Pollen nutrition structures bee and plant community interactions.

As bees' main source of protein and lipids, pollen is critical for their development, reproduction, and health. Plant species vary considerably in the macronutrient content of their pollen, and research in bee model systems has established that this variation both modulates performance and guides floral choice. Yet, how variation in pollen chemistry shapes interactions between plants and bees in natural communities is an open question, essential for both understanding the nutritional dynamics of plant-pollinator mutualisms and informing their conservation. To fill this gap, we asked how pollen nutrition (relative protein and lipid content) sampled from 109 co-flowering plant species structured visitation patterns observed among 75 subgenera of pollen-collecting bees in the Great Basin/Eastern Sierra region (USA). We found that the degree of similarity in co-flowering plant species' pollen nutrition predicted similarity among their visitor communities, even after accounting for floral morphology and phylogeny. Consideration of pollen nutrition also shed light on the structure of this interaction network: Bee subgenera and plant genera were arranged into distinct, interconnected groups, delineated by differences in pollen macronutrient values, revealing potential nutritional niches. Importantly, variation in pollen nutrition alone (high in protein, high in lipid, or balanced) did not predict the diversity of bee visitors, indicating that plant species offering complementary pollen nutrition may be equally valuable in supporting bee diversity. Nutritional diversity should thus be a key consideration when selecting plants for habitat restoration, and a nutritionally explicit perspective is needed when considering reward systems involved in the community ecology of pollination.

A neonicotinoid pesticide alters Drosophila olfactory processing.

Neonicotinoid pesticides are well-known for their sublethal effects on insect behavior and physiology. Recent work suggests neonicotinoids can impair insect olfactory processing, with potential downstream effects on behavior and possibly survival. However, it is unclear whether impairment occurs during peripheral olfactory detection, during information processing in central brain regions, or in both contexts. We used Drosophila melanogaster to explore the potential for neonicotinoids to disrupt olfaction by conducting electrophysiological analyses of single neurons and whole antennae of flies exposed to varying concentrations of the neonicotinoid imidacloprid (IMD) that were shown to cause relative differences in fly survival. Our results demonstrated that IMD exposure significantly reduced the activity of a single focal olfactory neuron and delayed the return to baseline activity of the whole antenna. To determine if IMD also impacts olfactory-guided behavior, we compared flies' relative preference for odor sources varying in ethanol content. Flies exposed to IMD had a greater relative preference for ethanol-laced pineapple juice than control flies, demonstrating that neuronal shifts induced by IMD that we observed are associated with changes in relative preference. Given the interest in the sensory impacts of agrochemical exposure on wild insect behavior and physiology, we highlight the potential of Drosophila as a tractable model for investigating the effects of pesticides at scales ranging from single-neuron physiology to olfactory-guided behavior.

Assessing the impact of recreational water use on carriage of antimicrobial resistant organisms.

Understanding the role of exposure to natural recreational waters in the acquisition and transmission of antimicrobial resistance (AMR) is an area of increasing interest. A point prevalence study was carried out in the island of Ireland to determine the prevalence of colonisation with extended-spectrum beta-lactamase-producing Enterobacterales (ESBL-PE) and carbapenem-resistant Enterobacterales (CRE) in recreational water users (WU) and matched controls. A total of 411 adult participants (199 WU, 212 controls) submitted at least one faecal sample between September 2020 - October 2021. In total, 80 Enterobacterales were isolated from 73 participants. ESBL-PE were detected in 29 (7.1 %) participants (7 WU, 22 controls), and CRE were detected in nine (2.2 %) participants (4 WU, 5 controls). No carbapenemase-producing Enterobacterales (CPE) were detected. WU were significantly less likely to harbour ESBL-PE than controls (risk ratio = 0.34, 95 % CI 0.148 to 0.776, χ2 7.37, p = 0.007). This study demonstrates the occurrence of ESBL-PE and CRE in healthy participants in Ireland. Recreational exposure to bathing water in Ireland was associated with a decreased prevalence of colonisation with ESBL-PE and CRE.

Architected Metal Selenides via Sequential Cation and Anion Exchange on Self-Organizing Nanocomposites.

Shape-preserving conversion reactions have the potential to unlock new routes for self-organization of complex three-dimensional (3D) nanomaterials with advanced functionalities. Specifically, developing such conversion routes toward shape-controlled metal selenides is of interest due to their photocatalytic properties and because these metal selenides can undergo further conversion reactions toward a wide range of other functional chemical compositions. Here, we present a strategy toward metal selenides with controllable 3D architectures using a two-step self-organization/conversion approach. First, we steer the coprecipitation of barium carbonate nanocrystals and silica into nanocomposites with controllable 3D shapes. Second, using a sequential exchange of cations and anions, we completely convert the chemical composition of the nanocrystals into cadmium selenide (CdSe) while preserving the initial shape of the nanocomposites. These architected CdSe structures can undergo further conversion reactions toward other metal selenides, which we demonstrate by developing a shape-preserving cation exchange toward silver selenide. Moreover, our conversion strategy can readily be extended to convert calcium carbonate biominerals into metal selenide semiconductors. Hence, the here-presented self-assembly/conversion strategy opens exciting possibilities toward customizable metal selenides with complex user-defined 3D shapes.

The Complex Interplay Between Antibiotic Resistance and Pharmaceutical and Personal Care Products in the Environment.

Antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are important environmental contaminants. Nonetheless, what drives the evolution, spread, and transmission of antibiotic resistance dissemination is still poorly understood. The abundance of ARB and ARGs is often elevated in human-impacted areas, especially in environments receiving fecal wastes, or in the presence of complex mixtures of chemical contaminants, such as pharmaceuticals and personal care products. Self-replication, mutation, horizontal gene transfer, and adaptation to different environmental conditions contribute to the persistence and proliferation of ARB in habitats under strong anthropogenic influence. Our review discusses the interplay between chemical contaminants and ARB and their respective genes, specifically in reference to co-occurrence, potential biostimulation, and selective pressure effects, and gives an overview of mitigation by existing man-made and natural barriers. Evidence and strategies to improve the assessment of human health risks due to environmental antibiotic resistance are also discussed. Environ Toxicol Chem 2023;00:1-16. © 2022 SETAC.

Research needs for optimising wastewater-based epidemiology monitoring for public health protection.

Wastewater-based epidemiology (WBE) is an unobtrusive method used to observe patterns in illicit drug use, poliovirus, and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). The pandemic and need for surveillance measures have led to the rapid acceleration of WBE research and development globally. With the infrastructure available to monitor SARS-CoV-2 from wastewater in 58 countries globally, there is potential to expand targets and applications for public health protection, such as other viral pathogens, antimicrobial resistance (AMR), pharmaceutical consumption, or exposure to chemical pollutants. Some applications have been explored in academic research but are not used to inform public health decision-making. We reflect on the current knowledge of WBE for these applications and identify barriers and opportunities for expanding beyond SARS-CoV-2. This paper critically reviews the applications of WBE for public health and identifies the important research gaps for WBE to be a useful tool in public health. It considers possible uses for pathogenic viruses, AMR, and chemicals. It summarises the current evidence on the following: (1) the presence of markers in stool and urine; (2) environmental factors influencing persistence of markers in wastewater; (3) methods for sample collection and storage; (4) prospective methods for detection and quantification; (5) reducing uncertainties; and (6) further considerations for public health use.

Discovery of octopamine and tyramine in nectar and their effects on bumblebee behavior.

Nectar chemistry can influence the behavior of pollinators in ways that affect pollen transfer, yet basic questions about how nectar chemical diversity impacts plant-pollinator relationships remain unexplored. For example, plants' capacity to produce neurotransmitters and endocrine disruptors may offer a means to manipulate pollinator behavior. We surveyed 15 plant species and discovered that two insect neurotransmitters, octopamine and tyramine, were widely distributed in floral nectar. We detected the highest concentration of these chemicals in Citrus, alongside the well-studied alkaloid caffeine. We explored the separate and interactive effects of these chemicals on insect pollinators in a series of behavioral experiments on bumblebees (Bombus impatiens). We found that octopamine and tyramine interacted with caffeine to alter key aspects of bee behavior relevant to plant fitness (sucrose responsiveness, long-term memory, and floral preferences). These results provide evidence for a means by which synergistic or antagonistic nectar chemistry might influence pollinators.

Infectious disease and cognition in wild populations.

Infectious disease is linked to impaired cognition across a breadth of host taxa and cognitive abilities, potentially contributing to variation in cognitive performance within and among populations. Impaired cognitive performance can stem from direct damage by the parasite, the host immune response, or lost opportunities for learning. Moreover, cognitive impairment could be compounded by factors that simultaneously increase infection risk and impair cognition directly, such as stress and malnutrition. As highlighted in this review, however, answers to fundamental questions remain unresolved, including the frequency, duration, and fitness consequences of infection-linked cognitive impairment in wild animal populations, the cognitive abilities most likely to be affected, and the potential for adaptive evolution of cognition in response to accelerating emergence of infectious disease.

Existing evidence on antibiotic resistance exposure and transmission to humans from the environment: a systematic map.

Background: Antimicrobial resistance (AMR) is predicted to become the leading cause of death by 2050 with antibiotic resistance being an important component. Anthropogenic pollution introduces antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) to the natural environment. Currently, there is limited empirical evidence demonstrating whether humans are exposed to environmental AMR and whether this exposure can result in measurable human health outcomes. In recent years there has been increasing interest in the role of the environment and disparate evidence on transmission of AMR to humans has been generated but there has been no systematic attempt to summarise this. We aim to create two systematic maps that will collate the evidence for (1) the transmission of antibiotic resistance from the natural environment to humans on a global scale and (2) the state of antibiotic resistance in the environment in the United Kingdom. Methods: Search strategies were developed for each map. Searches were undertaken in 13 bibliographic databases. Key websites were searched and experts consulted for grey literature. Search results were managed using EndNote X8. Titles and abstracts were screened, followed by the full texts. Articles were double screened at a minimum of 10% at both stages with consistency checking and discussion when disagreements arose. Data extraction occurred in Excel with bespoke forms designed. Data extracted from each selected study included: bibliographic information; study site location; exposure source; exposure route; human health outcome (Map 1); prevalence/percentage/abundance of ARB/antibiotic resistance elements (Map 2) and study design. EviAtlas was used to visualise outputs. Results: For Map 1, 40 articles were included, from 11,016 unique articles identified in searches, which investigated transmission of AMR from the environment to humans. Results from Map 1 showed that consumption/ingestion was the most studied transmission route. Exposure (n = 17), infection (n = 16) and colonisation (n = 11) being studied as an outcome a similar number of times, with mortality studied infrequently (n = 2). In addition, E. coli was the most highly studied bacterium (n = 16). For Map 2, we included 62 studies quantifying ARB or resistance elements in the environment in the UK, from 6874 unique articles were identified in the searches. The most highly researched species was mixed communities (n = 32). The most common methodology employed in this research question was phenotypic testing (n = 37). The most commonly reported outcome was the characterisation of ARBs (n = 40), followed by characterisation of ARGs (n = 35). Other genetic elements, such as screening for intI1 (n = 15) (which encodes a Class 1 integron which is used as a proxy for environmental ARGs) and point mutations (n = 1) were less frequently reported. Both maps showed that research was focused towards aquatic environments. Conclusions: Both maps can be used by policy makers to show the global (Map 1) and UK (Map 2) research landscapes and provide an overview of the state of AMR in the environment and human health impacts of interacting with the environment. We have also identified (1) clusters of research which may be used to perform meta-analyses and (2) gaps in the evidence base where future primary research should focus. Supplementary Information: The online version contains supplementary material available at 10.1186/s13750-022-00262-2.

Natural recreational waters and the risk that exposure to antibiotic resistant bacteria poses to human health.

Antimicrobial resistance (AMR) is widely recognised as a considerable threat to human health, wellbeing and prosperity. Many clinically important antibiotic resistance genes are understood to have originated in the natural environment. However, the complex interactions between humans, animals and the environment makes the health implications of environmental AMR difficult to quantify. This narrative review focuses on the current state of knowledge regarding antibiotic resistant bacteria (ARB) in natural bathing waters and implications for human health. It considers the latest research focusing on the transmission of ARB from bathing waters to humans. The limitations of existing evidence are discussed, as well as research priorities. The authors are of the opinion that future studies should include faecally contaminated bathing waters and people exposed to these environments to accurately parameterise environment-to-human transmission.

Measuring foraging preferences in bumble bees: a comparison of popular laboratory methods and a test for sucrose preferences following neonicotinoid exposure.

Animals develop food preferences based on taste, nutritional quality and to avoid environmental toxins. Yet, measuring preferences in an experimental setting can be challenging since ecologically realistic assays can be time consuming, while simplified assays may not capture natural sampling behavior. Field realism is a particular challenge when studying behavioral responses to environmental toxins in lab-based assays, given that toxins can themselves impact sampling behavior, masking our ability to detect preferences. We address these challenges by comparing different experimental methods for measuring sucrose concentration preference in bumble bees (Bombus impatiens), evaluating the utility of two preference chamber-based methods (ad libitum versus a novel restricted-sampling assay) in replicating bees' preferences when they fly freely between artificial flowers in a foraging arena. We find that the restricted-sampling method matched a free-flying scenario more closely than the ad libitum protocol, and we advocate for expanded use of this approach, given its ease of implementation. We then performed a second experiment using the new protocol to ask whether consuming the neonicotinoid pesticide imidacloprid, known to suppress feeding motivation, interfered with the expression of sucrose preferences. After consuming imidacloprid, bees were less likely to choose the higher-quality sucrose even as they gained experience with both options. Thus, we provide evidence that pesticides interfere with bees' ability to discriminate between floral rewards that differ in value. This work highlights a simple protocol for assessing realistic foraging preferences in bees and provides an efficient way for researchers to measure the impacts of anthropogenic factors on preference expression.

Microbes and pollinator behavior in the floral marketplace.

Pollinator foraging decisions shape microbial dispersal, and microbes change floral phenotypes in ways perceivable by pollinators. Yet, the role microbes play in the cognitive ecology of pollination is relatively unexplored. Reviewing recent literature on floral microbial ecology and pollinator behavior, we advocate for further integration between these two fields. Insights into pollinator learning, memory, and decision-making can help explain their responses to microbially-altered floral phenotypes. Specifically, considering how pollinators forage for multiple nutrients, cope with uncertainty, structure foraging bouts, and move through their environment could inform predictions about microbial dispersal within plant communities. We highlight how behavior connects microbial changes in floral phenotype to downstream effects on both microbial dispersal and plant fitness.

A global multinational survey of cefotaxime-resistant coliforms in urban wastewater treatment plants.

The World Health Organization Global Action Plan recommends integrated surveillance programs as crucial strategies for monitoring antibiotic resistance. Although several national surveillance programs are in place for clinical and veterinary settings, no such schemes exist for monitoring antibiotic-resistant bacteria in the environment. In this transnational study, we developed, validated, and tested a low-cost surveillance and easy to implement approach to evaluate antibiotic resistance in wastewater treatment plants (WWTPs) by targeting cefotaxime-resistant (CTX-R) coliforms as indicators. The rationale for this approach was: i) coliform quantification methods are internationally accepted as indicators of fecal contamination in recreational waters and are therefore routinely applied in analytical labs; ii) CTX-R coliforms are clinically relevant, associated with extended-spectrum ß-lactamases (ESBLs), and are rare in pristine environments. We analyzed 57 WWTPs in 22 countries across Europe, Asia, Africa, Australia, and North America. CTX-R coliforms were ubiquitous in raw sewage and their relative abundance varied significantly (<0.1% to 38.3%), being positively correlated (p < 0.001) with regional atmospheric temperatures. Although most WWTPs removed large proportions of CTX-R coliforms, loads over 103 colony-forming units per mL were occasionally observed in final effluents. We demonstrate that CTX-R coliform monitoring is a feasible and affordable approach to assess wastewater antibiotic resistance status.

Pandemic Guidance for Stroke Centers Aiding COVID-19 Treatment Teams.

The coronavirus disease 2019 (COVID-19) pandemic has in some regions overwhelmed the capacity and staffing needs of healthcare systems, necessitating the provision of resources and staff from different disciplines to aid COVID treatment teams. Stroke centers have multidisciplinary clinical and procedural expertise to support COVID treatment teams. Staff safety and patient safety are essential, as are open lines of communication between stroke center leaders and hospital leadership in a pandemic where policies and procedures can change or evolve rapidly. Support needs to be allocated in a way that allows for the continued operation of a fully capable stroke center, with the ability to adjust if stroke center volume or staff attrition requires.

What is the research evidence for antibiotic resistance exposure and transmission to humans from the environment? A systematic map protocol.

BACKGROUND: Antimicrobial resistance (AMR) is a public health crisis that is predicted to cause 10 million deaths per year by 2050. The environment has been implicated as a reservoir of AMR and is suggested to play a role in the dissemination of antibiotic resistance genes (ARGs). Currently, most research has focused on measuring concentrations of antibiotics and characterising the abundance and diversity of ARGs and antibiotic resistant bacteria (ARB) in the environment. To date, there has been limited empirical research on whether humans are exposed to this, and whether exposure can lead to measureable impacts on human health. Therefore, the objective of this work is to produce two linked systematic maps to investigate previous research on exposure and transmission of AMR to humans from the environment. The first map will investigate the available research relating to exposure and transmission of ARB/ARGs from the environment to humans on a global scale and the second will investigate the prevalence of ARB/ARGs in various environments in the UK. These two maps will be useful for policy makers and research funders to identify where there are significant gluts and gaps in the current research, and where more primary and synthesis research needs to be undertaken. METHODS: Separate search strategies will be developed for the two maps. Searches will be run in 13 databases, and grey literature will be sought from key websites and engagement with experts. Hits will be managed in EndNote and screened in two stages (title/abstract then full text) against predefined inclusion criteria. A minimum of 10% will be double screened with ongoing consistency checking. All included studies will have data extracted into a bespoke form designed and piloted for each map. Data to be extracted will include bibliographic details, study design, location, exposure source, exposure route, health outcome (Map 1); and prevalence/percentage of ARB/ARG (Map 2). No validity appraisal will be undertaken. Results will be tabulated and presented narratively, together with graphics showing the types and areas of research that has been undertaken and heatmaps for key exposure-health outcomes (Map 1) and exposure-prevalence (Map 2).

No evidence for neonicotinoid preferences in the bumblebee Bombus impatiens.

Neonicotinoid pesticides can have a multitude of negative sublethal effects on bees. Understanding their impact on wild populations requires accurately estimating the dosages bees encounter under natural conditions. This is complicated by the possibility that bees might influence their own exposure: two recent studies found that bumblebees (Bombus terrestris) preferentially consumed neonicotinoid-contaminated nectar, even though these chemicals are thought to be tasteless and odourless. Here, we used Bombus impatiens to explore two elements of these reported preferences, with the aim of understanding their ecological implication and underlying mechanism. First, we asked whether preferences persisted across a range of realistic nectar sugar concentrations, when measured at a series of time points up until 24 h. Second, we tested whether bees' neonicotinoid preferences were driven by an ability to associate their post-ingestive consequences with floral stimuli such as colour, location or scent. We found no evidence that foragers preferred to consume neonicotinoid-containing solutions, despite finding effects on feeding motivation and locomotor activity in line with previous work. Bees also did not preferentially visit floral stimuli previously paired with a neonicotinoid-containing solution. These results highlight the need for further research into the mechanisms underlying bees' responses to these pesticides, critical for determining how neonicotinoid-driven foraging preferences might operate in the real world for different bee species.

Learning of bimodal versus unimodal signals in restrained bumble bees.

Similar to animal communication displays, flowers emit complex signals that attract pollinators. Signal complexity could lead to higher cognitive load for pollinators, impairing performance, or might benefit them by facilitating learning, memory and decision making. Here, we evaluated learning and memory in foragers of the bumble bee Bombus impatiens trained to simple (unimodal) versus complex (bimodal) signals under restrained conditions. Use of a proboscis extension response protocol enabled us to control the timing and duration of stimuli presented during absolute and differential learning tasks. Overall, we observed broad variation in performance under the two conditions, with bees trained to compound bimodal signals learning and remembering as well as, better than or more poorly than bees trained to unimodal signals. Interestingly, the outcome of training was affected by the specific colour-odour combination. Among unimodal stimuli, the performance with odour stimuli was higher than with colour stimuli, suggesting that olfactory signals played a more significant role in the compound bimodal condition. This was supported by the fact that after 24 h, most bimodal-treatment bees responded to odour but not visual stimuli. We did not observe differences in latency of response, suggesting that signal composition affected decision accuracy, not speed. We conclude that restrained bumble bee workers exhibit broad variation of responses to bimodal stimuli and that components of the bimodal signal may not be used equivalently. The analysis of bee performance under restrained conditions enables accurate control of the multimodal stimuli provided to individuals and to study the interaction of individual components within a compound.

A cross-sectional study on the prevalence of illness in coastal bathers compared to non-bathers in England and Wales: Findings from the Beach User Health Survey.

The risks of illness associated with bathing in UK coastal waters have not been quantified since the early 1990s. Efforts have been made since then to improve the quality of bathing waters. The aim of this study was to quantify the prevalence of symptoms of illness associated with sea bathing in bathers in England and Wales. A cross-sectional study was conducted between June 2014 and April 2015. An online survey collected information from sea bathers and non-bathers on their visits to beaches in England and Wales along with the occurrence of symptoms of illness. 2631 people (1693 bathers, 938 non-bathers) responded to the survey. Compared to non-bathers, bathers were more likely to report skin ailments (adjusted prevalence odds ratio (AOR) = 2.64, 95% confidence interval (CI) 1.23 to 5.65, p = 0.01), ear ailments (AOR = 3.77, 95% CI 1.84 to 7.73, p < 0.001), and any symptoms of illness (AOR = 3.73, 95% CI 2.63 to 5.29, p < 0.001). There was weak evidence of an increase in the odds of gastrointestinal illness (AOR = 1.59, 95% CI 0.96 to 2.65, p = 0.07), respiratory ailments (AOR = 2.44, 95% CI 0.92 to 6.48, p = 0.07) and eye ailments (AOR = 2.12, 95% CI 0.83 to 5.39, p = 0.11). While the study design does not allow inference of causality, we do observe an association between sea bathing in England and Wales and reported symptoms of ill health. This suggests that despite higher rates of compliance with water quality criteria among bathing waters nowadays, the odds of illness for bathers relative to non-bathers is similar in magnitude to estimates made in the 1990s.

Exploring metabolic adaptation of Streptococcus pneumoniae to antibiotics.

The Gram-positive bacterium Streptococcus pneumoniae is one of the common causes of community acquired pneumonia, meningitis, and otitis media. Analyzing the metabolic adaptation toward environmental stress conditions improves our understanding of its pathophysiology and its dependency on host-derived nutrients. In this study, extra- and intracellular metabolic profiles were evaluated to investigate the impact of antimicrobial compounds targeting different pathways of the metabolome of S. pneumoniae TIGR4Δcps. For the metabolomics approach, we analyzed the complex variety of metabolites by using 1H NMR, HPLC-MS, and GC-MS as different analytical techniques. Through this combination, we detected nearly 120 metabolites. For each antimicrobial compound, individual metabolic effects were detected that often comprised global biosynthetic pathways. Cefotaxime altered amino acids metabolism and carbon metabolism. The purine and pyrimidine metabolic pathways were mostly affected by moxifloxacin treatment. The combination of cefotaxime and azithromycin intensified the stress response compared with the use of the single antibiotic. However, we observed that three cell wall metabolites were altered only by treatment with the combination of the two antibiotics. Only moxifloxacin stress-induced alternation in CDP-ribitol concentration. Teixobactin-Arg10 resulted in global changes of pneumococcal metabolism. To meet the growing requirements for new antibiotics, our metabolomics approach has shown to be a promising complement to other OMICs investigations allowing insights into the mode of action of novel antimicrobial compounds.

The Immunomodulator 1-Methyltryptophan Drives Tryptophan Catabolism Toward the Kynurenic Acid Branch.

Background: Animal model studies revealed that the application of 1-methyltryptophan (1-MT), a tryptophan (TRP) analog, surprisingly increased plasma levels of the TRP metabolite, kynurenic acid (KYNA). Under inflammatory conditions, KYNA has been shown to mediate various immunomodulatory effects. Therefore, the present study aims to confirm and clarify the effects of 1-MT on TRP metabolism in mice as well as in humans. Methods: Splenocytes from Balb/C or indoleamine 2,3-dioxygenase knockout (IDO1-/-) mice or whole human blood were stimulated with 1-MT for 6, 24, or 36 h. C57BL/6 mice received 1-MT in drinking water for 5 days. Cell-free supernatants and plasma were analyzed for TRP and its metabolites by tandem mass spectrometry (MS/MS). Results: 1-MT treatment induced an increase in TRP and its metabolite, KYNA in Balb/C, IDO-/- mice, and in human blood. Concurrently, the intermediate metabolite kynurenine (KYN), as well as the KYN/TRP ratio, were reduced after 1-MT treatment. The effects of 1-MT on TRP metabolites were similar after the in vivo application of 1-MT to C57BL/6 mice. Conclusions: The data indicate that 1-MT induced an increase of KYNA ex vivo and in vivo confirming previously described results. Furthermore, the results of IDO-/- mice indicate that this effect seems not to be mediated by IDO1. Due to the proven immunomodulatory properties of KYNA, a shift toward this branch of the kynurenine pathway (KP) may be one potential mode of action by 1-MT and should be considered for further applications.