1.
INTRODUCTION
1.1
Studies of air-borne
Aerobiology deals with
several airborne microorganisms and biological particles. Fungi are the main
part of the air microbiome. Studies have been conducted worldwide to explain their
effects on health, and agriculture. Most studies of air mycobiota around the
world focused on calm climate. They investigate the diversity of outdoor and
indoor airborne fungi and their health impacts as well as factors that affect
their population (Savković et al., 2021; Xin et al., 2021). (Liu et al., 2021;
Mendell, 2009; Al-Badr et al., 2018). Most of the predominant airborne fungi
are allergens and agents of human health disorders ( Kim et al., 2018; Garga et
al., 2019).
1.2
Dust storm
events
Official meteorological
agencies and studies mentioned serious changes in the Middle East's climate
(Waha et al.,2015; Ahmadalipour and Moradkhani
2018). An official report prepared by
Michael Carlowicz, the earth observatory and managing editor of NASA,
explains that since the beginning of April 2022, Iraq and other parts of the
Middle East region will be struck by a sequence of dust storms.
1.3
Study
airborne fungi in Iraq
Several
studies aimed to identify and discuss the fungal air-spora in Iraq; they
covered outdoor, indoor, and devices of air conditioning. Al-Bader (1995)
listed (34) genera by monthly outdoor sampling over a year, Cladosporium
and Alternaria were predominant. Abdullah and Al-Ani, (2003) recorded 29
genera from hospital indoor air samples. Badran et al. (2018) recorded 11
genera from indoor and outdoor samples, Cladosporium, Penicillium, and Alternaria
were predominates. Al-Bader et al. (2013) screened indoor airborne fungi and
their relationships with respiratory disorders. The fungal contamination of air conditioner units in five
hospitals in Erbil city was investigated by Al-Bader et al. (2018). They
recorded 13 genera, where Penicillium, Aspergillus, and Alternaria
showed the highest occurrence.
1.4
Storm dust
mycobiota
Microorganisms attached
to dust particles have been recognized to travel far away from their original
habitat (Favet et al., 2013). Dust storms hold and transmit fungi. They are a
probable source of asthma and several respiratory disorders. In Iran, Nourmoradi
et al. (2015) mentioned increasing colony-forming units (bacteria + fungi)
directly by increasing dust particle concentration. The common fungus was Mycosporium.
In KSA, Rajendran et al. (2017) observed that the most important fungal
allergens associated with storm dust were, Fusarium, Cladosporium,
Ulocladium, Aspergillus, and Alternaria. A study conducted by
(Moataz et al., (2010) in Iraq showed that Aspergillus and Candida
albicans were common after storm dust loads. In a study of the west Texas
air dust mycobiota, the common
genera were Cryptococcus, Aureobasidium, Alternaria, Cladosporium, and
Filobasidium (Elmassry
et al., 2020).
Due to the frequent
drought and desertification in Iraq and the frequent dust storms and the lack
of information on the fungi associated with dust, this study was conducted to
reveal the fungal community associated with dust and its difference from its
counterpart in the calm climate in Erbil city.
2.
MATERIALS and METHODS
2.1
Sample
collection
On May 23rd and 24th , 2022, thirty-two
samples from Erbil city were collected (S1). The source of storms were
southwest arid areas of Iraq which expand to KSA desert. The gathering place is
an outer edge of a window that is 15 meters above the ground and in a direction
that is blocked from direct air movement. The samples collection site was
absolutely free from trees in the vicinity of the place. The plating exposure
method was followed to collect the settle-down dust. The gathering place is an outer edge of a window 15 meters
above the ground. 16 Petri plates were used daily. Two plates were exposed per
hour starting from 9:00 am to 4:00 pm. The time of exposure was 10 minutes, and
the plates were wrapped with paraffin film and incubated at 25± 2. Two plates
were used as controls. Two types of culture
media were used, Sabouraud’s dextrose agar and pollen grain agar (Al-Bader,
2019). According to Erbil Metrologic agency (https://www.timeanddate.com/weather/iraq/irbil/historic), the mean temperature during sampling was 25-27oC,
the mean humidity was 25%, and with different wind directions (SW, W, WN). Samples
were recollected after the storm passed for 48 hours and the procedure of S1
was identically followed for a calm climate (S2).
2.2
Colonies
counting and identification
The plates were checked
after 3 days to count the number of colonies. Omeliansky’s
equation was used to calculate the colony forming units/m3 (N = 5a×104 (bt)−1
) where N= microbial CFU/m3 of air. a= number of colonies
/ Petri dish. b= dish surface, cm2 . t: exposure time, minutes (Fekadu
and Getachewu, 2015).
Petri plates were
checked periodically for 14 days to identify fungal genera, then fungi were
distinguished either directly or after the preparation of a pure culture. The
microscopic characteristics were confirmed according to (De Hoog et al., 2000;
Ellis et al., 2007).
2.3
Analysis of
the fungal population of S1 and S2
Total ocurance% (TO) and
total frequency% (TF) for fungal isolates were calculated for both S1 and S2.
Also, The total similarity (TS) between genera of S1 and S2 was explained via
the Jaccard index (Singh, 2012) according to the
following:
TO% = (No. of times
fungal appear *100) /No. of collected samples
TF%= (No. of fungal
isolates *100)/ No. of total fungalIsolates.
Jaccard’s
Index = 2 x(the number in both sets) / (the number in either set) x 100.
2.4
Statistical
analysis
Statistical analysis was
performed by paired t-test to compare the mean of the number of isolates,
occurrence, and frequency of fungal genera between a dust storm and a calm
climate. The SPSS software (Windows Version 23.0) was utilized for all
statistical processing. When the p-value was <0.05, the difference was
judged statistically significant.
3.
RESULTS
The total colony count
for 32 Petri dishes of S1 was 257 related to 13 genera and 2 unidentified
yeasts and mold. (143CFU/m3) while
they were only 110 colonies related to 5 genera in S2 (59CFU/m3) The statistical analysis showed a highly
significant difference between CFU for S1 and S2 (p≤0.0001), while it was less
and negative for O% and F% respectively (Table 1). The isolated
genera viz Alternaria, Aspergillus (5 sp.), Botrytis, Cladosporium,
Fusarium, Monilia, Morterilla, Mucor, Penicillium, Phoma, Stemphylum,
Ulocladium, Verticillium, and Yeast (creamy color), as well as
sterile mycelia(white) The predominant group was Hyphomycetes (10genera.)
followed by Zygomycetes (2 genera) and Coelomycetes (1 genus). 50% of
Hyphomycetes were dematiaceous (Table 1, Figure 1) The
abundance of isolates in the S1 samples ( isolate/plate= 8,3) was more than
that of the S2 samples (isolate/ plate =3.43) (Figure 2).
Figure
1.
Occurance% of Hyphomycetes (H), Zygomycetes (Z), and Coelomycetes (C)
The
predominant airborne genera of S1 include Aspergillus, Alternaria,
Cladosporium, and Penicillium besides the sterile mycelia. They are
the only genera investigated in normal climate samples (S2). The results showed low total similarity between S1 and S2
fungal populations (TS=35.7%). In S1, Aspergillus
was represented by A. fumigatus, A. niger, A. terreus, A. ochraceus, and A.
flavus. The genus has the highest occurrence (65.6%), and also it
had the highest frequency (15.9%), followed by
Alternaria, Cladosporium, and sterile mycelium (Table 1). In S2, Aspergillus
is the common genus with fewer species (2 sp. only), followed by Cladosporium.
4.
DISCUSSION
The
present study distinguishes the fugal components of one of the most severe dust
storms that hit Iraq and Erbil city during the previous years. The completely
identical methods of S1 and S2 showed a big difference between the total colony
count in the dust storm samples and their counterparts after passing through
the storm. The concentration (143CFU/m3) was higher than the level
of microbial contamination given by American Conference of Governmental
Industrial Hygienists Committee (100 CFU/m3 ) and lower than the guidelines
provided by WHO (500 CFU/m3 ). The low significant and non-significant differences
for O% and F% were due to the low number of genera (low diversity) in the S2
fungal community. The increase in the total airborne fungi of dust storms was
reported by several workers (Griffin et al., 2001; Kellogg et al., 2004). Also,
Nourmoradi et al. (2015) indicated a highly positive relationship between a
dust storm and aerobiological particles. The relatively minor differences among
previous studies are due to the original regions of the storms, which are
regarded as the main effective factor in air dust mycobiota (Peng et al.,2021).
Furthermore, the fungal populations in S1 and S2 showed a great dissimilarity
after Jaccard’s index that ranged from (0-1). The current study showed an
increase in the number of genera in S1 than in the S2 samples, while the
dominant genera were the same in both cases.
The same result was
reported in the north of Iran by Neisi et al. (2019), who listed Cladosporium.
Aspergillus and Penicillium as common genera.
The predominant genera of
the present study were recorded by Al-Bader et al (2016) in Kuwait. They
identified 17 genera viz Fusarium, Alternaria, Ulocladium, Phoma,
Aspergillus, Acremonium, and Penicillium were predominant. The
similarity with the present stud results relates to meteorological factors
rather than biological ones. Iraq and Kuwait are located in the same geographic
region and are approximately affected by the same
environmental factors, including dust storms, and this may explain why
the air dust mycobiota was the same. The similarity of current results with
such a study in KSA may refer to the fact that the origin of dust storms that
hit Iraq is the KSA deserts. A 50% of fungi
represented in the current study were identified in KSA sand storms; moreover,
the predominate genera are the same in both studies (Rajendran et
al.,2017).
The
predominant genera in the current study ( Alternaria, Aspergillus,
Cladosporium, and Ulocladium) are common airborne in the
Mediterranian region, they showed a significant increase in air mycobiota of
dust storms. And that may refer to several characteristics that help them
survive as aerobiological particles.
Aspergillus, Cladosporium, Fusarium, Penicillium, Stemphylum, Botrytis, and Phom were described as xerophilic and xero-tolerant
fungi (Petrovič et al.,2000)
Moreover, they are dematiaceous and can produce a
great number of dry conidia. Such traits enable them to survive along with the
storm’s dust (Peng et al., 2021).
There
is a lack of information about the aerobiology of dust storms in Iraq.
Al-Dabbas et al. (2010) discussed it according to a geological view, where the
study covered the middle part of Iraq, and the dust storms for 4 months
(12/2008-3/2009) were analyzed. They counted a total of 647 particles from 8 dust
storms, The largest isolates were related to culturable bacteria and fungi.
They counted 310 fungal colonies, and Aspergillus was predominant.
Khider et al. (2012) studied bacteria and fungi of cloud dust in Erbil city.
They depend on the ratio (no./wait) to explain and compare among samples. The
fungal population of the current study showed similarity (S = 87.55%). The high
similarity reflected the similarity of dust origin, which plays an important
role in fungal diversity. Al-Oumari and Mohammad (2013) focused on the fungi of
inpatient individuals before and after exposure to the dust storm. They
recognized the high incidence of Aspergillus, Candida, Penicillium,
Alternaria, and Fusarium in the nose, ear, and oral pharynx.
5.
conclusion
The results
indicated that the total colony count of air mycobiota and the fungal
population diversity in a dusty climate is markedly increased during the dust storms, yet the dominant genera remain the
same. The spatial factors affect on air fungal population more than the
temporal one.
Hence, Aspergillus, Candida, Penicillium,
Alternaria, and Fusarium were predominant in dust storms and were
well-known allergens. Further studies should be done on the significance of the
dust storm in terms of living and non-living particles of mycobiota.
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