Aerosol partitioning potential of bacteria presenting antimicrobial resistance from different stages of a small decentralized septic treatment system

The release of airborne pathogens with antimicrobial resistance is a growing global public health threat. The potential spread of antimicrobial resistant bacteria and antimicrobial resistance genes (ARB/ARGs) from wastewater effluents through aerosolization is not fully understood. Septic tanks are on-site wastewater treatment systems (OWTS) used in about 25% of households in the United States (US). The system in this study consists of four tanks connected by two different treatment types, with wastewater moving from the most contaminated, Tank 1, to the most purified holding, Tank 4. Aerosol samples at each tank were collected in the summer and winter with open and closed lids to observe their effect on bioaerosol emissions. The water inside each tank was also sampled to compare the bacteria concentration and composition. Results from microbial and molecular analysis indicate lower concentrations of bacteria in the aerosols compared to the water samples. The antibiotic testing indicates that aerosolized bacteria from the winter were more resistant to the antibiotics used compared to the aerosolized bacteria from the summer. The occurrence of aerosolized bacteria likely depends on operational conditions and discharge methods, on changes in humidity, temperature, and air velocity, while the effluent resistance can be influenced by quorum sensing. Further assessment of the water and bioaerosol microbiome should include the genomic analysis of antimicrobial resistance of bacterial isolates from both sources and thus provide an important link regarding human exposure to ARBs/ARGs near wastewater treatment systems.Copyright © 2023 American Association for Aerosol Research