Comparison of the in vitro activities of delafloxacin and comparators against Staphylococcus epidermidis clinical strains involved in osteoarticular infections: a CRIOGO multicentre retrospective study

OBJECTIVES

Staphylococcus epidermidis bone and joint infections (BJIs) on material are often difficult to treat. The activity of delafloxacin has not yet been studied on S. epidermidis in this context. The aim of this study was to assess its in vitro activity compared with other fluoroquinolones, against a large collection of S. epidermidis clinical strains.

METHODS

We selected 538 S. epidermidis strains isolated between January 2015 and February 2023 from six French teaching hospitals. One hundred and fifty-two strains were ofloxacin susceptible and 386 were ofloxacin resistant. Identifications were performed by MS and MICs were determined using gradient concentration strips for ofloxacin, levofloxacin, moxifloxacin and delafloxacin.

RESULTS

Ofloxacin-susceptible strains were susceptible to all fluoroquinolones. Resistant strains had higher MICs of all fluoroquinolones. Strains resistant to ofloxacin (89.1%) still showed susceptibility to delafloxacin when using the Staphylococcus aureus 2021 CA-SFM/EUCAST threshold of 0.25 mg/L. In contrast, only 3.9% of the ofloxacin-resistant strains remained susceptible to delafloxacin with the 0.016 mg/L S. aureus breakpoint according to CA-SFM/EUCAST guidelines in 2022. The MIC50 was 0.094 mg/L and the MIC90 was 0.38 mg/L.

CONCLUSIONS

We showed low delafloxacin MICs for ofloxacin-susceptible S. epidermidis strains and a double population for ofloxacin-resistant strains. Despite the absence of breakpoints for S. epidermidis, delafloxacin may be an option for the treatment of complex BJI, including strains with MICs of ≤0.094 mg/L, leading to 64% susceptibility. This study underlines the importance for determining specific S. epidermidis delafloxacin breakpoints for the management of BJI on material.

Mercury stable isotopes in seabirds in the Ebro Delta (NE Iberian Peninsula): Inter-specific and temporal differences

Mercury (Hg) is a global pollutant, which particularly affects aquatic ecosystems, both marine and freshwater. Top-predators depending on these environments, such as seabirds, are regarded as suitable bioindicators of Hg pollution. In the Ebro Delta (NE Iberian Peninsula), legacy Hg pollution from a chlor-alkali industry operating in Flix and located ca. 100 km upstream of the Ebro River mouth has been impacting the delta environment and the neighboring coastal area. Furthermore, levels of Hg in the biota of the Mediterranean Sea are known to be high compared to other marine areas. In this work we used a Hg stable isotopes approach in feathers to understand the processes leading to different Hg concentrations in three Laridae species breeding in sympatry in the area (Audouin's gull Ichthyaetus audouinii, black-headed gull Chroicocephalus ridibundus, common tern Sterna hirundo). These species have distinct trophic ecologies, exhibiting a differential use of marine resources and freshwater resources (i.e., rice paddies prey). Moreover, for Audouin's gull, in which in the Ebro Delta colony temporal differences in Hg levels were documented previously, we used Hg stable isotopes to understand the impact of anthropogenic activities on Hg levels in the colony over time. Hg stable isotopes differentiated the three Laridae species according to their trophic ecologies. Furthermore, for Audouin's gull we observed temporal variations in Hg isotopic signatures possibly owing to anthropogenic-derived pollution in the Ebro Delta. To the best of our knowledge this is the first time Hg stable isotopes have been reported in seabirds from the NW Mediterranean.

Temporal mercury dynamics throughout the rice cultivation season in the Ebro Delta (NE Spain): An integrative approach

During the last few decades, inputs of mercury (Hg) to the environment from anthropogenic sources have increased. The Ebro Delta is an important area of rice production in the Iberian Peninsula. Given the industrial activity and its legacy pollution along the Ebro river, residues containing Hg have been transported throughout the Ebro Delta ecosystems. Rice paddies are regarded as propitious environments for Hg methylation and its subsequent incorporation to plants and rice paddies' food webs. We have analyzed how Hg dynamics change throughout the rice cultivation season in different compartments from the paddies' ecosystems: soil, water, rice plants and fauna. Furthermore, we assessed the effect of different agricultural practices (ecological vs. conventional) associated to various flooding patterns (wet vs. mild alternating wet and dry) to the Hg levels in rice fields. Finally, we have estimated the proportion of methylmercury (MeHg) to total mercury in a subset of samples, as MeHg is the most bioaccumulable toxic form for humans and wildlife. Overall, we observed varying degrees of mercury concentration over the rice cultivation season in the different compartments. We found that different agricultural practices and flooding patterns did not influence the THg levels observed in water, soil or plants. However, Hg concentrations in fauna samples seemed to be affected by hydroperiod and we also observed evidence of Hg biomagnification along the rice fields' aquatic food webs.

Cutibacterium namnetense osteosynthetic cervical spine infections: experience with two cases

We report two uncommon cases of osteosynthetic cervical spine infection. Clinical patient features, microbiological strain characteristics, diagnostic methods, and treatment were analyzed. Both patients were male, and one had risk factors for surgical site infection. During surgery, perioperative samples were positive yielding an anaerobic microorganism identified as Cutibacterium namnetense by MALDI-TOF MS and confirmed by 16S rRNA/gyrB genes sequencing. All isolates were fully susceptible. C. namnetense osteosynthetic cervical spine infections are rare. Both cases were early surgical site infections. Bruker MALDI-TOF MS appears to be an excellent tool for rapid and accurate identification. Amoxicillin seems to be an option for the treatment.

Assessing comparability and uncertainty of analytical methods for methylated mercury species in seawater

BACKGROUND

The relative distribution and importance of monomethylmercury (MMHg) and dimethylmercury (DMHg) in seawater is still under debate. A lack of comparability between measurements at sub-picomolar levels hampered the further understanding of the biogeochemical Hg cycle. To overcome this, we assessed the relative standard measurement uncertainties (Uex,r) for direct measurements of MMHg and DMHg by species-specific isotope dilution ICP-MS and cryo-focusing GC-ICP-MS at femtomolar concentrations. Furthermore, Uex,r was determined for the indirect determination of DMHg (DMHgcalc = MeHg - MMHg) and MeHg (MeHgcalc = MMHg + DMHg) to compare the two methodologies.

RESULTS

Expanded Uex,r (confidence interval of 95%) for cryo-focusing GC-ICP-MS was 14.4 (<50 fM) and 14.2% (>50 fM) and for SS-ID GC-ICP-MS 5.6 (<50 fM) and 3.7% (>50 fM). For concentrations above 50 fM, Uex,r for DMHgcalc was always lower than for direct measurements (14.2%). For MeHgcalc, on the other hand, Uex,r was always higher for concentrations above 115 fM (range: 3.7-13.9%) than for direct measurements (3.7%). We evaluated the comparability of directly measured and calculated DMHg and MeHg concentrations based on Hg speciation measurements for two vertical profiles in the Mediterranean Sea. We show that directly measured and indirectly determined DMHg and MeHg concentrations yield comparable results.

SIGNIFICANCE

Our results validate the application of the indirect method for the determination of DMHg if a direct measurement method with a low Uex,r such as isotope dilution is used for MMHg and MeHg measurements. The validation of the indirect measurement approach opens new possibilities to generate more precise and accurate DMHg data in the global ocean.

Impact of forest fire on the mercury stable isotope composition in litter and soil in the Amazon

Mercury (Hg) emissions from forest fires, especially tropical forests such as the Amazonian forest, were shown to contribute significantly to the atmospheric mercury budget, but new methods are still necessary to improve the traceability and to reduce the great uncertainties related to this emission source. Recent studies have shown that the combustion process can result in Hg stable isotope fractionation that allows tracking coal combustion Hg emissions, as influenced by different factors such as combustion temperature. The main goal of the present study was, therefore, to investigate for the first time the potential of Hg stable isotopes to trace forest fire Hg emissions and pathways. More specifically, small-scale and a large scale prescribed forest fire experiments were conducted in the Brazilian Amazonian forest to study the impact of fire severity on Hg isotopic composition of litter, soil, and ash samples and associated Hg isotope fractionation pathways. In the small-scale experiment, no difference was found in the mercury isotopic composition of the samples collected before and after burning. In contrast, the larger-scale experiment resulted in significant mass dependent fractionation (MDF δ202Hg) in soils and ash suggesting that higher combustion temperature influence Hg isotopic fractionation with the emission of lighter Hg isotopes to the atmosphere and enrichment with heavier Hg in ashes. As for coal combustion, mass independent fractionation was not observed. To our knowledge, these results are the first to highlight the potential of forest fires to cause Hg isotopic fractionation, depending on the fire severity. The results also allowed to establish an isotopic fingerprint for tropical forest fire Hg emissions that corresponds to a mixture of litter and soil Hg isotopic composition (resulting atmospheric δ202Hg, Δ200Hg and Δ199Hg were -1.79 ± 0.24‰, -0.05 ± 0.04‰ and -0.45 ± 0.12‰, respectively).

Mercury Sources and Fate in a Large Brackish Ecosystem (the Baltic Sea) Depicted by Stable Isotopes

Identifying Hg sources to aquatic ecosystems and processes controlling the levels of monomethylmercury (MMHg) is critical for developing efficient policies of Hg emissions reduction. Here we measured Hg concentrations and stable isotopes in sediment, seston, and fishes from the various basins of the Baltic Sea, a large brackish ecosystem presenting extensive gradients in salinity, redox conditions, dissolved organic matter (DOM) composition, and biological activities. We found that Hg mass dependent fractionation (Hg-MDF) values in sediments mostly reflect a mixing between light terrestrial Hg and heavier industrial sources, whereas odd Hg isotope mass independent fractionation (odd Hg-MIF) reveals atmospheric inputs. Seston presents intermediate Hg-MDF and odd Hg-MIF values falling between sediments and fish, but in northern basins, high even Hg-MIF values suggest the preferential accumulation of wet-deposited Hg. Odd Hg-MIF values in fish indicate an overall low extent of MMHg photodegradation due to limited sunlight exposure and penetration but also reveal large spatial differences. The photodegradation extent is lowest in the central basin with recurrent algal blooms due to their shading effect and is highest in the northern, least saline basin with high concentrations of terrestrial DOM. As increased loads of terrestrial DOM are expected in many coastal areas due to global changes, its impact on MMHg photodegradation needs to be better understood and accounted for when predicting future MMHg concentrations in aquatic ecosystems.

Development and evaluation of automated synovial fluid total cell count on an Iris iQ® 200 for identifying patients at risk of septic arthritis

Septic arthritis is a diagnostic emergency. The white blood cell (WBC) count, in synovial fluid (SF), can guide the diagnosis. From November 2021 to November 2022, we included 350 SF. The WBC count was performed with the Iris iQ® 200 compared with the manual method. Automated and manual counts displayed good correlation. However, a Bland Altman plot demonstrates a higher percentage difference at higher WBC counts. The use of Iris iQ® 200 for SF analysis enables a rapid and accurate assessment for WBC count. Its implementation would advantageously replace the long and tedious optical analysis in daily routine.

Early-life exposure to methylmercury induces reversible behavioral impairments and gene expression modifications in one isogenic lineage of mangrove rivulus fish Kryptolebias marmoratus

Methylmercury (MeHg) is a ubiquitous bioaccumulative neurotoxicant present in aquatic ecosystems. It is known to alter behaviors, sensory functions and learning abilities in fish and other vertebrates. Developmental and early-life stages exposure to MeHg can lead to brain damage with immediate consequences on larvae behavior, but may also induce long term effects in adults after a detoxification period. However, very little is known about developmental origin of behavioral impairment in adults due to early exposure to MeHg. The aim of this study is to assess whether early-life MeHg exposure induces immediate and/or delayed effects on behaviors, related genes expression and DNA methylation (one of epigenetic mechanisms). To reach this goal, newly hatched larvae of mangrove rivulus fish, Kryptolebias marmoratus, were exposed to two sub-lethal concentrations of MeHg (90 μg/L and 135 µg/L) for 7 days, and immediate and delayed effects were assessed respectively in 7 dph (days post-hatching) and 90 dph fish. This species naturally produces isogenic lineages due to its self-fertilizing reproduction system, which is unique among vertebrates. It allows to study how environment stressors can influence organism's phenotype while minimizing genetic variability. As results, both MeHg exposures are associated with a decreased foraging efficiency and thigmotaxis, and a dose-dependent reduction in larvae locomotor activity. Regarding molecular analysis in larvae whole bodies, both MeHg exposures induced significant decreased expression of DNMT3a, MAOA, MeCP2 and NIPBL, and significant increase of GSS, but none of those genes underwent methylation changes in targeted CpGs. None of significant behavioral and molecular impairments observed in 7-dph larvae were found in 90-dph adults, which highlight a distinction between immediate and delayed effects of developmental MeHg exposure. Our results suggest implications of aminergic system and its neurotransmitters, redox/methylation trade-off and possibly other epigenetic mechanisms in MeHg neurotoxicity underlying behavioral alterations in rivulus.

Influence of oxygen, UV light and reactive dissolved organic matter on the photodemethylation and photoreduction of monomethylmercury in model freshwater

The key factors which affect the abiotic photodemethylation process of monomethylmercury (MMHg) in the freshwaters has remained unclear. Hence, this work aimed to better elucidate the abiotic photodemethylation pathway in a model freshwater. Anoxic and oxic conditions were implemented to investigate the simultaneous photodemethylation to Hg(II) and photoreduction to Hg(0). MMHg freshwater solution was irradiated through exposure to three wavelength ranges of full light (280-800 nm), without short UVB (305-800 nm), and visible light (400-800 nm). The kinetic experiments were performed following dissolved and gaseous Hg species concentrations (i.e., MMHg, iHg(II), Hg(0)). A comparison between two methods of post-irradiation purging and continuous-irradiation purging confirmed MMHg photodecomposition to Hg(0) is mainly induced by a first photodemethylation step to iHg(II) followed by a photoreduction step to Hg(0). Photodemethylation under full light extent normalized to absorbed radiation energy showed a higher rate constant in anoxic conditions at 18.0 ± 2.2 kJ^-1 compared to oxic conditions at 4.5 ± 0.4 kJ^-1. Moreover, photoreduction also increased up to four-fold under anoxic conditions. Normalized and wavelength-specific photodemethylation (K_pd) and photoreduction (K_pr) rate constants were also calculated for natural sunlight conditions to evaluate the role of each wavelength range. The relative ratio in wavelength-specific K_PAR: K_{long UVB+ UVA}: K _{short UVB} showed higher dependence on UV light for photoreduction at least ten-fold compared to photodemethylation, regardless of redox conditions. Both results using Reactive Oxygen Species (ROS) scavenging methods and Volatile Organic Compounds (VOC) measurements revealed the occurrence and production of low molecular weight (LMW) organic compounds that are as photoreactive intermediates responsible for MMHg photodemethylation and iHg(II) photoreduction in the dominant pathway. This study also supports the role of dissolved oxygen as an inhibitor for the photodemethylation pathways driven by LMW photosensitizers.

A century of mercury: Ecosystem-wide changes drive increasing contamination of a tropical seabird species in the South Atlantic Ocean

Mercury (Hg) is a highly toxic metal that adversely impacts human and wildlife health. The amount of Hg released globally in the environment has increased steadily since the Industrial Revolution, resulting in growing contamination in biota. Seabirds have been extensively studied to monitor Hg contamination in the world's oceans. Multidecadal increases in seabird Hg contamination have been documented in polar, temperate and subtropical regions, whereas in tropical regions they are largely unknown. Since seabirds accumulate Hg mainly from their diet, their trophic ecology is fundamental in understanding their Hg exposure over time. Here, we used the sooty tern (Onychoprion fuscatus), the most abundant tropical seabird, as bioindicator of temporal variations in Hg transfer to marine predators in tropical ecosystems, in response to trophic changes and other potential drivers. Body feathers were sampled from 220 sooty terns, from museum specimens (n = 134) and free-living birds (n = 86) from Ascension Island, in the South Atlantic Ocean, over 145 years (1876-2021). Chemical analyses included (i) total- and methyl-Hg, and (ii) carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotopes, as proxies of foraging habitat and trophic position, respectively, to investigate the relationship between trophic ecology and Hg contamination over time. Despite current regulations on its global emissions, mean Hg concentrations were 58.9% higher in the 2020s (2.0 μg g^-1, n = 34) than in the 1920s (1.2 μg g^-1, n = 107). Feather Hg concentrations were negatively and positively associated with δ¹³C and δ¹⁵N values, respectively. The sharp decline of 2.9 ‰ in δ¹³C values over time indicates ecosystem-wide changes (shifting primary productivity) in the tropical South Atlantic Ocean and can help explain the observed increase in terns' feather Hg concentrations. Overall, this study provides invaluable information on how ecosystem-wide changes can increase Hg contamination of tropical marine predators and reinforces the need for long-term regulations of harmful contaminants at the global scale.

In Vivo Mercury (De)Methylation Metabolism in Cephalopods under Different pCO2 Scenarios

This work quantified the accumulation efficiencies of Hg in cuttlefish, depending on both organic (MeHg) and inorganic (Hg(II)) forms, under increased pCO₂ (1600 μatm). Cuttlefish were fed with live shrimps injected with two Hg stable isotopic tracers (Me²⁰²Hg and ¹⁹⁹Hg(II)), which allowed for the simultaneous quantification of internal Hg accumulation, Hg(II) methylation, and MeHg demethylation rates in different organs. Results showed that pCO₂ had no impact on Hg bioaccumulation and organotropism, and both Hg and pCO₂ did not influence the microbiota diversity of gut and digestive gland. However, the results also demonstrated that the digestive gland is a key organ for in vivo MeHg demethylation. Consequently, cuttlefish exposed to environmental levels of MeHg could exhibit in vivo MeHg demethylation. We hypothesize that in vivo MeHg demethylation could be due to biologically induced reactions or to abiotic reactions. This has important implications as to how some marine organisms may respond to future ocean change and global mercury contamination.

Upside down sulphate dynamics in a saline inland lake

The sulphur cycle has a key role on the fate of nutrients through its several interconnected reactions. Although sulphur cycling in aquatic ecosystems has been thoroughly studied since the early 70's, its characterisation in saline endorheic lakes still deserves further exploration. Gallocanta Lake (NE Spain) is an ephemeral saline inland lake whose main sulphate source is found on the lake bed minerals and leads to dissolved sulphate concentrations higher than those of seawater. An integrative study including geochemical and isotopic characterization of surface water, porewater and sediment has been performed to address how sulphur cycling is constrained by the geological background. In freshwater and marine environments, sulphate concentration decreases with depth are commonly associated with bacterial sulphate reduction (BSR). However, in Gallocanta Lake sulphate concentrations in porewater increase from 60 mM at the water-sediment interface to 230 mM at 25 cm depth. This extreme increase could be caused by dissolution of the sulphate rich mineral epsomite (MgSO₄·7H₂O). Sulphur isotopic data was used to validate this hypothesis and demonstrate the occurrence of BSR near the water-sediment interface. This dynamic prevents methane production and release from the anoxic sediment, which is advantageous in the current context of global warming. These results underline that geological context should be considered in future biogeochemical studies of inland lakes with higher potential availability of electron acceptors in the lake bed compared to the water column.

Assessing and predicting the changes for inorganic mercury and methylmercury concentrations in surface waters of a tidal estuary (Adour Estuary, SW France)

Total and dissolved concentrations of inorganic mercury (IHg) and methylmercury (MeHg) in water (Adour Estuary) were determined during three sampling campaigns and related to biogeochemical variables (nutrients, organic matter). Factors (sampling time, sample type) were included in analysis of covariance with effect separation. The urban estuary suffered historically from anthropogenic sources, however, decreased emissions have reduced Hg concentrations. Total IHg (0.51-3.42 ng L^-1) and MeHg (25-81 pg L^-1) concentrations are additively described by suspended particulate matter and particulate organic carbon. Higher total concentrations, carried by organic-rich particles, were found near specific discharge points (0.79-8.02 ng L^-1 and 34-235 pg L^-1 for IHg and MeHg, respectively). The associated high dissolved MeHg concentrations could not be explained only by biogeochemical variables. Better efficiency of the models is found for total than for dissolved concentrations. Models should be checked with other contaminants or with estuaries, suffering from downstream contamination.

Dynamics, distribution, and transformations of mercury species from pyrenean high-altitude lakes

While mercury (Hg) is a major concern in all aquatic environments because of its methylation and biomagnification pathways, very few studies consider Hg cycling in remote alpine lakes which are sensitive ecosystems. Nineteen high-altitude pristine lakes from Western/Central Pyrenees were investigated on both northern (France) and southern (Spain) slopes (1620-2600 m asl.). Subsurface water samples were collected in June 2017/2018/2019 and October 2017/2018 for Hg speciation analysis of inorganic mercury (iHg(II)), monomethylmercury (MMHg), and dissolved gaseous mercury (DGM) to investigate spatial and seasonal variations. In June 2018/2019 and October 2018, more comprehensive studies were performed in four lakes by taking water column depth profiles. Besides, in-situ incubation experiments using isotopically enriched Hg species (¹⁹⁹iHg(II), ²⁰¹MMHg) were conducted to investigate Hg transformation mechanisms in the water column. While iHg(II) (0.08-1.10 ng L^-1 in filtered samples; 0.11-1.19 ng L^-1 in unfiltered samples) did not show significant seasonal variations in the subsurface water samples, MMHg (<0.03-0.035 ng L^-1 in filtered samples; <0.03-0.062 ng L^-1 in unfiltered samples) was significantly higher in October 2018, mainly because of in-situ methylation. DGM (0.02-0.68 ng L^-1) varies strongly and can exhibit higher levels in comparison with other pristine areas. Depth profiles and incubation experiments highlighted the importance of in-situ biotic methylation triggered by anoxic conditions in bottom waters. In-situ incubations confirm that significant methylation, demethylation and photoreduction extents are taking place in the water columns. Overall, drastic environmental changes occurring daily and seasonally in alpine lakes are providing conditions that can both promote Hg methylation (stratified anoxic waters) and MMHg photodemethylation (intense UV light). In addition, light induced photoreduction is a major pathway controlling significant gaseous Hg evasion. Global warming and potential eutrophication may thus have direct implications on Hg turnover and MMHg burden in those remote ecosystems.

Effect of exogenous and endogenous sulfide on the production and the export of methylmercury by sulfate-reducing bacteria

Mercury (Hg) is a global pollutant of environmental and health concern; its methylated form, methylmercury (MeHg), is a potent neurotoxin. Sulfur-containing molecules play a role in MeHg production by microorganisms. While sulfides are considered to limit Hg methylation, sulfate and cysteine were shown to favor this process. However, these two forms can be endogenously converted by microorganisms into sulfide. Here, we explore the effect of sulfide (produced by the cell or supplied exogenously) on Hg methylation. For this purpose, Pseudodesulfovibrio hydrargyri BerOc1 was cultivated in non-sulfidogenic conditions with addition of cysteine and sulfide as well as in sulfidogenic conditions. We report that Hg methylation depends on sulfide concentration in the culture and the sulfides produced by cysteine degradation or sulfate reduction could affect the Hg methylation pattern. Hg methylation was independent of hgcA expression. Interestingly, MeHg production was maximal at 0.1-0.5 mM of sulfides. Besides, a strong positive correlation between MeHg in the extracellular medium and the increase of sulfide concentrations was observed, suggesting a facilitated MeHg export with sulfide and/or higher desorption from the cell. We suggest that sulfides (exogenous or endogenous) play a key role in controlling mercury methylation and should be considered when investigating the impact of Hg in natural environments.

Arsenic Analysis in the Petroleum Industry: A Review

The presence of arsenic in natural gas and liquid hydrocarbons is of great concern for oil companies. In addition to health risks due to its toxicity as well as environmental issues, arsenic is responsible for irreversible poisoning of catalysts and clogging of pipes via the accumulation of As-containing precipitates. To address these problems and to better design treatment units, robust methods for the analysis of arsenic and its compounds in oil streams are required. In addition, the use of feedstocks as a novel source of energy is becoming increasingly important. Most biomasses used as feedstocks are contaminated with arsenic. To avoid problems related to the presence of this element, it is therefore also necessary to have reliable methods for the analysis of arsenic and its compounds in these new fluids. This review outlines the sampling techniques, sample preparation methods, and arsenic analysis techniques developed during recent decades and commonly used in the oil industry and in the new feedstock energy domain.

Assessment of the Performance of the Aptima Bacterial Vaginosis Assay Over a 3-Month Period in a French Hospital

Bacterial vaginosis (BV) is the most common cause of abnormal vaginal discharge. BV represents a dysbiosis with the acquisition of a diverse community of anaerobic bacteria and a reduction in lactobacilli burden. Our objective was to evaluate the Aptima BV assay kit for the diagnosis of BV. From May to August 2019, we enrolled outpatients and inpatients, including nonpregnant women above 18 with vaginosis symptoms, consulting at Nantes University hospital. The Aptima BV assay measures the loads of Gardnerella vaginalis, Atopobium vaginae, and Lactobacillus species in relation to overall bacterial load. The Aptima BV assay was compared to Nugent scoring (NS). A total of 456 women were enrolled, and 347 patients met the inclusion criteria with data available for the analysis. NS was used to classify the samples and 144 (41.5%) samples were classified as normal (NS = 0-3), 45 (13%) as BV (NS = 7-10), 38 (11%) presented an intermediate vaginal microbiota (3 < NS < 7), 79 (22.7%) had various bacteria (excluding vaginal flora), 29 (8.3%) had insufficient bacterial density, and 12 (3.5%) had a predominance of yeasts. The Aptima BV kit displayed a sensitivity of 91.1% and specificity of 94.4% with a positive predictive value (PPV) of 83.7% and a negative predictive (NPV) value of 97.1%. The results of this monocentric retrospective study show that Aptima BV kit has a good diagnostic correlation compared to standard of care for dysbiotic diagnosis cases. IMPORTANCE The possibility exists of the involvement of a new molecular test in the routine algorithm of bacterial vaginosis diagnosis in microbiology laboratories. This manuscript reports on our experience, and we propose an organization combining Nugent scoring and molecular testing, especially for intermediate Nugent scores.

Selenium distribution and speciation in waters of pristine alpine lakes from central-western Pyrenees (France-Spain)

The speciation of both redox reactive and volatile selenium (Se) compounds, barely reported in pristine aquatic environments, has never been investigated in remote alpine lakes, considered as sensitive ecosystems to detect the effect of global change. This work presents an integrated investigation on Se distribution and speciation conducted in 20 high altitude pristine lakes from the central-western Pyrenees. Five seasonal sampling campaigns were carried out after snowmelt (June/July) and in early fall (October) for the period 2017-2019. Concentrations of total dissolved Se (TDSe) ranged from 7 to 78 ng L^-1, with selenate being ubiquitously observed in most cases (median of 61% of TDSe). Selenite was only occasionally detected up to 4 ng L^-1, therefore a fraction of TDSe was presumably in the forms of elemental Se(0) and/or selenides. Depth profiles obtained in different lakes showed the occurrence of such Se(-II, 0) pools in bottom hypoxic to anoxic waters. The production of volatile Se compounds presented a low median total concentration (TVSe) of 33 pg L^-1 (range 3-120 pg L^-1), mainly in the form of dimethylselenide in subsurface samples (median of 82% of TVSe). The Se concentration in lake waters was significantly correlated with the sulphate concentration (ρ = 0.93, p < 0.0001), demonstrating that it is influenced by erosion and dissolution of Se and S-enriched parent bedrocks. In addition, for Se depleted alpine lake-bedrock systems, long-range transport and wet atmospheric depositions represent a major source of Se for lake waters.

In Situ Photochemical Transformation of Hg Species and Associated Isotopic Fractionation in the Water Column of High-Altitude Lakes from the Bolivian Altiplano

Photochemical reactions are major pathways for the removal of Hg species from aquatic ecosystems, lowering the concentration of monomethylmercury (MMHg) and its bioaccumulation in foodwebs. Here, we investigated the rates and environmental drivers of MMHg photodegradation and inorganic Hg (IHg) photoreduction in waters of two high-altitude lakes from the Bolivian Altiplano representing meso- to eutrophic conditions. We incubated three contrasting waters in situ at two depths after adding Hg-enriched isotopic species to derive rate constants. We found that transformations mostly occurred in subsurface waters exposed to UV radiation and were mainly modulated by the dissolved organic matter (DOM) level. In parallel, we incubated the same waters after the addition of low concentrations of natural MMHg and followed the stable isotope composition of the remaining Hg species by compound-specific isotope analysis allowing the determination of enrichment factors and mass-independent fractionation (MIF) slopes (Δ¹⁹⁹Hg/Δ²⁰¹Hg) during in situ MMHg photodegradation in natural waters. We found that MIF enrichment factors potentially range from -11 to -19‰ and average -14.3 ± 0.6‰ (1 SE). The MIF slope diverged depending on the DOM level, ranging from 1.24 ± 0.03 to 1.34 ± 0.02 for the low and high DOM waters, respectively, and matched the MMHg MIF slope recorded in fish from the same lake. Our in situ results thus reveal (i) a relatively similar extent of Hg isotopic fractionation during MMHg photodegradation among contrasted natural waters and compared to previous laboratory experiments and (ii) that the MMHg MIF recorded in fish is characteristic for the MMHg bonding environment. They will enable a better assessment of the extent and conditions conducive to MMHg photodegradation in aquatic ecosystems.

Rapid temporal decline of mercury in Greenland halibut (Reinhardtius hippoglossoides)

Mercury (Hg) pollution in the ocean is an issue of global concern, however bioaccumulation regimes of this ubiquitous pollutant in marine apex predators have important knowledge gaps. Our fish length and stable isotope (δ¹⁵N and δ¹³C) normalized data of Greenland halibut (GH) (Reinhardtius hippoglossoides) showed that Hg bioaccumulation in fillet tissue decreased by ~35-50 %, over a ten-year period from 2006 to 2015 (n = 7 individual sampling years). Hg was predominantly in the methylmercury form (>77 %). Results from a Bayesian information theoretic model showed that GH Hg concentrations decreased with time and its associated declines in Hg air emissions, estimated trophic position, and a potentially lower degree of demersal prey use as indicated by temporal trend shifts in nitrogen (δ¹⁵N) and carbon (δ¹³C) stable isotope values. GH trophic shifts accounted for about one third of the observed temporal reduction in Hg. Our study demonstrates the importance of simultaneously considering Hg emissions, food web dynamics and trophic shifts as important drivers of Hg bioaccumulation in a marine, deep water fish species and highlights the effectiveness of Hg regulations on ocean apex predator Hg concentrations and overall seafood safety.

Species-specific isotope tracking of mercury uptake and transformations by pico-nanoplankton in an eutrophic lake

The present study aims to explore the bioaccumulation and biotic transformations of inorganic (iHg) and monomethyl mercury (MMHg) by natural pico-nanoplankton community from eutrophic lake Soppen, Switzerland. Pico-nanoplankton encompass mainly bacterioplankton, mycoplankton and phytoplankton groups with size between 0.2 and 20 μm. Species-specific enriched isotope mixture of ¹⁹⁹iHg and ²⁰¹MMHg was used to explore the accumulation, the subcellular distribution and transformations occurring in natural pico-nanoplankton sampled at 2 different depths (6.6 m and 8.3 m). Cyanobacteria, diatoms, cryptophyta, green algae and heterotrophic microorganisms were identified as the major groups of pico-nanoplankton with diatoms prevailing at deeper samples. Results showed that pico-nanoplankton accumulated both iHg and MMHg preferentially in the cell membrane/organelles, despite observed losses. The ratios between the iHg and MMHg concentrations measured in the membrane/organelles and cytosol were comparable for iHg and MMHg. Pico-nanoplankton demethylate added ²⁰¹MMHg (~4 and 12% per day depending on cellular compartment), although the involved pathways are to further explore. Comparison of the concentrations of ²⁰¹iHg formed from ²⁰¹MMHg demethylation in whole system, medium and whole cells showed that 82% of the demethylation was biologically mediated by pico-nanoplankton. No significant methylation of iHg by pico-nanoplankton was observed. The accumulation of iHg and MMHg and the percentage of demethylated MMHg correlated positively with the relative abundance of diatoms and heterotrophic microorganisms in the pico-nanoplankton, the concentrations of TN, Mg²⁺, NO₃^-, NO₂^-, NH₄⁺ and negatively with the concentrations of DOC, K⁺, Na⁺, Ca²⁺, SO₄^2-. Taken together the results of the present field study confirm the role of pico-nanoplankton in Hg bioaccumulation and demethylation, however further research is needed to better understand the underlying mechanisms and interconnection between heterotrophic and autotrophic microorganisms.

Determination of the Intracellular Complexation of Inorganic and Methylmercury in Cyanobacterium Synechocystis sp. PCC 6803

Understanding of mercury (Hg) complexation with low molecular weight (LMW) bioligands will help elucidate its speciation. In natural waters, the rate of this complexation is governed by physicochemical, geochemical, and biochemical parameters. However, the role of bioligands involved in Hg intracellular handling by aquatic microorganisms is not well documented. Here, we combine the use of isotopically labeled Hg species (inorganic and monomethylmercury, iHg and MeHg) with gas or liquid chromatography coupling to elemental and molecular mass spectrometry to explore the role of intracellular biogenic ligands involved in iHg and MeHg speciation in cyanobacterium Synechocystis sp. PCC 6803, a representative phytoplankton species. This approach allowed to track resulting metabolic and newly found intracellular Hg biocomplexes (e.g., organic thiols) in Synechocystis sp. PCC 6803 finding different intracellular Hg species binding affinities with both high and low molecular weight (HMW and LMW) bioligands in the exponential and stationary phase. Furthermore, the parallel detection with both elemental and molecular ionization sources allowed the sensitive detection and molecular identification of glutathione (GSH) as the main low molecular weight binding ligand to iHg ((GS)₂-Hg) and MeHg (GS-MeHg) in the cytosolic fraction. Such a novel experimental approach expands our knowledge on the role of biogenic ligands involved in iHg and MeHg intracellular handling in cyanobacteria.

Hg isotopic composition of one-year-old spruce shoots: Application to long-term Hg atmospheric monitoring in Germany

The Hg isotopic composition of 1-year-old Norway spruce (Picea abies) shoots collected from Saarland cornurbation Warndt, Germany, since 1985 by the German Environmental Specimen Bank, were measured for a better understanding of the temporal trends of Hg sources. The isotopic data showed that Hg was mainly taken up as gaseous element mercury (GEM) and underwent oxidation in the spruce needles; this led to a significant decrease in the δ²⁰²Hg compared with the atmospheric Hg isotopic composition observed for deciduous leaves and epiphytic lichens. Observation of the odd mass-independent isotopic fractionation (MIF) indicated that Δ¹⁹⁹Hg and Δ²⁰¹Hg were close to but slightly lower than the actual values recorded from the atmospheric measurement of the GEM isotopic composition in non-contaminated sites in U.S. and Europe, whereas observation of the even-MIF indicated almost no differences for Δ²⁰⁰Hg. This confirmed that GEM is a major source of Hg accumulation in spruce shoots. Interestingly, the Hg isotopic composition in the spruce shoots did not change very significantly during the study period of >30 years, even as the Hg concentration decreased significantly. Even-MIF (Δ²⁰⁰Hg) and mass-dependent fractionation (MDF) (δ²⁰²Hg) of the Hg isotopes exhibited slight decrease with time, whereas odd-MIF did not show any clear trend. These results suggest a close link between the long-term evolution of GEM isotopic composition in the air and the isotopic composition of bioaccumulated Hg altered by mass-dependent fraction in the spruce shoots.

Pregnancy denial: a complex symptom with life context as a trigger? A prospective case-control study

Objective

To identify risk factors for a woman to experience pregnancy denial.

Design, setting and population

A French multicentric prospective case–control study with 71 mother–infant dyads having experienced a pregnancy denial versus a control group of 71 dyads.

Methods

Data were collected in the week after delivery using an observational leaflet and two psychiatric scales (MINI and QSSP).

Main outcome measures

Statistically significant differences between the two groups regarding social, demographic, medical and psychiatric data.

Results

Not being in a stable relationship (odds ratio [OR] 17.18, 95% CI 3.37–87.60]; P < 0.0001), not having a high school diploma (OR 1.11, 95% CI 1.04–1.38]; P < 0.0001) and having a psychiatric history (OR 6.33, 95% CI 1.62–24.76; P = 0.0002) were risk factors to experience pregnancy denial, whereas being older was a protective factor (OR 0.86, 95% CI 0.79–0.93; P = 0.0054) (logistic regression, Wald 95% CI). Other risk factors included late declarations of pregnancy history and past pregnancy denials (case n = 7, 9.7% versus 0% in controls; P = 0.01), past pregnancy denials in the family (case n = 13, 18% versus control n = 4, 5.6%; P = 0.03), and use of a contraceptive method (75% for cases versus 7% in control; P < 0.0001), primarily an oral contraceptive (75%).

Conclusion

Family or personal history of pregnancy denial should be part of the systematic anamnesis during the first visit of a patient of child‐bearing age. Further, our study points out that life context (young age, single status, socio‐economic precarity, pill‐based contraception) could be a trigger for pregnancy denial in certain women.

Tweetable abstract

Life context can be a trigger for pregnancy denial.

Life context can be a trigger for pregnancy denial.

Contamination levels and habitat use influence Hg accumulation and stable isotope ratios in the European seabass Dicentrarchus labrax

Hg accumulation in marine organisms depends strongly on in situ water or sediment biogeochemistry and levels of Hg pollution. To predict the rates of Hg exposure in human communities, it is important to understand Hg assimilation and processing within commercially harvested marine fish, like the European seabass Dicentrarchus labrax. Previously, values of Δ¹⁹⁹Hg and δ²⁰²Hg in muscle tissue successfully discriminated between seven populations of European seabass. In the present study, a multi-tissue approach was developed to assess the underlying processes behind such discrimination. We determined total Hg content (THg), the proportion of monomethyl-Hg (%MeHg), and Hg isotopic composition (e.g. Δ¹⁹⁹Hg and δ²⁰²Hg) in seabass liver. We compared this to the previously published data on muscle tissue and local anthropogenic Hg inputs. The first important finding of this study showed an increase of both %MeHg and δ²⁰²Hg values in muscle compared to liver in all populations, suggesting the occurrence of internal MeHg demethylation in seabass. This is the first evidence of such a process occurring in this species. Values for mass-dependent (MDF, δ²⁰²Hg) and mass-independent (MIF, Δ¹⁹⁹Hg) isotopic fractionation in liver and muscle accorded with data observed in estuarine fish (MDF, 0-1‰ and MIF, 0-0.7‰). Black Sea seabass stood out from other regions, presenting higher MIF values (≈1.5‰) in muscle and very low MDF (≈-1‰) in liver. This second finding suggests that under low Hg bioaccumulation, Hg isotopic composition may allow the detection of a shift in the habitat use of juvenile fish, such as for first-year Black Sea seabass. Our study supports the multi-tissue approach as a valid tool for refining the analysis of Hg sourcing and metabolism in a marine fish. The study's major outcome indicates that Hg levels of pollution and fish foraging location are the main factors influencing Hg species accumulation and isotopic fractionation in the organisms.

Drivers of variability in mercury and methylmercury bioaccumulation and biomagnification in temperate freshwater lakes

The four largest freshwater lakes in southwestern France are of both ecological and economic importance. However, some of them are subjected to mercury (Hg) contamination, resulting in the ban of human consumption of piscivorous fish. Moreover, beyond predatory fish, little information exist regarding Hg levels in other species of these ecosystems. In this context, we used a food web analytical approach to investigate Hg bioaccumulation and biomagnification in relation to the trophic structure of these four lakes. More specifically, various organisms (macrophytes, epiphyton, invertebrates and fish) were collected at the four lakes and analysed for carbon and nitrogen stable isotopes as well as for total Hg (THg) and methylmercury (MeHg). A spatial variability of bioaccumulation in organisms was observed, particularly in carnivorous fish, with higher Hg levels being found in the two more northern lakes (median±SE: 3491 ± 474 and 1113 ± 209 ng THg.g^-1 dw in lakes HC and L, respectively) than in the southern pair (600 ± 117 and 911 ± 117 ng THg.g^-1 dw in lakes CS and PB, respectively). Methylmercury biomagnification was observed through the food webs of all four lakes, with different trophic magnification slopes (HC = 0.16; L = 0.33; CS = 0.27; PB = 0.27), even though the length of the food chains was similar between the lakes. Our results suggest that rather than the food web structure, anthropogenic inputs (sulfate in northern lakes and phosphorus inputs in southern ones) may have a strong impact, more or less directly, on Hg methylation in freshwater environments, and lead to concentrations exceeding environmental recommendations despite low Hg backgrounds in sediment and water.

[The return to socio-professional life after a severe limb trauma]

The occurrence of severe limb trauma is a brutal event for all patients in any context. Many questions quickly arise, with a very broad scope - from the course of the intervention to family and social reintegration. The nurse has an essential role in listening, educating and supporting the patient before and after the operation. In addition to reassurance, she plays a central role in organising the return home and helping the patient to resume socio-professional activities.

A "seabird-eye" on mercury stable isotopes and cycling in the Southern Ocean

Since mercury (Hg) biogeochemistry in the Southern Ocean is minimally documented, we investigated Hg stable isotopes in the blood of seabirds breeding at different latitudes in the Antarctic, Subantarctic and Subtropical zones. Hg isotopic composition was determined in adult penguins (5 species) and skua chicks (2 species) from Adélie Land (66°39'S, Antarctic) to Crozet (46°25'S, Subantarctic) and Amsterdam Island (37°47'S, Subtropical). Mass-dependent (MDF, δ²⁰²Hg) and mass-independent (MIF, Δ¹⁹⁹Hg) Hg isotopic values separated populations geographically. Antarctic seabirds exhibited lower δ²⁰²Hg values (-0.02 to 0.79 ‰, min-max) than Subantarctic (0.88 to 2.12 ‰) and Subtropical (1.44 to 2.37 ‰) seabirds. In contrast, Δ¹⁹⁹Hg values varied slightly from Antarctic (1.31 to 1.73 ‰) to Subtropical (1.69 to 2.04 ‰) waters. The extent of methylmercury (MeHg) photodemethylation extrapolated from Δ¹⁹⁹Hg values was not significantly different between locations, implying that most of the bioaccumulated MeHg was of mesopelagic origin. The larger increase of MDF between the three latitudes co-varies with MeHg concentrations. This supports an increasing effect of specific biogenic Hg pathways from Antarctic to Subtropical waters, such as Hg biological transformations and accumulations. This "biogenic effect" among different productive southern oceanic regions can also be related to different mixed layer depth dynamics and biological productivity turnover that specifically influence the vertical transport between the mesopelagic and the photic zones. This study shows the first Hg isotopic data of the Southern Ocean at large scale and reveals how regional Southern Ocean dynamics and productivity control marine MeHg biogeochemistry and the exposure of seabirds to Hg contamination.

Relationship Between Hg Speciation and Hg Methylation/Demethylation Processes in the Sulfate-Reducing Bacterium Pseudodesulfovibrio hydrargyri: Evidences From HERFD-XANES and Nano-XRF

Microorganisms are key players in the transformation of mercury into neurotoxic methylmercury (MeHg). Nevertheless, this mechanism and the opposite MeHg demethylation remain poorly understood. Here, we explored the impact of inorganic mercury (IHg) and MeHg concentrations from 0.05 to 50 μM on the production and degradation of MeHg in two sulfate-reducing bacteria, Pseudodesulfovibrio hydrargyri BerOc1 able to methylate and demethylate mercury and Desulfovibrio desulfuricans G200 only able to demethylate MeHg. MeHg produced by BerOc1 increased with increasing IHg concentration with a maximum attained for 5 μM, and suggested a saturation of the process. MeHg was mainly found in the supernatant suggesting its export from the cell. Hg L₃-edge High- Energy-Resolution-Fluorescence-Detected-X-ray-Absorption-Near-Edge-Structure spectroscopy (HERFD-XANES) identified MeHg produced by BerOc1 as MeHg-cysteine₂ form. A dominant tetracoordinated βHgS form was detected for BerOc1 exposed to the lowest IHg concentrations where methylation was detected. In contrast, at the highest exposure (50 μM) where Hg methylation was abolished, Hg species drastically changed suggesting a role of Hg speciation in the production of MeHg. The tetracoordinated βHgS was likely present as nano-particles as suggested by transmission electron microscopy combined to X-ray energy dispersive spectroscopy (TEM-X-EDS) and nano-X ray fluorescence (nano-XRF). When exposed to MeHg, the production of IHg, on the contrary, increased with the increase of MeHg exposure until 50 μM for both BerOc1 and G200 strains, suggesting that demethylation did not require intact biological activity. The formed IHg species were identified as various tetracoordinated Hg-S forms. These results highlight the important role of thiol ligands and Hg coordination in Hg methylation and demethylation processes.

Contrasting Spatial and Seasonal Trends of Methylmercury Exposure Pathways of Arctic Seabirds: Combination of Large-Scale Tracking and Stable Isotopic Approaches

Despite the limited direct anthropogenic mercury (Hg) inputs in the circumpolar Arctic, elevated concentrations of methylmercury (MeHg) are accumulated in Arctic marine biota. However, the MeHg production and bioaccumulation pathways in these ecosystems have not been completely unraveled. We measured Hg concentrations and stable isotope ratios of Hg, carbon, and nitrogen in the feathers and blood of geolocator-tracked little auk Alle alle from five Arctic breeding colonies. The wide-range spatial mobility and tissue-specific Hg integration times of this planktivorous seabird allowed the exploration of their spatial (wintering quarters/breeding grounds) and seasonal (nonbreeding/breeding periods) MeHg exposures. An east-to-west increase of head feather Hg concentrations (1.74-3.48 μg·g^-1) was accompanied by significant spatial trends of Hg isotope (particularly Δ¹⁹⁹Hg: 0.96-1.13‰) and carbon isotope (δ¹³C: -20.6 to -19.4‰) ratios. These trends suggest a distinct mixing/proportion of MeHg sources between western North Atlantic and eastern Arctic regions. Higher Δ¹⁹⁹Hg values (+0.4‰) in northern colonies indicate an accumulation of more photochemically impacted MeHg, supporting shallow MeHg production and bioaccumulation in high Arctic waters. The combination of seabird tissue isotopic analysis and spatial tracking helps in tracing the MeHg sources at various spatio-temporal scales.

Hg isotopic composition and total Hg mass fraction in NIES Certified Reference Material No. 28 Urban Aerosols

An interlaboratory study on the National Institute for Environmental Studies (NIES) certified reference material (CRM) No. 28 Urban Aerosols, collected on the filters of a central ventilating system in a building in Beijing city center, was performed to obtain informative values of Hg isotopic composition and total Hg (THg) mass fraction. The THg mass fraction was determined by four organizations using atomic absorption spectrometry; it resulted in the mean value of 1.19 ± 0.12 mg/kg (2SD, n = 24). The Hg isotopic composition of the CRM was measured and intercompared at two different institutions by cold vapor generation system coupled to multicollector inductively coupled plasma mass spectrometry. Subsequently, a conventional dissolution method that uses a mixture of HNO₃/HCl/H₂O₂ in Hotblock® and two different dissolution methods that use a mixture of HNO₃/HCl with a microwave and a digestion bomb were applied. The Hg isotopic compositions were δ²⁰²Hg = − 1.26 ± 0.17‰, Δ¹⁹⁹Hg = − 0.23 ± 0.06‰, Δ²⁰⁰Hg = 0.01 ± 0.07‰, and Δ²⁰¹Hg = − 0.22 ± 0.09‰ (2SD, n = 18) for the conventional method, which agree well with those obtained using microwave and bomb digestion. Our results indicate that, for the quality control of particulate matter analyses, this CRM is appropriate for use in environmental and geochemical studies.

Mercury loads and fluxes from wastewater: A nationwide survey in Switzerland

Mercury (Hg) pollution threatens ecosystems and human health. Wastewater treatment plants (WWTPs) play a key role in limiting Hg discharges from wastewaters to rivers and lakes, but large-scale studies to estimate Hg loads and discharge at national levels are scarce. We assessed the concentration, flux, speciation, and removal of Hg in municipal wastewater throughout Switzerland by investigating 64 WWTPs in a pre-study and a subset of 28 WWTPs in the main study. We also studied the behavior and pathways of Hg along the various treatment steps in a state-of-the-art WWTP. The resulting dataset, representative of industrialized countries, provides an overview of (i) current Hg concentration ranges, (ii) average per capita loads, and (iii) wastewater Hg inputs into surface waters. The results allowed estimation of a total Hg (THg) load in Swiss wastewater of 130 ± 30 kg THg/year (15.7 mg/capita/y), of which 96 ± 4% is retained in sewage sludge. About 4.7 ± 0.5 kg THg/year (0.57 mg/capita/y) is discharged with the treated wastewater into surface waters. This corresponds to only 1.5-3% of the THg load carried by the major Swiss rivers, indicating that >95% of riverine Hg originates from other sources. Extrapolation to the population of Europe would yield a total amount of 11,700 kg THg/year in raw wastewater, with some 480 kg THg/year discharged to surface waters. Monomethyl mercury on average accounted for 0.23% of THg, and its fraction remained constant along the different treatment steps.

Shifts in mercury methylation across a peatland chronosequence: From sulfate reduction to methanogenesis and syntrophy

Peatlands are globally important ecosystems where inorganic mercury is converted to bioaccumulating and highly toxic methylmercury, resulting in high risks of methylmercury exposure in adjacent aquatic ecosystems. Although biological mercury methylation has been known for decades, there is still a lack of knowledge about the organisms involved in mercury methylation and the drivers controlling their methylating capacity. In order to investigate the metabolisms responsible for mercury methylation and methylmercury degradation as well as the controls of both processes, we studied a chronosequence of boreal peatlands covering fundamentally different biogeochemical conditions. Potential mercury methylation rates decreased with peatland age, being up to 53 times higher in the youngest peatland compared to the oldest. Methylation in young mires was driven by sulfate reduction, while methanogenic and syntrophic metabolisms became more important in older systems. Demethylation rates were also highest in young wetlands, with a gradual shift from biotic to abiotic methylmercury degradation along the chronosequence. Our findings reveal how metabolic shifts drive mercury methylation and its ratio to demethylation as peatlands age.

School-based vaccination programmes: An evaluation of school immunisation delivery models in England in 2015/16

Schools are increasingly being used to deliver vaccines. In 2015/16 three school-based vaccination programmes were delivered to adolescents in England: human papillomavirus (HPV), meningococcal groups A, C, W and Y disease (MenACWY) and tetanus, diphtheria and polio (Td/IPV). We assessed how school delivery models impact vaccine coverage and how a delivery model for one programme may impact another. Routinely collected national data were analysed to ascertain the school grade achieving highest coverage within each one-dose programme and to compare two-dose delivery models (within year vs across years) for the HPV vaccine. We also assessed whether the HPV delivery model was associated with coverage in other programmes. MenACWY and Td/IPV coverage was highest in younger school grades. Overall similar HPV coverage was achieved with both models (86.7% two doses within one year, 85.8% two doses across two years, p = 0.20). High two-dose HPV coverage in 2015/16 was reported in areas that achieved high HPV coverage in 2013/14 when three doses were required. Areas with high three-dose coverage in 2013/14 achieved higher coverage with a within-one-year approach (92.0% vs 85.2%, p < 0.001), whilst areas reporting low coverage in 2013/14 achieved lower but similar coverage in 2015/16 with both models (79.2% vs 80.9% p = 0.29). MenACWY and Td/IPV coverage were higher in areas with high HPV coverage in 2013/14. Among high HPV coverage areas, MenACWY coverage was higher when HPV doses were delivered within year. School-based programmes should be offered as early as feasible and acceptable to optimise coverage. The choice of delivery model for HPV should take into account local performance and provider experience. Single providers may delivery multiple vaccines and the delivery for one programme may affect the performance of other programmes. Providers should consider local circumstances including past and current vaccine coverage and factors influencing coverage when deciding what delivery model to adopt.

Mercury and methylmercury concentrations, sources and distribution in submarine canyon sediments (Capbreton, SW France): Implications for the net methylmercury production

Submarine canyons are important stocks of commercial interest fish, whose consumption is one of the main monomethymercury (MeHg) exposure to humans. Currently, biogeochemistry of mercury in those biologically productive system is unknown. In this work, inorganic mercury (Hg(II)) and organic mercury (MeHg) distributions were measured in sedimentary accumulative zones (slopes and terraces) against adjacent continental shelf sediments. Hg compound concentrations in these sediments show a huge range of concentrations (Hg(II) ranging from 18 to 973 ng g^-1 and MeHg ranging from 0.07 to 2.03 ng g^-1) exhibiting factors 50 and 20 fold, respectively. Higher values of mercury compounds were observed in canyon locations suggesting a high accumulation of mercury associated with higher values of clay fraction and organic matter content. The reactivity of mercury was investigated in sediment of three locations along Capbreton submarine canyon axis using slurry incubations experiments and isotopic tracers. Specific methylation and demethylation rate constants (k_M and k_D) were calculated. Results clearly showed that MeHg concentrations in these sediments are controlled by competing and simultaneous methylation and demethylation reactions mainly mediated by biotic process. Mercury reactivity was found higher in coastal stations compared to the offshore station due to more labile organic matter which may stimulate microbial activities. However, higher net MeHg production was estimated for the offshore station due to high Hg(II) concentrations suggesting a potential MeHg source for such marine environments.

Spatial distribution of mercury in seawater, sediment, and seafood from the Hardangerfjord ecosystem, Norway

Hardangerfjord is one of the longest fjords in the world and has historical mercury (Hg) contamination from a zinc plant in its inner sector. In order to investigate the extent of Hg transferred to abiotic and biotic ecosystem compartments, Hg and monomethylmercury (MeHg) concentrations were measured in seawater, sediment, and seafood commonly consumed by humans. Although total mercury in seawater has been described previously, this investigation reports novel MeHg data for seawater from Norwegian fjords. Total Hg and MeHg concentrations in seawater, sediment, and biota increased towards the point source of pollution (PSP) and multiple lines of evidence show a clear PSP effect in seawater and sediment concentrations. In fish, however, similar high concentrations were found in the inner part of another branch adjacent to the PSP. We postulate that, in addition to PSP, atmospheric Hg, terrestrial run-off and hydroelectric power stations are also important sources of Hg in this fjord ecosystem. Hg contamination gradually increased towards the inner part of the fjord for most fish species and crustaceans. Since the PSP and the atmospheric Hg pools were greater towards the inner part of the fjord, it is not entirely possible to discriminate the full extent of the PSP and the atmospheric Hg contribution to the fjord food web. The European Union (EU) Hg maximum level for consumption was exceeded in demersal fish species including tusk (Brosme brosme), blue ling (Molva dypterygia) and common ling (Molva molva) from the inner fjord (1.08 to 1.89 mg kg^-1 ww) and from the outer fjord (0.49 to 1.07 mg kg^-1 ww). Crustaceans were less contaminated and only European lobster (Homarus gammarus) from inner fjord exceeded the EU limit (0.62 mg kg^-1 ww). Selenium (Se) concentrations were also measured in seafood species and Se-Hg co-exposure dynamics are also discussed.

Multiple regression analysis to assess the spatial distribution and speciation of mercury in surface sediments of a contaminated lagoon

The concentrations of inorganic mercury (IHg) and methylmercury (MeHg) in surface sediments from the contaminated Aveiro Lagoon (Portugal) were determined by species-specific isotope dilution analysis. Different behaviour of IHg and MeHg was observed based upon multiple regression analysis, including geochemical characteristics of the surface sediments (fine fraction, concentrations of organic matter and metals) and non-Euclidean distances between sampling points. This data treatment method was valid over the entire concentration range of IHg and MeHg, allowing robust quantitative evaluation with respect to extrapolation. For IHg, there was statistical separation of the dispersion away from the contamination source and of Al concentration in the sediments. The MeHg concentrations followed those of IHg at high concentrations. The geochemical variables, such as concentrations of Ca (marine influence proxy), Mn and organic matter, were necessary to describe the behaviour of MeHg across the whole concentration range. The models for MeHg demonstrated that, close to the mouth of the lagoon, net production of MeHg was higher. In future, multiple regression analysis could be applied to separate and to evaluate quantitatively the effects of geochemistry and dispersion away from the contamination source in sediments contaminated with other substances.

The interplay between total mercury, methylmercury and dissolved organic matter in fluvial systems: A latitudinal study across Europe

Large-scale studies are needed to identify the drivers of total mercury (THg) and monomethyl-mercury (MeHg) concentrations in aquatic ecosystems. Studies attempting to link dissolved organic matter (DOM) to levels of THg or MeHg are few and geographically constrained. Additionally, stream and river systems have been understudied as compared to lakes. Hence, the aim of this study was to examine the influence of DOM concentration and composition, morphological descriptors, land uses and water chemistry on THg and MeHg concentrations and the percentage of THg as MeHg (%MeHg) in 29 streams across Europe spanning from 41°N to 64 °N. THg concentrations (0.06-2.78 ng L^-1) were highest in streams characterized by DOM with a high terrestrial soil signature and low nutrient content. MeHg concentrations (7.8-159 pg L^-1) varied non-systematically across systems. Relationships between DOM bulk characteristics and THg and MeHg suggest that while soil derived DOM inputs control THg concentrations, autochthonous DOM (aquatically produced) and the availability of electron acceptors for Hg methylating microorganisms (e.g. sulfate) drive %MeHg and potentially MeHg concentration. Overall, these results highlight the large spatial variability in THg and MeHg concentrations at the European scale, and underscore the importance of DOM composition on mercury cycling in fluvial systems.

Mercury Isotopic Fractionation during Pedogenesis in a Tropical Forest Soil Catena (French Guiana): Deciphering the Impact of Historical Gold Mining

We used natural mercury (Hg) stable isotopes to investigate the Hg cycle in a rainforest soil catena (French Guiana) partially gold-mined during the early 1950s. Litterfall showed homogeneous Δ¹⁹⁹Hg values [-0.18 ± 0.05‰, i.e., a modern gaseous elemental Hg (GEM) isotopic signature]. After litter decomposition, Hg bound to organic matter (OM) is mixed with Hg from pristine (-0.55 ± 0.22‰) or gold-mined (-0.09 ± 0.16‰) mineral materials. Negative Δ¹⁹⁹Hg values in deep pristine mineral horizons (-0.60 ± 0.16‰) suggest the transfer of Hg bound to dissolved OM depleted in odd isotopes due to mass-independent fractionation during Hg abiotic reduction. Perennial palm tree leaves collected above gold-mined and pristine soil recorded contrasting Δ¹⁹⁹Hg signatures likely resulting from GEM re-emission processes from soils and leaf surfaces. Upslope, soil δ²⁰²Hg signatures showed a negative shift (ε ∼ -1‰) with depth attributed to mass-dependent fractionation during Hg sorption and complexation onto iron oxides and dissolved OM. Downslope, higher δ²⁰²Hg values in soils resulted from hydromorphy [lower humification, greater Hg(II) reduction, etc.]. The unique Hg isotopic signatures of Amazonian soils probably result in multistep fractionation processes during pedogenesis (millions of years) and in a potentially different Hg isotopic signature of preanthropogenic background GEM.

Methylation and dealkykation of tin compounds by sulfate- and nitrate-reducing bacteria

In this study, axenic cultures of sulfate-reducing (SRB) and nitrate-reducing (NRB) bacteria were examined for their ability to methylate inorganic tin and to methylate or dealkylate butyltin compounds. Environmentally relevant concentrations of natural abundance tributyltin (TBT) and ¹¹⁶Sn-enriched inorganic tin were added to bacterial cultures to identify bacterial-mediated methylation and dealkylation reactions. The results show that none of the Desulfovibrio strains tested was able to induce any transformation process. In contrast, Desulfobulbus propionicus strain DSM-6523 degraded TBT either under sulfidogenic or non-sulfidogenic conditions. In addition, it was able to alkykate ¹¹⁶Sn-enriched inorganic tin leading to the formation of more toxic dimethyltin and trimethyltin. A similar capacity was observed for incubations of Pseudomonas but with a much greater dealkykation of TBT. As such, Pseudomonas sp. ADR42 degraded 61% of the initial TBT under aerobic conditions and 35% under nitrate-reducing conditions. This is the first work reporting a simultaneous TBT degradation and a methylation of both inorganic tin species and TBT dealkykation products by SRB and NRB under anoxic conditions. These reactions are environmentally relevant as they can control the mobility of these compounds in aquatic ecosystems; as well as their toxicity toward resident organisms.

Linking Microbial Activities and Low-Molecular-Weight Thiols to Hg Methylation in Biofilms and Periphyton from High-Altitude Tropical Lakes in the Bolivian Altiplano

The sources and factors controlling concentrations of monomethylmercury (MMHg) in aquatic ecosystems need to be better understood. Here, we investigated Hg transformations in sediments, periphyton associated with green algae's or aquatic plants, and benthic biofilms from the Lake Titicaca hydrosystem and compared them to the occurrence of active methylating microorganisms and extracellular Hg ligands. Intense Hg methylation was found in benthic biofilms and green algae's periphyton, while it remained low in sediments and aquatic plants' periphyton. Demethylation varied between compartments but remained overall in the same range. Hg methylation was mainly carried out by sulfate reducers, although methanogens also played a role. Its variability between compartments was first explained by the presence or absence of the hgcAB genes. Next, both benthic biofilm and green algae's periphyton exhibited a great diversity of extracellular low-molecular-weight (LMW) thiols (13 or 14 compounds) present at a range of a few nmol L^-1 or μmol L^-1 but clearly dominated by cysteine and 3-mercaptopropionic acid. Hg methylation was overall positively correlated to the total thiol concentrations, albeit to different extents according to the compartment and conditions. This work is the first examining the interplay between active methylating bacterial communities and extracellular ligands in heterotrophic biofilms and supports the involvement of LMW thiols in Hg methylation in real aquatic systems.

Role of the floodplain lakes in the methylmercury distribution and exchanges with the Amazon River, Brazil

Seasonal variability of dissolved and particulate methylmercury (F-MeHg, P-MeHg) concentrations was studied in the waters of the Amazon River and its associated Curuai floodplain during hydrological year 2005-2006, to understand the MeHg exchanges between these aquatic systems. In the oxic white water lakes, with neutral pH, high F-MeHg and P-MeHg concentrations were measured during the rising water stage (0.70±0.37pmol/L, n=26) and flood peak (14.19±9.32pmol/g, n=7) respectively, when the Amazon River water discharge into the lakes was at its maximum. The lowest mean values were reported during the dry season (0.18±0.07pmol/L F-MeHg, n=10 and 1.35±1.24pmol/g P-MeHg, n=8), when water and suspended sediments were outflowing from the lakes into the River. In these lakes, the MeHg concentrations were associated to the aluminium and organic carbon/nitrogen changes. In the black water lakes, with acidic pH and reducing conditions, elevated MeHg concentrations were recorded (0.58±0.32pmol/L F-MeHg, n=16 and 19.82±15.13pmol/g P-MeHg, n=6), and correlated with the organic carbon and manganese concentrations. Elevated values of MeHg partition coefficient (4.87<K_d<5.08log (L/kg) indicate that MeHg is mainly transported associated with the particulate phase. The P-MeHg enrichment detected in all lakes suggests autochthonous MeHg inputs from the sediments into the water column. The MeHg mass balance showed that the Curuai floodplain is not the source of P-MeHg for the Amazon River.

Flux model to estimate the transport of mercury species in a contaminated lagoon (Ria de Aveiro, Portugal)

The concentrations of dissolved and particulate inorganic mercury (IHg(II)) and methylmercury (MeHg) from the contaminated Laranjo Bay (main freshwater discharge from the Antuã River) were measured by species-specific isotope dilution during six sampling campaigns at high and at low tide. Different effective riverine concentrations were calculated, based on salinity profiles, for specific hydrological conditions. The export fluxes of total Hg and MeHg (324 and 1.24 mol year^-1, respectively) from the bay to the rest of the Aveiro Lagoon are much higher than the input fluxes from the Hg source (3.9 and 0.05 mol year^-1) and from the Antuã River (10.4 and 0.10 mol year^-1). Resuspension of contaminated sediments from Laranjo Bay is crucial for the transport of both IHg(II) and MeHg. Methylation and/or selective enrichment into biogenic particles is responsible for the mobilization of MeHg. Sorption of dissolved IHg(II) onto suspended particles limits its export flux. This is one of the rarest examples where both speciation fluxes and partitioning of mercury are studied in a contaminated coastal environment. Despite the lower fraction of total MeHg (relative to total Hg), the contaminated lagoon may have an impact on coastal areas, particularly if change in the lagoon geometry occurs, due to sea level rise.

Seabird Tissues As Efficient Biomonitoring Tools for Hg Isotopic Investigations: Implications of Using Blood and Feathers from Chicks and Adults

Blood and feathers are the two most targeted avian tissues for environmental biomonitoring studies, with mercury (Hg) concentration in blood and body feathers reflecting short and long-term Hg exposure, respectively. In this work, we investigated how Hg isotopic composition (e.g., δ²⁰²Hg and Δ¹⁹⁹Hg) of blood and feathers from either seabird chicks (skuas, n = 40) or adults (penguins, n = 62) can accurately provide information on exposure to Hg in marine ecosystems. Our results indicate a strong correlation between blood and feather Hg isotopic values for skua chicks, with similar δ²⁰²Hg and Δ¹⁹⁹Hg values in the two tissues (mean difference: -0.01 ± 0.25 ‰ and -0.05 ± 0.12 ‰, respectively). Since blood and body feathers of chicks integrate the same temporal window of Hg exposure, this suggests that δ²⁰²Hg and Δ¹⁹⁹Hg values can be directly compared without any correction factors within and between avian groups. Conversely, penguin adults show higher δ²⁰²Hg and Δ¹⁹⁹Hg values in feathers than in blood (mean differences: 0.28 ± 0.19‰ and 0.25 ± 0.13‰), most likely due to tissue-specific Hg temporal integration. Since feathers integrate long-term (i.e., the intermoult period) Hg accumulation, whereas blood reflects short-term (i.e., seasonal) Hg exposure in adult birds, the two tissues provide complementary information on trophic ecology at different time scales.

Mercury contamination level and speciation inventory in Lakes Titicaca & Uru-Uru (Bolivia): Current status and future trends

Aquatic ecosystems of the Bolivian Altiplano (∼3800 m a.s.l.) are characterized by extreme hydro-climatic constrains (e.g., high UV-radiations and low oxygen) and are under the pressure of increasing anthropogenic activities, unregulated mining, agricultural and urban development. We report here a complete inventory of mercury (Hg) levels and speciation in the water column, atmosphere, sediment and key sentinel organisms (i.e., plankton, fish and birds) of two endorheic Lakes of the same watershed differing with respect to their size, eutrophication and contamination levels. Total Hg (THg) and monomethylmercury (MMHg) concentrations in filtered water and sediment of Lake Titicaca are in the lowest range of reported levels in other large lakes worldwide. Downstream, Hg levels are 3-10 times higher in the shallow eutrophic Lake Uru-Uru than in Lake Titicaca due to high Hg inputs from the surrounding mining region. High percentages of MMHg were found in the filtered and unfiltered water rising up from <1 to ∼50% THg from the oligo/hetero-trophic Lake Titicaca to the eutrophic Lake Uru-Uru. Such high %MMHg is explained by a high in situ MMHg production in relation to the sulfate rich substrate, the low oxygen levels of the water column, and the stabilization of MMHg due to abundant ligands present in these alkaline waters. Differences in MMHg concentrations in water and sediments compartments between Lake Titicaca and Uru-Uru were found to mirror the offset in MMHg levels that also exist in their respective food webs. This suggests that in situ MMHg baseline production is likely the main factor controlling MMHg levels in fish species consumed by the local population. Finally, the increase of anthropogenic pressure in Lake Titicaca may probably enhance eutrophication processes which favor MMHg production and thus accumulation in water and biota.