Aerobiology, Volume 1, Issue 2 (December 2023) – 3 articles

Although studies focusing on the physicochemical properties of aerosols/clouds have not been performed extensively, even less attention has been given to hailstones and their biological composition. Here, we present the results of the physical and microbiological characterisation of 20 hailstones collected in Southern Brazil originating from two storms. Nearly half of the hailstones (9 out of 20, or 45%) did not contain any cultivable bacteria or fungi. A total of 18 bacterial species were found in hailstones from both storms, and the genus Bacillus was found in 5 out of the 11 hailstones, with Bacillus cereus being the most frequent bacterial species. Fungi, on the other hand, were only present in four hailstones derived from a single storm, with three fungal species identified and Epicoccum nigrum being the most frequent fungal species. HYSPLIT modelling indicated the different flow of air masses from the Amazon and Pacific Ocean that contributed to the loading of microorganisms found in the clouds at the time of the two storms. Our findings suggest that ca. 50% of hailstones have cultivable bacterial or fungal species, which came mainly from the local landscape with intrusions of air masses derived from the Amazon and the Pacific Ocean. Full article

UV irradiation has shown potential in reducing bacterial and viral loadings. This is a pilot study aimed at investigating the antimicrobial effect of a novel pulsed UVA and UVC technology on bacteria and human coronavirus 229E. The selection of these microorganisms is based on their relevance and significance in real-world scenarios. This study consists of independent experiments for the assessment of antibacterial and antiviral activities by using a lawn plate approach, measuring levels of adenine triphosphate (ATP) in three bacterial strains, Escherichia coli, Staphylococcus epidermidis and Bacillus subtilis, and performing Median Tissue Culture Infectious Dose (TCID₅₀) of HCoV-229E on MRC-5 human lung fibroblast cell line. The results demonstrated the ability of UVA and UVC irradiation to reduce levels of adenine triphosphate (ATP) over a 12 h exposure period in all three bacterial strains, comparative to dark and artificial/natural light conditions using non-pulsing experiments. In addition to this, there was a reduction in colonies exposed to UVA and UVC pulsing experiments for E. coli K12 and S. epidermis compared to bacteria stored in artificial/natural and dark conditions. Furthermore, using dose-dependent modelling, it was demonstrated that the cross-contamination risk was reduced by 50% using E. coli as a typical model. Regarding the antiviral assay, the results showed that TCID₅₀ of HCoV-229E was reduced after the first cycle of UV engagement. No cytopathic effect (CPE) was detected after three cycles using Protocol 1. The findings showed that UVA and UVC were effective under the conditions outlined in this paper for a reduction in the number of bacteria with additional applications to viruses. Full article

Avian influenza virus (AIV) can have a serious impact on both human and animal health. In this study, we used an environmentally controlled chamber and a hemagglutination assay (HA) to evaluate the ability of membrane-less electrolyzed water (MLEW) spraying to inactivate H6N1 AIV aerosol. MLEW was generated by electrolyzing sodium chloride solution, and then sprayed into the chamber at free available chlorine (FAC) concentrations of 50, 100 and 200 mg/L by means of high-pressure air pumping to inactivate airborne H6N1 AIV aerosols individually. The results showed that MLEW spraying effectively neutralized H6N1 AIV aerosol. In addition, the virucidal ability of MLEW increased as the FAC concentration increased. Five minutes after MLEW spraying at an FAC concentration of 200 mg/L, the H6N1 viral HA titer decreased from 2⁴ to 2⁰. Our work provides important new evidence of the value of spraying with MLEW disinfectant to protect against AIV, which may be further applied for indoor decontamination purposes to promote animal and human health. Full article