Aerobiologia

, 24:99

Keratinophilic fungi inhabiting floor dusts of student houses at the South Valley University in Egypt

Authors

  • Thanaa A. Maghraby
    • Botany Department, Faculty of ScienceSouth Valley University
    • Biological Sciences Department, Faculty of ScienceTaif University
  • Mohamed A. Hussein
    • Botany Department, Faculty of ScienceSouth Valley University
Original Paper

DOI: 10.1007/s10453-008-9089-z

Cite this article as:
Maghraby, T.A., Gherbawy, Y.A.M.H. & Hussein, M.A. Aerobiologia (2008) 24: 99. doi:10.1007/s10453-008-9089-z

Abstract

Keratinophilic fungi include true fungi that vigorously degrade keratin as well as a number of important human pathogenic dermatophytes. We identified 41 species and one variety belonging to 19 genera in 50 floor dust samples following culture on Sabouraud’s dextrose agar medium at 28°C. Dermatophytes and closely related fungi were represented by six species—Aphanoascus fulvescens, Aphanoascus sp., Arthroderma cuniculi, Chrysosporium lucknowense, Gymnoascus uncinatus and Trichophyton rubrum. There were 35 species and one variety of other fungal species, with members of Aspergillus and Penicllium being the most prevalent. Twenty-seven species and 1 variety belonging to 14 genera were identified from 24 dust samples gathered at 2-week intervals from male student housing at El-Kenose during January–December 2005 that had been cultured on Sabauraud’s dextrose agar at 28°C. The monthly counts of keratinophilic fungi showed irregular fluctuations, with a peak in April and the lowest point in November. Dermatophytes and closely related fungi were represented by Aphanoascus fulvescens, Aphanoascus sp., Chrysosporium lucknowense, Gymnoascus uncinatus, and Trichophyton rubrum. In conclusion, the study reports the incidences of some dermatophytes found in the floor dust of student houses of South Valley University, Egypt.

Keywords

AphanoascusChrysosporiumDermatophytesFloor dustKeratinophilic fungi

1 Introduction

Keratinophilic fungi are a group of fungi that colonize various keratinous substrates and degrade them to their low-molecular-weight components. A variety of filamentous fungi, mainly comprising hyphomycetes, including dermatophytic and a large number of non-dermatophytic filamentous fungi, and several other taxonomic groups are classified as keratinophilic. Most of the keratinophilic non-dermatophytic filamentous fungi occur as saprophytes in soil, and some are plant pathogens (Gugnani 2000). The term dermatophytes is used to designate a closely related group of keratinophilic fungi that cause infections of the skin, hair and nails. Most of these fungi were originally described as hyphomycetes, but several have subsequently been shown to possess the perfect state (teleomorph) of the family Gymnoascaceae (order Eurotiales) (Howard 1983). Keratinophilic and dermatophytic fungi show asexual states (anamorph), but some do show sexual states (teleomorph); for example, the sexual state or teleomorph of Chrysosporium is Aphanoascus.

Soil is the main habitat of fungi (Chmel et al. 1972). Soil rich in keratin residues constitute either a permanent or occasional reservoir for dermatophytes and other keratinophilic fungi and are a source of potential infection for humans and animals (Ajello 1980; Filipello 1986). In India, Vidyasagar et al. (2005) isolated several keratinophilic fungi from hospital dust and soil sampled from public places. These researchers found that among the dermatophytes isolated from their soil samples, Trichophyton mentagrophytes occurred the most frequently, followed by Microsporum gypseum and Chrysosporium tropicum, C. keratinophilium, M. nanum, T. terrestre and C. lobatum. Of the non-dermatophytes isolated, Aspergillus fumigatus and Penicllium chrysogenum were the most frequent, with each contributing 5.4% to the total fungal flora, while Microsporumfulvum and Candida parapsilosis contributed at least 1.2%. In Iran, Hedayati et al. (2004) isolated pathogenic fungi from potted plants in Sari hospitals. A total of 13 different species of fungi were isolated, with Penicllium sp., Acremonium sp. and Paecilomyces sp. predominating and Rhizopus sp. and Mucor sp. occurring only infrequently.

In Egypt, there have been many studies on the occurrence of fungi in soil/dust samples. Abdel-Mallek et al. (1988) isolated 12 species of keratinophilic and other fungi from the floor dust of students residential halls at Assiut University. The keratinophilic fungi were represented by seven species belonging to Chrysosporium, Arthroderma and Trichophyton. Abdel-Hafez et al. (1990) found that Chrysosporium was the most frequently encountered genus in sedimented dusts and was represented by ten species, Chrysosporium asperatum, C. sexual form of Arthroderma tuberculatum, C. indicum, C. inops, C. keratinophilum, C. merdarium, C. pannorum, C. queeslandium, C. tropicum and C. xerophilium; Trichophyton verrucosum and Trichophyton sp., two dermatophytes, were also identified. In addition, numerous fungi tolerating high levels of cycloheximide were encountered, but at different incidences, such as members of Acremonium, Aspergillus, and Penicllium. Abdel-Hafez (1991) isolated three dermatophytes from the playgrounds of a number of Egyptian schools: Microsporum gypseum, Trichophyton mentagrophytes and T. terrste. Fungi closely related to dermatophytes were isolated only infrequently, such as Arthroderma cuniculi, Chrysosporium asperatum, C. lobatum, C. keratinophilum, C. pannicola and C. tropicum. Other saprobic fungi were also collected, including members of Acremonium, Alternaria, Aspergillus, Chaetomium, Fusarium, Penicllium, Scopulariopsis and others.

Little is known about seasonal fluctuations in the fungi inhabiting floor dust particles. In Copenhagen (Denmark), Andersen (1985) studied the occurrence of viable microfungi in house dust and found that the most frequently encountered genera were Acremonium, Alternaria, Aspergillus, Chaetomium, Cladosporium, Rhizopus, Rhodotorula and other yeasts. In India (Madhya Pradesh), Shukia et al. (2003) studied the isolation and characterization of a dermatophyte, Microsporumgypseum, from poultry farm soils. In Egypt, Ismail (1990) found the highest counts of keratinophilic and cycloheximide-resistant fungi in soil obtained from the Hibis temple at the El-Khargha oasis in September 1988. The most prevalent species were Aphanoascus terreus, Aphanoascus sp., Aspergillus flavus, A. fumigatus, A. niger, Penicllium funiculosum, and Tritirachiumalbum.

The components of dust particles are the sources of the most potent allergens. It is a well-known fact that microfungi can provoke allergy (Maunsell 1971; Gravesen 1979; Salvaggio and Aukrust 1981). Earlier studies have shown that the identification of the agents of various infectious disease very quickly leads to remarkably effective methods of control. The aim of this study was to evaluate the distribution, occurrence and numbers of keratinophilic fungi inhabiting dusts collected from student houses of the South Valley University (Egypt) and determine the seasonal fluctuations in floor dust fungi in these houses.

2 Materials and methods

2.1 Collection of dust samples

Fifty floor dust samples were collected from student houses of the South Valley University in the Aswan (12 samples), Qena (14), Sohage (12) and Red Sea (12) governorates, Egypt. (Table 1).
Table 1

Different student houses in the Aswan, Qena, Sohage and Red Sea governorates from which dust samples were collected

Governorates name

Sample number

Location

Aswan

6

Abou-Elrish male student house

5

Sahhary female student house

Qena

6

El-Kenose male student house

6

Female student house

Sohage

5

Male student house

5

Female student house

Red sea

5

Male student house

5

Female student house

Each floor sample was a composite of material collected with vacuum cleaner from 10 to 15 rooms chosen randomly from each University student house and mixed thoroughly several times. Each sample was put in a polyethylene bag, sealed and put in another bag which was also sealed to minimize the loss of water content and provide sufficient aeration. Samples were transferred immediately to the mycological laboratory and sifted through a 0.425-mm mesh screen to remove large dust particles. All samples were stored in a refrigerator (2–5°C) until fungal analysis.

2.2 Mycoflora analysis of floor dust particles

The dilution-plate method (Johnson and Curl 1972) was used to estimate mycoflora dust particles as described by Abdel-Hafez and Shoreit (1985b) and Abdel-Hafez et al. (1990). Sabouraud’s dextrose (Moss and Mc Quown 1969) agar medium (peptone, 10 g l−1; glucose, 40 g l−1; agar, 15 g l−1) supplemented with two antibiotics, chloramphenicol (0.5 mg ml medium−1) to inhibit the growth of bacteria and cycloheximide (actidione) (0.5 mg ml medium−1) to inhibit the growth of other saprophytic fungi, was used as the culture medium. The first antibiotic was dissolved separately in sterile distilled water and the second was dissolved in methanol prior to being added to the agar medium.

2.3 Seasonal fluctuations in floor dust fungi

Student house No. 2 at the EL-Kenose student housing complex, Qena governorate, is the largest of the student houses sampled. Twenty-four floor dust samples were collected from this student house at 14-day intervals in the period January–December 2005. As for the mycofloral analysis, the dilution-plate method was used to analyze seasonal variations in the dust fungi populations. Three plates of agar medium were used for each sample, and the plates were incubated at 28°C for 2–3 weeks. The developing colonies were counted, examined and identified (Ainsworth 1971; Rebell and Taplin; 1974; Ajello 1977; Van Oorschot 1980; Pitt 1988; Burgess et al. 1988; Klich and Pitt 1988; Watanabe 1994; Pitt and Hocking 1997), and the number per gram dry dust was calculated.

3 Results and discussion

3.1 Floor dust fungi

In total, 41 species and one species variety belonging to 19 genera of floor dust fungi were collected from the 50 floor dust samples cultured on Sabouraud’s dextrose agar at 28°C (Table 2).
Table 2

Average total counts, percentage counts (%C) and percentage frequency (%F) of the occurrence of various fungal genera and species identified from 50 dust floor samples on Sabouraud’s dextrose agar at 28°C

Genera and species

ATC

%C

%F

Dermatophytes and related fungi

Aphanoascus

5,145.2

13.4

58.0

 A. fulvescens

2,585.6

6.7

50.0

 Aphanoascus sp.

2,559.6

6.6

20.0

Arthroderma cuniculi

493.3

1.3

4.0

Chrysosporium lucknowense

4,999.9

13.0

42.0

Gymnoascus uncinatus

1,946.0

5.1

38.0

Trichophyton rubrum

26.6

0.1

2.0

Other fungi

Alternaria

626.6

1.6

22.0

 A. alternate

479.6

1.2

16.0

 A. citri

146.6

0.4

6.0

Aspergillus

10,130.4

26.3

92.0

 A. alutaceus

4,066.1

3.5

26.0

 A. flavus

1,839.7

10.5

38.0

 A. flavus var. columnaris

199.9

4.8

24.0

 A. fumigatus

759.6

0.5

10.0

 A.niger

1,332.9

2.0

20.0

 A. parasiticus

533.1

1.4

14.0

 A. sulphureus

839.5

2.2

20.0

 A. terreus

279.8

0.7

12.0

 A. ustus

279.8

0.7

10.0

Candida albicans

2,172.0

5.0

28.0

Cladosporium

826.1

2.1

24.0

 C. cladosporioides

386.4

1.0

12.0

 C. sphearospermum

439.7

1.1

12.0

Cunninghamella

586.3

1.5

14.0

 C. echinulata

226.5

0.6

8.0

 C. elegans

359.8

0.9

8.0

Emercilla nidulans

66.6

0.2

4.0

Geotrichium candidum

1,039.9

2.7

12.0

Gibberella pulicaris

186.4

0.5

8.0

Mucor

1,412.9

3.7

36.0

 M. circinelloides

373.2

1.0

12.0

 M. hiemalis

799.7

2.1

20.0

 M. racemosus

240.0

0.6

4.0

Nectria haematococca

213.2

0.6

6.0

Paecilomyces lilacinus

346.5

0.9

6.0

Penicllium

5,197.5

13.5

82.0

 P. brevicompactum

120.0

0.3

4.0

 P. cammemberti

519.8

1.4

8.0

 P. chrysogenum

2,132.6

5.5

46.0

 P. citrinium

266.6

0.7

8.0

 P. duclauxi

319.7

0.8

10.0

 P. funiculosum

679.7

1.8

22.0

 P. griseofulvum

359.8

0.9

6.0

 P. oxalicum

160.0

0.4

8.0

 P. purpurogenum

319.6

0.8

14.0

 P. rubrum

319.7

0.8

12.0

Rhizopus stolonifer

26.6

0.1

2.0

Rhodotorula rubra

2,386.1

6.2

24.0

Sterile mycelia

706.3

1.8

30.0

Gross total count

38,534.4

  

Number of genera

19

  

Number of species

41 + 1 var

  

ATC, Average total counts (calculated per gram dry dust in each sample); %C, percentage counts (calculated per total fungal counts); %F, percentage frequency of occurrence (%F out of 50 samples)

Dermatophytes and closely related fungi were represented by six species belonging to five genera. Aphanoascus was the most common genus and was represented by one species and one unidentified species: A. fulvescens (anamorph: Chrysosporium keratinophilium) and Aphanoascus sp. (anamorph: C. tropicum). Thesee two species were isolated from 50 and 20% of all samples and constituted 6.7 and 6.7% of the total isolated fungi, respectively. Abdel-Mallek et al. (1988) found that these species appeared in 25 and 35% of dust samples collected from student residential halls of Assiut University (Egypt), while Abdel-Hafez et al. (1990) isolated ten species of Chrysosporium, but with different numbers and incidences, from 50 dust samples collected from the Delta area and Upper Egypt. In the latter samples, C. keratinophilium (76% of the samples), C. indicum (20%) and C. tropicum (68%) were the most common. Vidyasagar et al. (2005) isolated C. keratinophilium and C. tropicum from 57.1% and 47.6% of soil samples, respectively, collected from public places at Gulbaraga (India). In general, these species have worldwide distribution in soils (Filipello 1986; Marsella and Mercantini 1986; Chabasse 1988; Melake and Erwin 1991; Ulfig et al. 1996; Rapini et al. 1998; Deshmukh 1999, 2002a, b, 2004).

Chrysosporium lucknowense and Gymnoascus uncinatus (anamorph: Chrysosporium merdarium) were recovered at moderate frequencies of occurrence [in 21 (42%) and 19 (38%) of 50 samples, respectively] and constituted 13.0 and 5.1% of the total fungi, respectively. El-Said (1995) isolated six species of Chrysosporium from soils of Yemen, of which C. lucknowence was found in 10% of the samples. Gherbawy (1999) also isolated six species of Chrysosporium from graveyard soil and air in the city of Qena; C. xerophilium was isolated from 28% of the samples), C. carmichaelii from 10% and C. lucknowense from 4%. Chrysosporium merdarium was isolated by Nigam and Kushwaha (1990) and Ali-Shtayeh et al. (2002).

Arthroderma cuniculi (Chrysosporium anamorph of Arthroderma cuniculi) and Trichophyton rubrum were isolated only rarely from our samples (two and out of 50 samples, respectively) cultured on Sabouraud’s dextrose agar medium. El-Said (1995) isolated Arthroderma cuniculi in 12% of the soil samples taken from the Yemen Arab Republic. Abdel-Raouf (2000) also isolated A. cuniculi, but at a higher frequency (20%), from dust samples gathered from schools of the Sohage region. This species was also isolated, albeit infrequently, from dusts of some schools or play grounds in the west bank of Jordan (Ali-Shtayeh and Al-Sheik 1988; Ali-Shtayeh 1989) as well as from field soils (Ali-Shtayeh et al. 1998). Ramesh and Hilda (1999) isolated the Chrysosporium anamorph of Arthroderma cuniculi from the soil of primary schools and public parks of Madras, India. Trichophyton rubrum was only rarely isolated from the soil of Idfu-Marsa Alam road in the eastern desert (Abdel-Hafez et al. 1991) and from graveyard soil in the city of Qena (Gherbawy 1999).

We also isolated other saprobic and cycloheximide-resistant fungi from the floor dust samples. In total, 35 species and one variety belonging to 14 genera were identified, of which Aspergillus (eight species + one variety) and Penicllium (ten species) were the most common on Sabouraud’s dextrose agar. The most common species were Aspergillus flavus, A. ochraceus and Penicllium chrysogenum. These species were also found to be prevalent in dust from Egypt (Gherbawy 1999; Abdel-Raouf 2000) and Saudi Arabia (Abdel-Hafez and Shoreit 1985a) and in soil taken from fields of Palestine (Ali-Shtayeh et al. 1998). Members of Aspergillus and Penicllium have been isolated at different frequencies from various types of soils in many parts of the world (Ali-Shtayeh and Arda 1989; Chabasse et al. 1989; El-Said 1995; Anbu et al. 2004 and others).

In our study, other fungi were isolated at different concentrations and frequencies, including Alternaria (two species), Candida (one), Cladosporium (two), Cunninghamella (two), Emercilla (one), Geotrichium (one), Gibberella (one), Mucor (three), Nectria (one), Paecilomyces (one), Rhizopus (one), Rhodotorula (one), and sterile mycelia. Most of the above species have been encountered in previous studies of different soil types around the world (El-Said 1995; Gherbawy 1999; Abdel-Hafez et al. 2000; Anbu et al. 2004; Hedayati et al. 2004; Vidyasagar et al. 2005, and others).

3.2 Seasonal variations of floor dust fungi in Qena

Following the culture of the floor dust collected from 14 student houses (24 samples) in Qena governorate on Sabouraud’s dextrose agar at 28°C, we identified 27 species and one species variety. These represent 14 genera. The monthly average total counts of these fungi showed irregular fluctuations, varying from 746.3 to 2226.3 colonies g dry dust−1, with a peak in April and the lowest point in November (Table 3).
Table 3

Average total counts and the number of genera and species recovered from 12 dust floor samples on Sabouraud’s dextrose agar at 28°C

Months

ATC

Number of genera

Number of species

January

1292.9

7

8

February

1733.1

5

6

March

1172.8

9

9

April

2226.3

6

6 + 1 var

May

1753.0

7

9 + 1 var

June

1199.4

8

12

July

1146.1

10

16 + 1 var

August

1319.6

5

7

September

1853.0

4

8

October

1639.7

3

5 + 1 var

November

746.3

4

5

December

1132.8

8

10

ATC, Average total counts (calculated per gram dry dust in each sample)

Dermatophytes and closely related fungi were represented by five species belonging to four genera, of which Chrysosporium (C. lucknowense ) was the most common genus (Table 4). The monthly average total counts of C. lucknowense showed irregular fluctuations, with a peak during April. Aphanoascus (A. fulvescens, and Aphanoascus sp.) was found in 54.2% of the samples and Gymnoascus uncinatus in 25%; their monthly average total counts showed irregular fluctuations, with maxima during November and June, respectively. Trichophyton rubrum was recovered only during November. Chrysosporium lucknowense had bee isolated in earlier studies, but at different frequencies than those reported here and from different types of soil (El-said 1995; Gherbawy 1999). Aphanoascus fulvescens and Aphanoascus sp. were also found earlier in the New Valley, Western desert, Egypt, but again at different incidences from those reported here (Abdel-Hafez et al. 2000). These fungi have been isolated, at varying frequencies, from soils collected from the Delta area and Upper Egypt (Abdel-Fattah et al. 1982; Abdel-Mallek et al. 1989; Abdel-Hafez et al. 1989; Youssef et al. 1989; Karam El-Din et al. 1990; Maghraby 1994; Gherbawy 1999; Abdel-Raouf 2000; Abdel-Hafez et al. 2000).
Table 4

Average total counts, maximum values and percentage frequency of occurrence (%F) of various fungal genera and species recovered from 24 dust floor samples cultured on Sabouraud’s dextrose agar at 28°C

Genera and species

ATC

%C

%F

Dermatophytes and related fungi

Aphanoascus

680.0

8.0

54.2

 A. fulvescens

500.0

6.0

54.2

 Aphanoascus sp.

180.0

2.1

12.5

Chrysosporium lucknowense

2,300.0

25.5

75.0

Gymnoascus uncinatus

120.0

1.6

25.0

Trichophyton rubrum

20.0

0.2

4.2

Other moulds

Alternaria

100.0

0.9

12.5

 A. alternate

60.0

0.6

8.3

 A. citri

40.0

0.4

4.2

Aspergillus

2,080.0

23.9

75.0

 A. flavus

1,600.0

19.2

54.2

 A. flavus var. columnaris

120.0

1.2

20.8

 A. fumigatus

20.0

0.2

4.2

 A. niger

80.0

0.7

12.5

 A. ochraceus

60.0

0.6

8.3

 A. parasiticus

100.0

1.0

12.5

 A. sulphureus

100.0

1.0

12.5

Candida albicans

380.0

4.2

25.0

Cladosporium

160.0

1.6

25.0

 C. cladosporioides

100.0

1.1

16.6

 C. sphearospermum

60.0

0.5

8.3

Geotrichium candidum

140.0

1.5

8.3

Gibberella pulicaris

40.0

0.4

8.3

Mucor hiemalis

1,260.0

13.6

50.0

Penicllium

820.0

8.3

58.3

 P. chrysogenum

280.0

2.6

41.7

 P. duclauxi

20.0

0.2

4.2

 P. funiculosum

400.0

4.6

20.8

 P. griseofulvum

20.0

0.2

4.2

 P. oxalicum

60.0

0.5

8.3

 P. rubrum

40.0

0.2

4.2

Rhodotorula rubra

100.0

1.0

12.5

Sterile mycelia

860.0

9.3

58.3

Syncephalastrum racemosum

20.0

0.2

4.2

Gross total count

16,915.0

  

Number of genera

14

  

Number of species

27 + 1 var

  

ATC, Average total counts (calculated per gram dry dust in each sample); %C, percentage counts (calculated per total fungal counts); %F, percentage frequency of occurrence (%F out of 24samples)

Other keratinophilic fungi collected from floor dust included members of Alternaria, Aspergillus, Candida, Cladosporium, Gibberilla, Geotrichium, Mucor, Penicllium, Rhodotorula, sterile mycelia and Syncephalastrum (Table 4). Their monthly average total counts showed irregular fluctuations, with peaks at different times of the year. This result closely resembles those obtained from sedimented dusts in earlier studies (Ismail 1990; El-Ghazaly 1991; Maghraby 1994). The keratinophilic fungi listed above have also been found in various soil types around the world, although at different frequencies (Filipello 1986; Marsella and Mercantini 1986: Cano et al. 1987; Ali-Shtayeh 1988, 1989; Chabasse 1988; Larrondo and Calvo 1989; Melake and Erwin 1991; Ramesh and Hilda 1999; Anbu et al. 2004; Hedayati et al. 2004; Vidyasagar et al. 2005).

In conclusion, the study shows the incidences of a number of dermatophytes and related fungi in floor dust samples collected from student houses of the South Valley University in Egypt.

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© Springer Science+Business Media B.V. 2008