Antimicrobial Resistance in the Environment: Towards Elucidating the Roles of Bioaerosols in Transmission and Detection of Antibacterial Resistance Genes.

Antimicrobial resistance (AMR) is continuing to grow across the world. Though often thought of as a mostly public health issue, AMR is also a major agricultural and environmental problem. As such, many researchers refer to it as the preeminent One Health issue. Aerial transport of antimicrobial-resistant bacteria via bioaerosols is still poorly understood. Recent work has highlighted the presence of antibiotic resistance genes in bioaerosols. Emissions of AMR bacteria and genes have been detected from various sources, including wastewater treatment plants, hospitals, and agricultural practices; however, their impacts on the broader environment are poorly understood. Contextualizing the roles of bioaerosols in the dissemination of AMR necessitates a multidisciplinary approach. Environmental factors, industrial and medical practices, as well as ecological principles influence the aerial dissemination of resistant bacteria. This article introduces an ongoing project assessing the presence and fate of AMR in bioaerosols across Canada. Its various sub-studies include the assessment of the emissions of antibiotic resistance genes from many agricultural practices, their long-distance transport, new integrative methods of assessment, and the creation of dissemination models over short and long distances. Results from sub-studies are beginning to be published. Consequently, this paper explains the background behind the development of the various sub-studies and highlight their shared aspects.

Assessing Environmental Control Strategies in Cage-Free Egg Production Systems: Effect on Spatial Occupancy and Natural Behaviors.

Animal welfare concerns have been a challenging issue for producers and international marketing. In laying hen production, cage-free systems (CFS) have been identified as an alternative to ensure the laying hens' well-being. Nevertheless, in CFS, important environmental issues have been reported, decreasing indoor air quality. Environmental control strategies (ECS) have been designed to enhance indoor air quality in CFSs. However, little information exists about the effect of these ECSs on natural animal behaviors. Four strategies and one control were tested in an experimental CFS, previously designed to track behavioral variables using video recordings over seven time-lapses of 1 hour per day. Spatial occupancy (SO) and laying hen behaviors (LHB) were registered. One statistical analysis was applied to evaluate the effect of ECS on SO and LHB using a multinomial response model. Results show lower chances to use litter area within the reduction of litter allowance treatment (T17) (p < 0.05). Neither the four ECSs nor the control implemented in this experiment affected the natural behaviors of the hens. However, stress patterns and high activity were reported in the T17 treatment. This study shows that it is possible to use these ECSs without disrupting laying hens' natural behaviors.

Parameters determining the performance of passive flux samplers proposed as a tool to estimate N2O emissions: evaluation at farm level and perspectives.

The passive flux sampling is an economic and easy way to estimate gas emissions from agriculture sources. In the last decade, specific passive flux samplers (PFSs) have been developed to estimate nitrous oxide (N2O) emissions from agriculture sources. Packed with silica gel and zeolite 5A, the PFSs were placed facing the emission source direction close to the ventilation shafts. For validation, air samples were taken at different sampling time during 3 days on two commercial sites. The adsorbed mass of N2O in PFSs was recovered by thermal desorption in the laboratory. Results indicated that the mass of N2O adsorbed in PFSs was from 1.5 to 5.5 µg. A specific adsorption pattern was observed for each sampling. In farm 1, the mass of N2O adsorbed in the PFSs presented a linear behavior as a function of sampling time, and the most determined coefficient values were higher than 0.80. In farm 2, in addition to the sampling time, the N2O concentration and the air flow rate presented an effect on the mass adsorbed in the PFSs. On the other hand, comparison of PFSs versus other techniques indicated that PFSs offer different advantages. However, the selectivity and capacity of the adsorbent bed used need to be improved to enhance the use of PFSs proposed as a tool to estimate N2O emissions. Graphical Abstract PFSs enabled N2O sampling that followed a linear behavior as a function of sampling time. Sampling time, [N2O], and air flow rate determined the mass of N2O collected in PFSs.

Filter feeders increase sedimentation of titanium dioxide: The case of zebra mussels.

Titanium dioxide particles (TiO2) are widely used to produce whitens (titanium white) and different class of nanomaterials (semiconductors, photo catalysts and nanotubes). Nanomaterials are excellent adsorbents and catalysts with a wide range of applications. However, these are reported to induce biological and genetic alterations among several invertebrate groups. Invasive species such as zebra mussels can be used as model organisms to study the behavior of particles and nanoparticles (NPs) due to their wide distribution; mussels have been extensively used for monitoring water pollution. In the present study, TiO2 particles were dispersed and added to a Chlorella culture to emulate a natural scenario. To study the reaction of zebra mussels to different TiO2 concentrations, they were fed with 0.35, 0.7 and 3.5 mgTiO2/L of the suspension for 3days and the titanium was measured in the water column, mussels and sediments with ICP-AES. Zebra mussels obtained from the Port of Quebec had up 61.62mgTi/kg wet tissue at the time of capture. After 10days of depuration, they had from 0.23 to 16.28mgTi/kg wet tissue. Mussels accumulated TiO2 after 36h of exposition as a function of TiO2 concentration, but mussels did not present significant mortality due to TiO2 toxicity until concentrations higher than 0.7ppm. A second set of experiments was run to understand the TiO2 pathway attached to microalgae vs free TiO2. Results indicated that mussels accumulated slightly more Ti when it was mixed with microalgae. However, the statistical difference was non- significant. A 100 times higher accumulation of Ti in sediments was identified when mussels are present. Thus, it was concluded that the sedimentation of TiO2 is enhanced by the zebra mussels' filtration activity.

Parameters determining the use of zeolite 5A as collector medium in passive flux samplers to estimate N2O emissions from livestock sources.

The present study analyzes the effect of parameters that determine the use of the zeolite 5A as collector medium in passive flux samplers (PFS) developed to estimate N2O emissions from livestock buildings. The study analyzes the mass of N2O collected on the zeolite 5A as a function of gas flow rate (40 and 130 ml/min), inlet mass of N2O to the PFS (from 7 to 84 µg), adsorbent mass (4 and 13.6 g), length of the adsorbent bed (1.9 and 10.9 cm), and inlet N2O concentration (0.6 and 2 ppmv). The mass of N2O collected on the zeolite 5A ranged from 1.24 to 6.19 µg of N2O/g of adsorbent, which was mainly affected by inlet N2O concentration and mass of adsorbent contained in the PFS. The mass of N2O collected presented a significant relationship with the inlet N2O concentration and the adsorbent bed. Tests were performed using PFS in a laboratory farm under semi-real conditions. It was found that at sampling time of 1.5 h, the accuracy and precision of PFS was appropriate. Under evaluated conditions, a maximum variation between PFS and direct detection of around 12% was estimated.