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1. Introduction:

The major portion of the airspora consists of airborne fungal spores. These airborne fungal spores have a very significant role in the cause of respiratory allergy. 70% to 85% of the airspora is made up of fungal spores [1]. Most of fungi cause asthmatic and allergic problems, due to their differential deposition in the respiratory system. Inhalation of airborne allergic spores is responsible for initiating sensitization reactions which will lead to the respiratory allergic diseases.

Intramural aeromycology deals with airborne fungal particles inside close systems (buildings, apartments, houses, offices, libraries). Decrease of building ventilation for the purpose of space conservation and the fact that people spend majority of their time in indoors, exposes them to greater duration and concentration of indoor bioparticles [2]. Although Bengaluru is popularly known as the “Garden city of India”, it has a sizeable portion of residents suffering from respiratory allergic disorders. The most frequently encountered disorders are allergic asthma and allergic rhinitis. Allergy prone individuals show an increase in their symptoms in Bengaluru.

2. Materials and Methods:

2.1. Study site:

     The study site was the ground floor of a house in Malleshwaram, in the northern part of Bengaluru. The house measures 850 sq feet, bedroom measures 100 sq feet.

2.2. Samplings:

Three petriplates (of same size) containing MRBA (Martin’s Rose Bengal Streptomycin Agar) medium were carried to the study sites in sterilized container and exposed to the bedroom air for standardized ten minutes to receive the of air borne fungal spores on the media plates. The exposure time was standardized to ten minutes to get countable number of fungal colonies/colony forming units per plate. After exposure and sealed with parafilm, Petri plates from site were brought separately to the Mycology Lab, Department of Botany, Joseph’s college, Bengaluru.

3. Result and Discussion:

3.1. Qualitative and Quantitative Variations of the Aeromycoflora:

Aeromycological survey was carried out during 2016 to 2017 at Malleshwaram (Table 1; appendix 1). The results of the one year aeromycological survey showed that the bedroom was never free from fungal spores. The fungi varied with season and weather. A total of 37 fungal species were recorded from the set.

The incidence of fungal Colony Forming Units (CFUs) of the Site (Malleshwaram) for 2016-2017 (Table 1) has been provided. During the study period, 1120 CFUs were formed. The seasonal variations in the concentrations of CFUs were reported (figure 1). The percentage of CFUs was higher in winter (41.43%) and it was the lowest during summer (28.39%). The highest monthly count was reported in December with a total of 140 CFUs and the lowest count (38 CFUs) was reported in the month of March.

      Aspergillus niger constituted the first highest fraction of the CFUs of the bedroom atmosphere with an annual incidence 214 CFUs (19.11%). Penicillium chrysogenum (137 CFUs, 12.23%), Candida tropicalis (72 CFUs 6.43%) was the third dominant among the airborne CFUs. Cladosporium cladosporioides (70 CFUs, 6.25%) was the fourth dominant fungus, whereas Cladosporium bruhnei (106 CFUs, 3.42%) occupied the

fifth dominant place. A. silvaticus (61 CFUs, 5.45%), Candida albicans (60 CFUs, 5.36%), Rhizopus nigricans (55CFUs, 4.91%), Alternaria alternata (54CFUs 4.82%) and Curvularia clavata (43 CFUs, 3.84%) were the other prevalent dominant CFUs at the Site.

The above dominant fungi were sporadic in their occurrence at the site. Dry fungal spores like Cladosporium, Alternaria and Aspergillus, are saprophytic fungi. So their concentration depends mainly on the availability of plant debris and the velocity of the wind which release these spores. As reported in this study, Swaebly and Christensen (1952) [3] also reported that Aspergillus and Penicillium were predominant indoors, where as Cladosporium and Alternaria were most frequently monitored outdoors. The predominance of Aspergillus and Penicillium was reported by Dingmeng et al (2020) [4]. Amir et al (2017) [5] reported that Cladosporium and Candida were the frequently indoor monitored genera. Cladosporium and Candida were also found to be dominant in the present study.

3.2.Seasonal Variations of Aeromycoflora:

Site had December 2016, November 2016 and February 2017 as high CFU months, whereas the number of CFUs recorded was low in March 2016, May 2016, and August 2016. From the above results, it is obvious that the CFUs concentration was not uniform throughout the year. Seasonal variations of aeromycoflora were also reported [6],[7],[8],[9].  Winter has shown dominance of CFUs (41.43%). Winter which begins with the end of the North-East Monsoon favors greater growth of fungi. The moisture provided by the tail end of the monsoon and cooler months of the winter help in the proliferation of fungi and their dispersal. The fungal spores are normally dispersed from the conidiophores by hydrostatic pressure and wind.  The summer stood in least dominance of CFUs (28.39%). The dry months of summer with the paucity of moisture inhibits fungal growth. The results of the present study are in conformity with Jurado et al, (1990) [10]; Kuo and Li, (1994) [11] and Kuder (2003) [12] and Rodriguez et al, (2005) [13]. The highest count of Penicillium chrysogenum, Candida tropicalis (Figure 2 and 3) and C. albicans was registered in winter. The summer season showed the same fungal types as seen in winter, but had much lesser numbers (Figure 1).

3.3. Confirmation of Airborne Fungi by Molecular Identification:

Identification of one dominant species of fungi was confirmed by 18S rDNA sequencing. GenBank Accession Numbers were obtained from NCBI (National Center for Biotechnology Information) for the selected dominant fungus. This technique was adopted when doubts about their species level persisted even after pure culture.  The identity of the species which were confirmed was Candida tropicalis (Figure 4) (Accession number: MH879817). The study showed C. tropicalis to be one of the common aerospora, where as Candida species marginally less investigated by other workers.

4. Conclusion:

In this study, it is found that Aspergillus is the most common indoor fungi present at the indoor environment. The finding correlates with the results of Agashe and Anuradha (1998) [14], Dharmage et al., (2002) [15], and Michael et al., 2016 [16]. In environments, such as tropical habitat, these fungi are dominant and are known for their allergenicity [17]. This study indicates that more moisture, less temperature with lower hygiene resulted in high airborne fungal concentration.