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Short communication
Fungal contamination of bedding
Asthma prevalence has increased progressively over the
past three decades in the UK. Numerous theories have
been promulgated including the hygiene hypothesis,
additional exposure to house dust mite etc., none of
which have been substantiated on detailed study. An
association with fungal exposure is less well studied. It is
often assumed that such exposures generally occur
outside, apart from mouldy buildings.
One substantial life-style change over the last 30 years
has been altered bedding – from feather/flock pillows and
sheets/blankets, to mainly polyester pillows and quilts.
With no need for feather containment, the covers on
pillows are more porous with pore size increasing from 2
to >10 lm. Synthetic pillows are a risk for both
prevalence and for severity of asthma. Butland et al.
estimated that the increase in synthetic bedding could
explain 50% of the increase in prevalence in wheezing (1).
We have considered the hypothesis that fungi growing
on bedding could be an environmental health risk. Adults
may produce up to 100 l of sweat in bed every year, which
for approximately 8 h/24 is at approximately 30C and
high humidity – an ideal fungal culture medium. Fungal
contamination of kapok pillows was noted in 1936, and
associated with wheezing (2).
Methods
Both synthetic and feather pillows that had been used for years in
family homes, were collected and stored in sterile bags prior to
culture. All pillows were cut into nine equal sections and then
smaller samples (swatches) were prepared from each section of
pillow; approximately 2 ·2·2 cm for synthetic pillows and 0.25 g
for feather pillows. For five pillows, additional dust samples for
culture were obtained by vacuuming the pillow through the cover
for 2 min, prior to culture processing.
Pillow swatches and vacuum dust samples were transferred into
20 and 10 ml of Sabouraud glucose liquid medium containing
antibiotics (ciprofloxacin 2 mg/l, gentamicin 16 mg/l and vancomy-
cin 8 mg/l) respectively, vortexed for 20 s and then allowed to stand
for 24 h or 7 days. The pillow swatch broths were vortexed and
haemocytometer counts were performed to give an estimation of
fungal load. Vacuum dust broths were vortexed, centrifuged
(3000 rpm/10 min) and the supernatant was counted on a haemo-
cytometer. Based on these counts, two selected 10-fold dilutions of
each broth in phosphate-buffered saline were inoculated onto
Sabouraud glucose agar in duplicate, and then the plates were
incubated at room temperature, 30Cor37C for up to 1 week.
Colony counts were performed and isolates identified using stand-
ard laboratory methods. Any isolate that could not be identified in
our laboratory was sent to Centraalbureau voor Schimmelcultures
(CBS), the Netherlands. Isolates were quantitated by colony-
forming units (CFU) per gram pillow.
Background: It is currently believed that most fungal exposure occurs external to
the home.
Aims: To enumerate the fungal flora of used synthetic and feather pillows and
the dust vacuumed from them, in the UK.
Methods: 10 pillows aged between 1.5 and >20 years in regular use were col-
lected and quantitatively cultured for fungi. Swatches were taken from nine
sections of the pillow and dust was also collected by vacuum from five pillows.
Pillow vacuuming was carried out prior to pillow culture. All were cultured at
room temperature, 30 and 37C for 7 days in broth before plating, and a subset
were also cultured for 24 h in broth and then plated. Fungi were identified by
standard morphological methods.
Results: The commonest three species isolated were Aspergillus fumigatus
(n¼10), Aureobasidium pullulans (n¼6) and Rhodotorula mucilaginosa (n¼6).
Another 47 species were isolated from pillows and vacuum dust. The number of
species isolated per pillow varied from 4 to 16, with a higher number from
synthetic pillows. Compared with the nonallergenic A. pullulans,more
A. fumigatus was found in synthetic than feather pillows.
Conclusions: We have examined pillows for fungal contamination, and show that
the typical used pillow contains a substantial load of many species of fungi,
particularly A. fumigatus. Given the time spent sleeping, and the proximity of the
pillow to the airway, synthetic and feather pillows could be the primary source of
fungi and fungal products. This has important implications for patients with
respiratory disease, and especially asthma and sinusitis.
A. A. Woodcock
1
, N. Steel
2
,
C. B. Moore
2
, S. J. Howard
2
,
A. Custovic
1
, D. W. Denning
1,2
1
North West Lung Centre, Wythenshawe Hospital
and University of Manchester, Manchester;
2
Antifungal Laboratory, Microbiology Department,
Hope Hospital, Stott Lane, Salford, UK
Key words: brevicaulis;Cladosporium;flavus;
Penicillium; vacuum.
Ashley A. Woodcock
North West Lung Centre
Wythenshawe Hospital and University of
Manchester
Southmoor Road
Manchester M23 9LT
UK
Accepted for publication 11 June 2005
Allergy 2005 DOI: 10.1111/j.1398-9995.2005.00941.x Copyright Blackwell Munksgaard 2005
ALLERGY
DOI: 10.1111/j.1398-9995.2005.00941.x
Results
Pillows ranged in age from 18 months to >20 years.
Substantial quantities of numerous fungi were cultured
from all pillows. The commonest three species in pillow
swatches were Aspergillus fumigatus (n¼10), Aureoba-
sidium pullulans (n¼6) and the yeast Rhodotorula
mucilaginosa (n¼6) (Table 1). Other species cultured
from pillows included Aspergillus flavus (n¼5), A. niger
(n¼1), A. sydowii (n¼1), A. glaucus (n¼1) and
another unidentified Aspergillus species, Penicillium spp.
(n¼6), Cladosporium herbarum (n¼6, all only at room
temperature), C. cladosporioides (n¼2) and C. tenuiss-
imum (n¼1), Epicoccum nigrum (n¼1), Botrytis cinerea
(grey mould of grape; n¼1), Pithomyces chartarum (n¼
1), probable Trametes spp. (bracket fungus; n¼1), three
different species of Agaricales (typical gilled mushrooms),
Stereum cf. sanguinolentum (encrustation or bracket
fungus on stumps; n¼1), Arthrinium phaeospermum
(n¼1), Pholiota spp. (colourful inedible gilled mush-
rooms; n¼1) and 2 yeasts comprising Candida parapsi-
losis (n¼1) and C. guilliermondii (n¼1). Vacuum dust
usually grew A. pullulans, but also Pithomyces chartarum
(n¼2), A. vitus (n¼2), Scopulariopsis brevicaulis (n¼
1), R. mucilaginosa (n¼1) and Ar. phaeospermum (n¼
1). Some isolates (all filamentous fungi; n¼16) were not
identifiable by us or at CBS.
The actual yield and quantitative culture results varied
substantially by temperature of incubation and time (24 h
or 7 days). Species yield was always higher at 7 days, and
A. fumigatus CFU climbed by about 5 logs between 24 h
and 7 days. There was a thick layer of matted hyphae and
conidia on the surface of the culture broth after 7 days
incubation, and so the increase in A. fumigatus CFU was
probably artefactual. Incubation at 37C inhibited the
growth of A. pullulans, and slightly reduced the growth of
R. mucilaginosa.
There was a poor relationship between the species
cultured directly from pillows and the dust collected prior
to pillow culture. In particular A. fumigatus was never
cultured from vacuum samples, although it was the most
prevalent fungus found in the pillow. The same was true
of A. flavus, but not of A. vitus, which was isolated from
the vacuum samples of two pillows. In contrast much
higher CFU of A. pullulans were obtained from vacuum
samples than in the pillow itself (Table 1).
Comparison of synthetic pillows with feather pillows
showed a larger number of species cultured from synthetic
pillows (Table 2), although there was substantial differ-
ences between individual pillows. In addition, the pre-
dominant species in synthetic pillows was A. fumigatus,
whereas it was A. pullulans in feather pillows.
Discussion
We have shown high levels of fungi in pillows with
substantial interpillow variation in flora and some differ-
ences between feather and synthetic pillows.
Of the three most abundant fungi found, A. fumigatus
is a well recognized allergenic fungus. Indeed more
allergens have been identified in A. fumigatus than any
other fungus to date. In addition to the approved 18
allergens (3), another 60+ immunoglobulin E (IgE)-
binding proteins have been identified (4). In contrast,
A. pullulans is also common in the environment but
without any allergens described, although it has been
associated with an outbreak of extrinsic allergic alveolitis,
when found in profusion in an air conditioning system
(5). Rhodotorula mucilaginosa has been found to be
allergenic in skin prick testing (6), and a single enolase
antigen identified (7). Some of the other fungi found in
the pillows are allergenic including C. herbarum,A. flavus,
A. niger and Penicillium spp. Of note, we did not grow
Alternaria from any pillow, a common allergenic fungus
in outdoor air closely associated with so-called Ôthunder-
storm asthmaÕ(8).
Synthetic pillows are made of inert hollow fibrils of
polyester, with a variety of coatings, e.g. oleic acid, for
ease of spinning. It might be expected that the closer
weave of feather pillow covers might prevent larger
spores from entering or exiting feather pillows, but we
grew E. nigrum which has spores of 15–30 lm from a
Table 1. Quantitative results from 24 h cultures of pillows (n¼6) and vacuum
samples (n¼4)
Sample Species N(%)
Pillow (CFU/g),
mean (range)
Pillow swatch Aspergillus fumigatus 6 (100) 2130 (110–4500)
Aspergillus pullulans 5 (83) 3571 (436–8530)
Rhodotorula mucilaginosa* 2 (33) 6500 (2500–10 500)
Aspergillus flavus 2 (33) 236 (226–245)
Cladosporium spp. 4 (67) 73 (28–133)
Vacuum from
pillow surface
Aureobasidium pullulans 4 (100) 90 520
(34 800–2 910 000)
Penicillium spp. 1 (25) 15 100
Aspergillus vitus
1 (25) 27 800
Rhodotorula mucilaginosa
1 (25) 69 400
Aspergillus glaucus
1 (25) 41 700
Scopulariopsis brevicaulis
1 (25) 13 900
*Previously known as Rhodotorula rubrum.
Isolated from one feather pillow.
Table 2. Comparison of feather and synthetic pillows
Pillow type N
Predominant
species
Mean
(CFU/g, 24 h)
Morphologically
identifiable species
cultured*, mean (range)
Synthetic 5 Aspergillus fumigatus 2745 10 (6–16)
Aureobasidium pullulans 1926
Feather 5 Aspergillus fumigatus 1863 7.8 (4–12)
Aureobasidium pullulans 5110
*Includes vacuum samples.
Woodcock et al.
feather pillow. Both colonisation and exit of larger fungal
spores (Cladosporium etc.) will be greater although the
coarser weave cover on synthetic pillows, consistent with
Butland et al.Õs (1) data, although some escape of the
small 2–3 lm spores of A. fumigatus is likely through the
finer weave covers.
Human respiratory tract exposure could be to the spores
themselves, to hyphae, to volatile fungal secondary
metabolites or to fungal degradation products. Only a
few recognized antigens are found on the spore surface (9),
most being expressed once spore swelling and germination
have taken place, although often very early after germina-
tion (10). Thus, direct mucosal exposure to spores may not
induce a typical allergic response, if the respiratory tract is
normal and spore germination does not take place. Sinus
or airways blockage from respiratory infection, with excess
mucous and local epithelial damage, may however provide
a germination medium, allowing antigenic exposure. This
might explain why adults are so much more frequently
sensitized to fungi than children. Asthma severity in adults
is related to fungal sensitization in long-standing asthma-
tics (11, 12) in which varying degrees of bronchiectasis
is common. In these patients, fungal colonisation and
germination may be a semipermanent fixture of the
airways, and so providing continuous antigenic exposure.
Exposure during sleep because of fungal contamination of
bedding could initiate and drive the process.
The majority of asthma commences in childhood.
Evidence of abnormal lung function is present in a
substantial proportion of 3-year-old children with a family
history of allergy (13). This implies that lung damage
sustained in early life may lead to the later development of
asthma, when permanent airway remodelling is present.
Fungal products in pillows/bedding could damage the
airways at a sensitive time in their development. For
example, b-(1,3)-glucan, an important constituent of
many fungal cell walls, is proinflammatory (14).
Further work is required on the ecology of fungi in
bedding, including the environmental factors which are
important and the relative contribution of duvets and
pillows. Measures of individual fungal exposure need
development. There is little correlation between reser-
voir and airborne fungal levels (15), and it may be that
direct exposure from bedding is more important. The
use of a tight woven or other protective cover such as
Goretex
TM
(W. L. Gore, Livingston, UK) cover might
be protective, and needs investigating. It is extraordin-
ary that such a major unidentified source of fungal
exposure has literally been staring us in the face.
Author contributions
AA Woodcock conceived the idea, and wrote the primary draft of
the paper. N Steel, SJ Howard and CB Moore undertook the
cultures, quantitation and identification of the fungi. A Custovic
and DW Denning contributed to the research plan and writing the
paper.
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Fungal contamination of bedding
