Abstract
BackgroundAirborne fungi are responsible for the majority of fungal infections in humans and animals. Outdoor air markedly influences the prevalence of fungal spore levels in indoor air and thus, it is the major source of fungal infections in indoor environments especially in hospitalized individuals.MethodsUsing a settle plate method, air sampling (1092 air samples from 93 sampling sites in 22 geographic regions of Tehran) was performed by exposing 90 mm settle plates containing Malt extract agar and Potato dextrose agar to the air for 30 min. The plates were incubated at 28°C for 2–3 weeks and examined daily for visible fungal growth. Purified fungal colonies were identified at the genus level based on morphological criteria according to standard methods.ResultsA total of 6455 colonies belonging to 24 different fungal genera were isolated. Area V situated in the city center was the most contaminated region with 2523 fungal colonies (39.1%), while area IV in the West showed the least contamination rate (636 colonies; 9.8%). Airborne fungi isolated were classified into 4 classes including hyaline Hyphomycetes (53.5%), dematiaceous Hyphomycetes (41.6%), Zygomycetes (2.8%) and Coelomycetes (0.2%). Aspergillus (31.3%) was the most prominent isolated fungus followed by Cladosporium (22.1%), Penicillium (13.8%) and Alternaria (12.2%).ConclusionOur results indicate that outdoor air is a potential threat to public health because of harboring a wide array of pathogenic and allergenic airborne fungal spores which can serve as the main source of contamination of indoor environments such as homes, offices and hospitals.
Highlights
Exposure to airborne pathogens is a major risk factor for human health [1]
A total of 1092 settle plates of outdoor air sampled from 93 sampling sites were studied
It may be due to the fact that Aspergillus, Penicillium and Cladosporium produce numerous small and light spores that generally remain in the air for a long period of time, whereas other fungal genera produce fewer, larger and heavier spores which tend to have faster settling [17]
Summary
Exposure to airborne pathogens is a major risk factor for human health [1]. It has been shown that microorganisms (e.g., fungi, viruses, and bacteria) from environmental sources may disperse over great distances by air currents and be inhaled, ingested, or come into contact with individuals who have had no contact with the infectious source. Filamentous fungi grow and sporulate in various substrates and constitute significant sources of airborne fungal conidia and hyphal fragments in indoor environments. With respect to the adverse effects on the human health, many studies have been carried out about the fungal community both in outdoor and indoor environments. The genera Cladosporium, Alternaria, Penicillium, and Aspergillus comprise the major part of fungal community in the atmosphere. It has been demonstrated that the abundance of airborne fungal spores in outdoor air vary from place to place and it influences mainly by climatic conditions and human activities [1]. Airborne fungi are responsible for the majority of fungal infections in humans and animals. Outdoor air markedly influences the prevalence of fungal spore levels in indoor air and it is the major source of fungal infections in indoor environments especially in hospitalized individuals
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