsis-induced acute lung injury in mice, which may be attributed to attenuation of increased plasma TNFalpha levels, and elevated IL-10 plasma levels as well as reduced ICAM-1 expression and inhibited NF-kappaB activity in the lungs.

Therapeutic approach to regulate innate immune response by Toll-like receptor 4 antagonist E5564 in rats with D-galactosamine-induced acute severe liver injury

BACKGROUND AND AIMS

Toll-like receptor 4 (TLR4) is a transmembrane protein, existing mainly in macrophages, such as Kupffer cells of the liver. It plays an important role in recognizing and mediating macrophage activation and pro-inflammatory cytokine release. Activation of pro-inflammatory cytokines, including tumor necrosis factor (TNF)-alpha is pivotal in the progression of liver injury. Gut-derived endotoxin has been considered to play an important role in the development and progression of a D-galactosamine (GalN)-induced acute severe liver injury (ALI) model. E5564, a synthetic analog of the lipid A component of endotoxin, inhibits endotoxin-stimulated inflammation and is under study for patients with sepsis. In this study, we seek to explore the effect of TLR4 antagonist E5564 on GalN-induced ALI in rats.

METHODS

ALI was induced in male Wistar rats by the i.p. injection of 1 g/kg bodyweight of GalN and immediately after GalN injection they were treated with an i.v. injection of 3 mg/kg bodyweight of E5564. At 24 h after GalN injection with or without E5564, serum levels of total bilirubin (T.Bil), alanine aminotransferase (ALT) and TNF-alpha were analyzed. Expression levels of TNF-alpha, TLR4 and CD14 mRNA in the whole liver of rats was detected by reverse transcription polymerase chain reaction analysis.

RESULTS

The i.v. injection of E5564 reduced the elevation of serum T.Bil, ALT and TNF-alpha levels in rats treated with GalN. The expression level of TNF-alpha mRNA in the whole liver, which was increased at 24 h after GalN injection, was also reduced by i.v. injection of E5564.

CONCLUSION

TLR4 antagonist E5564 reduced GalN-induced ALI in rats. It may contribute to the treatment of acute liver failure through blocking endotoxin-induced TNF-alpha overproduction of macrophages.

CD14 expression in the first 24h of sepsis: effect of -260C>T CD14 SNP

Sepsis is defined as systemic inflammation caused by infection. The membrane bound CD14 (mCD14) or the soluble form (sCD14) play a crucial role facing Gram-negative and Gram-positive sepsis since they are pattern recognition receptors of the innate immune response enabling cells to produce inflammatory cytokines against bacterial infections. A -260C>T single nucleotide polymorphism (SNP) was detected in the promoter modulating the CD14 gene expression. We hypothesized that the CD14 expression depends of the genetic inheritance of -260C>T CD14 SNP and it is modulated by sepsis condition. We investigated human CD14 expression on early sepsis diagnosis (in vivo) and after LPS stimulation (in vitro), and determined the -260C>T CD14 SNP. We found that TT homozygotes showed higher mCD14 density (p = 0.0207), but not different sCD14 levels when compared to the CT+CC genotypes. Monocyte mCD14 density and sCD14 serum levels in our sample of early 14 septic patients were significantly higher than normal 30 controls (p<0.0001). Our results suggest that the -260TT CD14 genotype is associated with higher monocyte mCD14, but not sCD14 expression, and that in the first 24 h after sepsis diagnosis, both monocyte mCD14 density and sCD14 levels are elevated, similarly to what is observed in vitro upon challenge with LPS.

Using innate immunity to characterize the host response to microbial invasion in severe sepsis

Severe sepsis is a life-threatening systemic inflammatory response to microbial infection. Although mortality from severe sepsis has decreased modestly over the past three decades, its incidence is increasing dramatically. Current treatment of severe sepsis relies primarily on identification and appropriate antibiotic coverage of the invading pathogen, with supportive therapies aimed primarily at reducing the risk of associated organ injury. Current efforts to identify the invading pathogens are successful in approximately only 50% of patients with severe sepsis. In this review, we examine host-pathogen interactions through the Toll-like receptors and Nod signaling systems as principal mechanisms of the innate immune response, and explore the application of high-throughput genomic technologies that have permitted a more complete dissection of the innate immune response during severe sepsis. Early controlled studies suggest that these genome-wide tools can readily identify pathogen-specific host responses in macrophages and dendritic cells. However, despite considerable progress, clinical application of these approaches to pathogen recognition in hospitalized patients with severe sepsis is still years away.

Sepsis and septic shock: selection of empiric antimicrobial therapy

This article is a brief overview of empiric antibiotic selection for sepsis and septic shock. The article includes a differential diagnosis of the mimics of sepsis and stresses a strategy for avoiding problems associated with antibiotic resistance. Although early appropriate empiric therapy is the cornerstone of sepsis and septic shock therapy, nonantibiotic interventions are critical as well. In patients with septic shock, adequate and effective early volume replacement is essential. Early surgical intervention is critical in controlling and eliminating the septic focus if sepsis is related to perforation of a viscus (eg, the colon); obstruction of the biliary, gastrointestinal, or urinary tract; or presence of an abscess that requires drainage. If device-related infection is the cause of sepsis, device removal is essential. Empiric monotherapy for sepsis and septic shock is preferred. Multiple-drug therapy is more expensive, has an increased potential for drug-drug interactions, has a higher likelihood of side effects, and does not decrease the resistance potential of the antibiotics being used. For these reasons, early empiric monotherapy is optimal and de-escalation is not necessary if initial mono therapy was wisely selected.

Bench-to-bedside review: sepsis, severe sepsis and septic shock - does the nature of the infecting organism matter?

International guidelines concerning the management of patients with sepsis, septic shock and multiple organ failure make no reference to the nature of the infecting organism. Indeed, most clinical signs of sepsis are nonspecific. In contrast, in vitro data suggest that there are mechanistic differences between bacterial, viral and fungal sepsis, and imply that pathogenetic differences may exist between subclasses such as Gram-negative and Gram-positive bacteria. These differences are reflected in different cytokine profiles and mortality rates associated with Gram-positive and Gram-negative sepsis in humans. They also suggest that putative anti-mediator therapies may act differently according to the nature of an infecting organism. Data from some clinical trials conducted in severe sepsis support this hypothesis. It is likely that potential new therapies targeting, for example, Toll-like receptor pathways will require knowledge of the infecting organism. The advent of new technologies that accelerate the identification of infectious agents and their antimicrobial sensitivities may allow better tailored anti-mediator therapies and administration of antibiotics with narrow spectra and known efficacy.

Serum procalcitonin elevation in critically ill patients at the onset of bacteremia caused by either Gram negative or Gram positive bacteria

Background

In the ICU, bacteremia is a life-threatening infection whose prognosis is highly dependent on early recognition and treatment with appropriate antibiotics. Procalcitonin levels have been shown to distinguish between bacteremia and noninfectious inflammatory states accurately and quickly in critically ill patients. However, we still do not know to what extent the magnitude of PCT elevation at the onset of bacteremia varies according to the Gram stain result.

Methods

Review of the medical records of every patient treated between May, 2004 and December, 2006 who had bacteremia caused by either Gram positive (GP) or Gram negative (GN) bacteria, and whose PCT dosage at the onset of infection was available.

Results

97 episodes of either GN bacteremia (n = 52) or GP bacteremia (n = 45) were included. Procalcitonin levels were found to be markedly higher in patients with GN bacteremia than in those with GP bacteremia, whereas the SOFA score value in the two groups was similar. Moreover, in the study population, a high PCT value was found to be independently associated with GN bacteremia. A PCT level of 16.0 ng/mL yielded an 83.0% positive predictive value and a 74.0% negative predictive value for GN-related bacteremia in the study cohort (AUROCC = 0.79; 95% CI, 0.71–0.88).

Conclusion

In a critically ill patient with clinical sepsis, GN bacteremia could be associated with higher PCT values than those found in GP bacteremia, regardless of the severity of the disease.

Sepsis since the discovery of Toll-like receptors: disease concepts and therapeutic opportunities

OBJECTIVE

Sepsis and its sequelae are the leading cause of death in critically ill patients. Discovery in the late 1990s of Toll-like receptors as primary sensors of microbial infection led to significant advances in understanding the pathogenesis of sepsis, including emerging differences between Gram-positive and Gram-negative infection and the potential for the manipulation of Toll-like receptors for the treatment of sepsis. This review describes these advances.

METHODS

Bibliographic search of the literature since 1999, with particular emphasis on the conceptual and therapeutic implications of Toll-like receptors for patients with systemic sepsis.

RESULTS AND CONCLUSIONS

Toll-like receptors initiate the inflammatory processes that underlie the clinical response to infection and therefore represent an important putative target for therapeutic intervention.

Tracking the Microbes in Sepsis: Advancements in Treatment Bring Challenges for Microbial Epidemiology

During the 1980s and 1990s, sepsis research propelled dozens of potential therapeutic candidates into clinical trials without a single novel therapeutic approach entering the clinical arena. After the publication of the landmark PROWESS trial in 2001, which showed survival benefit associated with the use of recombinant activated protein C for treatment of severe sepsis, there have been a series of positive sepsis intervention trials studying intensive glycemic control, low-dose steroid therapy, and early goal-directed therapy. The fact that the efficacy of these interventions is not restricted to certain types of infection should not detract from the importance of a full understanding of the microbial epidemiology of sepsis. Empirical antimicrobial therapy remains the mainstay of sepsis treatment. Furthermore, among a number of promising novel therapies that are in phase II and III clinical trials, several have pathogen-specific modes of action. The optimal targeting of antibiotics and such novel treatments toward the specific patient groups who will benefit represents a major challenge to reducing sepsis mortality. This requires detailed, up-to-date, and local epidemiological data. It is becoming increasingly clear that the nature of the infection underlying sepsis is a major determinant of outcome, and future trials of sepsis interventions, guided by high-quality data on microbial epidemiology, may well have to focus on subgroups of patients with different forms of infection. Finally, with the rapidly increasing challenge of antimicrobial resistance and the paucity of novel antibiotics, particularly for infections with gram-negative pathogens, it is more important than ever that we properly understand the forces that drive changes in the microbial epidemiology of sepsis.

Sepsis-associated cholestasis is critically dependent on P-selectin-dependent leukocyte recruitment in mice

Cholestasis is a major complication in sepsis although the underlying mechanisms remain elusive. The aim of this study was to evaluate the role of P-selectin and leukocyte recruitment in endotoxemia-associated cholestasis. C57BL/6 mice were challenged intraperitoneally with endotoxin (0.4 mg/kg), and 6 h later the common bile duct was cannulated for determination of bile flow and biliary excretion of bromosulfophthalein. Mice were pretreated with an anti-P-selectin antibody or an isotype-matched control antibody. Leukocyte infiltration was determined by measuring hepatic levels of myeloperoxidase. Tumor necrosis factor-alpha and CXC chemokines in the liver was determined by ELISA. Liver damage was monitored by measuring serum levels of alanine aminotransferase and aspartate aminotransferase. Apoptosis was quantified morphologically by nuclear condensation and fragmentation using Hoechst 33342 staining. Endotoxin induced a significant inflammatory response with increased TNF-alpha and CXC chemokine concentrations, leukocyte infiltration, liver enzyme release, and apoptotic cell death. This response was associated with pronounced cholestasis indicated by a >70% decrease of bile flow and biliary excretion of bromosulfophthalein. Immunoneutralization of P-selectin significantly attenuated endotoxin-induced leukocyte infiltration reflected by a >60% reduction of hepatic myeloperoxidase levels. Interference with P-selectin decreased endotoxin-mediated hepatocellular apoptosis and necrosis, but did not affect hepatic levels of tumor necrosis factor-alpha and CXC chemokines. Of interest, inhibition of P-selectin restored bile flow and biliary excretion of bromosulfophthalein to normal levels in endotoxin-challenged animals. Our study demonstrates for the first time that P-selectin-mediated recruitment of leukocytes, but not the local production of proinflammatory mediators, is the primary cause of cholestasis in septic liver injury.

Intravenous polyclonal IgM-enriched immunoglobulin therapy in sepsis: a review of clinical efficacy in relation to microbiological aetiology and severity of sepsis

The efficacy of intravenous polyclonal immunoglobulin (IVIG) as adjunct therapy in sepsis has long been debated. Clinical trials have yielded contradicting results, in part due to the varying study design and varying microbiological aetiologies. In most trials, the study drug has been IVIG containing polyclonal IgG. However, in recent reports, the efficacy of IgM-enriched IVIG as adjunct therapy in sepsis has been highlighted. Here we review studies on IgM-enriched IVIG therapy in sepsis and we discuss the clinical efficacy in relation to microbiological aetiology and severity of sepsis. The results suggest that patients most likely to benefit from IgM-enriched IVIG therapy are those with Gram-negative septic shock.

The role of infection and comorbidity: Factors that influence disparities in sepsis

OBJECTIVE

Large healthcare disparities exist in the incidence of sepsis based on both race and gender. We sought to determine factors that may influence the occurrence of these healthcare disparities, with respect to the source of infection, causal organisms, and chronic comorbid medical conditions.

DESIGN

Historical cohort study.

SETTING

U.S. acute care hospitals from 1979 to 2003.

PATIENTS

Hospitalized patients with a diagnosis of sepsis were identified from the National Hospital Discharge Survey per codes of the International Statistical Classification of Diseases, Ninth Revision (ICD-9CM). Chronic comorbid medical conditions and the source and type of infection were characterized by corresponding ICD-9CM diagnoses.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Sepsis incidence rates are mean cases per 100,000 after age adjustment to the 2000 U.S. Census. Males and nonwhite races were confirmed at increased risk for sepsis. Both proportional source distribution and incidence rates favored respiratory sources of sepsis in males (36% vs. 29%, p < .01) and genitourinary sources in females (35% vs. 27%, p < .01). Incidence rates for all common sources of sepsis were greater in nonwhite races, but proportional source distribution was approximately equal. After stratification by the source of infection, males (proportionate ratio 1.16, 95% confidence interval 1.04-1.29) and black persons (proportionate ratio 1.25, 95% confidence interval 1.18-1.32) remained more likely to have Gram-positive infections. Chronic comorbid conditions that alter immune function (chronic renal failure, diabetes mellitus, HIV, alcohol abuse) were more common in nonwhite sepsis patients, and cumulative comorbidities were associated with greater acute organ dysfunction. Compared with white sepsis patients, nonwhite sepsis patients had longer hospital length of stay (2.0 days, 95% confidence interval 1.9-2.1) and were less likely to be discharged to another medical facility (30% whites, 25% blacks, 18% other races). Case-fatality rates were not significantly different across racial and gender groups.

CONCLUSIONS

Healthcare disparities exist in the incidence of sepsis within all major sources of infection, and males and blacks have greater frequency of Gram-positive infections independent of the infection source. The differential distribution of specific chronic comorbid medical conditions may contribute to these disparities. Large cohort and administrative studies are required to confirm discrete root causes of sepsis disparities.

Incidence of sepsis in hospitalized patients

In recent years, several epidemiological studies have helped expand our knowledge of the incidence of sepsis at the intensive care unit (ICU) and population levels. However, more data are needed from developing countries. Overall, even with a lack of standardized definitions--particularly of sepsis-associated organ dysfunction, hypoperfusion or hypotension, and septic-induced cardiovascular failure despite adequate fluid resuscitation--the incidence of sepsis seems higher in Brazil, the United Kingdom, and Portugal. In the future, in order to better identify patients that need early ICU admission, aggressive care, and new therapies, we must develop and apply better instruments for definition and risk stratification, especially for evaluating the risk of progressing from sepsis to severe sepsis and septic shock.

Toll-Like Receptor-4 Message Is Up-Regulated in Lipopolysaccharide-Exposed Rat Lung Pericytes

BACKGROUND

Pericytes are multifunctional, polymorphic perivascular cells that lie within the microvessel basal lamina, are located on the abluminal side of endothelial cells, and are thought to play a regulatory role in capillary leak observed in sepsis. Toll-Like receptor 4 (TLR-4) has been implicated as the proximal transmembrane receptor for the LPS/CD 14 complex during the activation of lipopolysacharide (LPS)-induced sepsis. It is our hypothesis that TLR-4 is present on lung pericytes and is up-regulated in response to LPS.

METHODS

Rat microvascular lung pericytes were isolated and cultured. Cells from passage 3-5 were used and treated with LPS (control, 10 ng/mL, and 100 ng/mL) for 18 h. Immunostaining and immunoblotting were performed to detect the presence of CD-14, TLR-2, and TLR-4. Real-time polymerase chain reaction was used to analyze the presence and quantity of mRNA for CD-14, TLR-2, and TLR-4.

RESULTS

Immunostaining and immunoblotting revealed the presence of CD-14, TLR-2, and TLR-4 in pericytes from each treatment group, and real-time polymerase chain reaction confirmed the presence of mRNA for CD-14, TLR-2, and TLR-4. An increase in the mRNA was observed in CD-14, TLR-2, and TLR-4 in the presence of increasing LPS 4 h after treatment. At 18 h after LPS treatment, a decrease in mRNA was noted.

CONCLUSIONS

The up-regulation of TLR-4 in the presence of increasing LPS suggests its importance in pericyte LPS-induced activation. Pericyte TLR-4 recognition of LPS could play a role in capillary leak seen in sepsis. These data also demonstrates that pericytes, once thought to be passive participants in the inflammatory cascade, may be active members.

Protective effect of fasudil, a Rho-kinase inhibitor, on chemokine expression, leukocyte recruitment, and hepatocellular apoptosis in septic liver injury

Rho-kinase signaling regulates important features of inflammatory reactions. Herein, we investigated the effect and mechanisms of action of the Rho-kinase inhibitor fasudil in endotoxemic liver injury. C57/BL/6 mice were challenged with lipopolysaccharide (LPS) and D-galactosamine, with or without pretreatment with the Rho-kinase inhibitor fasudil. Six hours after endotoxin challenge, leukocyte-endothelium interactions in the hepatic microvasculature were studied by use of intravital fluorescence microscopy and tumor necrosis factor alpha (TNF-alpha); CXC chemokines as well as liver enzymes and apoptosis were determined. Administration of fasudil reduced LPS-induced leukocyte adhesion in postsinusoidal venules and sequestration in sinusoids. Moreover, we found that fasudil abolished extravascular infiltration of leukocytes as well as production of TNF-alpha and CXC chemokines in the liver of endotoxemic mice. Liver enzymes and hepatocellular apoptosis were markedly reduced, and sinusoidal perfusion was improved significantly in endotoxemic mice pretreated with fasudil. Our novel data document that fasudil is a potent inhibitor of endotoxin-induced expression of TNF-alpha and CXC chemokines as well as leukocyte infiltration and hepatocellular apoptosis in the liver. Based on the present findings, it is suggested that inhibition of the Rho-kinase signaling pathway may be a useful target in the treatment of septic liver injury.

Deoxynivalenol and satratoxin G potentiate proinflammatory cytokine and macrophage inhibitory protein 2 induction by Listeria and Salmonella in the macrophage

Health risks from microbial pathogens and toxins encountered in food and the environment continue to be of worldwide concern. The purpose of this research was to test the hypothesis that trichothecene mycotoxins amplify inflammatory responses to foodborne bacterial pathogens. We assessed the capacity of deoxynivalenol (DON) and satratoxin G (SG) to potentiate chemokine and proinflammatory cytokine production in RAW 264.7 murine macrophages induced by Listeria monocytogenes and Salmonella Typhimurium. When macrophage cultures were incubated with killed irradiated suspensions of the pathogens for 24 h, the minimum Listeria concentrations for induction of macrophage inhibitory protein 2 (MIP-2), interleukin-1beta (IL-beta), IL-6, and tumor necrosis factor alpha (TNF-alpha) were 0.01, 0.01, 1.0, and 1.0 microg/ml (P < 0.05) and the minimum Salmonella concentrations were 0.01, 0.01, 0.1, and 0.1 microg/ml, respectively (P < 0.05). Induction of all four mediators by both pathogens was potentiated by DON (at 100 and 250 ng/ml); observed responses were significantly higher than predicted additive responses (P < 0.05). SG (at 2 and 5 ng/ml) also significantly amplified induction of IL-1beta and TNF-alpha (P < 0.05) by both Listeria and Salmonella. These results indicate that DON encountered in Fusarium-contaminated food and SG from Stachybotrys-contaminated indoor environments could magnify innate inflammatory responses to foodborne bacterial pathogens.

Statin use and mortality within 180 days after bacteremia: a population-based cohort study

OBJECTIVE

To examine the association between preadmission statin use and mortality among patients with bacteremia in a population-based setting.

DESIGN

Observational study based on prospective registration of bacteremia episodes and mortality over a 6-yr period.

SETTING

North Jutland County, Denmark (population, 500,000).

PATIENTS

A total of 5,353 adult patients hospitalized with bacteremia from 1997 to 2002. Individuals treated with statins (n = 176) were identified by record-linkage with the County Prescription Database.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We compared mortality rates 0-30 and 31-180 days after bacteremia in patients with and without preadmission statin use, adjusted for gender, age group, level of comorbidity, alcohol-related conditions, use of immunosuppressive drugs and systemic antibiotics, and focus on infection. The 30-day mortality in statin users vs. nonusers was similar (20.0% vs. 21.6%, adjusted mortality rate ratio 0.93, 95% confidence interval 0.66-1.30). Among survivors after 30 days, however, statin therapy was associated with a substantially decreased mortality up until 180 days after the bacteremia (8.4% vs. 17.5%, adjusted mortality rate ratio 0.44, 95% confidence interval 0.24-0.80). This tendency toward similar short-term and decreased longer term mortality associated with statin use was observed consistently in both community-acquired and nosocomial bacteremia episodes and when analyses were restricted to patients with previous cardiovascular discharge diagnoses or diabetes.

CONCLUSIONS

This study provides evidence against the hypothesis that statin use has an effect on short-term mortality after bacteremia. Statin use was, however, associated with a substantially decreased mortality between 31 and 180 days after bacteremia.

Molecular pathology: future issues

CONTEXT

The field of molecular pathology is expanding in complexity. To achieve competency, vigilance is required.

OBJECTIVE

To review the advances in clinically useful molecular biologic techniques and to identify their applications in clinical practice, as presented at the 13th Annual William Beaumont Hospital DNA Symposium.

DATA SOURCES

The 4 manuscripts submitted were reviewed and their major findings were compared with the literature on the same or related topics.

STUDY SELECTION

Manuscripts address the use of molecular or immunophenotyping by flow cytometry to evaluate the origin or presence of sepsis, respectively; the use of imatinib mesylate to treat chronic myeloid leukemia and the nature of resistance to imatinib; and the use of 9 and 10 fluorochromes during clinical flow cytometric studies.

DATA SYNTHESIS

The epidemiologic evaluation of a septic outbreak may be monitored using molecular techniques that track the relatedness of isolates. A potential biomarker for the presence of early sepsis is CD64. Intracellular signal transduction pathways are altered in malignancy. Imatinib mesylate inhibits the BCR-ABL kinase created by translocation of the long arms of chromosomes 9 and 22 in chronic myeloid leukemia. Resistance to imatinib may be secondary to mutation in the BCR-ABL kinase domain or residual leukemic stem cells that imatinib does not kill. The use of 9 or 10 fluorochromes simultaneously during flow cytometry has many clinical advantages; however, software for data analysis is needed.

CONCLUSION

The current postgenomic era will continue to emphasize the use of microarrays and database software for genomic, transcriptomic, proteomic, nutrigenomic, and pharmacogenomics screening to search for a useful clinical assay. The number of molecular pathologic techniques will expand as additional disease-associated mutations are defined.

Physiological Response to Superantigen-Adsorbing Hemoperfusion in Toxin-Concentration-Controlled Septic Swine

BACKGROUND/AIMS

Superantigens are suspected of being potent initiators of gram-positive sepsis, and new therapies for superantigen elimination are required. The effects of hemoadsorption with a superantigen-adsorbing device (SAAD) were evaluated in septic swine.

METHODS

Toxic shock syndrome toxin-1 (TSST-1) was infused, and blood concentration was maintained at the clinical level for 6 h. Endotoxin was then infused to induce lethal shock. All animals were hemoperfused with SAAD or a control column for 8 h and changes in pathological parameters and mortality were examined.

RESULTS

Animals perfused with SAAD had a highly significant (p < 0.01) survival advantage compared with control groups at 24 h after initiation of the TSST-1 infusion. SAAD also suppressed the increase in the arteriovenous shunt ratio and decrease of partial arterial oxygen pressure at 6 h after TSST-1 infusion initiation.

CONCLUSION

We suggest that there is a potential application of SAAD in treating superantigen-induced respiratory dysfunction and sepsis.

Septic shock caused by Streptococcus pneumoniae in a post-splenectomy patient successfully treated with recombinant human activated protein C

We present a case of severe sepsis due to Streptococcus pneumoniae, serotype 22F treated with recombinant human activated protein C (drotrecogin alpha activated) (DrotAA). APACHE II score at admission was 34 with a predicted mortality of 81%. A wide range of cytokines, chemokines and receptors was measured before and after DrotAA treatment. Soon after infusion of 24 microg DrotAA per kg bodyweight and h (microg/kg/h) over a period of 96 h, cytokine levels fell markedly. The patient survived and was discharged after 6 weeks of hospitalization. In conclusion, administration of DrotAA in a case of Streptococcus pneumoniae-induced septic shock was followed by dramatic changes in serum levels of immuno-regulatory cytokines.

Superantigen-induced multiple organ dysfunction in a toxin-concentration-controlled and sequential parameter-monitored swine sepsis model

OBJECTIVE

In order to examine the biological activity of low-dose and continuously infused superantigen, and to establish a superantigen-induced multiple organ dysfunction animal model, several pathophysiological parameters were sequentially monitored in a toxin-concentration-controlled pig model.

METHODS

Anesthetized, mechanically ventilated and Swan-Ganz thermodilution catheter-inserted pigs were treated with toxic shock syndrome toxin-1 (TSST-1) by infusion at 2 microg/kg/h for 5 h. Monitoring was performed for both the infusion period and a subsequent 1-h post-infusion period.

RESULTS

The serum concentration of TSST-1 was controlled so as to elevate it to a level over 1000 pg/mL within 1 h of initiation of infusion, and then gradually increased further and reached a plateau of about 2500 pg/mL at 4h after initiation. The animals showed a significant increase in cardiac output, the intrapulmonary arteriovenous shunt ratio, and infiltration of white blood cells into the lung. Although the observed increase in pulmonary vascular resistance was not statistically significant, it did correlate with the reduction in white blood cell counts.

CONCLUSION

The superantigen TSST-1 plays an important role in the pathogenesis of Gram-positive bacterial sepsis by inducing multiple organ dysfunction. Thus, this model provides the first tool to allow the simultaneous examination of the serum toxin levels and other organ parameters in a time-course manner.

THE USE OF IMMUNOCOMPROMISED ANIMALS AS MODELS FOR HUMAN SEPTIC SHOCK

Although it is generally understood that no single animal model truly reflects human sepsis, the study of sepsis in immunocompromised animals is highly relevant to human sepsis research. The majority of patients with severe sepsis have significant underlying diseases that may alter innate immune defenses, disrupt microbial clearance mechanisms, and complicate the pathophysiology of human sepsis. Septic shock itself has significant effects upon the innate and adaptive host immune responses that may contribute to a state of sepsis-induced immune dysregulation. A number of animal models of sepsis displaying an array of immunocompromised states are now available. Most of these systems are small animal models with genetically defined defects of immune defenses or acquired defects from receipt of immunosuppressive or myeloablative agents. Greater emphasis should be placed on preclinical models of immunocompromised animals in the future to assess the potential clinical utility of novel drugs for human septic shock.

Molecular mechanisms involved in the pathogenesis of septic shock

Pathogenesis of the development of sepsis is highly complex and has been the object of study for many years. The inflammatory phenomena underlying septic shock are described in this review, as well as the enzymes and genes involved in the cellular activation that precedes this condition. The most important molecular aspects are discussed, ranging from the cytokines involved and their respective transduction pathways to the cellular mechanisms related to accelerated catabolism and multi-organic failure.

Recognition of Staphylococcus aureus by the innate immune system

The gram-positive bacterium Staphylococcus aureus is a major pathogen responsible for a variety of diseases ranging from minor skin infections to life-threatening conditions such as sepsis. Cell wall-associated and secreted proteins (e.g., protein A, hemolysins, and phenol-soluble modulin) and cell wall components (e.g., peptidoglycan and alanylated lipoteichoic acid) have been shown to be inflammatory, and these staphylococcal components may contribute to sepsis. On the host side, many host factors have been implicated in the innate detection of staphylococcal components. One class of pattern recognition molecules, Toll-like receptor 2, has been shown to function as the transmembrane component involved in the detection of staphylococcal lipoteichoic acid and phenol-soluble modulin and is involved in the synthesis of inflammatory cytokines by monocytes/macrophages in response to these components. Nod2 (nucleotide-binding oligomerization domain 2) is the intracellular sensor for muramyl dipeptide, the minimal bioactive structure of peptidoglycan, and it may contribute to the innate immune defense against S. aureus. The staphylococcal virulence factor protein A was recently shown to interact directly with tumor necrosis factor receptor 1 in airway epithelium and to reproduce the effects of tumor necrosis factor alpha. Finally, peptidoglycan recognition protein L is an amidase that inactivates the proinflammatory activities of peptidoglycan. However, peptidoglycan recognition protein L probably plays a minor role in the innate immune response to S. aureus. Thus, several innate immunity receptors may be implicated in host defense against S. aureus.

Improved diagnostic approaches to infection/sepsis detection

Sepsis is a major healthcare problem from the perspective of mortality and economics. Advances in diagnostic detection of infection and sepsis have been slow, but recent advances in both soluble biomarker detection and quantitative cellular measurements promise the availability of improved diagnostic techniques. Though the promise of cytokine measurements reaching clinical practice have not matured, procalcitonin levels are currently available in many countries and appear to offer enhanced diagnostic distinction between bacterial and viral etiologies. Cellular diagnostics is poised to enter clinical laboratory practice in the form of neutrophil CD64 measurements, which offer superior sensitivity and specificity to conventional laboratory assessment of sepsis. Neutrophil CD64 expression is negligible in the healthy state. However, it increases as part of the systemic response to severe infection or sepsis. The combination of cellular proteomics, as in the case of neutrophil CD64 quantification, and selected soluble biomarkers of the inflammatory response, such as procalcitonin or triggering receptor expressed on myeloid cells (TREM)-1, is predicted to remove the current subjectivity and uncertainty in the diagnosis and therapeutic monitoring of infection and sepsis.

Infection of Human Endothelial Cells with Staphylococcus aureus Induces Transcription of Genes Encoding an Innate Immunity Response

Staphylococcus aureus is a gram-positive bacterium frequently isolated from patients with bloodstream infections. Endothelial cells (EC) play an important role in host defence against bacteria, and recent reports have shown that infection of EC with S. aureus induces expression of cytokines and cell surface receptors involved in activating the innate immune response. The ability of S. aureus to invade nonphagocytic cells, including EC, has been documented. However, the knowledge of the role of EC in pathogenesis of S. aureus infection is still limited. In this study, we investigate the gene-expression program in human EC initiated by internalized S. aureus, using microarray analysis. We found 156 genes that were differentially regulated at least threefold, using arrays representing 14,239 genes. Many of the upregulated genes code for proteins involved in innate immunity, such as cytokines, chemokines and cell adhesion proteins. Other upregulated genes encode proteins involved in antigen presentation, cell signalling and metabolism. Furthermore, intracellular bacteria survived for days without inducing EC death.

Severe community-acquired pneumonia as a cause of severe sepsis: data from the PROWESS study

OBJECTIVE

To investigate community-acquired pneumonia (CAP) as a cause of severe sepsis in the PROWESS (Recombinant Human Activated Protein C Worldwide Evaluation in Severe Sepsis) trial and to evaluate the effect of drotrecogin alfa (activated) (DrotAA) in this subgroup.

DESIGN

Retrospective analysis of the severe CAP subgroup in the PROWESS trial.

SETTING

Tertiary care institutions in 11 countries.

INTERVENTIONS

DrotAA (n = 850), 24 microg.kg.hr for 96 hrs, or placebo (n = 840).

PARTICIPANTS

The 1,690 patients with severe sepsis enrolled in the PROWESS trial.

MEASUREMENTS AND MAIN RESULTS

Patients were classified as having CAP if lung was the primary site of infection and if they were enrolled directly from home (private residence) with </=4 days in the hospital before receipt of study drug in the PROWESS trial. Survival at 28 days, hospital discharge, and 90 days was compared in DrotAA and placebo groups in the CAP subgroup of PROWESS and CAP subgroups based on disease severity. Of the 1,690 PROWESS patients, 35.6% (DrotAA, n = 324; placebo, n = 278) were classified as severe CAP. Of these severe CAP patients, 26.1% had Streptococcus pneumoniae infections. Within CAP, 79.1% were enrolled by the end of the second calendar day in the hospital, and approximately 90% of CAP patients were at high risk of death according to the Pneumonia Severity Index category. Based on their dependence on vasopressors, 59% of CAP patients were judged at high risk of death. Biomarkers of coagulation and inflammation were markedly abnormal in severe CAP patients. In severe CAP patients treated with DrotAA, a relative risk reduction in mortality of 28% was observed at 28 days, with a relative risk reduction in mortality of 14% observed at 90 days from the start of study drug infusion. The survival benefit was most pronounced in severe CAP patients with S. pneumoniae and in severe CAP patients at high risk of death as indicated by Acute Physiology and Chronic Health Evaluation II score of >/=25, Pneumonia Severity Index score of >/=4, or CURB-65 (confusion, urea, respiratory rate, blood pressure, age) score of >/=3.

CONCLUSIONS

CAP associated with a high Pneumonia Severity Index score, bacteremia, or an intense coagulation and inflammatory response requiring intensive care unit care were indicators of a high risk of death from severe sepsis. In patients with severe sepsis resulting from CAP, a readily identifiable disease, DrotAA, improved survival compared with placebo.