[Air Microbial Contamination and Risk of Respiratory Exposure of Workers in Chicken Farms].

Animal farms are important sources of microbial contamination in the air environment. However, there are few reports on the time-regularity characteristics of airborne microbial contamination in farms. In the context of this situation, a study was conducted for more than 80 weeks using 16S rRNA gene amplicon sequencing to characterize the bacterial distribution and respiratory exposure in the farm air and fecal environment, respectively, taking a layer farm as an example. The results showed that 16S rRNA concentrations in air and manure samples ranged from 6.08×105-4.90×106 copies·m-3 and 4.27×108-1.15×1010 copies·g-1, respectively. The mean values of airborne bacterial concentrations were significantly higher in winter than in summer, whereas the biodiversity showed the opposite trend. The dominant bacterial phylum in both air and manure in the layer farm was Firmicutes. During the investigated time, the top three dominant genera in the air were relatively stable, in the order of Lactobacillus, Bacteroides, and Faecalibacterium, whereas the dominant genera in feces fluctuated with the increase in breeding time. The correlation between the community structure of bacteria and pathogenic bacteria in both air and manure was not significant, but the concentrations of both target microorganisms in different media were significantly correlated. The bioaerosolization index of bacteria in manure showed an increasing trend with increasing breeding time, whereas the opposite trend was observed for pathogenic bacteria. In this case, [Ruminococcus]_torques_group, Bacteroides, and Faecalibacterium were the top three pathogenic genera that were the most prone to aerosolization. There were seasonal differences in bacterial respiratory exposures of chicken farm workers, with mean intake values of 2.54×107 copies·d-1 and 2.87×105 copies·d-1 for bacteria and pathogenic bacteria, respectively. The results of this study will provide a scientific basis for systematically assessing the contamination characteristics and potential health risks of airborne microorganisms on farms and for developing corresponding industry standards for occupational exposure and prevention and control measures.

Resistance valves in circulatory loops have a significant impact on in vitro evaluation of blood damage caused by blood pumps: a computational study.

Background: Hemolysis and its complications are major concerns during the clinical application of blood pumps. In-vitro circulatory testing loops have been employed as the key procedure to evaluate the hemolytic and thrombogenic performance of blood pumps during the development phase and before preclinical in-vivo animal studies. Except for the blood damage induced by the pump under test, blood damage induced by loop components such as the resistance valve may affect the accuracy, reproducibility, and intercomparability of test results. Methods: This study quantitatively investigated the impact of the resistance valve on in vitro evaluation of blood damage caused by blood pumps under different operating points. A series of idealized tubing models under the resistance valve with different openings were created. Three pumps - the FDA benchmark pump, the HeartMate 3 LVAD, and the CH-VAD - were involved in hypothetical tests. Eight operating points were chosen to cover a relatively wide spectrum of testing scenarios. Computational fluid dynamics (CFD) simulations of the tubing and pump models were conducted at the same operating points. Results and Conclusion: Overall, hemolysis and platelet activation induced by a typical resistance valve are equivalent to 17%-45% and 14%-60%, respectively, of those induced by the pump itself. Both ratios varied greatly with flow rate, valve opening and pump models. Differences in blood damage levels between different blood pumps or working conditions can be attenuated by up to 45%. Thus, hemolysis and platelet activation induced by the resistance valve significantly affect the accuracy of in-vitro hemocompatibility evaluations of blood pumps. A more accurate and credible method for hemocompatibility evaluations of blood pumps will benefit from these findings.

Particle-size stratification of airborne antibiotic resistant genes, mobile genetic elements, and bacterial pathogens within layer and broiler farms in Beijing, China.

The particle-size distribution of antimicrobial resistant (AMR) elements is crucial in evaluating their environmental behavior and health risks, and exposure to the fecal microbiome via particle mass (PM) is an important route of transmission of AMR from livestock to humans. However, few studies have explored the association between air and fecal AMR in farm environments from the perspective of particle-size stratification. We collected feces and PMs of different sizes from layer and broiler farms, quantified antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and human pathogenic bacteria (HPB) using Droplet digital PCR (ddPCR), and analyzed the bacterial communities based on 16S rRNA sequencing. The particle-size distributions of 16S rRNA and AMR elements were similar and generally increased with larger particle sizes in chicken farms. In broiler farms, we observed a bimodal distribution with two peaks at 5.8-9.0 µm and 3.3-4.7 µm. The dominant airborne bacterial phyla were Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes. The dominant phyla in the feces were the same as those in the air, but the order of relative abundance varied. The particle-size distributions of specific bacterial genera differed between the animal-farm types. Overall, the degree of association between feces and different particulates increased with increasing particle size. The microbial communities in the coarse particles were similar to those in fecal samples. Escherichia coli, Staphylococcus spp., Campylobacter spp., and sul 2 (sulfonamide ARGs) tended to attach to small particles. We highlight the particle size-specific relationship between fecal and air microbes involving ARGs, MGEs, and HPB and provide valuable information for comprehensively assessing the transmission of fecal microorganisms through the airpath and its environmental and occupational health risks.