Association of a sepsis initiative on broad spectrum antibiotic use and outcomes in an ED population.

INTRODUCTION: Sepsis identification and treatment is a priority for emergency department (ED) providers and payors alike. However, aggressive metrics aimed at improving sepsis care could have unintended consequences for patients who do not have sepsis. METHODS: All ED patient visits for a one month period before and after a quality initiative to increase early antibiotic use in septic patients were included. Overall broad spectrum (BS) antibiotic use, admission rates, and mortality were compared in the 2 time periods. A more detailed chart review was performed on those who received BS antibiotics in the before and after cohorts. Patient were excluded for pregnancy, age < 18, COVID-19 infection, hospice patients, left ED against medical advice, and if antibiotics were given for prophylaxis. In BS antibiotic treated patients, we sought to determine mortality, rates of subsequent multidrug resistant (MDR) or Clostridium Difficile (CDiff) infections and rates of non-infected patients receiving BS antibiotics. RESULTS: There were 7967 and 7407 ED visits in the pre- and post-implementation periods, respectively. Of those, BS antibiotics were administered in a total of 3.9% pre-implementation and 6.2% post-implementation (p ≤ 0.00001). Admission was more common in the post-implementation period, but overall mortality was unchanged (0.9% pre-implementation and 0.8% post-implementation, p = 0.41). After exclusions, 654 patients treated with BS antibiotics were included in the secondary analyses. Baseline characteristics were similar between the pre-implementation and post-implementation cohorts. There was no difference in the rate of CDiff infection or the proportion of patients receiving BS antibiotics who were not infected, but there was an increase in the post-implementation period in MDR infections after ED BS antibiotics, 0.72% vs. 0.35% of the entire ED cohorts, p = 0.0009. CONCLUSIONS: We found that a QI sepsis initiative was associated with an increase in the proportion of patients who received BS antibiotics in the ED, and a small absolute increase in associated subsequent MDR infections, with no apparent effect on mortality in all ED patients or the subset treated with BS antibiotics. Further research is needed to assess the impact on all patients affected by aggressive sepsis protocols and initiatives, rather than only those with sepsis.

Performance improvement evaluation of forward aeromedical evacuation platforms in Operation Enduring Freedom.

BACKGROUND: The following three helicopter-based medical evacuation platforms operate in Southern Afghanistan: the US Army emergency medical technician (basic)-led DUSTOFF, US Air Force paramedic-led PEDRO, and UK physician-led medical emergency response team (MERT). Nearly 90% of battlefield deaths occur in the prehospital phase, comparative outcomes for these en route care platforms are unknown. The objective of this investigation was to characterize the nature of injuries in patients transported by three evacuation platforms. In addition, it aimed to compare observed versus predicted mortality among these provider groups. METHODS: A performance improvement study involving 975 coalition patients injured in Southern Afghanistan, transported from the point of injury to a military hospital, was performed. All patients were alive on admission with prehospital documentation recorded in the US Department of Defense Trauma Registry from June 2009 to June 2011. The main outcome measure was in-hospital mortality and observed versus predicted (Trauma and Injury Severity Score [TRISS]) survival were the primary end points. RESULTS: MERT transported more amputation and polytrauma casualties and included patients with higher mean Injury Severity Score (ISS) compared with PEDRO and DUSTOFF (16 [13] vs. 11 [10] and 10 [10] respectively; p < 0.001). DUSTOFF was excluded from the subgroup analysis owing to insufficient numbers of severely injured casualties with only one death. The overall mortality for MERT and PEDRO was similar (4.2% vs. 4.6%, p = 0.967). Stratifying by ISS, there was lower mortality in MERT compared with PEDRO in the range of 20 to 29 (4.8% vs. 16.2%, p = 0.021). The observed mortality among PEDRO casualties was as predicted with the exception of the range of 20 to 29, while mortality in MERT was lower than predicted for all ISS groups with greater than 10. CONCLUSION: MERT achieves greater than predicted survival, which may be related to the additional capabilities onboard. This supports the adoption of a versatile medical evacuation system with scalable crew and equipment configurations that adapt to meet the medical, tactical, and operational needs of future conflicts.

Macrophage p38 mitogen-activated protein kinase activity regulates invariant natural killer T-cell responses during Borrelia burgdorferi infection.

The interaction of macrophages with infectious agents leads to the activation of several signaling cascades, including mitogen-activated protein (MAP) kinases, such as p38. We now demonstrate that p38 MAP kinase-mediated responses are critical components to the immune response to Borrelia burgdorferi. The pharmacological and genetic inhibition of p38 MAP kinase activity during infection with the spirochete results in increased carditis. In transgenic mice that express a dominant negative form of p38 MAP kinase specifically in macrophages, production of the invariant natural killer T (iNKT) cell-attracting chemokine MCP-1 and of the antigen-presenting molecule CD1d are significantly reduced. The expression of the transgene therefore results in the deficient infiltration of iNKT cells, their decreased activation, and a diminished production of interferon γ (IFN-γ), leading to increased bacterial burdens and inflammation. These results show that p38 MAP kinase provides critical checkpoints for the protective immune response to the spirochete during infection of the heart.

CD14 cooperates with complement receptor 3 to mediate MyD88-independent phagocytosis of Borrelia burgdorferi.

Phagocytosis of Borrelia burgdorferi, the causative agent of Lyme disease, is a poorly understood process, despite its importance during the host immune response to infection. B. burgdorferi has been shown to bind to different receptors on the surface of phagocytic cells, including the ß(2) integrin, complement receptor 3 (CR3). However, whether these receptors mediate the phagocytosis of the spirochete remains unknown. We now demonstrate that CR3 mediates the phagocytosis of the spirochete by murine macrophages and human monocytes. Interaction of B. burgdorferi with the integrin is not sufficient, however, to internalize the spirochete; phagocytosis requires the interaction of CR3 with the GPI-anchored protein, CD14, independently of TLR/MyD88-induced or inside-out signals. Interestingly, the absence of CR3 leads to marked increases in the production of TNF in vitro and in vivo, despite reduced spirochetal uptake. Furthermore, the absence of CR3 during infection with B. burgdorferi results in the inefficient control of bacterial burdens in the heart and increased Lyme carditis. Overall, our data identify CR3 as a MyD88-independent phagocytic receptor for B. burgdorferi that also participates in the modulation of the proinflammatory output of macrophages. These data also establish a unique mechanism of CR3-mediated phagocytosis that requires the direct cooperation of GPI-anchored proteins.

The tick saliva immunosuppressor, Salp15, contributes to Th17-induced pathology during Experimental Autoimmune Encephalomyelitis.

Salp15 is a tick saliva protein that inhibits CD4(+) T cell differentiation through its interaction with CD4. The protein inhibits early signaling events during T cell activation and IL-2 production. Because murine Experimental Autoimmune Encephalomyelitis development is mediated by central nervous system-infiltrating CD4(+) T cells that are specific for myelin-associated proteins, we sought to determine whether the treatment of mice with Salp15 during EAE induction would prevent the generation of proinflammatory T cell responses and the development of the disease. Surprisingly, Salp15-treated mice developed more severe EAE than control animals. The treatment of EAE-induced mice with the tick saliva protein did not result in increased infiltration of T cells to the central nervous system, indicating that Salp15 had not affected the permeability of the blood-brain barrier. Salp15 treatment did not affect the development of antibody responses against the eliciting peptide or the presence of IFNγ in the sera. The treatment with Salp15 resulted, however, in the increased differentiation of Th17 cells in vivo, as evidenced by higher IL-17 production from PLP(139-151)-specific CD4(+) T cells isolated from the central nervous system and the periphery. In vitro, Salp15 was able to induce the differentiation of Th17 cells in the presence of IL-6 and the absence of TGFß These results suggest that a conductive milieu for the differentiation of Th17 cells can be achieved by restriction of the production of IL-2 during T cell differentiation, a role that may be performed by TGFß and other immunosuppressive agents.

Phosphorylation of Nur77 by the MEK-ERK-RSK cascade induces mitochondrial translocation and apoptosis in T cells.

Nur77, an orphan nuclear receptor, plays a key role in apoptosis in T cells. In cancer cell lines, Nur77 can induce apoptosis through the intrinsic apoptotic pathway, but the mechanism by which Nur77 kills T cells remains controversial. In this study, we provide biochemical, pharmacological, and genetic evidence demonstrating that Nur77 induces apoptosis through the activation of the intrinsic pathway in T cells. We also show that Nur77 is a physiological substrate of the MEK-ERK-RSK cascade. Specifically, we demonstrate that RSK phosphorylates Nur77 at serine 354 and this modulates Nur77 nuclear export and intracellular translocation during T cell death. Our data reveal that Nur77 phosphorylation and mitochondrial targeting, regulated by RSK, defines a role for the MEK1/2-ERK1/2 cascade in T cell apoptosis.

Local production of IFN-gamma by invariant NKT cells modulates acute Lyme carditis.

The Lyme disease spirochete Borrelia burgdorferi is the only known human pathogen that directly activates invariant NKT (iNKT) cells. The number and activation kinetics of iNKT cells vary greatly among different strains of mice. We now report the role of the iNKT cell response in the pathogenesis of Lyme disease using C57BL/6 mice, a strain with optimal iNKT cell activation that is resistant to the development of spirochetal-induced inflammation. During experimental infection of B6 mice with B. burgdorferi, iNKT cells localize to the inflamed heart where they are activated by CD1d-expressing macrophages. Activation of iNKT cells in vivo results in the production of IFN-gamma, which we demonstrate ameliorates the severity of murine Lyme carditis by at least two mechanisms. First, IFN-gamma enhances the recognition of B. burgdorferi by macrophages, leading to increased phagocytosis of the spirochete. Second, IFN-gamma activation of macrophages increases the surface expression of CD1d, thereby facilitating further iNKT activation. Collectively, our data demonstrate that in the resistant background, B6, iNKT cells modulate the severity of murine Lyme carditis through the action of IFN-gamma, which appears to self-renew through a positive feedback loop during infection.

p38 mitogen-activated protein kinase controls NF-kappaB transcriptional activation and tumor necrosis factor alpha production through RelA phosphorylation mediated by mitogen- and stress-activated protein kinase 1 in response to Borrelia burgdorferi antigens.

The interaction of Borrelia burgdorferi, the causative agent of Lyme borreliosis, with phagocytic cells induces the activation of NF-kappaB and the expression of proinflammatory cytokines including tumor necrosis factor alpha (TNF-alpha). B. burgdorferi-induced TNF-alpha production is also dependent on the activation of p38 mitogen-activated protein (MAP) kinase. The specific contribution of these signaling pathways to the response of phagocytic cells to the spirochete and the molecular mechanisms underlying this response remain unresolved. We now show that p38 MAP kinase activity regulates the transcriptional activation of NF-kappaB in response to spirochetal lysate stimulation of phagocytic cells. The regulation occurs at the nuclear level and is independent of the translocation of the transcription factor to the nucleus or its capacity to bind to specific DNA target sequences. In RAW264.7 cells, p38alpha MAP kinase regulates the phosphorylation of NF-kappaB RelA. p38 MAP kinase phosphorylates the nuclear kinase mitogen- and stress-activated protein kinase 1 (MSK1). MSK1 in turn phosphorylates the transcriptionally active subunit of NF-kappaB, RelA. The repression of MSK1 expression with small interfering RNA results in reduced RelA phosphorylation and a significant decrease in the production of TNF-alpha in response to B. burgdorferi lysates. Overall, these results clarify the contribution of the signaling pathways that are activated in response to the interaction of spirochetes with phagocytic cells to TNF-alpha production. Our results situate p38 MAP kinase activity as a central regulator of the phagocytic proinflammatory response through MSK1-mediated transcriptional activation of the transcription factor NF-kappaB.

Control of Borrelia burgdorferi-specific CD4+-T-cell effector function by interleukin-12- and T-cell receptor-induced p38 mitogen-activated protein kinase activity.

Infection with Borrelia burgdorferi, the causative agent of Lyme disease, results in a Th1 response and proinflammatory cytokine production. Mice deficient for MKK3, an upstream activator of p38 mitogen-activated protein (MAP) kinase, develop a lower Th1 response and exhibit an impaired ability to produce proinflammatory cytokines upon infection with the spirochete. We investigated the contribution of p38 MAP kinase activity in gamma interferon (IFN-gamma) production in CD4+ T cells in response to specific antigen through T-cell receptor (TCR)- and interleukin-12 (IL-12)-mediated signals. The specific inhibition of p38 MAP kinase in T cells and the administration of a pharmacological inhibitor of the kinase during the course of infection with the spirochete resulted in reduced levels of IFN-gamma in the sera of infected mice. Our results also demonstrate that although p38 MAP kinase activity is not required for the differentiation of B. burgdorferi-specific CD4+ T cells, the production of IFN-gamma by Th1 effector cells is regulated by the kinase. Both TCR engagement and IL-12 induced the production of the Th1 cytokine through the activation of the p38 MAP kinase pathway. Thus, the inhibition of this pathway in vitro resulted in decreased levels of IFN-gamma during restimulation of B. burgdorferi-specific T cells in response to anti-CD3 and IL-12 stimulation. These results clarify the specific contribution of the p38 MAP kinase in the overall immune response to the spirochete and its role in the effector function of B. burgdorferi-specific T cells.