Air microbial quality in certain public buildings, Egypt: A comparative study

This study aims to determine microbiological air quality in public buildings: libraries, faculties, schools, child daycare centers and hospitals and its association with microclimatic conditions, particulate matter (PM) and ventilation type. Airborne bacteria and fungi were collected using Andersen two-stage sampler, it divides particles into coarse (≥7 μm) and fine (<2.5 μm) size ranges. Bacterial and fungal concentrations ranged between 0 ‒ 105 CFU/m3 and 0-103 CFU/m3, respectively. The 95th percentile values were 3399 CFU/m3 for environmental bacteria; 2299 CFU/m3 for mesophilic bacteria and 513 CFU/m3 for fungi. The Global Index of Microbial Contamination (GIMC/m3) exceeded 2000 CFU/m3 in hospitals' admission rooms and educational buildings. Index of Mesophilic Bacterial Contamination (IMC) achieved the greatest value in the faculty of specific education (F.SE), indicating overcrowding and hypoventilation. Fine particle fraction ranged within 2-41% for bacteria and 47-94% for fungi. Bacillus subtilis and Bacillus atrophaeus were the common bacterial species. Aspergillus, Alternaria, Penicillium and Cladosporium were the common fungal types. The secondary and tertiary fungal colonizers were detected in low counts. Agreement ratios showed that, outdoor air was the main contributor of indoor fungal flora, and accumulated dust was important contributor of fungal and bacterial flora in schools and faculties. Indoor/outdoor (I/O) ratios of PM concentrations exceeded 1 in ∼37% of the public buildings. Temperature negatively affected bacterial culturability while, relative humidity and PM supported fungal culturability in indoor environment. However¸ PM positively affected bacterial culturability and temperature negatively affected bacterial and fungal curturability in outdoor environment.