Reviving Decades-Old Wisdom: Longitudinal Analysis of Renin-Angiotensin System Inhibitors and Its Effects on Acute Ischemic Stroke to Improve Outcomes.

BACKGROUND: While renin-angiotensin system (RAS) inhibitors have a longstanding history in blood pressure control, their suitability as first-line in-patient treatment may be limited due to prolonged half-life and kidney failure concerns. METHODS: Using a cohort design, we assessed the impact of RAS inhibitors, either alone or in combination with beta-blockers, on mortality, while exploring interactions, including those related to end-stage renal disease and serum creatinine levels. Eligible subjects were Acute Ischemic Stroke (AIS) patients aged 18 or older with specific subtypes who received in-patient antihypertensive treatment. The primary outcome was mortality rates. Statistical analyses included cross-sectional and longitudinal approaches, employing generalized linear models, G-computation, and discrete-time survival analysis over a 20-day follow-up period. RESULTS: In our study of 3,058 AIS patients, those using RAS inhibitors had significantly lower in-hospital mortality (2.2%) compared to non-users (12.1%), resulting in a relative risk (RR) of 0.18 (95% CI: 0.12-0.26). Further analysis using G-computation revealed a marked reduction in mortality risk associated with RAS inhibitors (0.0281 vs. 0.0913, risk difference [RD] of 6.31% or 0.0631, 95% CI: 0.046-0.079). Subgroup analysis demonstrated notable benefits, with individuals having creatinine levels below and above 1.3 mg/dl exhibiting statistically significant RD (RD -0.0510 vs. -0.0895), and a significant difference in paired comparison (-0.0385 or 3.85%, CI 0.023-0.054). Additionally, longitudinal analysis confirmed a consistent daily reduction of 0.93% in mortality risk associated with the intake of RAS inhibitors. CONCLUSIONS: RAS inhibitors are associated with a significant reduction in in-hospital mortality in AIS patients, suggesting potential clinical benefits in improving patient outcomes.

Implications of built and social environments on the academic success among African American youth: testing Strong African American Families intervention effects on parental academic racial socialization.

Studies exploring widening academic disparities have highlighted the role of racialized school settings, which have given way to incidents of discrimination and unfair treatment for students of color, disproportionately affecting African American youth. Research also shows that family-based preventive interventions may avert negative outcomes for this population through the promotion of protective socialization practices. Consequently, the current study tests the efficacy of a culturally tailored preventive family-based program to foster induced changes in academic promotive parenting practices that prepare youth to advance academically by navigating negative race-related experiences in school settings. Data collected over four time periods from the Strong African American Families (SAAF) efficacy trial (Murry and Brody, 2004) with 667 African American families in rural Georgia were used for this study. Structural equation modeling analyses demonstrated that the SAAF program was associated with positive intervention induced changes in parental academic race-related socialization, which in turn, was indirectly associated with reduced school compromising behaviors through the enhancement of racial pride. While discrimination compromised academic success, our findings highlight the protective nature of racial pride in dissuading academic failure and school dropout through the promotion of academic success. This study confirms that a family-based prevention program holds promise to address academic disparities through the enhancement of parenting and youth protective processes that buffer youth from succumbing to racialized social environments such as schools. Implications for research, educational policy, and preventive interventions are discussed.

Occurrences, distribution and risk assessment of polar pesticides in Niger River valley and its tributary the Mekrou River (Niger Republic).

The increase in food needs due to high population growth in Niger has led to the intensification of urban agriculture and the increased use of pesticides. The objective of this study is primarily to assess the polar pesticide contamination (mainly herbicides) of the Niger River and its tributary, the Mekrou River, in Niger, using both grab sampling and POCIS (Polar Organic Chemical Integrative Samplers), and then to evaluate the risk to the aquatic environment. Two water sampling campaigns were carried out during the wet and dry seasons. The polar pesticides were analyzed by liquid chromatography coupled with tandem mass spectrometry, which allowed the identification of compounds with concentrations in the grab samples above the WHO guide values and the EU directive: diuron with 2221 ng/L (EU quality guideline: 200 ng/L), atrazine with 742 ng/L (EU quality guideline: 600 ng/L) and acetochlor with 238 ng/L (EU quality guideline: 100 ng/L). The risk assessment study indicated that diuron and atrazine present a high risk for the aquatic environment during the wet season. The main source of water contamination is the intensive use of pesticides in urban agriculture near the city of Niamey, and the intensive cotton farming in the Benin. Moreover, the surveys (30 producers interviewed) showed that 70% of the pesticides used are not approved by the Interstate Committee for Drought Control in the Sahel (CILSS) and some are prohibited in Niger. The inventory of pesticides sold in the zone showed that active ingredients used by producers are 48% insecticides, 45% herbicides, and 7% fungicides.

Surface Functionalization Strategies of Polystyrene for the Development Peptide-Based Toxin Recognition.

The development of a robust surface functionalization method is indispensable in controlling the efficiency, sensitivity, and stability of a detection system. Polystyrene (PS) has been used as a support material in various biomedical fields. Here, we report various strategies of polystyrene surface functionalization using siloxane derivative, divinyl sulfone, cyanogen bromide, and carbonyl diimidazole for the immobilization of biological recognition elements (peptide developed to detect ochratoxin A) for a binding assay with ochratoxin A (OTA). Our objective is to develop future detection systems that would use polystyrene cuvettes such as immobilization support of biological recognition elements. The goal of this article is to demonstrate the proof of concept of this immobilization support. The results obtained reveal the successful modification of polystyrene surfaces with the coupling agents. Furthermore, the immobilization of biological recognition elements, for the OTA binding assay with horseradish peroxidase conjugated to ochratoxin A (OTA-HRP) also confirms that the characteristics of the functionalized peptide immobilized on polystyrene retains its ability to bind to its ligand. The presented strategies on the functionalization of polystyrene surfaces will offer alternatives to the possibilities of immobilizing biomolecules with excellent order- forming monolayers, due to their robust surface chemistries and validate a proof of concept for the development of highly efficient, sensitive, and stable future biosensors for food or water pollution monitoring.

The Strong African American Families Program: Disrupting the Negative Consequences of Racial Discrimination Through Culturally Tailored, Family-Based Prevention.

Racism continues to be a major source of stress for African Americans and can impair psychological functioning. Adolescents experiencing discrimination may engage in self-soothing, but risky behaviors, which leave them at risk for negative life trajectories. Black pride has been identified as a key factor in explaining the heterogeneity in responses to discrimination. Racial socialization, strategies parents use to promote Black pride and protect youth from discrimination, is an important focus of family-based prevention programs serving African American families. This study tests the efficacy of a culturally tailored preventive intervention for rural African American families to disrupt the negative consequences of discrimination on adolescent psychological functioning. Four waves of data from the Strong African American Families (SAAF) efficacy trial (Murry & Brody in Journal of Marital & Family Therapy 30(3):271-283, 2004) with 667 African American families in rural Georgia were used for this study. Structural equation modeling was used to test study hypotheses. Adolescent experiences with discrimination at age 15 predicted concurrent psychological functioning and multiple risk behaviors at age 16, including sexual risk behavior, substance use problems, academic failure, and juvenile justice involvement. Mediation analyses demonstrated that psychological functioning was a significant mediator of these relations. The SAAF program was associated with increases in racial socialization, which in turn fostered gains in adolescent Black pride. Black pride was indirectly associated with reduced risk behavior through adolescent psychological functioning, but Black pride did not moderate the effect of discrimination on psychological functioning. This study confirms that family-based prevention can support African American adolescent mental health in the context of discrimination. However, more emphasis on reducing exposure to discrimination is needed.

Culture-Related Adaptive Mechanisms to Race-Related Trauma Among African American and US Latinx Youth.

African American and US Latinx families have faced over two centuries of systemic racism and discrimination, elevating risk for trauma, adversity, and disparities for their youth. These circumstances have compromised the health and well-being of many of these youth. However, many other African American and US Latinx youth are able to succeed despite these challenges. In recent years, scholars have begun to identify ways in which minoritized youth adapt and respond to adversity to become competent, well-functioning individuals. Drawing on two conceptual models of cultural resilience, one grounded in the study of African American youth and one grounded in the study of US Latinx youth, we summarize supportive research associated with each model. Using these conceptual models to guide our critical review of extant studies, we present an integrative review of work to guide the design of strength-based, cultural asset-centered research studies and preventive interventions targeting African American and US Latinx youth.

Monoculture and co-culture tests of the toxicity of four typical herbicides on growth, photosynthesis and oxidative stress responses of the marine diatoms Pseudo-nitzschia mannii and Chaetoceros decipiens.

The toxicity of four herbicides in mixture (alachlor, diuron, des-isopropyl-atrazine and simazine) on the growth and the photosynthesis parameters of two marine diatoms Pseudo-niszchia mannii and Chaetoceros decipiens have been investigated for 9 days in monoculture and co-culture tests. The catalase (CAT) and guaiacol peroxidase (GPX) were also monitored to assess the oxidative stress response. In single-species assays, while both species displayed no affected instantaneous growth rate by herbicides, their physiological responses were different. Chl a content of P. mannii significantly decreased upon herbicide exposure, due probably to pigment destruction or inhibition of their synthesis. This decrease was associated with a reduction in the chlorophyll fluorescence parameters (ABS0/RC, TR0/RC, ET0/RC and DI0/RC). In contrast, C. decipiens maintained an effective photosynthetic performance under herbicide exposure, as Chl a per cell content and the specific energy fluxes per reaction center remained unchanged relative to control values. GPX activity was significantly higher in contaminated P. mannii and C. decipiens monocultures than in controls at early herbicide exposure (1 day), whereas a significant induction of CAT activity occurred later (from day 3 for C. decipiens and at day 9 for P. mannii) in response to herbicides. In control co-culture, P. mannii was eliminated by C. decipiens. As observed in the monoculture, the herbicides did not affect the photosynthetic performance of C. decipiens in co-culture, but significantly reduced its instantaneous growth rate. The oxidative stress response in co-culture has similar trends to that of C. decipiens in monoculture, but the interspecies competition likely resulted in higher CAT activity under herbicide exposure. Results of this study suggest that herbicide toxicity for marine diatoms might be amplified by interspecies interactions in natural communities, which might lead to different physiological and growth responses.

Rural Hospital Closures in Tennessee: Centering Community Residents' Voices to Identify Public Health Ethical Issues and Inform Policy Strategies.

The US is witnessing rapid hospital closures in rural communities, with devastating consequences for community residents beyond decreased access to health care services. Hospital closures have been associated with outmigration of younger generations due to loss of employment opportunities and economic decline, and with creating uncertainty and a sense of powerlessness among residents. While great efforts have been undertaken to document the effects of hospital closures on health care access, particularly during the COVID-19 epidemic, limited attention has been given to the public health ethics associated with dismantling health care for populations in greatest need. Drawing on the narratives of community stakeholders and residents, several themes evolved around processes, structures, and spillover effects of hospital closures on their daily lives, including decision making processes of when and how to close hospitals. Concerns arose regarding lack of transparency and disregard for alternative health care services to meet the needs of rural communities. The researchers analyzed participants' stories using the six core values of the American Public Health Association's code of ethics to determine the extent to which the multilevel crisis emerging from rural hospital closures contradicts the public health ethical responsibility of ensuring access to health care in rural communities. Centering the voices of rural community stakeholders and residents is critical to inform and guide public health strategies and in turn address health care needs of rural communities.

Longitudinal study of the cascading effects of racial discrimination on parenting and adjustment among African American youth.

Attachment theory posits that parenting plays akey role in children's attachment and subsequent development. Given the normativity of racial discrimination on everyday life experiences of African American families, there is a need to integrate historical and socio-environmental processes in studies to understand how minoritized parents raise secure and stable children. Results from the current study revealed direct associations between mothers' reports of discrimination and heightened depression and anxiety. Maternal discriminatory experiences were indirectly associated with more negative parenting and compromised parent-child relationship quality, through mothers' psychological functioning. Elevated emotional and behavioral management problems among youth were directly associated with exposure to racial discrimination. Exposure to discrimination during middle childhood facilitated adapted or learned strategies to manage similar situations as youth transitioned into adolescence, with reduced patterns of depressive symptomology. No significant gender effects emerged. Implications for theoretical advancement and future research are provided.

Contribution of settling measurements to the study of polycyclic aromatic hydrocarbons' (PAHs) mobilisation during resuspension of PAHs-associated sediment.

This paper aims to investigate the effect of the settling behaviour of sediment particles during resuspension on the mobilisation of pollutants such as polycyclic aromatic hydrocarbons (PAHs). Sediments were collected in different areas (basin, channel, beach) of a Mediterranean harbour, located in the south of France (the Grau du Roi harbour), and then separated into different size fractions: large (80-1000 µm), intermediate (40-80 µm), and fine (< 40 µm). Total PAHs concentrations in the initial sediment ranged from 320 to 1043 µg kg-1. Study of the settling behaviour of the PAH-contaminated sediment revealed two sedimentation regimes: sedimentation by mass, which exhibits a sharp interface between the supernatant and the deposit, and sedimentation by clarification with no interface. It appears that sediment particles settle either by the clarification regime or by a combination of the two sedimentation regimes, depending on the size fraction. Particle size distribution monitoring during the settling process allowed the identification of sediment particles less than 20 µm which remain in the water column up to 20 min after resuspension and appear to be the ones that can potentially mobilise PAHs.

Characterization of a member of the CEACAM protein family as a novel marker of proton pump-rich ionocytes on the zebrafish epidermis.

In humans, several members of the CEACAM receptor family have been shown to interact with intestinal pathogens in an inflammatory context. While CEACAMs have long been thought to be only present in mammals, recent studies have identified ceacam genes in other vertebrates, including teleosts. The function of these related genes remains however largely unknown. To gain insight into the function of CEACAM proteins in fish, we undertook the study of a putative member of the family, CEACAMz1, identified in Danio rerio. Sequence analysis of the ceacamz1 gene product predicted a GPI-anchored extracellular protein containing eleven immunoglobulin domains but revealed no evident orthology with human CEACAMs. Using a combination of RT-PCR analyses and in situ hybridization experiments, as well as a fluorescent reporter line, we showed that CEACAMz1 is first expressed in discrete cells on the ventral skin of zebrafish larvae and later on in the developing gills. This distribution remains constant until juvenile stage is reached, at which point CEACAMz1 is almost exclusively expressed in gills. We further observed that at late larval stages, CEACAMz1-expressing cells mostly localize on the afferent side of the branchial filaments and possibly in the inter-lamellar space. Using immunolabelling and 3D-reconstructions, we showed that CEACAMz1 is expressed in cells from the uppermost layer of skin epidermis. These cells are embedded within the keratinocytes pavement and we unambiguously identified them as proton-pump rich ionocytes (HR cells). As the expression of ceacamz1 is turned on concomitantly to that of other known markers of HR cells, we propose that ceacamz1 may serve as a novel marker of mature HR cells from the zebrafish epidermis.

Chemical contamination alters the interactions between bacteria and phytoplankton.

Bacteria and phytoplankton are key players in aquatic ecosystem functioning. Their interactions mediate carbon transfer through the trophic web. Chemical contamination can alter the function and diversity of phytoplankton and bacterioplankton, with important consequences for ecosystem functioning. The aim of the present study was to assess the impact of chemical contamination on the interactions between both biological compartments. Two contrasting marine coastal ecosystems, offshore waters and lagoon waters, were exposed to chemical contamination (artificial or produced from resuspension of contaminated sediment) in microcosms in four seasons characterized by distinct phytoplankton communities. Offshore waters were characterized by a complex phytoplankton-bacterioplankton network with a predominance of positive interactions between both compartments, especially with Haptophyta, Cryptophyta, and dinoflagellates. In contrast, for lagoon waters, the phytoplankton-bacterioplankton network was simpler with a prevalence of negative interactions with Ochrophyta, Cryptophyta, and flagellates. Contamination with an artificial mix of pesticides and trace metal elements resulted in a decrease in the number of interactions between phytoplankton and bacterioplankton, especially for offshore waters. Resuspension of contaminated sediment also altered the interactions between both compartments. The release of nutrients stored in the sediment allowed the growth of nutrient limited phytoplankton species with marked consequences for the interactions with bacterioplankton, with a predominance of positive interactions, whereas in lagoon waters, negative interactions were mostly observed. Overall, this study showed that chemical contamination and sediment resuspension resulted in significant effects on phytoplankton-bacterioplankton interactions that can alter the functioning of anthropogenic coastal ecosystems.

Damage-Induced Calcium Signaling and Reactive Oxygen Species Mediate Macrophage Activation in Zebrafish.

Immediately after a wound, macrophages are activated and change their phenotypes in reaction to danger signals released from the damaged tissues. The cues that contribute to macrophage activation after wounding in vivo are still poorly understood. Calcium signaling and Reactive Oxygen Species (ROS), mainly hydrogen peroxide, are conserved early wound signals that emanate from the wound and guide neutrophils within tissues up to the wound. However, the role of these signals in the recruitment and the activation of macrophages is elusive. Here we used the transparent zebrafish larva as a tractable vertebrate system to decipher the signaling cascade necessary for macrophage recruitment and activation after the injury of the caudal fin fold. By using transgenic reporter lines to track pro-inflammatory activated macrophages combined with high-resolutive microscopy, we tested the role of Ca²âº and ROS signaling in macrophage activation. By inhibiting intracellular Ca²âº released from the ER stores, we showed that macrophage recruitment and activation towards pro-inflammatory phenotypes are impaired. By contrast, ROS are only necessary for macrophage activation independently on calcium. Using genetic depletion of neutrophils, we showed that neutrophils are not essential for macrophage recruitment and activation. Finally, we identified Src family kinases, Lyn and Yrk and NF-κB as key regulators of macrophage activation in vivo, with Lyn and ROS presumably acting in the same signaling pathway. This study describes a molecular mechanism by which early wound signals drive macrophage polarization and suggests unique therapeutic targets to control macrophage activity during diseases.

First study of passive sampling to monitor short-chain chlorinated paraffins in water: Comparing capabilities of Chemcatcher® and silicone rubber samplers.

Short-chain chlorinated paraffins (SCCPs) are high-volume chemicals raising concerns because of their classification as priority hazardous substances by the European Water Framework Directive (WFD) and their recent inclusion in the persistent organic pollutants' (POPs) list by the Stockholm convention. As this group cover up to 5000 isomers, their measurement is still challenging. Hence the SCCPs occurrence in the environment is poorly documented in comparison with other POPs, especially in matrices where they are present at ultratrace levels such as waters. In the two-past decades, passive sampling has been increasingly used as it overcomes some major drawbacks associated to the conventional grab sampling. This study constitutes the first work aiming to examine the passive sampling's applicability for the monitoring of such complex analytes' mixtures in waters. Optimization and calibration of two proven passive samplers, namely silicone rubbers and Chemcatcher®, were performed through batch and laboratory pilot experiments. Despite the thousands of molecules present in the SCCPs mixture, the resulting global kinetic uptakes fitted well with the theorical model, for both samplers. Sampling rates of 8.0 L d-1 for silicone rubbers and 0.53 L d-1 for Chemcatcher® were found, and logKsw determined for silicone rubbers equaled 4.24 to 4.95. These values are in complete agreement with published data for other HOCs. A field trial carried out in marine coastal environments provided further evidence to demonstrate the applicability of the passive samplers to measure CPs amounts in water bodies. All these results unveil that passive sampling using silicone rubbers or Chemcatcher® can be a relevant approach to track traces of such complex mixtures in water.

Study of passive sampler calibration (Chemcatcher®) for environmental monitoring of organotin compounds: Matrix effect, concentration levels and laboratory vs in situ calibration.

Application of Chemcatcher® to monitor organotin compounds [monobutyltin (MBT), dibutyltin (DBT) and tributlytin (TBT)] in sea water has been little developed. Prior to the measurement of the time-weighted average water concentrations (TWAC), a calibration step is required to determine sampling rates (Rs) which is usually assessed in a flow-through laboratory pilot where experimental conditions are well controlled. This paper investigates the effect of the water matrix (tap water vs real sea water from the harbor of Port Camargue in France) and organotin concentrations on the uptake rates of organotin compounds. Laboratory calibrations provided sampling rates in the range of 66-225 mL.day-1 in high concentration (usually used for laboratory calibrations) and in the range of 30-56 mL.day-1 at low concentrations (environmental range). When the tank is filled with real sea water, sampling rates were found to be in the range of 38-177 mL.day-1. In order to demonstrate the efficiency of Chemcatcher® in real conditions, in situ calibration was done in the harbor of Port Camargue. This calibration has been done in order to replicate environmental conditions: compounds concentrations, hydrodynamic and water matrix effects. To compare the impact of calibration procedures on TWAC determination, Chemcatcher® was deployed in the harbor of Port Camargue and spot sampling was performed to monitor the concentrations of organotins in water throughout the exposure period. Results obtained using the field Rs determined by in situ calibration were more reliable. In this case, TWAC is in agreement with spot sampling concentration.

Integration of biophysical connectivity in the spatial optimization of coastal ecosystem services.

Ecological connectivity in coastal oceanic waters is mediated by dispersion of the early life stages of marine organisms and conditions the structure of biological communities and the provision of ecosystem services. Integrated management strategies aimed at ensuring long-term service provision to society do not currently consider the importance of dispersal and larval connectivity. A spatial optimization model is introduced to maximise the potential provision of ecosystem services in coastal areas by accounting for the role of dispersal and larval connectivity. The approach combines a validated coastal circulation model that reproduces realistic patterns of larval transport along the coast, which ultimately conditions the biological connectivity and productivity of an area, with additional spatial layers describing potential ecosystem services. The spatial optimization exercise was tested along the coast of Central Chile, a highly productive area dominated by the Humboldt Current. Results show it is unnecessary to relocate existing management areas, as increasing no-take areas by 10% could maximise ecosystem service provision, while improving the spatial representativeness of protected areas and minimizing social conflicts. The location of protected areas was underrepresented in some sections of the study domain, principally due to the restriction of the model to rocky subtidal habitats. Future model developments should encompass the diversity of coastal ecosystems and human activities to inform integrative spatial management. Nevertheless, the spatial optimization model is innovative not only for its integrated ecosystem perspective, but also because it demonstrates that it is possible to incorporate time-varying biophysical connectivity within the optimization problem, thereby linking the dynamics of exploited populations produced by the spatial management regime.

Seasonal changes of chemical contamination in coastal waters during sediment resuspension.

The potential of remobilization of pollutants is a major problem for anthropogenic ecosystems, because even when the anthropogenic source of pollution is identified and removed, pollutants stored in sediments can be released into the water column and impact pelagic communities during sediment resuspension provoked by dredging, storms or bottom trawling. The objectives of the present study were to assess the changes observed in the chemical composition of the water column following resuspension of a polluted marine sediment and the consequences for the chemical composition of adjacent marine waters according to season. For that purpose, an experimental sediment resuspension protocol was performed on four distinct occasions, spring, summer, fall and winter, and the changes in nutrients, organic contaminants and inorganic contaminants were measured after mixing sediment elutriate with lagoon waters and offshore waters sampled nearby. Significant seasonal variations in the chemical composition of the contaminated sediments were observed, with a strong accumulation of PAHs in fall, whereas minimum PAH concentrations were observed during winter. In all seasons, sediment resuspension provoked a significant enrichment in nutrients, dissolved organic carbon, and trace metal elements like Ni, Cu, and Zn in offshore waters and lagoon waters, with enrichment factors that were season and site dependent. The most pronounced changes were observed for offshore waters, especially in spring and winter, whereas the chemical composition of lagoon waters was weakly impacted by the compounds supplied by sediment resuspension.

Evaluating polar pesticide pollution with a combined approach: a survey of agricultural practices and POCIS passive samplers in a Tunisian lagoon watershed.

A study of pesticides in the Bizerte lagoon watershed on the Mediterranean coast of Tunisia showed that herbicides and fungicides are the most commonly used compounds. A survey was made of selected farmers. Pesticide contamination was monitored in the water column and sediments at four selected sampling sites (lagoon (A) and in three oueds-Chegui (B), Garaa (C), and Tinja (D)). Polar organic chemical integrative samplers (POCIS) were used to assess pesticide contamination. Thirty-two pesticides were investigated; the total concentration of active ingredients ranged from 35.9 ng L-1 in Tinja oued to 1246 ng L-1 in Chegui oued. In the lagoon, the total concentration of pesticides was 67.7 ng L-1. In the sediments, the highest concentration was measured in Chegui oued in the spring (31 ng g-1 dw). The main compounds found in the analyzed sediments were prosulfocarb and tebuconazole molecules.

Neutrophils use superoxide to control bacterial infection at a distance.

Understanding the roles of neutrophils and macrophages in fighting bacterial infections is a critical issue in human pathologies. Although phagocytic killing has been extensively studied, little is known about how bacteria are eliminated extracellularly in live vertebrates. We have recently developed an infection model in the zebrafish embryo in which leukocytes cannot reach the injected bacteria. When Escherichia coli bacteria are injected within the notochord, both neutrophils and macrophages are massively recruited during several days, but do not infiltrate the infected tissue presumably because of its tough collagen sheath. Nevertheless, the bacteria are killed during the first 24 hours, and we report here that neutrophils, but not macrophages are involved in the control of the infection. Using genetic and chemical approaches, we show that even in absence of phagocytosis, the bactericidal action relies on NADPH oxidase-dependent production of superoxide in neutrophils. We thus reveal a host effector mechanism mediated by neutrophils that eliminates bacteria that cannot be reached by phagocytes and that is independent of macrophages, NO synthase or myeloperoxidase.