Evaluating the effects of climate change and chemical, physical, and biological stressors on nearshore coral reefs: A case study in the Great Barrier Reef, Australia.

An understanding of the combined effects of climate change (CC) and other anthropogenic stressors, such as chemical exposures, is essential for improving ecological risk assessments of vulnerable ecosystems. In the Great Barrier Reef, coral reefs are under increasingly severe duress from increasing ocean temperatures, acidification, and cyclone intensities associated with CC. In addition to these stressors, inshore reef systems, such as the Mackay-Whitsunday coastal zone, are being impacted by other anthropogenic stressors, including chemical, nutrient, and sediment exposures related to more intense rainfall events that increase the catchment runoff of contaminated waters. To illustrate an approach for incorporating CC into ecological risk assessment frameworks, we developed an adverse outcome pathway network to conceptually delineate the effects of climate variables and photosystem II herbicide (diuron) exposures on scleractinian corals. This informed the development of a Bayesian network (BN) to quantitatively compare the effects of historical (1975-2005) and future projected climate on inshore hard coral bleaching, mortality, and cover. This BN demonstrated how risk may be predicted for multiple physical and biological stressors, including temperature, ocean acidification, cyclones, sediments, macroalgae competition, and crown of thorns starfish predation, as well as chemical stressors such as nitrogen and herbicides. Climate scenarios included an ensemble of 16 downscaled models encompassing current and future conditions based on multiple emission scenarios for two 30-year periods. It was found that both climate-related and catchment-related stressors pose a risk to these inshore reef systems, with projected increases in coral bleaching and coral mortality under all future climate scenarios. This modeling exercise can support the identification of risk drivers for the prioritization of management interventions to build future resilient reefs. Integr Environ Assess Manag 2024;20:401-418. © 2023 Norwegian Institute for Water Research and The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC). This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Applicability of Chronic Multiple Linear Regression Models for Predicting Zinc Toxicity in Australian and New Zealand Freshwaters.

Bioavailability models, for example, multiple linear regressions (MLRs) of water quality parameters, are increasingly being used to develop bioavailability-based water quality criteria for metals. However, models developed for the Northern Hemisphere cannot be adopted for Australia and New Zealand without first validating them against local species and local water chemistry characteristics. We investigated the applicability of zinc chronic bioavailability models to predict toxicity in a range of uncontaminated natural waters in Australia and New Zealand. Water chemistry data were compiled to guide a selection of waters with different zinc toxicity-modifying factors. Predicted toxicities using several bioavailability models were compared with observed chronic toxicities for the green alga Raphidocelis subcapitata and the native cladocerans Ceriodaphnia cf. dubia and Daphnia thomsoni. The most sensitive species to zinc in five New Zealand freshwaters was R. subcapitata (72-h growth rate), with toxicity ameliorated by high dissolved organic carbon (DOC) or low pH, and hardness having a minimal influence. Zinc toxicity to D. thomsoni (reproduction) was ameliorated by both high DOC and hardness in these same waters. No single trophic level-specific effect concentration, 10% (EC10) MLR was the best predictor of chronic toxicity to the cladocerans, and MLRs based on EC10 values both over- and under-predicted zinc toxicity. The EC50 MLRs better predicted toxicities to both the Australian and New Zealand cladocerans to within a factor of 2 of the observed toxicities in most waters. These findings suggest that existing MLRs may be useful for normalizing local ecotoxicity data to derive water quality criteria for Australia and New Zealand. The final choice of models will depend on their predictive ability, level of protection, and ease of use. Environ Toxicol Chem 2023;42:2614-2629. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Sediment spiking and equilibration procedures to achieve partitioning of uranium similar to contamination in tropical wetlands near a mine site.

The derivation of sediment quality guideline values (SQGVs) presents significant challenges. Arguably the most important challenge is to conduct toxicity tests using contaminated sediments with physico-chemistry that represents real-world scenarios. We used a novel metal spiking method for an experiment that ultimately aims to derive a uranium SQGV. Two pilot studies were conducted to inform the final spiking design, i.e. percolating a uranyl sulfate solution through natural wetland sediments. An initial pilot study that used extended mixing equilibration phases produced hardened sediments not representative of natural sediments. A subsequent percolation method produced sediment with similar texture to natural sediment and was used as the method for spiking the sediments. The range of total recoverable uranium (TR-U) concentrations achieved was 8-3200 mg/kg. This reflected the concentrations found in natural wetlands and water management ponds found on a uranium mine site and was above natural levels. Dilute-acid extractable uranium (AE-U) concentrations were >80% of total concentrations, indicating that much of the uranium in the spiked sediment was labile and potentially bioavailable. The portion of TR-U extractable as AE-U was similar at the start and end of the 4.5-month field-deployment. Porewater uranium (PW-U) analyses indicated that partition coefficients (Kd) were 2000-20,000 L/kg, and PW-U was greater in post- than pre-field-deployed samples when TR-U was ≤1500 mg/kg, indicating the binding became weaker during the field-deployment period. At higher spiked-U concentrations, the PW-U was lower post-field-deployment. Comparing the physico-chemical data of the spiked sediments with environmental monitoring data from sediments in the vicinity of a uranium mining operation indicated that they were representative of sediments contaminated by mining and that the U-spiked sediments had a clear U concentration gradient. This confirmed the suitability of the spiking procedure for preparing sediments that were suitable for deriving a SQGV for uranium.

Acute and chronic toxicity of nickel on freshwater and marine tropical aquatic organisms.

Water quality guidelines and ecological risk assessment of chemical substances like nickel (Ni) in tropical regions such as South East Asia and Melanesia are often based on temperate information as a result of fewer Ni ecotoxicity data available for tropical species. This leaves an unknown margin of uncertainty in the risk assessment in the tropics. In order to fill this data gap, this study was designed to conduct standard toxicity tests on Ni with two freshwater species (acute tests) and three marine species (acute and chronic tests) originated from tropical Hong Kong. All tests were carried out using measured concentrations of Ni with control mortality below 15%. The median lethal concentrations (LC50s) were determined as 2520 (95% confidence interval: 2210, 2860) and 426 (351, 515) µg Ni L-1 for the freshwater gastropods Pomacea lineata (48 h) and Sulcospira hainanensis (96 h), respectively, while 96 h LC50s of 4300 (3610, 5090), 18,200 (6470, 51,200), 62,400 (56,800, 68,500), and 71,700 (68,200, 75,400) µg Ni L-1 were derived for the marine copepod Tigriopus japonicus, the gastropod Monodonta labio, juvenile and adult of the marine fish Oryzias melastigma, respectively. The chronic effect concentration of 10% (EC10) based on the intrinsic rate of increase of the population of T. japonicus was 29 (12, 69) µg Ni L-1. In terms of growth inhibition, the chronic EC10 for M. labio was 34 (17, 67) µg Ni L-1. The results also indicated that T. japonicus in maturation stage (LC10: 484 (349, 919) µg Ni L-1) was less sensitive than its nauplii stage (LC10: 44 (27, 72) µg Ni L-1). This study represents an important addition of high-quality toxicity data to the tropical Ni toxicity database which can be used for future ecological risk assessment of Ni and derivation of its water quality guidelines in tropical regions.

Validation of the nickel biotic ligand model for locally relevant species in Australian freshwaters.

Australian freshwaters have relatively low water hardness and different calcium (Ca) to magnesium (Mg) ratios compared with those in Europe. The hardness values of a substantial proportion of Australian freshwaters fall below the application boundary of the existing European nickel biotic ligand models (Ni BLMs) of 2 mg Ca/L. Toxicity testing was undertaken using Hydra viridissima to assess the predictive ability of the existing Ni BLM for this species in extremely soft waters. This testing revealed an increased competitive effect of Ca and Mg with Ni for binding to the biotic ligand in soft water (<10 mg CaCO3 /L) than at higher water hardness. Modifications were made to the Ni BLM by increasing the binding constants for Ca and Mg at the biotic ligand to account for softer waters encountered in Australia and the more important competitive effect of Ca and Mg on Ni toxicity. To validate the modified Ni BLM, ecotoxicity testing was performed on 5 Australian test species in 5 different natural Australian waters. Overall, no single water chemistry parameter was able to indicate the trends in toxicity to all of the test species. The modified Ni BLMs were able to predict the toxicity of Ni to the test species in the validation studies in natural waters better than the existing Ni BLMs. The present study suggests that the overarching mechanisms defining Ni bioavailability to freshwater species are globally similar and that Ni BLMs can be used in all freshwater systems with minor modifications. Environ Toxicol Chem 2018;37:2566-2574. © 2018 SETAC.

Toxicity of nickel to tropical freshwater and sediment biota: A critical literature review and gap analysis.

More than two-thirds of the world's nickel (Ni) lateritic deposits are in tropical regions, and just less than half are within South East Asia and Melanesia (SEAM). With increasing Ni mining and processing in SEAM, environmental risk assessment tools are required to ensure sustainable development. Currently, there are no tropical-specific water or sediment quality guideline values for Ni, and the appropriateness of applying guideline values derived for temperate systems (e.g., Europe) to tropical ecosystems is unknown. Databases of Ni toxicity and toxicity tests for tropical freshwater and sediment species were compiled. Nickel toxicity data were ranked, using a quality assessment, identifying data to potentially use to derive tropical-specific Ni guideline values. There were no data for Ni toxicity in tropical freshwater sediments. For tropical freshwaters, of 163 Ni toxicity values for 40 different species, high-quality chronic data, based on measured Ni concentrations, were found for just 4 species (1 microalga, 2 macrophytes, and 1 cnidarian), all of which were relevant to SEAM. These data were insufficient to calculate tropical-specific guideline values for long-term aquatic ecosystem protection in tropical regions. For derivation of high-reliability tropical- or SEAM-specific water and sediment quality guideline values, additional research effort is required. Using gap analysis, we recommend how research gaps could be filled. Environ Toxicol Chem 2018;37:293-317. © 2017 SETAC.

Spectators or participants: How can SETAC become more engaged in international climate change research programs?

Environmental toxicologists and chemists have been crucial to evaluating the chemical fate and toxicological effects of environmental contaminants, including chlorinated pesticides, before and after Rachel Carson's publication of Silent Spring in 1962. Like chlorinated pesticides previously, global climate change is widely considered to be one of the most important environmental challenges of our time. Over the past 30 yr, climate scientists and modelers have shown that greenhouse gases such as CO2 and CH4 cause radiative forcing (climate forcing) and lead to increased global temperatures. Despite significant climate change research efforts worldwide, the climate science community has overlooked potential problems associated with chemical contaminants, in particular how climate change could magnify the ecological consequences of their use and disposal. It is conceivable that the impacts of legacy or new chemical contaminants on wildlife and humans may be exacerbated when climate changes, especially if global temperatures rise as predicted. This lack of attention to chemical contaminants represents an opportunity for environmental toxicologists and chemists to become part of the global research program, and our objective is to highlight the importance of and ways for that to occur. Environ Toxicol Chem 2017;36:1971-1977. © 2017 SETAC.

A review of nickel toxicity to marine and estuarine tropical biota with particular reference to the South East Asian and Melanesian region.

The South East Asian Melanesian (SEAM) region contains the world's largest deposits of nickel lateritic ores. Environmental impacts may occur if mining operations are not adequately managed. Effects data for tropical ecosystems are required to assess risks of contaminant exposure and to derive water quality guidelines (WQG) to manage these risks. Currently, risk assessment tools and WQGs for the tropics are limited due to the sparse research on how contaminants impact tropical biota. As part of a larger project to develop appropriate risk assessment tools to ensure sustainable nickel production in SEAM, nickel effects data were required. The aim of this review was to compile data on the effects of nickel on tropical marine, estuarine, pelagic and benthic species, with a particular focus on SEAM. There were limited high quality chronic nickel toxicity data for tropical marine species, and even fewer for those relevant to SEAM. Of the data available, the most sensitive SEAM species to nickel were a sea urchin, copepod and anemone. There is a significant lack of high quality chronic data for several ecologically important taxonomic groups including cnidarians, molluscs, crustaceans, echinoderms, macroalgae and fish. No high quality chronic nickel toxicity data were available for estuarine waters or marine and estuarine sediments. The very sparse toxicity data for tropical species limits our ability to conduct robust ecological risk assessment and may require additional data generation or read-across from similar species in other databases (e.g. temperate) to fill data gaps. Recommendations on testing priorities to fill these data gaps are presented.

Copper Uptake, Intracellular Localization, and Speciation in Marine Microalgae Measured by Synchrotron Radiation X-ray Fluorescence and Absorption Microspectroscopy.

Metal toxicity to aquatic organisms depends on the speciation of the metal and its binding to the critical receptor site(s) (biotic ligand) of the organism. The intracellular nature of the biotic ligand for Cu in microalgal cells was investigated using the high elemental sensitivity of microprobe synchrotron radiation X-ray fluorescence (SR-XRF) and X-ray absorption near-edge spectroscopy (XANES). The marine microalgae, Ceratoneis closterium, Phaeodactylum tricornutum, and Tetraselmis sp. were selected based on their varying sensitivities to Cu (72-h 50% population growth inhibitions of 8-47 µg Cu/L). Intracellular Cu in control cells was similar for all three species (2.5-3.2 × 10(-15) g Cu/cell) and increased 4-fold in C. closterium and Tetraselmis sp. when exposed to copper, but was unchanged in P. tricornutum (72-h exposure to 19, 40, and 40 µg Cu/L, respectively). Whole cell microprobe SR-XRF identified endogenous Cu in the central compartment (cytoplasm) of control (unexposed) cells. After Cu exposure, Cu was colocated with organelles/granules dense in P, S, Ca, and Si and this was clearly evident in thin sections of Tetraselmis sp. XANES indicated coexistence of Cu(I) and Cu(II) in control and Cu-exposed cells, with the Cu ligand (e.g., phytochelatin) in P. tricornutum different from that in C. closterium and Tetraselmis sp. This study supports the hypothesis that Cu(II) is reduced to Cu(I) and that polyphosphate bodies and phytochelatins play a significant role in the internalization and detoxification of Cu in marine microalgae.

Environmental Enteric Dysfunction Is Associated With Poor Linear Growth and Can Be Identified by Host Fecal mRNAs.

OBJECTIVE: Environmental enteric dysfunction (EED) can be assessed by the lactulose:mannitol (L:M) test. Our objective was to determine if selected host fecal transcripts were correlated with EED, and whether transcripts and clinical characteristics could be used to predict EED in rural African children. METHODS: Demographic and sanitation characteristics, along with L:M testing and host fecal transcript analyses from 798 asymptomatic Malawian children aged 12 to 61 months were compared with linear growth over the subsequent 3 months. Fecal host mRNA analysis included quantification of expression of 18 transcripts associated with L:M. Permeability was categorized as normal (L:M ≤ 0.15), moderate (0.15

Droplet digital PCR quantifies host inflammatory transcripts in feces reliably and reproducibly.

The gut is the most extensive, interactive, and complex interface between the human host and the environment and therefore a critical site of immunological activity. Non-invasive methods to assess the host response in this organ are currently lacking. Feces are the available analyte which have been in proximity to the gut tissue. We applied a method of concentrating host transcripts from fecal specimens using a existing bead-based affinity separation method for nucleic acids and quantified transcripts using droplet digital PCR (ddPCR) to determine the copy numbers of a variety of key transcripts in the gut immune system. ddPCR compartmentalizes the reaction in a small aqueous droplet suspended in oil, and counts droplets as either fluorescent or non-fluorescent. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used to normalize transcript concentration. This method was applied to 799 fecal samples from rural Malawian children, and over 20,000 transcript concentrations were quantified. Host mRNA was detected in >99% samples, a threshold for target detection was established at an average expression of 0.02 copies target/GAPDH, above which correlation coefficient between duplicate measurements is >0.95. Quantities of transcript detected using ddPCR were greater than standard qPCR. Fecal sample preservation at the time of collection did not require immediate freezing or the addition of buffers or enzymes. Measurements of transcripts encoding immunoactive proteins correlated with a measure of gut inflammation in the study children, thereby substantiating their relevance. This method allows investigators to interrogate gene expression in the gut.

Environmental Enteric Dysfunction Includes a Broad Spectrum of Inflammatory Responses and Epithelial Repair Processes.

BACKGROUND & AIMS: Environmental enteric dysfunction (EED), a chronic diffuse inflammation of the small intestine, is associated with stunting in children in the developing world. The pathobiology of EED is poorly understood because of the lack of a method to elucidate the host response. This study tested a novel microarray method to overcome limitation of RNA sequencing to interrogate the host transcriptome in feces in Malawian children with EED. METHODS: In 259 children, EED was measured by lactulose permeability (%L). After isolating low copy numbers of host messenger RNA, the transcriptome was reliably and reproducibly profiled, validated by polymerase chain reaction. Messenger RNA copy number then was correlated with %L and differential expression in EED. The transcripts identified were mapped to biological pathways and processes. The children studied had a range of %L values, consistent with a spectrum of EED from none to severe. RESULTS: We identified 12 transcripts associated with the severity of EED, including chemokines that stimulate T-cell proliferation, Fc fragments of multiple immunoglobulin families, interferon-induced proteins, activators of neutrophils and B cells, and mediators that dampen cellular responses to hormones. EED-associated transcripts mapped to pathways related to cell adhesion, and responses to a broad spectrum of viral, bacterial, and parasitic microbes. Several mucins, regulatory factors, and protein kinases associated with the maintenance of the mucous layer were expressed less in children with EED than in normal children. CONCLUSIONS: EED represents the activation of diverse elements of the immune system and is associated with widespread intestinal barrier disruption. Differentially expressed transcripts, appropriately enumerated, should be explored as potential biomarkers.

Increased Exclusivity of Breastfeeding Associated with Reduced Gut Inflammation in Infants.

INTRODUCTION: The development of the intestinal gut is largely influenced by early nutrition. Infant immunity is challenged by the exposure of the gut to foreign bodies, which mediate inflammation of the gut. This study assessed the levels of gut inflammation in relation to the percentage of breastmilk consumed/the exclusivity of breastfeeding in South African infants. This is the first study to examine markers of gut inflammation in infants in relation to exclusivity of breastfeeding measured by a gold standard method. METHODOLOGY: Twenty-four black South African infants were included in this study. The categorization of different degrees of exclusivity of breastfeeding was made using an objective gold standard method developed by the International Atomic Energy Agency (deuterium dilution method). Markers of gut inflammation were measured noninvasively by sampling stool from the infants averaging 6 months of age. Gut inflammation was investigated by running multiple Droplet Digital™ (Bio-Rad, Hercules, CA) polymerization chain reaction tests profiling a panel of five mRNA probes (interleukin-8 [IL-8], S100 calcium-binding protein A8 [S100A8], Toll-like receptor-4, human leukocyte antigen on chromosome 6 region 6p21.31, and defensin alpha 8). These mRNA biomarkers expressions were tested in proportion to number of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) copies as GAPDH is constitutively expressed in most cells. RESULTS: Two previously described robust mRNA markers of gut inflammation (S100A8 and IL-8) were found to correlate significantly to the percentage of breastmilk intake (r(2) = 0.4302, p = 0.0004 and r(2) = 0.3633, p = 0.002, respectively) in the range of 75-100% in 22 samples analyzed. CONCLUSIONS: This study using objective methodology has shown that higher percentages of breastmilk intake are associated with significantly lower levels of gut inflammation. This further supports the health benefits observed in exclusively breastfed infants.

Copper-induced changes in intracellular thiols in two marine diatoms: Phaeodactylum tricornutum and Ceratoneis closterium.

Phytochelatins and glutathione (reduced (GSH) and oxidised (GSSG)) are important intracellular ligands involved in metal sequestration and detoxification in algae. Intracellular ratios of GSH:GSSG are sensitive indicators of metal stress in algae, and like phytochelatin production are influenced by metal speciation, concentration, exposure time and the biological species. This study investigated the effect of copper exposure on phytochelatin and glutathione content in two marine diatoms Phaeodactylum tricornutum and Ceratoneis closterium at various time intervals between 0.5 and 72h. Liberation of cellular glutathione and phytochelatins was optimised using freeze/thaw cycles and chemical extraction, respectively. Extracted phytochelatins were derivatised (by fluorescent tagging of thiol compounds), separated and quantified using HPLC with fluorescence detection. Glutathione ratios were determined using a commercially available kit, which uses the enzyme glutathione reductase to measure total and oxidised glutathione. Despite similarities in size and shape between the two diatoms, differences in internalised copper, phytochelatin production (both chain length and quantity) and reduced glutathione concentrations were observed. P. tricornutum maintained reduced glutathione at between 58 and 80% of total glutathione levels at all time points, which would indicate low cellular stress. In C. closterium reduced glutathione constituted <10% of total glutathione after 48h. P. tricornutum also produced more phytochelatins and phytochelatins of longer chain length than C. closterium despite the latter species internalising significantly more copper.

The use of immobilised metal affinity chromatography (IMAC) to compare expression of copper-binding proteins in control and copper-exposed marine microalgae.

Toxicity of metals to aquatic organisms is dependent on both external factors, such as exposure concentration and water quality parameters, and intracellular processes including specific metal-binding sites and detoxification. Current models used to predict copper toxicity in microalgae do not adequately consider these intracellular processes. This study compared the copper-binding proteins from four species of marine microalgae, Dunaliella tertiolecta, Tetraselmis sp., Phaedactylum tricornutum and Ceratoneis closterium, in controls (no added copper) and following a 72-h exposure to copper (sufficient to inhibit growth by approximately 50%). Cells were lysed by sonication, which was optimised to obtain 54-94% cell rupture for the different algae. Cell lysates were processed by immobilised metal affinity chromatography (IMAC) using Cu(2+) as the bound metal (i.e. Cu-IMAC). Bound proteins were subsequently analysed by SDS-PAGE, comparing proteins recovered from algae that were exposed to copper versus untreated control cells. Individual proteins for which copper exposure resulted in changes to proteins present were excised from gels and further analysed by nano LC ESI-MS/MS; proteins were identified using the Mascot database. Proteins identified in this way included heat-shock proteins, rubisco, α- and ß-tubulins and ATP synthase (ß subunit). The results established that Cu-IMAC is a useful approach to identify proteins involved in copper binding in algae. This study identified several proteins that may play an active role in responses to copper toxicity in marine microalgae.

Intestinal inflammatory biomarkers and outcome in pediatric Clostridium difficile infections.

OBJECTIVES: To identify specific fecal biomarkers for symptomatic Clostridium difficile infection and predictors of poor outcomes. STUDY DESIGN: We enrolled 65 children with positive C difficile testing (cases) and 37 symptomatic controls. We also analyzed stool samples from colonized and non-colonized asymptomatic children. We performed enzyme immunoassays to determine fecal interleukin (IL)-8, lactoferrin, and phosphorylated-p38 protein concentrations, and quantitative polymerase chain reaction to determine IL-8 and chemokine ligand (CXCL)-5 RNA relative transcript abundances, and C difficile bacterial burden. RESULTS: Of 68 asymptomatic controls, 16 were colonized with C difficile. Phosphorylated-p38 was specific for C difficile infection but lacked sensitivity. Fecal cytokines were elevated in samples from symptomatic children, whether cases or controls. In children with C difficile infection, fecal CXCL-5 and IL-8 messenger RNA abundances at diagnosis correlated with persistent diarrhea after 5 days of C difficile infection therapy and with treatment with vancomycin. When children with concomitant viral gastroenteritis were excluded, these correlations persisted. Time-to-diarrhea resolution was significantly longer in patients with elevated fecal cytokines at diagnosis. A logistic regression model identified high CXCL-5 messenger RNA abundance as the only predictor of persistent diarrhea. Conversely, fecal C difficile bacterial burden was not different in symptomatic and asymptomatic children and did not correlate with any clinical outcome measure. CONCLUSIONS: Fecal inflammatory cytokines may be useful in distinguishing C difficile colonization from disease and identifying children with C difficile infection likely to have prolonged diarrhea.

Viral co-infections are common and are associated with higher bacterial burden in children with clostridium difficile infection.

Clostridium difficile infections in children are increasing. In this cohort study, we enrolled 62 children with diarrhea and C difficile. We performed polymerase chain reaction assays to detect viral agents of gastroenteritis and quantify C difficile burden. Fifteen (24%) children diagnosed as having C difficile infection had a concomitant viral co-infection. These patients tended to be younger and had a higher C difficile bacterial burden than children with no viral co-infections (median difference = 565,957 cfu/mL; P = 0.011), but were clinically indistinguishable. The contribution of viral co-infection to C difficile disease in children warrants future investigation.

Markers of intestinal inflammation, not bacterial burden, correlate with clinical outcomes in Clostridium difficile infection.

BACKGROUND: Clostridium difficile is a leading hospital-acquired infection. Many patients remain symptomatic for several days on appropriate antibiotic therapy. To assess the contribution of ongoing infection vs persistent inflammation, we examined the correlation between fecal cytokine levels, fecal C. difficile burden, and disease outcomes in C. difficile infection (CDI). METHODS: We conducted a prospective cohort study in Barnes Jewish Hospital between June 2011 and May 2012 of hospitalized adults with CDI. We determined fecal interleukin 8 (IL-8) and lactoferrin protein concentrations by enzyme immunoassay. We used real-time polymerase chain reaction (PCR) to measure relative fecal IL-8 and CXCL-5 RNA transcript abundances, and quantitative PCR to enumerate C. difficile burden. RESULTS: Of 120 study subjects, 101 (84%) were started on metronidazole, and 33 of those (33%) were subsequently given vancomycin. Sixty-two (52%) patients had diarrhea persistent for 5 or more days after starting CDI therapy. Initial fecal CXCL-5 messenger RNA (mRNA), IL-8 mRNA, and IL-8 protein correlated with persistent diarrhea and use of vancomycin. Time to diarrhea resolution was longer in patients with elevated fecal cytokines at diagnosis. Fecal cytokines were more sensitive than clinical severity scores in identifying patients at risk of treatment failure. Clostridium difficile burden did not correlate with any measure of illness or outcome at any point, and decreased equally with metronidazole and vancomycin. CONCLUSIONS: Persistent diarrhea in CDI correlates with intestinal inflammation and not fecal pathogen burden. These findings suggest that modulation of host response, rather than adjustments to antimicrobial regimens, might be a more effective approach to patients with unremitting disease.

Ecological risk assessment in the context of global climate change.

Changes to sources, stressors, habitats, and geographic ranges; toxicological effects; end points; and uncertainty estimation require significant changes in the implementation of ecological risk assessment (ERA). Because of the lack of analog systems and circumstances in historically studied sites, there is a likelihood of type III error. As a first step, the authors propose a decision key to aid managers and risk assessors in determining when and to what extent climate change should be incorporated. Next, when global climate change is an important factor, the authors recommend seven critical changes to ERA. First, develop conceptual cause-effect diagrams that consider relevant management decisions as well as appropriate spatial and temporal scales to include both direct and indirect effects of climate change and the stressor of management interest. Second, develop assessment end points that are expressed as ecosystem services. Third, evaluate multiple stressors and nonlinear responses-include the chemicals and the stressors related to climate change. Fourth, estimate how climate change will affect or modify management options as the impacts become manifest. Fifth, consider the direction and rate of change relative to management objectives, recognizing that both positive and negative outcomes can occur. Sixth, determine the major drivers of uncertainty, estimating and bounding stochastic uncertainty spatially, temporally, and progressively. Seventh, plan for adaptive management to account for changing environmental conditions and consequent changes to ecosystem services. Good communication is essential for making risk-related information understandable and useful for managers and stakeholders to implement a successful risk-assessment and decision-making process.