Microbial aerosol characteristics and health implications in the highly arid environment

Investigations into the suspected airborne transmission of pathogens in healthcare environments have posed a challenge to researchers for more than a century. If carried by a favorable air flow, bioaerosol material may be distributed over large distances with potentially fatal results. So the objective of this study is to perform the characterization of culturable and non-culturable bacteria, and fungi, and identify health-significant and antibiotic-resistant microbes. The ambient bioaerosols samples were collected in the greater Doha area, Qatar, during the autumn, winter, and summer seasons. Bacterial and fungal concentration, size distribution, and diversity were investigated by culture studies coupled with biochemical assays and next-generation sequencing. A total of over 70 samples were collected and processed with the Coriolis micro–microbial air sampler in each season from 7 stations. There was a significant increase in the concentration of bacteria and fungus during and after the rain. These concentrations were much lower than those in most cities worldwide may be due to the arid climate feature. The average concentration of bacteria was higher than the fungus throughout the winter season. Identification of culturable bacteria was done by biochemical assays using API 20E kit and fungus identification was done by microscopic analysis. Over 484 microbial species were detected using 16SrRNA gene-based next-generation sequencing.  Biodiversity analysis shows that bacterial and fungal diversity was the same at all the stations regardless of the location which shows that the local factors don’t have much impact on the bacterial and fungal biodiversity. However, there was a difference in microbial diversity in the winter season as compared to the summer, spring, and transition seasons. A scan of health significant pathogens has been performed on the identified microbes’ data. Several health-significant bacterial and fungal species were identified in Qatar ambient air including staphylococci, legionellae, tuberculous and nontuberculous, bacterial spore formers Clostridium difficile and Bacillus anthracis, and fungi Aspergillus, Penicillium, and Cladosporium spp and Stachybotrys chartarum which are strongly associated with allergic respiratory disease, especially asthma. Despite emerging significant public health concerns of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) in urban air, it has not received significant attention. On the other hand, current air pollution health studies rely heavily on PM mass concentration, without considering biological parameters such as ARGs or ARB. An identification of the antibiotic-resistant strains was carried out according to the WHO priority classification and several microbes including Acinetobacter baumannii (WHO Priority 1: CRITICAL), Enterococcus faecium, Staphylococcus aureus, Campylobacter coli and Streptococcus pneumonia  (Priority 2: HIGH) were found in the ambient air.