Macroinvertebrate community response to inter-annual and regional river flow regime dynamics

Spatio-temporal variability in river flow is a fundamental control on instream habitat structure and riverine ecosystem biodiversity and integrity. However, long-term riverine ecological time-series to test hypotheses about hydrology–ecology interactions in a broader temporal context are rare, and studies spanning multiple rivers are often limited in their temporal coverage to less than five years. To address this research gap, a unique spatio-temporal hydroecological analysis was conducted of long-term instream ecological responses (1990–2000) to river flow regime variability at 83 sites across England and Wales. The results demonstrate clear hydroecological associations at the national scale (all data). In addition, significant differences in ecological response are recorded between three ‘regions’ identified (RM1–3*) associated with characteristics of the flow regime. The effect of two major supra-seasonal droughts (1990–1992 and 1996–1997) on inter-annual (IA) variability of the LIFE scores is evident with both events showing a gradual decline before and recovery of LIFE scores after the low flow period. The instream community response to high magnitude flow regimes (1994 and 1995) is also apparent, although these associations are less striking. The results demonstrate classification of rivers into flow regime regions offers a way to help unravel complex hydroecological associations. The approach adopted herein could easily be adapted for other geographical locations, where datasets are available. Such work is imperative to understand flow regime–ecology interactions in a longer term, wider spatial context and so assess future hydroecological responses to climate change and anthropogenic modification of riverine ecosystems

Selection of river flow indices for the assessment of hydroecological change

A wide range of ‘ecologically relevant’ hydrological indices (variables) have been identified as potential drivers of riverine communities. Recently, concerns have been expressed regarding index redundancy (i.e. similar patterns of variance) across the host of hydrological descriptors on offer to researchers and water resource managers. Some guiding principles are required to aid selection of the most statistically defensible and meaningful river flow indices for hydroecological analysis. In this short communication, we investigate the utility of a principal components analysis (PCA)-based method that identifies 25 hydrological variables to characterise the major modes of statistical variation in 201 hydrological indices for 83 rivers across England and Wales. The emergent variables, and all 201 hydrological variables, are used to develop regression models [for the whole data set and three river flow regime shape (i.e. annual hydrograph form) classes] for an 11-year macroinvertebrate community dataset (i.e. LIFE scores). The same ‘best’ models are produced using the PCA-based method and all 201 hydrological variables for two of the three river flow regime groups. However, weaker models are yielded by the PCA-based method for the remaining (flashy) river flow regime class and the whole data set (all 83 rivers). Thus, it is important to exercise caution when employing data reduction/ index redundancy approaches, as they may reject variables of ecological significance due to the assumption that the statistically dominant sources of hydrological variability are the principal drivers of, perhaps more subtle (sensitive), hydroecological associations

Feature tracking microfluidic analysis reveals differential roles of viscosity and friction in sickle cell blood

Characterization of blood flow rheology in hematological disorders is critical for understanding disease pathophysiology. Existing methods to measure blood rheological parameters are limited in their physiological relevance, and there is a need for new tools that focus on the microcirculation and extract properties at finer resolution than overall flow resistance. Herein, we present a method that combines microfluidic systems and powerful object-tracking computational technologies with mathematical modeling to separate the red blood cell flow profile into a bulk component and a wall component. We use this framework to evaluate differential contributions of effective viscosity and wall friction to the overall resistance in blood from patients with Sickle Cell Disease (SCD) under a range of oxygen tensions. Our results demonstrate that blood from patients with SCD exhibits elevated frictional and viscous resistances at all physiologic oxygen tensions. Additionally, the viscous resistance increases more rapidly than the frictional resistance as oxygen tension decreases, which may confound analyses that extract only flow velocities or overall flow resistances. Furthermore, we evaluate the impact of transfusion treatments on the components of the resistance, revealing patient variability in blood properties that may improve our understanding of the heterogeneity of clinical responses to such treatments. Overall, our system provides a new method to analyze patient-specific blood properties and can be applied to a wide range of hematological and vascular disorders

Macroinvertebrate responses to flow and stream temperature variability across regulated and non-regulated rivers

Flow regulation via impoundments threatens lotic ecosystems and the services they provide globally. Impoundments drastically alter flow and stream temperature variability within fluvial environments, but efforts to quantify ecohydrological and ecothermal responses to flow regulation in conjunction have been sparsely explored to date. This study examined macroinvertebrate community responses to river flow (discharge) and stream temperature variability across paired regulated and non-regulated systems associated with three reservoirs located in adjacent catchments. Community abundances, functional traits and biomonitoring indices were examined and ecological differences between non-regulated and regulated sites were quantified, with the most sensitive faunal response being correlated against a suite of flow and thermal indices. Regulated sites exhibited reduced low-flow variability and rapid increases in discharge during peak flows that regularly exceeded those conveyed by non-regulated sites, whilst stream temperature variability was highly congruent between sites. Macroinvertebrate functional traits were particularly sensitive to flow regulation and incorporating biomonitoring indices marginally improved the ecological discrimination between regulated and non-regulated sites. Unlike community abundances, functional traits did not vary spatially between catchments, highlighting that such information could guide the implementation of regionally uniform environmental flows. Macroinvertebrate communities responded significantly to various hydrological parameters, particularly those associated with the timing of extreme flows, but were less sensitive to thermal controls. Future research should explore ecological responses to antecedent hydrological and stream temperature variability associated with flow regulation to provide a better understanding of the underlying mechanisms driving biotic alterations, which could guide future environmental flow methodologies

Habitat-specific invertebrate responses to hydrological variability, anthropogenic flow alterations, and hydraulic conditions

© 2019 The Authors. Freshwater Biology Published by John Wiley & Sons Ltd. Quantifying ecological responses to river flow regimes is a key scientific approach underpinning many environmental flow (e-flow) strategies. Incorporating habitat-scale influences (e.g. substrate composition and organic matter cover) within e-flow frameworks has the potential to provide a broader understanding of the causal mechanisms shaping instream communities, which may be used to guide river management strategies. In this study, we examined invertebrate communities inhabiting three distinct habitat groups (HGs—defined by coarse substrates, fine sediments, and the fine-leaved macrophyte Ranunculus sp.) across four rivers (each comprising two study sites) within a single catchment. We tested the structural and functional responses of communities inhabiting different HGs to three sets of flow-related characteristics: (1) antecedent hydrological (discharge—m3/s) variability; (2) antecedent anthropogenic flow alterations (percentage of discharge added to or removed from the river by human activity); and (3) proximal hydraulic conditions (characterised by the Froude number). The former two were derived from groundwater model daily time series in the year prior to the collection of each invertebrate sample, while the latter was collected at the point of sampling. While significant effects of hydrological and anthropogenic flow alteration indices were detected, Froude number exerted the greatest statistical influence on invertebrate communities. This highlights that habitat-scale hydraulic conditions to which biota are exposed at the time of sampling are a key influence on the structure and function of invertebrate communities. Mixed-effect models testing invertebrate community responses to flow-related characteristics, most notably Froude number, improved when a HG interaction term was incorporated. This highlights that different mineralogical and organic habitat patches mediate ecological responses to hydraulic conditions. This can be attributed to HGs supporting distinct taxonomic and functional compositions and/or providing unique ecological functions (e.g. flow refuges), which alter how instream communities respond to hydraulic conditions. While the individual importance of both flow and small-scale habitat effects on instream biota has been widely reported, this study provides rare evidence on how their interactive effects have a significant influence on riverine ecosystems. These findings suggest that river management strategies and e-flow frameworks should not only aim to create a mosaic of riverine habitats that support ecosystem functioning, but also consider the management of local hydraulic conditions within habitat patches to support specific taxonomic and functional compositions

Macroinvertebrate community responses to river impoundment at multiple spatial scales

River impoundment by the construction of dams potentially modifies a wide range of abiotic and biotic factors in lotic ecosystems and is considered one of the most significant anthropogenic impacts on rivers globally. The past two decades have witnessed a growing body of research centred on quantifying the effects of river impoundment, with a focus on mitigating and managing the effects of individual large dams. This study presents a novel multi-scale comparison of paired downstream and control sites associated with multiple water supply reservoirs (n = 80) using a spatially extensive multi-year dataset. Macroinvertebrate community structure and indices were analysed in direct association with spatial (e.g. region) and temporal variables (e.g. season) to identify consistent patterns in ecological responses to impoundment. Macroinvertebrate communities at monitoring sites downstream of water supply reservoirs differed significantly from those at control sites at larger spatial scales, both in terms of community structure and taxa richness. The effect was most significant at the regional scale, while biogeographical factors appeared to be important drivers of community differences at the national scale. Water supply reservoirs dampened natural seasonal patterns in community structure at sites downstream of impoundments. Generally, taxonomic richness was higher and %EPT richness lower at downstream sites. Biomonitoring indices used for river management purposes were able to detect community differences, demonstrating their sensitivity to river regulation activities. The results presented improve our understanding of the spatially extensive and long-term effects of water supply reservoirs on instream communities and provide a basis for the future implementation of mitigation measures on impounded rivers and heavily modified waterbodies

677. Systematic Review of the Early Use Experince of Cefiderocol in Real World Practice

Abstract Background Gram-negative bacteria (GNB) with resistance to carbapenems is a growing global public health concern. The World Health Organisation have listed three priority GNB pathogens for the development of novel antimicrobial agents; Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacterales. The purpose of this systematic review (SR) was to report evidence on the use of cefiderocol (FDC), a siderophore cephalosporin, for patients with GNB infections in compassionate use or expanded access settings. Methods Searches were undertaken to identify relevant evidence up to December 2021. Two independent reviewers screened the records retrieved for relevance to the SR with disagreements adjudicated by a third reviewer. Patients receiving FDC in a compassionate use, expanded access setting or those with limited treatment options for the treatment of GNB infection were eligible. Eligible case reports and case series were assessed for quality using predefined tools and data were extracted (by a single reviewer with data checking performed by a second reviewer), tabulated and summarised. Results Forty-four studies (n=150 patients) were identified reporting the use of FDC; 3 case series studies and 41 case reports. The most commonly reported pathogens were P. aeruginosa (41.3%), A. baumannii (36.0%) and A. xylosoxidans (14.3%). The diagnoses varied widely across the included patients. All patients were administered FDC at a dose between 750 mg and 2 g per day on various schedules, adjusted for renal function for between one and six weeks. Clinical cure was reported in 137 patients using author-specified definitions with 74 patients (54.0%) reporting clinical cure and 18 (13.1%) reporting failure. Microbiological eradication was reported in 78 patients of whom 56 (71.8%) reported success, while 22 (28.2%) reported failure. For mortality (n=123) 80 patients (65.0%) remained alive at the end of treatment, while 43 (35.0%) died. Adverse event (AE) data was reported for 53 patients of whom 13 (24.5%) reported AEs, while 40 (75.5%) did not. See Table 1.0. Conclusion FDC is a promising therapy for patients with GNB infections with limited treatment options. Real world practice shows a high microbiological eradication rate and a small number of AEs. Disclosures Carlo Tascini, n/a, Shionogi: Grant/Research Support Aurelien Dinh, Professor of Infectious Disease, Shionogi: Advisor/Consultant|Shionogi: Board Member Christopher M. Longshaw, PhD, Shionogi: Employee Anita C. Fitzgerald, MPH, Shionogi: Shionogi commissioned York Health Economics Consortium of which I am an associate, to conduct the systematic review we are submitting to IDWeek Hannah Wood, BA MA, Shionogi: Shionogi commissioned York Health Economics Consortium of which I am an employee, to conduct the systematic review we are submitting to IDWeek Jacoby Vivien M. Patterson, MA Cantab, MB BChir, FFPH MD, Shionogi: Shionogi commissioned York Health Economics Consortium of which I am an associate, to conduct the systematic review we are submitting to IDW Deborah Watkins, MSc, Shionogi: Shionogi commissioned York Health Economics Consortium of which I am an employee, to conduct the systematic review we are submitting to IDWeek Katy Wilson, LLM, Shionogi: Shionogi commissioned York Health Economics Consortium of which I am an employee to conduct the systematic review we are submitting to IDWeek Karan Gill, Master of Science, Shionogi: Employee

Flow variability and macroinvertebrate community response within riverine systems

River flow regimes, controlled by climatic and catchment factors, vary over a wide range of temporal and spatial scales. This hydrological dynamism is important in determining the structure and functioning of riverine ecosystems; however, such hydroecological associations remain poorly quantified. This paper explores and models relationships between a suite of flow regime predictors and macroinvertebrate community metrics from 83 rivers in England and Wales. A two-stage analytical approach was employed: (1) classification of 83 river basins based upon the magnitude and shape (form) of their long-term (1980 – 1999) average annual regime to group basins with similar flow responses; and (2) examination of relationships between a total of 201 flow regime descriptors identified by previous researchers and macroinvertebrate community metrics for the whole data set and long-term flow regime classes over an 11-year period (1990 – 2000). The classification method highlighted large-scale patterns in river flow regimes, identifying five magnitude classes and three shape classes. A west–east trend of flow regime magnitude (high-low) and timing (early-late peak) was displayed across the study area, reflecting climatic gradients and basin controls (e.g. lithology). From the suite of hydrological variables, those associated with the magnitude of the flow regime consistently produced the strongest relationships with macroinvertebrate community metrics for all sites and for the long-term regime composite classes. The results indicate that the classification (subdivision) of rivers into flow regime regions potentially offers a means of increasing predictive capacity and, in turn, better management of fluvial hydrosystems

High prevalence of subclinical tuberculosis in HIV-1-infected persons without advanced immunodeficiency: implications for TB screening

Background The prevalence of asymptomatic tuberculosis (TB) in recently diagnosed HIV-1-infected persons attending pre-antiretroviral therapy (ART) clinics is not well described. In addition, it is unclear if the detection of Mycobacterium tuberculosis in these patients clearly represents an early asymptomatic phase leading to progressive disease or transient excretion of bacilli. Objective To describe the prevalence and outcome of subclinical TB disease in HIV-1-infected persons not eligible for ART. Methods The study was conducted in 274 asymptomatic ART-naive HIV-1-infected persons in Khayelitsha Day Hospital, Cape Town, South Africa. All participants were screened for TB using a symptom screen and spoligotyping was performed to determine genotypes. Results The prevalence of subclinical TB disease was 8.5% (95% CI 5.1% to 13.0%) (n = 18; median days to culture positivity 17 days), with 22% of patients being smear-positive. Spoligotyping showed a diverse variety of genotypes with all paired isolates being of the same spoligotype, effectively excluding cross-contamination. 56% of patients followed up developed symptoms 3 days to 2 months later. All were well and still in care 6-12 months after TB diagnosis; 60% were started on ART. A positive tuberculin skin test (OR 4.96, p = 0.064), low CD4 count (OR 0.996, p = 0.06) and number of years since HIV diagnosis (OR 1.006, p = 0.056) showed trends towards predicting TB disease. Conclusion This study found a high prevalence but good outcome (retained in care) of subclinical TB disease in HIV-1-infected persons. The results suggest that, in high HIV/TB endemic settings, a positive HIV-1 test should prompt TB screening by sputum culture irrespective of symptoms, particularly in those with a positive tuberculin skin test, longer history of HIV infection and low CD4 count. Operational difficulties in resource-constrained settings with respect to screening with TB culture highlight the need for rapid and affordable point-of-care tests to identify persons with clinical and subclinical TB disease.Immunogenetics and cellular immunology of bacterial infectious disease