Abstract
Sampling campaigns indoors have shown that occupants exposed to contaminated air generally exhibit diverse health outcomes. This study intends to assess the deposition rates of total settleable dust and bioburden in the indoor air of dwellings onto quartz fiber filters and electrostatic dust collectors (EDCs), respectively. EDC extracts were inoculated onto malt extract agar (MEA) and dichloran glycerol (DG18) agar-based media used for fungal contamination characterization, while tryptic soy agar (TSA) was applied for total bacteria assessment, and violet red bile agar (VRBA) for Gram-negative bacteria. Azole-resistance screening and molecular detection by qPCR was also performed. Dust loading rates ranged from 0.111 to 3.52, averaging 0.675 μg cm−2 day−1. Bacterial counts ranged from undetectable to 16.3 colony-forming units (CFU) m−2 day−1 and to 2.95 CFU m−2 day−1 in TSA and VRBA, respectively. Fungal contamination ranged from 1.97 to 35.4 CFU m−2 day−1 in MEA, and from undetectable to 48.8 CFU m−2 day−1 in DG18. Penicillium sp. presented the highest prevalence in MEA media (36.2%) and Cladosporium sp. in DG18 (39.2%). It was possible to observe: (a) settleable dust loadings and fungal contamination higher in dwellings with pets; (b) fungal species considered indicators of harmful fungal contamination; (c) Aspergillus section Candidi identified in supplemented media with voriconazole and posaconazole; (d) specific housing typologies and (e) specific housing characteristics influencing the microbial contamination.
Highlights
The prevalence of azole resistant fungi in dwellings, especially in homes of immunocompromised individuals or patients with respiratory diseases, represents a significant health risk that supports the need for assessments of the prevalence of azole resistance in indoor environments of different regions [13,14]
Dust loading rates ranged from 0.111 to 3.52, averaging 0.675 μg cm−2 day−1. These mass loadings of household dust are in line with the mean values (0.429 μg cm−2 day−1 in winter, 0.570 μg cm−2 day−1 in summer) reported for different dwellings located in the coastal district of Aveiro, in Portugal [3,4]
Much higher mean dust loading rates of 22.6 and 117 μg cm−2 day−1 were measured by Khoder et al [39] inside and outside of domestic houses, respectively, in an urban area of Giza, Egypt
Summary
The prevalence of azole resistant fungi in dwellings, especially in homes of immunocompromised individuals or patients with respiratory diseases, represents a significant health risk that supports the need for assessments of the prevalence of azole resistance in indoor environments of different regions [13,14]. Electrostatic dust collectors (EDCs) constitute a simple and cost-effective passive sampling method able to characterize bioburden present in settleable dust [3,4,19,20,21,22,23] Given their simplicity, low cost, independence from noisy pumps and power supply, possibility of allowing simultaneous sampling in multiple locations, and ability to provide indications of exposure over longer time frames, passive samplers are regarded as a good alternative in indoor air quality and exposure assessment studies [24,25]. The investigation included the molecular detection of toxigenic fungal species and the analysis of antifungal resistance profiles
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