Biological Tracer Research Articles

A new flow path: eDNA connecting hydrology and biology

AbstractEnvironmental DNA (eDNA) has revolutionized ecological research, particularly for biodiversity assessment in various environments, most notably aquatic media. Environmental DNA analysis allows for non‐invasive and rapid species detection across multiple taxonomic groups within a single sample, making it especially useful for identifying rare or invasive species. Due to dynamic hydrological processes, eDNA samples from running waters may represent biodiversity from broad contributing areas, which is convenient from a biomonitoring perspective but also challenging, as hydrological knowledge is required for meaningful biological interpretation. Hydrologists could also benefit from eDNA to address unsolved questions, particularly concerning water movement through catchments. While naturally occurring abiotic tracers have advanced our understanding of water age distribution in catchments, for example, current geochemical tracers cannot fully elucidate the timing and flow paths of water through landscapes. Conversely, biological tracers, owing to their immense diversity and interactions with the environment, could offer more detailed information on the sources and flow paths of water to the stream. The informational capacity of eDNA as a tracer, however, is determined by the ability to interpret the complex biological heterogeneity at a study site, which arguably requires both biological and hydrological expertise. As eDNA data has become increasingly available as part of biomonitoring campaigns, we argue that accompanying eDNA surveys with hydrological observations could enhance our understanding of both biological and hydrological processes; we identify opportunities, challenges, and needs for further interdisciplinary collaboration; and we highlight eDNA's potential as a bridge between hydrology and biology, which could foster both domains.This article is categorized under: Science of Water > Hydrological Processes Science of Water > Methods Water and Life > Nature of Freshwater Ecosystems

Microzooplankton and phytoplankton of Ross Sea polynya areas and potential linkage among functional traits

The Ross Sea is characterized by a series of subsystems with different characteristics making it an extremely productive area. To understand whether species composition and functional traits of the plankton community can be used as biological tracers, we have analyzed the composition of phytoplankton and microzooplankton, and their potential relationships, in two different polynyas of the Ross Sea during the austral summer 2017. Sampling activities were carried out near Terra Nova Bay, between Cape Washington and the northern shore of the Drygalski Ice Tongue, and in the South-Central Ross Sea. We investigated the phytoplankton and microzooplankton structure using the phytoplankton body size classes and the tintinnids lorica oral diameter as functional traits, speculating on the relationship between the two plankton communities and their use as biological indicators in a changing Southern Ocean. Our data showed significant differences in terms of plankton composition and related functional traits between the two areas, suggesting the existence of distinct ecological dynamics despite the similar total carbon content. In Terra Nova Bay, heterotrophic dinoflagellates were the most abundant microzooplankton, in association with a large phytoplankton biomass mainly represented by diatoms and nano- and micro-phytoplankton. Tintinnids with large lorica oral diameters were abundant in Central Ross Sea, where phytoplankton was dominated by Phaeocystis antarctica and by the micro size class. Among microzooplankton, Protoperidinium defectum, P. applanatum and P. incertum were the most abundant dinoflagellates species, while Codonellopsis gaussi, C. gaussi forma cylindroconica, Laackmanniella prolongata and Cymatocylis drygalskii were the most abundant tintinnids. The phytoplankton was dominated by diatoms Pseudo-nitzschia subcurvata, Fragilariopsis cylindrus, F. curta and by the haptophyte P. antarctica. Our data indicate that beyond physical and chemical features defining distinct sectors of the Ross Sea, both species composition and functional traits of phytoplankton and microzooplankton represent a valid monitoring tool, especially with the ongoing global warming and its effects on Antarctic food webs.

Relating Ocean Biogeochemistry and Low‐Level Cloud Properties Over the Southern Oceans

AbstractThere is growing evidence that marine microorganisms may influence cloud cover over the ocean through their impact on sea spray and trace gas emissions, further forming cloud droplets or ice crystals. However, evidence of a robust causal relationship based on observations is still pending. In this study, we use 4 years of multi‐instrument satellite data to segregate low‐level clouds into ice‐containing and liquid‐water clouds to obtain clear relationships between cloud types and ocean biological tracers, especially with nanophytoplankton cell abundances. Results suggest that microorganisms may be involved in compensating effects on cloud properties, increasing the frequency of occurrence of warm‐liquid clouds, and decreasing the occurrence of ice‐containing clouds in most regions during springtime. The relationships observed in most regions do not apply to the South Pacific Ocean in the 40°S–50°S latitude band. These results shed light on overlooked potential compensating effects of ocean microorganisms on cloud cover.

Authentication of a food product based on DNA analysis of an added natural biological tracer: Testing the application to dry cured hams

Food authenticity is crucial for all value chains, including many meat products. Various methods have been developed to authenticate meat products based on the intrinsic DNA information of the animals from which the products originated. In this study, we propose an alternative method of authentication based on DNA analysis of a biological tracer added to the product. To demonstrate its effectiveness, we conducted a pilot study focused on dry-cured hams that were authenticated using genetically characterised wheat flours, obtained from different accessions. The study consisted of three main steps: first, we analysed 23 wheat accessions using random amplified polymorphic DNA assays and seven wheat microsatellites to assess the accession homogeneity/homozygosity and establish accession specific microsatellite fingerprinting; next, we tested, as a proof-of-concept, the feasibility of using genetically characterised wheat flours as natural tracers when mixed with lard (used to cover the skin-free part of the legs) and ink (used to label the legs), which are routinely applied in ham production; finally, we tested the possibility of authenticating hams by retrieving DNA information from the applied matrices (lard and ink mixed with flour) on the legs that were cured and ripened for 16 months. The DNA fingerprinting was consistent throughout all evaluation stages enabling the authentication of the marked hams. One advantage of this system is that the tracer (and its DNA profile) is known only to the authentication system managers. This approach can be adapted to authenticate many other food products.

Decadal Trends in the Zooplankton Community of the Western Mediterranean

Decadal trends in the zooplankton community were seasonally investigated in multiple monitoring transects of the western Mediterranean Sea during a period of increasing and record-high water temperatures. The transition area around the Baleares archipelago can be separated into two regions: the Alborán Sea and the Balearic Sea. Differences were found in the abundance and structure of the dominant zooplankton groups: the cladocerans and copepods. The highest zooplankton abundances were found during the stratified summer season, when cladoceran numbers peaked. However, copepods were more abundant during the winter. A marked seasonality was found in all groups and the dominant taxa: 114 species of copepods and 5 species of cladocerans were identified, but less than 8 species of copepods and 2 species of cladocerans dominated the populations. During the 2007–2017 study, warm and salty waters were observed in the Balearic Sea. In the Alborán Sea, cool and fresh waters were observed, along with a decline in chlorophyll. Irregular group and species trends were observed in both regions, exhibiting both increases and decreases depending on region and season. Trends differed, often oppositely, for the Alborán versus the Balearic Sea, with the transition region between them mirroring one or the other, switching with the seasons. The most dominant species, including Penilia avirostris and Clausocalanus arcuicornis, but also Evadne spinifera, C. lividus, C. furcatus, Paracalanus parvus, Acartia clausi, Centropages typicus, Subeucalanus monachus, and Calanus helgolandicus, are proposed as biological tracers to be used in further studies on climate and zooplankton community changes in the western Mediterranean Sea.

Evaluating the microbial aerosol generated by dental instruments: addressing new challenges for oral healthcare in the hospital infection

BackgroundUsing a rotary instrument or ultrasonic instrument for tooth preparation is a basic operation in the dental clinic that can produce a significant number of droplets and aerosols. The dental droplet and aerosol can lead to the transfer of harmful germs. The goal of this study was to analyze the properties of microbiological aerosol created by droplets and aerosol generated by three common tooth-preparation instruments.MethodsStreptococcus mutans UA159 was used as the biological tracer to visualize the droplets and aerosols. The passive sampling method was used to map the three-dimensional spatial distribution and the six-stage Andersen microbial sampler (AMS) was used as the active sampling method to catch aerosol particles at a specific time.ResultsThe aerosol concentration is related to instruments, three-dimensional spatial distribution, and dissipation time. Most aerosols were generated by air turbines. More microorganisms are concentrated at the 1.5 m plane. The majority of the post dental procedure contamination was detected within the 0–10-min period and it decreased rapidly within 30 min.ConclusionThis study is conducive to the proposal and improvement of relevant infection control measures in dental procedures and provides a basis for the assessment of measures, reducing the risk of nosocomial infection.

Effects of cadmium chloride on testicular autophagy and blood-testis barrier integrity in prepubertal male rats

Objective: To study the effects of cadmium chloride (CdCl(2)) exposure on testicular autophagy levels and blood-testis barrier integrity in prepubertal male SD rats and testicular sertoli (TM4) cells. Methods: In July 2021, 9 4-week-old male SD rats were randomly divided into 3 groups: control group (normal saline), low dose group (1 mg/kg·bw CdCl(2)) and high dose group (2 mg/kg·bw CdCl(2)), and were exposed with CdCl(2) by intrabitoneal injection. 24 h later, HE staining was used to observe the morphological changes of testis of rats, biological tracer was used to observe the integrity of blood-testis barrier, and the expression levels of microtubule-associated protein light chain 3 (LC3) -Ⅰ and LC3-Ⅱ in testicular tissue were detected. TM4 cells were treated with 0, 2.5, 5.0 and 10.0 μmol/L CdCl(2) for 24 h to detect the toxic effect of cadmium. The cells were divided into blank group (no exposure), exposure group (10.0 μmol/L CdCl(2)), experimental group[10.0 μmol/L CdCl(2)+60.0 μmol/L 3-methyladenine (3-MA) ] and inhibitor group (60.0 μmol/L 3-MA). After 24 h of treatment, Western blot analysis was used to detect the expression levels of LC3-Ⅱ, ubiquitin binding protein p62, tight junction protein ZO-1 and adhesion junction protein N-cadherin. Results: The morphology and structure of testicular tissue in the high dose group were obvious changed, including uneven distribution of seminiferous tubules, irregular shape, thinning of seminiferous epithelium, loose structure, disordered arrangement of cells, abnormal deep staining of nuclei and vacuoles of Sertoli cells. The results of biological tracer method showed that the integrity of blood-testis barrier was damaged in the low and high dose group. Western blot results showed that compared with control group, the expression levels of LC3-Ⅱ in testicular tissue of rats in low and high dose groups were increased, the differences were statistically significant (P<0.05). Compared with the 0 μmol/L, after exposure to 5.0, 10.0 μmol/L CdCl(2), the expression levels of ZO-1 and N-cadherin in TM4 cells were significantly decreased, and the expression level of p62 and LC3-Ⅱ/LC3-Ⅰ were significantly increased, the differences were statistically significant (P<0.05). Compared with the exposure group, the relative expression level of p62 and LC3-Ⅱ/LC3-Ⅰ in TM4 cells of the experimental group were significantly decreased, while the relative expression levels of ZO-1 and N-cadherin were significantly increased, the differences were statistically significant (P<0.05) . Conclusion: The mechanism of the toxic effect of cadmium on the reproductive system of male SD rats may be related to the effect of the autophagy level of testicular tissue and the destruction of the blood-testis barrier integrity.

Chemical and biological tracers to identify source and transport pathways of septic system contamination to streams in areas with low permeability soils

Septic systems are widely used in rural areas that lack centralized sewage treatment systems. Incomplete removal of domestic wastewater contaminants in septic systems can lead to leaching of nutrients (P and N), bacteria/viruses, and trace contaminants to surrounding groundwater and surface water. This study focuses on delineating the fate of wastewater contaminants in localities where septic systems are installed in moderate to fine-grained overburden materials to assess potential impacts on groundwater and surface water quality in these settings. Nutrients and a suite of anthropogenic tracers, including host-specific fecal indicator bacteria (bovine- and human-specific Bacteroides), pharmaceutical compounds (caffeine, carbamazepine, gemfibrozil, ibuprofen, naproxen, and sulfamethoxazole), and an artificial sweetener (acesulfame-K), were selected to evaluate differences in transport properties. Surface water samples (n = 103) were collected from streams upstream (US) and downstream (DS) of three rural hamlets up to two times monthly over one year. Results indicate the presence of wastewater indicators in the streams, with DS locations showing significantly elevated concentrations of both chemical and biological anthropogenic tracers. Human-specific Bacteroides, caffeine, and acesulfame-K were consistently observed at elevated concentrations at all DS sites. Nutrients exhibited varied concentrations between US and DS locations at three study sites. The occurrence of human-specific Bacteroides in the surface water samples suggests the presence of preferential flow pathways within the silt/clay overburden. These results demonstrate the advantages of using a combined tracer approach, involving a conservative tracer such as acesulfame-K coupled with the human-specific biological indicator Bacteroides (BacHum), to understand not only impacting sources but also potential transport pathways of septic system contamination to nearby streams. Septic systems may be an underappreciated contaminant source in rural hamlets located in fine-grained overburden materials; although, a distinction of specific nutrient sources (septic systems vs. agriculture) remains challenging.

The minnow Phoxinus lumaireul (Leuciscidae) shifts the Adriatic-Black Sea basin divide in the north-western Dinaric Karst region.

Karst landscapes are characterized by intermittent and sinking streams. The most common method used to study underground hydrological connections in karst is tracing tests. However, a more biologically oriented approach has been suggested: analysis of the genetic structure of aquatic organisms. Biological tracers can be sought among trogloxenes, that is, surface species that occasionally enter caves and groundwater. One such example is the fish genus Phoxinus, which exhibits high genetic diversity and complex phylogeography in the Balkan Peninsula. In the north‐western Dinaric Karst, the complex hydrological network was digitalized in 2020. Contemporaneously, Phoxinus lumaireul populations in the Slovenian Dinaric Karst were intensively sampled and analysed for fragments of two mitochondrial genes and one nuclear gene. The derived phylogeographic structure and data on hydrological connections were compared to evaluate support for three alternative scenarios: The genetic structure (1) is a consequence of the ongoing geneflow through underground connections, (2) reflects a previous hydrological network or (3) is an outcome of anthropogenic translocations. The results suggest that the first two scenarios seem to have played a major role, while the third has not had profound effects on the genetic composition. Comparison between the genetic structure of Slovenian Dinaric Karst sampling sites and that of hydrologically isolated reference sampling sites indicated a greater genetic connectivity in the former. Moreover, the range of Adriatic (1a) and Black Sea (1c) haplotypes does not correspond to the Adriatic–Black Sea basin divide but is shifted northwards.

Bacterioplankton communities reveal horizontal and vertical influence of an Island Mass Effect.

Coral reefs are highly productive ecosystems with distinct biogeochemistry and biology nestled within unproductive oligotrophic gyres. Coral reef islands have often been associated with a nearshore enhancement in phytoplankton, a phenomenon known as the Island Mass Effect (IME). Despite being documented more than 60 years ago, much remains unknown about the extent and drivers of IMEs. Here we utilized 16S rRNA gene metabarcoding as a biological tracer to elucidate horizontal and vertical influence of an IME around the islands of Mo'orea and Tahiti, French Polynesia. We show that those nearshore oceanic stations with elevated chlorophyll a included bacterioplankton found in high abundance in the reef environment, suggesting advection of reef water is the source of altered nearshore biogeochemistry. We also observed communities in the nearshore deep chlorophyll maximum (DCM) with enhanced abundances of upper euphotic bacterioplankton that correlated with intrusions of low-density, O2 rich water, suggesting island influence extends into the DCM.

Characterization of sub-pollen particles in size-resolved atmospheric aerosol using chemical tracers.

Pollen grains may contain allergens that exacerbate allergic respiratory diseases like asthma and rhinitis. In the presence of water, pollen grains (10–100 μm) can rupture to produce sub-pollen particles (SPP) with diameters <2.5 μm, which in comparison to intact pollen grains, have longer atmospheric lifetimes and greater penetration to the lower lung. The current study examines SPP, fungal spores, and bacteria in size-resolved atmospheric particulate matter (PM) using chemical and biological tracers. During springtime tree pollen season in Iowa City, Iowa, fine particle (PM2.5) concentrations of fructose (a pollen chemical tracer) increased on rainy sampling periods, especially during severe thunderstorms, and peaked when a tornado struck nearby. Submicron fluorescent particles, measured by single-particle fluorescence spectroscopy, were also enhanced during rain events, particularly thunderstorms in agreement with the chemical tracer measurements. PM2.5 sucrose (a pollen chemical tracer) concentrations were higher in early spring when nighttime temperatures were closer to freezing, while fructose concentrations were higher in late spring with warmer temperatures, consistent with chemical tracers being sensitive to seasonal temperature influences. The first co-located measurements of fructose and Bet v 1 (birch pollen allergen), indicated that SPP ranged in diameter from <0.25 to 2.5 μm during rainy sampling periods and that allergens and carbohydrates exhibited distinct size distributions. Meanwhile, mannitol (a fungal spore tracer) peaked on warm, dry days following rain and was primarily in supermicron particles (>1.0 μm), which is consistent with intact fungal spore diameters (1–30 μm). Bacterial endotoxins in PM also increased during extreme weather events, primarily in supermicron particles. While the concentrations of fructose, mannitol, and endotoxin all increased in PM2.5 μm during thunderstorms, the greatest relative increase in concentration was observed for fructose. Together, these observations suggest that SPP containing starch granules and allergens (Bet v 1) were released during rainy sampling periods. This study advances the use of chemical tracers to track SPP and other bioaerosols in the atmosphere, by providing new insight to their size distribution and response to extreme weather conditions.

Fine-scale habitat associations of medusae and ctenophores along a gradient of river influence and dissolved oxygen

Environmental drivers of abundance and distribution are poorly described for many gelatinous zooplankton (GZ), yet this knowledge is essential to understanding the role of GZ in ecosystems and potential ecological impacts. In situ imaging systems are a contemporary approach to describe the relationship between GZ and their environment, providing detailed information on distribution and habitat preference. Here we quantify patterns in the abundance and distribution of medusae and ctenophores (>1 cm) related to oceanographic data collected with in situ imaging on the stratified northern Gulf of Mexico shelf. Fourteen taxa were identified, typically to genus level, including ctenophores, scyphomedusae, and hydromedusae. The site with the most freshwater influence and widespread bottom water hypoxia contained the highest taxonomic diversity of GZ, with Aequorea, Chrysaora, and Pelagia occurring only at this site. Although most taxa aggregated in particular oceanographic micro-habitats (e.g., surface, low salinity, high temperature, or deeper, high salinity, low temperature), some were habitat generalists, found evenly dispersed throughout the water column (e.g., Eutima) or bimodally distributed near the surface and bottom (e.g., Liriope). Paired day/night sampling revealed that most taxa did not vertically migrate, suggesting they remain in their preferred micro-habitats for extended periods of time and potentially serve as biological tracers of water masses. Imaging offers the ability to monitor these under-described size classes of GZ with higher taxonomic resolution and describe their fine-scale habitat preferences and vertical migration behaviors, which ultimately improves our understanding of how GZ disperse and interact with other zooplankton in stratified shelf waters.

Emerging techniques in atherosclerosis imaging

Atherosclerosis is a chronic immunomodulated disease that affects multiple vascular beds and results in a significant worldwide disease burden. Conventional imaging modalities focus on the morphological features of atherosclerotic disease such as the degree of stenosis caused by a lesion. Modern CT, MR and positron emission tomography scanners have seen significant improvements in the rapidity of image acquisition and spatial resolution. This has increased the scope for the clinical application of these modalities. Multimodality imaging can improve cardiovascular risk prediction by informing on the constituency and metabolic processes within the vessel wall. Specific disease processes can be targeted using novel biological tracers and smart contrast agents. These approaches have the potential to inform clinicians of the metabolic state of atherosclerotic plaque.&#x0D; This review will provide an overview of current imaging techniques for the imaging of atherosclerosis and how various modalities can provide information that enhances the depiction of basic morphology.&#x0D; This publication is the reprint with Russian translation from original: Syed MB, Fletcher AJ, Forsythe RO, Kaczynski J, Newby DE, Dweck MR, van Beek EJ. Emerging techniques in atherosclerosis imaging. Br J Radiol. 2019;92(1103):20180309. doi: 10.1259/bjr.20180309.

Submesoscale Mixing Across the Mixed Layer in the Gulf of Mexico

Submesoscale circulations influence momentum, buoyancy and transport of biological tracers and pollutants within the upper turbulent layer. How much and how far into the water column this influence extends remain open questions in most of the global ocean. This work evaluates the behavior of neutrally buoyant particles advected in simulations of the northern Gulf of Mexico by analyzing the trajectories of Lagrangian particles released multiple times at the ocean surface and below the mixed layer. The relative role of meso- and submesoscale dynamics is quantified by comparing results in submesoscale permitting and mesoscale resolving simulations. Submesoscale circulations are responsible for greater vertical transport across fixed depth ranges and also across the mixed layer, both into it and away from it, in all seasons. The significance of the submesoscale-induced transport, however, is far greater in winter. In this season, a kernel density estimation and a detailed vertical mixing analysis are performed. It is found that in the large mesoscale Loop Current eddy, upwelling into the mixed layer is the major contributor to the vertical fluxes, despite its clockwise circulation. This is opposite to the behavior simulated in the mesoscale resolving case. In the “submesoscale soup,” away from the large mesoscale structures such as the Loop Current and its detached eddies, upwelling into the mixed layer is distributed more uniformly than downwelling motions from the surface across the base of the mixed layer. Maps of vertical diffusivity indicate that there is an order of magnitude difference among simulations. In the submesoscale permitting case values are distributed around 10–3 m2 s–1 in the upper water column in winter, in agreement with recent indirect estimates off the Chilean coast. Diffusivities are greater in the eastern portion of the Gulf, where the submesoscale circulations are more intense due to sustained density gradients supplied by the warmer and saltier Loop Current.

Critical Aspects on the Chemical Stability of NaYF4-Based Upconverting Nanoparticles for Biomedical Applications.

This review summarizes essential information about the chemical stability of NaYF4-based upconverting nanoparticles (UCNPs) in aqueous solutions, a crucial aspect for achieving high quality standards for biomedical materials. We present an in-depth analysis of the major experimental evidence and proposed mechanisms that provide a theoretical framework for understanding UCNPs degradation, destabilization, and dissolution under different conditions such as media composition, temperature, particle size, and the synthetic methods employed. The ion release and disintegration of the UCNP crystal structure may trigger cytotoxic events within living organisms and impact on their optical properties, precluding their safe use in biological environments. Also, we present a summary of the characterization techniques' toolbox employed for monitoring and detecting these degradation processes. Closing the existing "information gap" that links UCNP physicochemical properties, such as solubility and chemical stability, with the biological response of living organisms or tissues, is vital for using these nanoparticles as biological tracer probes, theranostic vehicles, or for clinical purposes. The understanding of chemical phenomena at the nanoparticle solid-liquid interface is mandatory to complete the molecular picture of nanosized objects, orienting in a rational manner the efforts of research and development in the early stages of these functional materials.

The Organic Isotopologue Frontier

Organic molecules are key components of the Earth-life system. Their stable isotope composition provides information on various problems such as past climate, energy resources, or the synthesis of prebiotically relevant molecules on Earth and elsewhere. Organic molecules are made of isotopologues, molecules differing in the number and/or position of isotope substitution. Recent years have witnessed a boom in technological development dedicated to isotopologue measurement, leading to an unprecedented degree of information regarding organic (bio)synthesis. While applications in Earth and planetary sciences has been limited so far to simple hydrocarbons, typically methane, isotopologue proxies are expected to rapidly emerge in biogeochemistry, providing new types of environmental and biological tracers. This review describes principles and measurement techniques, as well as present and potential biogeochemical applications. ▪ Stable isotopes of organic molecules are widely used in biogeo-chemistry. ▪ Isotope analysis at the intramolecular level is expected to provide new information on the origin of molecules. ▪ Recent technological developments unlocked the potential of intramolecular isotope analysis, providing new proxies in biogeochemistry and new opportunities to clarify questions related to Earth and planetary sciences.

Use of a Biological Tracer to Investigate Microbial Aerosols Generated by Heater-Cooler Units

Background: A multinational outbreak of Mycobacterium chimaera endocarditis following cardiac surgery has been attributed to the use of heater-cooler units (HCUs) during cardiopulmonary bypass. It is hypothesized that mycobacteria can be transmitted to the surgical site via the aerosolization of contaminated water from within the unit. In the United Kingdom, M. chimaera infections have been linked to 1 specific make and model of HCU, which was shown to generate microbial aerosols when circulating water. The manufacturer has since modified this HCU and claims that the dispersal of aerosols has now been prevented. M. chimaera is a common contaminant of HCUs, regardless of make, model, and manufacturer. To help inform local decision making, hospitals require evidence that this modified HCU and/or alternative heater-cooler systems can reduce the risk of mycobacterial infection by incorporating design features that prevent the generation of microbial aerosols external to the device. The time required to culture M. chimaera means investigations focusing on naturally or artificially contaminated HCUs are problematic. Instead, specialist aerobiological techniques incorporating a nonpathogenic, aerostable, biological tracer (Bacillus atrophaeus) were used to investigate microbial aerosols generated and released from brand-new and ‘upgraded’ HCUs. Methods: 4 HCUs (A–D), supplied directly by the manufacturers, were filled with filtered tap water, and high numbers of B. atrophaeus (109 CFU/L) were added to the tanks. High-volume cyclone samplers were used to sample the air when each HCU was switched off and during different operational phases. Samplers were operated for 5 minutes and the collecting fluid cultured for B. atrophaeus. The number of colonies was converted to CFU per cubic meter of air. Results: Under controlled experimental conditions, HCU-A released a small but significant level of aerosol during operational phases (eg, cooling) that resulted in increased pressure within the tank. The filler flap was identified as the principal area of aerosol release. The circulation of water within HCU-B and HCU-C was shown to generate an aerosol but, when connected to an ‘aerosol collection set,’ this aerosol was not released. However, it is essential that effective and sufficient vacuum is maintained. There was no aerosol release from HCU-D. Conclusions: A specialist in aerobiology using a biological tracer can determine the level of aerosol released from an HCU and its location. However, transmission of M. chimaera could occur via aerosolization of contaminated water, but it is not the only possible route of infection. The efficacy of recommended decontamination procedures must also be assured.Funding: NoneDisclosures: None

Optimization of subsampling, decontamination, and DNA extraction of difficult peat and silt permafrost samples

This study aims to act as a methodological guide for contamination monitoring, decontamination, and DNA extraction for peaty and silty permafrost samples with low biomass or difficult to extract DNA. We applied a biological tracer, either only in the field or both in the field and in the lab, via either spraying or painting. Spraying in the field followed by painting in the lab resulted in a uniform layer of the tracer on the core sections. A combination of bleaching, washing, and scraping resulted in complete removal of the tracer leaving sufficient material for DNA extraction, while other widely used decontamination methods did not remove all detectable tracer. In addition, of four widely used commercially available DNA extraction kits, only a modified ZymoBIOMICS DNA Microprep kit was able to acquire PCR amplifiable DNA. Permafrost chemical parameters, age, and soil texture did not have an effect on decontamination efficacy; however, the permafrost type did influence DNA extraction. Based on these findings, we developed recommendations for permafrost researchers to acquire contaminant-free DNA from permafrost with low biomass.

Topographic aspects of airborne contamination caused by the use of dental handpieces in the operative environment

BackgroundThe use of dental handpieces produces aerosols containing microbial agents, bacteria, and viruses representing a high-risk situation for airborne cross infections. The aim of this study was to map and quantify the biological contamination of a dental operatory environment using a biological tracer. MethodsStreptococcus mutans suspension was infused into the mouth of a manikin, and an operator performed standardized dental procedures using an air turbine, a contra-angle handpiece, or an ultrasonic scaler. The presence of the tracer was measured at 90 sites on the dental unit and the surrounding surfaces of the operatory environment. ResultsAll tested instruments spread the tracer over the entire dental unit and the surrounding environment, including the walls and ceiling. The pattern and degree of contamination were related to the distance from the infection source. The maximum distance of tracer detection was 360 centimeters for air turbine, 300 cm for contra-angle handpiece, and 240 cm for ultrasonic scaler. No surface of the operative environment was free from the tracer after the use of the air turbine. ConclusionsAttention should be paid to minimize or avoid the use of rotary and ultrasonic instruments when concerns for the airborne spreading of pandemic disease agents are present. Practical ImplicationsThis study supports the recommendations of dental associations to avoid treatments generating aerosols, especially during pandemic periods. Guidelines for the management of dental procedures involving aerosols, as well as methods for the modification of aerosols aimed to inactivate the infective agent, are urgently needed.

Emerging techniques in atherosclerosis imaging.

Atherosclerosis is a chronic immunomodulated disease that affects multiple vascular beds and results in a significant worldwide disease burden. Conventional imaging modalities focus on the morphological features of atherosclerotic disease such as the degree of stenosis caused by a lesion. Modern CT, MR and positron emission tomography scanners have seen significant improvements in the rapidity of image acquisition and spatial resolution. This has increased the scope for the clinical application of these modalities. Multimodality imaging can improve cardiovascular risk prediction by informing on the constituency and metabolic processes within the vessel wall. Specific disease processes can be targeted using novel biological tracers and “smart” contrast agents. These approaches have the potential to inform clinicians of the metabolic state of atherosclerotic plaque. This review will provide an overview of current imaging techniques for the imaging of atherosclerosis and how various modalities can provide information that enhances the depiction of basic morphology.