Airborne bacterial communities and biological factors associated with their viability and survival.

Nosocomial infections remain a significant global public health challenge, driven by antimicrobial resistance and ventilation-related transmission (S. Raoofi et al., 2023; W. R. Miller & C. A. Arias, 2024). The burden is particularly high in middle-income countries (R. Balasubramanian et al., 2023). Despite increasing recognition of aerosol biology in human health, methods for detecting viable airborne pathogens remain limited, and sampling strategies strongly influence detection outcomes. Interactions between pathogenic and non-pathogenic microbial communities are also poorly understood, especially in airborne environments. While gut microbiome studies demonstrate that such interactions affect disease progression, similar research in respiratory systems is scarce (C. C. Naidoo et al., 2019). This study investigates cell-to-cell communication signals, including metabolic and biochemical activity, linked to bacterial virulence in airborne pathogens.
A portable air sampling device was used to collect outdoor air samples in a garden environment using both active and passive methods. The device featured two sampling heads: one fitted with an agar plate and the other with a membrane filter for active sampling. For passive sampling, agar plates were placed on the ground. Aerosols were collected at a flow rate of 100 L/min for 5 minutes. Microbial identification and metabolic activity were assessed using the Odin Biolog system. Pure colonies were swabbed into inoculating fluid, and 100 µl aliquots were transferred into GEN III Microplates, and incubated at 33°C for 24 hours.
A total volume of 1000 litters were sampled. Distinct bacterial colonies appeared after 24-48 hours of incubation at 30°C. Metabolic profiling was conducted using 71 carbon utilization and 23 chemical sensitivity assays, generating phenotypic fingerprints that reflect respiration-based substrate use.
Different microorganisms were found, both bacterial and fungal airborne. These findings provide preliminary insight into the diversity and metabolic activity of airborne bacterial communities, highlighting their adaptability in harsh environments. The results have implications for understanding airborne transmission relevant to hospital-acquired infections. Further research, including metagenomics analysis will identify specific signalling molecules and microbial interactions including environmental metadata.