Assessment of the Pathogenic Potential of Microorganisms in Atmospheric Aerosols of Novosibirsk and Its Suburbs

Introduction: The atmosphere of Novosibirsk is characterized by increased levels of suspended particles, a significant part of which are bioaerosols. The latter include bacteria and fungi that can induce infectious diseases, allergies, and other negative responses in the population. Yet, the microbiota of ambient air of Novosibirsk and the region is poorly studied.

Objective: To determine the concentration and composition of microorganisms in atmospheric aerosols of Novosibirsk and the region isolated in spring/summer 2023 and to test the microbial isolates for pathogenicity.

Materials and methods: To isolate microorganisms from ambient aerosols, air was filtered applying Sartorius reinforced Teflon membrane filters and Hopar compressors. Their desorption from the filters was carried out by shaking in a physiological solution on a rocker and vortex followed by sowing the resulting suspensions onto nutrient media. We determined pathogenic signs by the presence of aggression enzymes and sensitivity of microbial isolates to antibiotics by the disk diffusion method. Sequencing of the 16S rRNA gene was performed by Sanger method; full genome sequencing was performed using the NextSeq 550 system.

Results: During the study of the microbiota of atmospheric aerosols in Novosibirsk and the region in spring/summer 2023, fungi, spore-forming and non-spore-forming bacteria, both saprotrophic and pathogenic, were isolated with concentrations in the aerosol ranging from 100 to 8×10³ CFU/m³, including multiple drug resistant ones. Fungi were generally represented by opportunistic and allergenic species of the genera Aspergillus, Alternaria, Cladosporium, Aureobasidium, and Penicillium, while bacteria – by a large variety of spore-forming and non-spore-forming bacterial species. Based on the results of analyzing phenotypic traits and the 16S rRNA gene sequencing, 119 bacterial isolates were identified. Full genome sequencing analysis and pathogenicity testing by secretion of catalase, hemolysins, lecithinase, lipase, plasma coagulase, alkaline phosphatase, gelatinase were performed for 49 of them along with testing for antibiotic resistance. We identified twenty-nine strains belonging to B. safensis, B. cereus, P. megaterium, B. mycoides, P. agglomerans, S. equorum, A. lwoffii, and a number of others with 5 to 7 positive reactions out of 9 in pathogenicity testing, capable of causing infectious diseases. Eleven strains showed resistance to 4 to 7 antibiotics, enabling their classification as multidrug-resistant.

Conclusions: Detection of fungi and bacteria, which are among the most dangerous pathogens with multiple antimicrobial resistance, prove the necessity of constant control of the composition of bioaerosols in the urban environment.

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