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Occupational asthma due to
spores of Pleurotus ostreatus
A. Vereda*, S. Quirce, M. Fern?ndez-Nieto,
B. Bartolom?, J. Sastre
Key words: Air Sentinel; occupational asthma;
Pleurotus; specific inhalation challenge.
Basidiomycetes, the most morphologi-
vanced of the
basidiospores is known to give rise to
allergic rhinoconjunctivitis, asthma, and
hypersensitivity pneumonitis (1–4).
Pleurotus ostreatus is one of the most
A 49-year-old man, a nonatopic, had
worked as a seller of fruits and vegetables
for the last 30 years at one of the biggest
market in Spain. In the last 3 years he
had experienced dyspnea, cough, and
wheezing 1 or 2 h after large quantities of
different mushrooms were unload at the
market. He had never had cutaneous or
rhinoconjunctival symptoms. He had not
experienced constitutional symptoms,
such as fever, weight loss, or myalgia.
He related his respiratory symptoms to
environmental exposure to the mush-
room P. ostreatus, being symptom-free
during holidays and when mushrooms
were not available. He could eat all
foodstuffs without any ill effect.
The blood tests revealed eosinophilia
(547 eosinophils/mm3). Chest radiogra-
phy and spirometry were normal. The
patient was still working during the
study. Skin prick tests to common aero-
allergens were negative (including com-
mon environmental molds like
Aspergillus fumigatus, Alternaria
alternata, Penicillium notatum, and
Cladosporium herbarum). Skin prick tests
were positive to commercial P. ostreatus
extract (10 mg/ml) (Bial-Aristegui,
Bilbao, Spain) and to home-made
P. ostreatus spore extract (10% w/v).
Prick-prick with fresh P. ostreatus was
The methacholine inhalation test
revealed bronchial hyperresponsiveness
(PC200.39 mg/ml). Specific inhalation
challenge was carried out by the tidal
breathing method as previously described
(5) with nebulized P. ostreatus spores
extract. At a concentration of 1.25 mg/ml
it elicited an early asthmatic response
(maximum fall in FEV1from baseline of
31%) and an incipient late asthmatic
reaction (16% fall in FEV1) 9 h later.
Induced sputum when he was at work
showed marked eosinophilia (56%). The
sputum obtained 24 h after the specific
inhalation challenge showed a further
increase in airway eosinophilia (70%
eosinophils). Bronchial hyperresponsive-
ness to methacholine increased 24 h after
the challenge (PC20< 0.125 mg/ml).
To verify the existence of airborne
allergens that could be triggering the
symptoms of our patient, environmental
sampling was performed using a volu-
metric air sampler (Air Sentinel) located
inside the cold chamber used to store the
mushrooms during a regular working
day. Airborne particles were collected
onto polytetrafluoroethylene filters (6)
and an extract was prepared for the
in vitro study (immunoblotting and im-
Total serum IgE was 514 IU/ml.
Determination of specific IgE measured
by EAST (Enzyme AllergoSorbent Test)
technique was positive to Pleurotus
spores extract (2.1 kU/l) and to the
workplace air sample extract (0.6 kU/l).
Specific IgE was negative for several
molds (A. fumigatus, A. alternata,
P. notatum, and C. herbarum).
Immunoblotting performed with the
Pleurotus spores extract (Fig. 1A)
showed several IgE-binding bands, ran-
ging from 17 to 85 kDa. Immunoblot-
ting-inhibition studies were carried out
using the air sample extract as the solid
A case of occupational
asthma due to Pleurotus
ostreatus? spores inhala-
tion, and the environmental
study is reported
Figure 1. (A) SDS-PAGE immunoblotting for Pleurotus spores extract. P: Patient’s serum. C: Control’s
serum. M: Molecular mass marker. ()): Non-reducing conditions. (+): Reducing conditions. (B) SDS-
PAGE immunoblotting inhibition using the filter extract as the solid phase. Nonreducing conditions.
S: Patient’s serum pre-incubated with the Pleurotus spores extract. C: Patient’s serum preincubated with
lamb extract, as negative control. M: Molecular mass marker.
phase (Fig. 1B). When the patient’s Download full-text
serum was preincubated with the Pleuro-
tus spores extract, a wide IgE-binding
band disappeared (around 66 kDa),
whereas it was present when the patient’s
serum was preincubated with a nonre-
lated extract (lamb, as negative control).
In conclusion, the clinical history and
the results of the allergologic work-up
including the specific inhalation chal-
lenge, the variation of airway hyperre-
sponsiveness and sputum eosinophilia
post-challenge point out that this patient
had developed occupational asthma
caused by P. ostreatus spores. The envi-
ronmental study demonstrated that air-
borne allergens from Pleurotus are
present in the workplace.
*Servicio de Alergologı´a
Fundacion Jimenez Diaz
Avda. Reyes Catolicos, 2
Accepted for publication 29 October 2006
Allergy 2007: 62:211–212
? 2007 The Authors
Journal compilation ? 2007 Blackwell
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