New sensitive tools to characterize meta-metabolome response to short- and long-term cobalt exposure in dynamic river biofilm communities.

Untargeted metabolomics is a non-a priori analysis of biomolecules that characterizes the metabolome variations induced by short- and long-term exposures to stressors. Even if the metabolite annotation remains lacunar due to database gaps, the global metabolomic fingerprint allows for trend analyses of dose-response curves for hundreds of cellular metabolites. Analysis of dose/time-response curve trends (biphasic or monotonic) of untargeted metabolomic features would thus allow the use of all the chemical signals obtained in order to determine stress levels (defense or damage) in organisms. To develop this approach in a context of time-dependent microbial community changes, mature river biofilms were exposed for 1 month to four cobalt (Co) concentrations (from background concentration to 1 × 10-6 M) in an open system of artificial streams. The meta-metabolomic response of biofilms was compared against a multitude of biological parameters (including bioaccumulation, biomass, chlorophyll a content, composition and structure of prokaryotic and eukaryotic communities) monitored at set exposure times (from 1 h to 28 d). Cobalt exposure induced extremely rapid responses of the meta-metabolome, with time range inducing defense responses (TRIDeR) of around 10 s, and time range inducing damage responses (TRIDaR) of several hours. Even in biofilms whose structure had been altered by Co bioaccumulation (reduced biomass, chlorophyll a contents and changes in the composition and diversity of prokaryotic and eukaryotic communities), concentration range inducing defense responses (CRIDeR) with similar initiation thresholds (1.41 ± 0.77 × 10-10 M Co2+ added in the exposure medium) were set up at the meta-metabolome level at every time point. In contrast, the concentration range inducing damage responses (CRIDaR) initiation thresholds increased by 10 times in long-term Co exposed biofilms. The present study demonstrates that defense and damage responses of biofilm meta-metabolome exposed to Co are rapidly and sustainably impacted, even within tolerant and resistant microbial communities.

Meta-metabolomic responses of river biofilms to cobalt exposure and use of dose-response model trends as an indicator of effects.

The response of the meta-metabolome is rarely used to characterize the effects of contaminants on a whole community. Here, the meta-metabolomic fingerprints of biofilms were examined after 1, 3 and 7 days of exposure to five concentrations of cobalt (from background concentration to 1 × 10-5 M) in aquatic microcosms. The untargeted metabolomic data were processed using the DRomics tool to build dose-response models and to calculate benchmark-doses. This approach made it possible to use 100% of the chemical signal instead of being limited to the very few annotated metabolites (7%). These benchmark-doses were further aggregated into an empirical cumulative density function. A trend analysis of the untargeted meta-metabolomic feature dose-response curves after 7 days of exposure suggested the presence of a concentration range inducing defense responses between 1.7 × 10-9 and 2.7 × 10-6 M, and of a concentration range inducing damage responses from 2.7 × 10-6 M and above. This distinction was in good agreement with changes in the other biological parameters studied (biomass and chlorophyll content). This study demonstrated that the molecular defense and damage responses can be related to contaminant concentrations and represents a promising approach for environmental risk assessment of metals.

IL-32 Drives the Differentiation of Cardiotropic CD4+ T Cells Carrying HIV DNA in People With HIV.

Interleukin 32 (IL-32) is a potent multi-isoform proinflammatory cytokine, which is upregulated in people with HIV (PWH) and is associated with cardiovascular disease (CVD) risk. However, the impact of IL-32 isoforms on CD4 T-cell cardiotropism, a mechanism potentially contributing to heart inflammation, remains unknown. Here we show that IL-32 isoforms ß and γ induce the generation of CCR4+CXCR3+ double positive (DP) memory CD4 T-cell subpopulation expressing the tyrosine kinase receptor c-Met, a phenotype associated with heart-homing of T cells. Our ex vivo studies on PWH show that the frequency of DP CD4 T cells is significantly higher in individuals with, compared to individuals without, subclinical atherosclerosis and that DP cells from antiretroviral-naive and treated individuals are highly enriched with HIV DNA. Together, these data demonstrate that IL-32 isoforms have the potential to induce heart-homing of HIV-infected CD4 T cells, which may further aggravate heart inflammation and CVD in PWH.

Treatment of severe human mpox virus infection with tecovirimat: A case series.

Background: Tecovirimat (TCV, TPOXX®) is an orthopox-specific antiviral drug indicated for the treatment of smallpox. There is also a mechanistic basis for its use in mpox infection. However, its approval was based on animal studies, and its efficacy and side-effect profile in human patients with disease is unknown. Methods: During the 2022 international mpox epidemic, clinicians in Canada accessed TCV from the Public Health Agency of Canada's National Emergency Strategic Stockpile for severe cases of mpox disease. We describe the use of TCV in nine adults with severe mpox virus infection in Montréal, Canada. Results: Five patients were treated for severe and potentially life-threatening head and neck symptoms, while four were treated for genitourinary or anorectal disease. Two-thirds of patients were also treated for suspected bacterial superinfection. All patients recovered (median time to resolution of severe symptoms: nine days) without relapse or hospital readmission. No patients reported adverse events attributable to TCV and no patients stopped their treatment early. Conclusion: Our experience suggests that TCV is well tolerated and may accelerate recovery in severe cases. These preliminary, observational data may also be explained by concomitant treatment for superinfection and are limited by the absence of a control group. Controlled, clinical trials should be conducted to clarify the attributable benefit of TCV in severe mpox infection.

A comparative study of the accumulation and detoxification of copper and zinc in Chlamydomonas reinhardtii: The role of extracellular polymeric substances.

Extracellular polymeric substances (EPS) form an interface between microalgae and the surrounding water environment. Copper (Cu) and zinc (Zn) are essential micronutrients but may negatively affect microbial growth when their concentrations reach toxic thresholds. However, how EPS affect the accumulation and resistance of Cu and Zn in microalgae remains largely unknown. Here, we investigated EPS production upon Cu/Zn exposure and compared the tolerance strategies to the two metals by Chlamydomonas reinhardtii with and without EPS. Microalgal EPS synthesis was induced by Cu/Zn treatments, and the functional groups of polysaccharides and proteins were involved in complexation with metal ions. The extraction of EPS aggravated the toxicity and reduced the removal of metals from solution, but the effect was more pronounced for Cu than for Zn. Copper bound on the cell surface accounted for 54.6 ± 2.0 % of the Cu accumulated by C. reinhardtii, whose EPS components strongly correlated with Cu adsorption. In contrast, 74.3 ± 3.0 % of accumulated Zn was absorbed in cells, and glutathione synthesis was significantly induced. Redundancy and linear correlation analyses showed that the polysaccharide, protein and DNA contents in EPS were significantly correlated with Cu accumulation, absorption and adsorption but not with Zn. Data fitted to a Michaelis-Menten model further showed that the EPS-intact cells had higher binding capacity for Cu2+ but not for Zn2+. These differential impacts of EPS on Cu/Zn sorption and detoxification contribute to a more comprehensive understanding of the roles of microalgal EPS in the biogeochemical cycle of metals.

Mycoplasma genitalium infection among gay, bisexual and other men who have sex with men in Montréal, Canada.

Background: The bacteria Mycoplasma genitalium has been identified as a causative agent of urethritis in men, especially in gay, bisexual and other men who have sex with men (gbMSM). Canadian clinic-based data have identified a high prevalence of M. genitalium and resistance to antibiotic treatments. This article estimates the prevalence of M. genitalium infections among Montréal gbMSM, explores correlates for M. genitalium infection and estimates the prevalence of mutations associated with antimicrobial resistance (AMR). Methods: Engage Cohort Study is a multi-site longitudinal study on sexually active gbMSM, aged 16 years and older, recruited via respondent-driven sampling in Montréal, Toronto and Vancouver. Participants completed a questionnaire on behaviour and were tested for sexually transmitted and blood-borne infections at each visit. For this sub-study, Montréal participants with a follow-up visit that occurred between November 2018 and November 2019 were included. Results: A total of 2,064 samples were provided by 716 participants. Prevalence of M. genitalium infection was 5.7% at rectal and/or urethral sites, 4.0% at rectal site and 2.2% at urethral site. Correlates for M. genitalium infection were younger age and reporting six or more sexual partners in the past six months. Prevalence of macrolide resistance associated mutations (MRAM), quinolone resistance associated mutations (QRAM) and either MRAM or QRAM, was 82%, 29% and 85%, respectively. Conclusion: This first population-based study among gbMSM in Canada documents a high prevalence of urethral and rectal M. genitalium infection and high levels of AMR. Our results highlight the importance of access to testing and AMR detection when indicated.

Evaluation of the performance of multiple immunoassay diagnostic platforms on the National Microbiology Laboratory SARS-CoV-2 National Serology Panel.

BACKGROUND: Serological assays designed to detect SARS-CoV-2 antibodies are being used in serological surveys and other specialized applications. As a result, and to ensure that the outcomes of serological testing meet high quality standards, evaluations are required to assess the performance of these assays and the proficiency of laboratories performing them. METHODS: A panel of 60 plasma/serum samples from blood donors who had reverse transcriptase-polymerase chain reaction (RT-PCR) confirmed SARS-CoV-2 infections and 21 SARS-CoV-2 negative samples were secured and distributed to interested laboratories within Canada (n = 30) and the United States (n = 1). Participating laboratories were asked to provide details on the diagnostic assays used, the platforms the assays were performed on, and the results obtained for each panel sample. Laboratories were blinded with respect to the expected outcomes. RESULTS: The performance of the different assays evaluated was excellent, with the high-throughput platforms of Roche, Ortho, and Siemens demonstrating 100% sensitivity. Most other high-throughput platforms had sensitivities of >93%, with the exception of the IgG assay using the Abbott ARCHITECT which had an average sensitivity of only 87%. The majority of the high-throughput platforms also demonstrated very good specificities (>97%). CONCLUSION: This proficiency study demonstrates that most of the SARS-CoV-2 serological assays utilized by provincial public health or hospital laboratories in Canada have acceptable sensitivity and excellent specificity.

HISTORIQUE: Les dosages sérologiques conçus pour dépister les anticorps anti-SRAS-CoV-2 sont utilisés dans les études sérologiques et d'autres applications spécialisées. Par conséquent, et pour s'assurer que leurs résultats respectent des normes de qualité, il faut procéder à des évaluations de leur performance et de la compétence des laboratoires à les effectuer. MÉTHODOLOGIE: Les chercheurs ont obtenu une batterie de 60 prélèvements de plasma et de sérum chez des donneurs dont l'amplification en chaîne par polymérase après transcription inverse (RT-PCR) avait confirmé des infections par le SRAS-CoV-2 et de 21 prélèvements dont les résultats étaient négatifs au SRAS-CoV-2 et les ont distribués aux laboratoires intéressés du Canada (n = 30) et des États-Unis (n = 1). Ils ont invité les laboratoires participants à fournir de l'information détaillée sur les dosages diagnostiques utilisés, les plateformes sur lesquelles les dosages étaient exécutés et les résultats obtenus pour chaque échantillon. Les chercheurs ont demandé aux laboratoires participants de fournir de l'information détaillée sur les dosages diagnostiques utilisés, les plateformes sur lesquelles les dosages ont été effectués, et les résultats obtenus à l'égard de chaque échantillon. Les laboratoires ont mené les études à l'insu des résultats escomptés. RÉSULTATS: Les divers dosages avaient une excellente exécution, les plateformes à haut débit de Roche, d'Ortho et de Siemens démontrant une sensibilité de 100 %. La plupart des autres plateformes à haut débit avaient des sensibilités de plus de 93 %, à l'exception des dosages des IgG faisant appel à l'analyseur ARCHITECT d'Abbott, dont la sensibilité moyenne était de seulement 87 %. La majorité des plateformes à haut débit avaient également une très bonne spécificité (plus de 97 %). CONCLUSION: La présente étude de compétence démontre que la plupart des dosages sérologiques du SRAS-CoV-2 évalués dans des laboratoires sanitaires provinciaux ou les laboratoires hospitaliers du Canada possèdent une sensibilité acceptable et une excellente spécificité.

Vulnerability and tolerance to nickel of periphytic biofilm harvested in summer and winter.

Metals are naturally present in freshwater ecosystems but anthropogenic activities like mining operations represent a long-standing concern. Metals released into aquatic environments may affect microbial communities such as periphytic biofilm, which plays a key role as a primary producer in stream ecosystems. Using two 28-day microcosm studies involving two different photoperiods (light/dark cycle of 16/8 vs 8/16), the present study assessed the effects of four increasing nickel (Ni) concentrations (0-6 µM) on two natural biofilm communities collected at different seasons (summer and winter). The two communities were characterized by different structural profiles and showed significant differences in Ni accumulated content for each treatment. For instance, the biofilm metal content was four times higher in the case of summer biofilm at the highest Ni treatment and after 28 days of exposure. Biomarkers examined targeted both heterotrophic and autotrophic organisms. For heterotrophs, the ß-glucosidase and ß-glucosaminidase showed no marked effects of Ni exposure and were globally similar between the two communities suggesting low toxicity. However, the photosynthetic yield confirmed the toxicity of Ni on autotrophs with maximum inhibition of 81 ± 7% and 60 ± 1% respectively for the summer and winter biofilms. Furthermore, biofilms previously exposed to the highest long-term Ni concentration ([Ni2+] = 6 µM) revealed no acute effects in subsequent toxicity based on the PSII yield, suggesting a tolerance acquisition by the phototrophic community. Taken together, the results suggest that the biofilm response to Ni exposure was dependent of the function considered and that descriptors such as biofilm metal content could be seasonally dependent, information of great importance in a context of biomonitoring.

New insights in copper handling strategies in the green alga Chlamydomonas reinhardtii under low-iron condition.

Copper (Cu) is a redox-active transition element critical to various metabolic processes. These functions are accomplished in tandem with Cu-binding ligands, mainly proteins. The main goal of this work was to understand the mechanisms that govern the intracellular fate of Cu in the freshwater green alga, Chlamydomonas reinhardtii, and more specifically to understand the mechanisms underlying Cu detoxification by algal cells in low-Fe conditions. We show that Cu accumulation was up to 51-fold greater for algae exposed to Cu in low-Fe medium as compared to the replete-Fe growth medium. Using the stable isotope 65Cu as a tracer, we studied the subcellular distribution of Cu within the various cell compartments of C. reinhardtii. These data were coupled with metallomic and proteomic approaches to identify potential Cu-binding ligands in the heat-stable proteins and peptides fraction of the cytosol. Cu was mostly found in the organelles (78%), and in the heat-stable proteins and peptides (21%) fractions. The organelle fraction appeared to also be the main target compartment of Cu accumulation in Fe-depleted cells. As Fe levels in the medium were shown to influence Cu homeostasis, we found that C. reinhardtii can cope with this additional stress by utilizing different Cu-binding ligands. Indeed, in addition to expected Cu-binding ligands such as glutathione and phytochelatins, 25 proteins were detected that may also play a role in the Cu-detoxification processes in C. reinhardtii. Our results shed new light on the coping mechanisms of C. reinhardtii when exposed to environmental conditions that induce high rates of Cu accumulation.

Covid-19 vaccine immunogenicity in people living with HIV-1.

INTRODUCTION: COVID-19 vaccine efficacy has been evaluated in large clinical trials and in real-world situation. Although they have proven to be very effective in the general population, little is known about their efficacy in immunocompromised patients. HIV-infected individuals' response to vaccine may vary according to the type of vaccine and their level of immunosuppression. We evaluated immunogenicity of an mRNA anti-SARS CoV-2 vaccine in HIV-positive individuals. METHODS: HIV-positive individuals (n = 121) were recruited from HIV clinics in Montreal and stratified according to their CD4 counts. A control group of 20 health care workers naïve to SARS CoV-2 was used. The participants' Anti-RBD IgG responses were measured by ELISA at baseline and 3-4 weeks after receiving the first dose of an mRNA vaccine). RESULTS: Eleven of 121 participants had anti-COVID-19 antibodies at baseline, and a further 4 had incomplete data for the analysis. Mean anti-RBD IgG responses were similar between the HIV negative control group (n = 20) and the combined HIV+ group (n = 106) (p = 0.72). However, these responses were significantly lower in the group with <250 CD4 cells/mm3. (p < 0.0001). Increasing age was independently associated with decreased immunogenicity. CONCLUSION: HIV-positive individuals with CD4 counts over 250 cells/mm3 have an anti-RBD IgG response similar to the general population. However, HIV-positive individuals with the lowest CD4 counts (<250 cells/mm3) have a weaker response. These data would support the hypothesis that a booster dose might be needed in this subgroup of HIV-positive individuals, depending on their response to the second dose.

Role of iron in gene expression and in the modulation of copper uptake in a freshwater alga: Insights on Cu and Fe assimilation pathways.

Metal uptake and toxicity can generally be related to its aqueous speciation and to the presence of competitive ions as described by the biotic ligand model. Beyond these simple chemical interactions at the surface of aquatic organisms, several internal biological feedback mechanisms can also modulate metal uptake. This is particularly important for essential elements for which specific transport systems were developed over the course of evolution. Based on the results of short-term Cu2+ uptake experiments and on the analysis of the expression of certain genes involved in Cu and Fe homeostasis, we studied the effects of Fe3+ on Cu2+ uptake by the freshwater green alga Chlamydomonas reinhardtii. We observed a significant increase in Cu2+ uptake rate in algal cells acclimated to a low Fe3+ medium up to 4.7 times greater compared to non-acclimated algal cells. The overexpression of the ferroxidase FOX1 and permease FTR1 genes suggests an activation of the high affinity Fe3+ assimilation system, which could constitute a plausible explanation for the increase in Cu2+ uptake rate in acclimatized algae. We show that Fe availability can have a significant impact on Cu uptake. Our observations reinforce the importance of considering physiological factors to better predict metal bioavailability.

Temperature and Photoperiod Affect the Sensitivity of Biofilms to Nickel and its Accumulation.

Whereas metal impacts on fluvial communities have been extensively investigated, effects of abiotic parameters on community responses to contaminants are poorly documented. Variations in photoperiod and temperature commonly occur over the course of a season and could affect aquatic biofilm communities and their responses to contaminants. Our objective was to characterize the influence of environmental conditions (photoperiod and temperature) on nickel (Ni) bioaccumulation and toxicity using a laboratory-grown biofilm. Environmental parameters were chosen to represent variations that can occur over the summer season. Biofilms were exposed for 7 days to six dissolved Ni treatments (ranging from 6 to 115 µM) at two temperatures (14 and 20 °C) using two photoperiods (16:8 and 12:12-h light:dark cycle). Under these different scenarios, structural (dry weight biomass and chlorophyll-a) and functional biomarkers (photosynthetic yield and Ni content) were analyzed at four sampling dates, allowing us to evaluate Ni sensitivity of biofilms over time. The results highlight the effects of temperature on Ni accumulation and tolerance of biofilms. Indeed, biofilms exposed at 20 °C accumulated 1.6-4.2-fold higher concentrations of Ni and were characterized by a lower median effect concentration value using photosynthetic yield compared with those exposed at 14 °C. In terms of photoperiod, significantly greater rates of Ni accumulation were observed at the highest tested Ni concentration for biofilms exposed to a 12:12-h compared with a 16:8-h light:dark cycle. Our study demonstrates the influence of temperature on biofilm metabolism and illustrates that environmental factors may influence Ni accumulation response and thus Ni responses of phototrophic biofilms. Environ Toxicol Chem 2022;41:1649-1662. © 2022 SETAC.

Effects of thorium on bacterial, microalgal and micromeiofaunal community structures in a periphytic biofilm.

Few ecotoxicity studies are available on thorium (Th) which hinders the ability to evaluate its ecotoxicological risk. Its release in the environment is often associated with the extraction of rare earth elements and uranium, as well as the field applications of phosphate fertilizers. This study investigates the effects of Th on microbial communities of periphytic biofilms. Ceramic plates were left to colonize for one month in the laboratory with a biofilm sampled from Cap Rouge river (QC, Canada). Plates were randomly placed in channels containing culture media representing three different conditions: a control condition (C0; background Th concentrations of 0.004 ± 0.002 nM), a low Th concentration condition (C1; 0.18 ± 0.09 nM Th) and a moderately high Th condition (C10; 8.7 ± 3.4 nM) for up to 4 weeks. The presence of Th modified the diatom community by changing its taxonomic structure, reducing diversity and increasing cell density. The taxonomic structure of the bacterial community, followed by 16S metabarcoding analysis, was affected with a significant decrease in Pseudanabaena and Shingopyxis genera in the two Th exposed conditions. No direct toxic effect of Th was observed on counted micromeiofauna but the changes in diatom and bacterial communities could explain the higher number of individual diatoms and micromeiofauna observed in Th-exposed conditions. This work shows that low concentrations of Th can modify biofilm structure, which, in turn, could disturb its ecologically key functions.

Community-Based Prevalence Estimates of Chlamydia trachomatis and Neisseria gonorrhoeae Infections Among Gay, Bisexual, and Other Men Who Have Sex With Men in Montréal, Canada.

BACKGROUND: Reported cases of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) infections are increasing among Canadian men. Estimates of community-based CT/NG prevalence are lacking among gay, bisexual, and other men who have sex with men (GBM). METHODS: Respondent driven sampling was used to recruit GBM in Montréal, Canada between February 2017 and June 2018. Specimens provided from urogenital, rectal, and pharyngeal sites were analyzed using nucleic acid amplification test to detect CT/NG. Prevalence estimates of CT/NG, overall and by anatomical site were calculated. All estimates are respondent-driven sampling-adjusted. RESULTS: Among 1177 GBM, the prevalence of rectal, urogenital, pharyngeal and overall were respectively 2.4%, 0.4%, 0.4%, and 2.8% for CT infections, and 3.1%, 0.4%, 3.5%, and 5.6% for NG infections. If testing had been limited to the urogenital site, 80% and 94% of CT and NG infections, respectively, would have been missed. CONCLUSIONS: This community-based study among GBM shows that the CT prevalence was about half of that observed for NG. A large part of CT/NG infections involves only the extragenital sites, highlighting the need for systematic multisite screening regardless of symptoms. In the mist of the COVID-19 pandemic and the limited CT/NG screening capacity due to test kits shortage, it might be considered to prioritize rectal and pharyngeal CT/NG testing over urogenital testing in asymptomatic GBM.

Exploring the role of water chemistry on metal accumulation in biofilms from streams in mining areas.

Biofilms play a key role in aquatic ecosystems. They are ubiquitous, even in the most contaminated ecosystems, and have great potential as biomonitors of exposure to contaminants such as metals. Freshwater biofilms and surface waters were sampled in two active mining areas of Canada: in the northern part of Nunavik (Quebec) and in the Greater Sudbury area (Ontario). Significant linear relationships were found between both total dissolved and free metal ion concentrations with biofilm metal contents for Cu and Ni, but not for Cd. When pH was below 6, biofilms accumulated less metals than at higher pHs. These results confirm that protons have a protective effect, leading to lower internalized metal concentrations. When considering only the sites where pH was above 6, the linear relationships between metal concentrations in water and in biofilms were improved for all three studied metals. The presence of metal ions could also modify the internalization of a given metal. To further study the role of cations as competitors to Cu, Ni and Cd uptake, relationships between the ratio of biofilm metal contents (Cu, Ni and Cd) on the ambient free metal ion concentrations were built as a function of potential cation competitors, such as major cations and metals. Surprisingly, our data suggest that calcium plays a minor role in preventing metal accumulation as compared to magnesium and possibly other metals. At a global scale, metal accumulation remained highly consistent between the two studied regions and over the sampling period, despite differences in ambient physicochemical water characteristics, climate or types of ecosystems. Metal bioaccumulation is thus a promising biomarker to assess metal bioavailability in a mining context. Nevertheless, more data are still required to further highlight the contribution of each competitor in metal accumulation by biofilms and to be able to build a unifying predictive model.

Thorium Exposure Drives Fatty Acid and Metal Transfer from Biofilms to the Grazer Lymnaea sp.

Aquatic ecotoxicological risks associated with tetravalent metallic elements such as thorium (Th) are still poorly understood. Periphytic biofilm represents an important food source in aquatic environments; thus, such risks could severely affect nutrient and energy cycling in these ecosystems. The present study investigated the potential for Th to change the fatty acid composition of biofilm communities. Bioaccumulation of Th and fatty acids were measured after 4 wk to 2 exposure conditions: a control (C0) and Th exposure (C10). Some major fatty acids such as C16:1n-7 and docosahexaenoic acid C22:6n-3 differed significantly between control and C10 conditions. To determine if Th can be trophically transferred and to investigate the impacts of nutritional quality changes on primary consumers, common pond snails (Lymnaea sp.) were fed for 4 wk with control and Th-exposed biofilm. Thorium appeared to be trophically transferable to the grazers, although we cannot exclude that part of the Th accumulated by the snails may have been taken from the water through release from the biofilms. The composition of major fatty acids observed in the grazers was also significantly affected, notably by a decrease of total polyunsaturated fatty acids. These results indicate that very low Th concentrations can decrease the nutritional quality of organisms at the base of the food chain. Environ Toxicol Chem 2021;40:2220-2228. © 2021 SETAC.

Development of Quantitative Ion Character-Activity Relationship Models to Address the Lack of Toxicological Data for Technology-Critical Elements.

Recent industrial developments have resulted in an increase in the use of so-called technology-critical elements (TCEs), for which the potential impacts on aquatic biota remain to be evaluated. In the present study, quantitative ion character-activity relationships (QICARs) have been developed to relate intrinsic metal properties to their toxicity toward freshwater aquatic organisms. In total, 23 metal properties were tested as predictors of acute median effect concentration (EC50) values for 12 data-rich metals, for algae, daphnids, and fish (with and without species distinction). Simple and multiple linear regressions were developed using the toxicological data expressed as a function of the total dissolved metal concentrations. The best regressions were then tested by comparing the predicted EC50 values for the TCEs (germanium, indium, gold, and rhenium) and platinum group elements (iridium, platinum, palladium, rhodium, and ruthenium) with the few measured values that are available. The 8 "best" QICAR models (adjusted r2 > 0.6) used the covalent index as the predictor. For a given metal ion, this composite parameter is a measure of the importance of covalent interactions relative to ionic interactions. Toxicity was reasonably well predicted for most of the TCEs, with values falling within the 95% prediction intervals for the regressions of the measured versus predicted EC50 values. Exceptions included Au(I) (all test organisms), Au(III) (algae and fish), Pt(II) (algae, daphnids), Ru(III) (daphnids), and Rh(III) (daphnids, fish). We conclude that QICARs show potential as a screening tool to review toxicity data and flag "outliers," which might need further scrutiny, and as an interpolating or extrapolating tool to predict TCE toxicity. Environ Toxicol Chem 2021;40:1139-1148. © 2020 SETAC.

Gradient diffusion susceptibility testing for Neisseria gonorrhoeae: an accurate alternative to agar dilution in high-MIC strains?

INTRODUCTION: The correlation of antimicrobial susceptibility testing (AST) between agar dilution and gradient diffusion for Neisseria gonorrhoeae is not well established, especially in strains with high MICs. AIM: The objective of this study was to evaluate the accuracy of gradient diffusion for N. gonorrhoeae . METHODS: Fifty strains of N. gonorrhoeae , all tested by the agar dilution method according to CLSI methods and confirmed to be genetically distinct using molecular typing (NG-MAST), were selected. Isolates with high MICs were targeted. Gradient diffusion was performed for ceftriaxone (CRO), cefixime (CFX), azithromycin (AZT), tetracycline (TET) and fosfomycin (FOS) using two different commercial antimicrobial strips on different culture media (a non-commercial GC agar base with 1 % defined growth supplement and two commercial media). The performance of agar gradient diffusion was assessed based on accuracy, using essential and category agreements (EA and CA). RESULTS: Essential and categorical agreement were over 90 % for CRO, CFX and AZT on the two commercial agar media tested. Category disagreements were seen for CFX and AZT, mostly just very major errors. For TET, EA ranged from 80 to 96 % and CA ranged from 38 to 76 %, most of the misclassifications being minor errors. Finally, EA for FOS ranged between 80 and 98 %. CONCLUSION: Gradient diffusion is an accurate and acceptable alternative for CRO, CFX and AZT. Caution is advised when MICs are reported by gradient diffusion approach breakpoints because of the possibility of very major errors. The use of gradient diffusion is limited for TET because of the high rate of minor errors.

Unravelling Metal Speciation in the Microenvironment Surrounding Phytoplankton Cells to Improve Predictions of Metal Bioavailability.

A lack of knowledge on metal speciation in the microenvironment surrounding phytoplankton cells (i.e., the phycosphere) represents an impediment to accurately predicting metal bioavailability. Phycosphere pH and O2 concentrations from a diversity of algae species were compiled. For marine algae in the light, the average increases were 0.32 pH units and 0.17 mM O2 in the phycosphere, whereas in the dark the average decreases were 0.10 pH units and 0.03 mM O2, in comparison to bulk seawater. In freshwater algae, the phycosphere pH increased by 1.28 units, whereas O2 increased by 0.38 mM in the light. Equilibrium modeling showed that the pH alteration influenced the chemical species distribution (i.e., free ion, inorganic complexes, and organic complexes) of Al, Cd, Co, Cu, Fe, Hg, Mn, Ni, Pb, Sc, Sm, and Zn in the phycosphere, and the O2 fluctuation increased oxidation rates of Cu(I), Fe(II) and Mn(II) from 2 to 938-fold. The pH/O2-induced changes in phycosphere metal chemistry were larger for freshwater algae than for marine species. Reanalyses of algal metal uptake data in the literature showed that uptake of the trivalent metals (Sc, Sm and Fe), in addition to divalent metals, can be better predicted after considering the phycosphere chemistry.