Caroline Duchaine’s research while affiliated with Université Laval and other places

The evaporation dynamics of water-based aerosol droplets carrying pathogens, such as Legionella from cooling towers, is critical for assessing the risks of airborne transmission. Yet, the evaporation of contaminated aerosol droplets remains poorly understood and is often overlooked by current risk assessment models. Changes in water properties, such as viscosity and surface tension, induced by the presence of nonvolatile solids or contaminants, affect the evaporation time, the droplet nuclei size, and the time resolved size evolution. The effect of these parameters was experimentally and analytically studied. Surfactants lowering surface tension introduced non-linearity in droplet size evolution, extending evaporation time by up to 14% and halting it at high concentrations. Increased viscosity delayed evaporation onset without affecting nuclei size, which remained around 8–9 μm compared to 0.5 μm for reference water droplets. High concentration of solids, covering over 60% of the droplet surface, nearly doubled the evaporation time and increased nuclei size to 20 μm. Existing evaporation models do not fully account for temporal size changes and the variability in nuclei size due to solids concentration. Improving evaporation models and incorporating them into microbial contamination risk assessments are critical to develop effective mitigation strategies, such as using efficient drift eliminators for cooling towers.

Background: Pembrolizumab is a monoclonal antibody (mAb) approved for treating Non-Small Cell Lung Cancer (NSCLC), melanoma and lymphomas. Commercialized in single-size (100 mg/4 mL) vials, the pembrolizumab solution contains no preservative. As such, the manufacturer recommends using pembrolizumab vials only once, and thus, to rapidly dispose of any unused portion. Thus, appreciable amounts of this costly product are wasted. Objective: To evaluate the physical, chemical and microbiological stability of pembrolizumab vial leftovers stored at room temperature or at 4 °C, 7 and 14 days after first vial puncturing. Methods: Following pH assessments, submicronic aggregation and turbidity of pembrolizumab were measured by dynamic light scattering (DLS) and spectrophotometry, respectively. In addition, SE-HPLC (size-exclusion high-performance liquid chromatography), IEX-HPLC (ion exchange HPLC) and peptide mapping HPLC served to respectively evaluate aggregation and fragmentation, distribution of charge and primary structure of pembrolizumab. Incubation at 37 °C for 48 h of pembrolizumab vial leftovers on blood agar plates was used to determine their microbiological stability. Results: Physical, chemical and microbiological stability of pembrolizumab leftovers was demonstrated for at least two full weeks. Conclusions: These results argue forcefully in favor of allowing prolongation of pembrolizumab vial leftovers usage well beyond a single day.

In Quebec, the phase-out of the conventional cage (CC) system for egg production, is expected to be completed by 2036, with a transition to alternative systems such as enriched colonies (ECs) and cage-free (CF) housing. This study aimed to assess Greenhouse gas (GHG), and ammoniac (NH3) emissions associated with those systems. The investigation involved one visit per farm to 30 commercial laying hen facilities in Southern Québec, Canada. The findings revealed that the CF system exhibited the highest numerical average of CO2 emissions (3207 ± 2423 mg h-1 hen-1), followed by CCs (2835 ± 877 mg h-1 hen-1) and ECs (2597 ± 949 mg h-1 hen-1). Furthermore, the EC system had the lowest average CH4 emissions (0.93 ± 0.54 mg h-1 hen-1), while CC (1.07 ± 0.41 mg h-1 hen-1) and CF (1.27 ± 1.11 mg h-1 hen-1) facilities had higher values. Emissions of N2O were similar across all three systems (0.04 to 0.05 ± 0.05 mg h-1 hen-1). The study revealed significant differences in NH3 emissions among CC (2.0 ± 1.0 mg h-1 hen-1), EC (2.5 ± 2.0 mg h-1 hen-1), and CF egg production systems (11.2 ± 15.9 mg h-1 hen-1).

Highlights Fan exhaust air sampling is a reliable monitoring proxy for indoor bioaerosols from livestock operations. Air samples collected indoors and at fan exhaust have highly similar bacterial diversity. At low indoor concentrations, specific microbial markers are still detectable in the air collected at the fan exhaust. Abstract. The incidence of animal and zoonotic diseases is expected to increase in the coming years, imposing the reinforcement of biosecurity measures for livestock operations. Airborne transmission of certain infectious agents underscores the importance of surveilling bioaerosols. However, having access to livestock operations for monitoring purposes is now challenging. Hence, it has become imperative to explore alternative strategies to assess indoor bioaerosols. This study aimed to compare bacterial diversity and quantify microbial markers found in bioaerosols indoors and at the fan exhausts of pig-finishing buildings (PFBs) and broiler chicken barns (BCBs). Bioaerosols were collected using a filter-based, high-flow rate air sampler in 12 facilities (10 PFBs and 2 BCBs) during the warm season in Eastern Canada, corresponding to maximal ventilation rate operations. Four farms—PFB-1, PFB-2, BCB-1, and BCB-2—were visited multiple times, while the other eight PFBs (PFB-3 to PFB-10) were visited once. At each farm, indoor air samples were paired with samples from the corresponding sidewall extraction fans. Amplicon-based sequencing and quantitative PCR (qPCR) were performed to describe bacterial diversity and quantify specific microbial (bacterial and archaeal 16S rRNA genes, Enterococcus spp., and a phage of Aerococcus viridans) and animal (swine and poultry DNA) markers. No significant differences in OTUs abundance and diversity between indoor bioaerosols and their corresponding fan exhaust samples were observed. There were also no significant differences between an indoor and its corresponding fan exhaust air sample when comparing OTUs relative abundance and their presence-absence. Similarly, concentrations of bacterial 16S rRNA genes in indoor samples (10 ⁶ –10 ⁸ ) did not significantly differ from those found in samples collected at the fan exhaust (10 ⁵ –10 ⁸ ) for both PFBs and BCBs. Strong correlations were observed between sampling sites for Archaea, Enterococcus, and A. viridans phage concentrations while poultry and swine DNA concentrations at fan exhausts did not correlate with indoor levels. All investigated markers were detectable at fan exhausts, even at low indoor concentrations (10 ² –10 ³ ). Our study suggests that air sampling at the fan exhaust of barns provides a representative picture of the indoor bioaerosols both for bacterial diversity and barn-specific indicators when the fans are in use. This method appears promising for characterizing indoor air quality based on emissions and could be highly valuable in cases where biosecurity measures or outbreaks restrict access to barns. Keywords: Air sampling, Airborne microbiota, Bioaerosols, Broiler, Fan exhaust, Livestock operations, Pig.

Background/Objectives: Antibiotic resistance gene (ARG) spread is driven by horizontal gene transfer (HGT). Ciliated protozoa may contribute to this process, as their predation has been shown to facilitate HGT in certain bacteria. Here, this phenomenon was further investigated using A. salmonicida subsp. salmonicida. This fish pathogen bears an extensive and dynamic plasmidome, suggesting a high potential for HGT. Methods: A. salmonicida strains carrying one of three conjugative plasmids bearing ARGs (pSN254b, pRAS1b or pAsa4b) were cocultured with a recipient, either A. salmonicida, E. coli or A. hydrophila. Conjugation rates were assessed in the presence and absence of the ciliate Tetrahymena borealis. PCR genotyping confirmed the acquisition of the conjugative plasmids and was used to verify the mobilization of other plasmids. Results: The basal rate of conjugation observed was high. Under the conditions studied, ciliate predation did not appear to influence the conjugation rate, except at higher proportions of ciliates, which typically hampered conjugation. Microscopy revealed that most bacteria were digested in these conditions. PCR screening demonstrated that small mobilizable plasmids from A. salmonicida (pAsa1, pAsa2, pAsa3, and pAsal1) were acquired by the recipients along with the conjugative plasmids, with a slight effect of the ciliates in some donor/recipient cell combination. Conclusions: These results highlight how A. salmonicida can conjugate efficiently with different species and how complex its relationship with ciliates is.

Antibiotic resistance is one of the biggest challenges to public health. While the discovery of antibiotics has decreased pathogen-caused mortality, the overuse of these drugs has resulted in the increased transfer and evolution of antibiotic resistance genes (ARGs) in bacteria. ARGs naturally occur in wild bacterial communities, but are also found in increased concentrations in environments contaminated by wastewater effluent. Although such ARGs are relatively well described in temperate environments, little is known about the distribution and dissemination of these genes in the Arctic. We characterized the ARGs in microbial communities from aerosols, lakes and microbial mats around a remote Arctic hamlet using metagenomic approaches. Specific objectives were to (i) compare ARGs across habitats, (ii) to characterize ARG populations along a continuum of anthropogenically influenced environments, and (iii) to identify ARGs of viral origin. We identified ARGs in all habitats throughout the watershed, and found that microbial mats in the most impacted area had the highest diversity of ARGs relative to uncontaminated sites, which may be a remnant signal of wastewater effluent inputs in the area during the 20th century. Although we identified ARGs predominantly in bacterial genomes, our data suggests that mimiviruses may also harbor ARGs.