Assessment of airborne bacterial diversity and antibiotic resistance patterns in hospitals, public transport and wastewater treatment plants in Botswana

There is presently insufficient information on the atmospheric microbial level in Botswana, the occurrence and diversity of airborne microbes in Botswana is not well understood. In addition, there is also growing concern in the global spread of antimicrobial resistant bacterial pathogens that continue to emerge and pose a huge challenge to human health. This study, being the first of its kind in the country was aimed at understanding the occurrence, distribution and relative diversity of bacteria in the atmosphere surrounding wastewater treatment plants, in hospitals and public transport. The focus was also to further understand the effects of atmospheric conditions, temperature and humidity on the concentration of airborne bacteria. Air impaction was applied for the collection of airborne bacterial community samples using Microbial Air Sampler MAS-100 NT® device at a flow rate of 100 L/min. Air sampling was done in three different months representing 3 seasons between 2016 and 2017.Antibiotic susceptibility was assessed qualitatively. Antibiotic resistance genes were detected through Polymerase Chain Reaction assays. The highest level of culturable bacteria was detected in aerosols (up to 4.4 x102 CFU/m3) wastewater treatment plant (Palapye) downwind.. The assessment of airborne bacteria in clinical environment revealed abundance of bacteria in paediatric wards than in the operating theatres. The highest bacterial concentration was observed at LMH paediatric ward (5.7 x102 CFU/m3). At all the wastewater treatment plants, highest bacterial concentrations in the air were isolated from the downwind of the WWTP. The downwind air of PWWTP had the highest average bacterial concentrations (4.4 x102 CFU/m3). The atmospheric bacterial population was directly affected by temperature and relative humidity; the highest airborne bacterial concentration was recorded during autumn followed by spring while the lowest was observed during winter season. In all the environments (hospitals, public transport and wastewater treatment plants), Pseudomonas species was the most frequently detected bacterium (27.1%) followed by Brucella (15.3 %), Listeria (10.7 %) and Staphylococcus (8.9 %) species. Diversity of genes encoding resistance to various antibiotics was also detected in air samples collected in various environments. This study remains important to better understand and monitor the atmospheric basal microbial levels in Botswana.