1.Isolation and identification of mites associated with raw and commercial farm edible bird nests
Tropical Biomedicine 2015;32(4):761-775
The global demand for edible bird nests (EBNs) is high, especially from Hong Kong
and Peoples Republic of China. Recently, this industry was greatly affected when China
banned the import of all the EBNs from Malaysia (except for canned version) due to detection
of high levels of nitrites. Several cases of anaphylaxis following ingestion of EBNs were
reported. The source(s) of these allergens remain unknown. Mites have been reported to
trigger allergic responses. Hence, this study was designed to quantify, isolate and identify the
mites that are associated with EBNs. The raw EBNs were purchased from swiftlet farms in
five locations in Peninsular Malaysia while the commercial nests were purchased from five
different Chinese traditional medicinal shops. The average mite density of all the raw nests
was 285 ± 603 mites per gram of EBN while the commercial nests had a much lower mean
value of 21 ± 32 mites per gram of EBN (p = 0.082). Among the raw EBNs, the nests from
Kajang had the highest average mite density (946 ± 1443 mites/g of EBN) whereas the nests
from Kuala Sanglang had the lowest (54 ± 34 mites/g of EBN). Among the commercial EBNs,
the nests from Company D had the highest average mite density (76 ± 18 mites/g of EBN)
whereas the nests from Company A were free of mites. Overall, the average densities of
mites in the raw nests obtained from southern regions of Malaysia (Selangor and Johor) were
higher than those nests obtained from the northern regions (Kedah and Kelantan). Thirty
types of mites were isolated from both the raw and commercial nests. Among these, some are
probably feather mites (Eustathia cultrifer, Pteroherpus garrulacis, Pterodectes
amaurochalinus, Laminalloptes sp., Berlesella alata and Neochauliacia sp.), house dust and
storage mites (Suidasia sp., Austroglycyphagus sp., and Aleuroglyphus ovatus), mesostigmatid
mites (Dermanyssus sp.), prostigmatid mites (Cheyletus sp., tarsonemid and cunaxid mites),
astigmatid mites (Collocalidectes sp., Streetacarus sp. and Hemisarcoptes sp.) and oribatid
mites. This study provides baseline information on the density and type of mites that are
probably associated with EBNs. This study also heightens the importance of mites as a
possible source of EBN-associated anaphylaxis.
2.Antigenic profile of Blomia tropicalis, Aleuroglyphus ovatus and Glycycometus malaysiensis
Tang, J.C. ; Wong, S.F.* ; Mak, J.W. ; Ho, T.M.
Tropical Biomedicine 2011;28(2):223-236
House dust mites and storage mites are well-known causes for allergenic diseases.
The aim of this study was to investigate the immunogenic sites of Blomia tropicalis,
Aleurogyphus ovatus and Glycycometus malaysiensis. The mites were maintained in a
culture medium at 25ºC and 75% relative humidity. Mites were harvested either with heat
escape or floatation method, purified, homogenized, quantified and used for the production of
polyclonal antibody and immunostaining. For each species of mites, five male mice and five
male rats were randomly selected and immunized intraperitoneally with respective crude
mite extract at two-weekly intervals. Blomia tropicalis, A. ovatus or G. malaysiensis whole
mites and paraffin-embedded mite sections were immunostained with the respective polyclonal
antibody. The faecal pellets of mites were intensely stained for all the three species in the
present study. The legs of sectioned A. ovatus were not immunogenic as compared with
those of G. malaysiensis and B. tropicalis. The outer layer (cuticle) of whole mites and the
eggs for these species were very immunogenic. Hence, the polyclonal antibodies obtained in
this study may serve as potential tools in detecting the eggs and immature mites in
environmental samples. Future studies should focus on the antigenic components of eggs
since they were relatively abundant in dust and highly antigenic as seen in the present study.
3.Sero-prevalence study of IgE responses to allergens from Malaysian house dust (HDM) and storage mites (SM)
Chong, K.T., Wong, S.F., Mak, J.W., Loh, L.C., Ho, T.M.
Tropical Biomedicine 2015;32(3):524-539
Allergens of Dermatophagoides and Blomia species are well-characterized but
not for other species. This study was conducted to determine the prevalence of allergic
sensitization to house dust (HDM) and storage mites (SM). One hundred adult subjects (aged
> 18) were recruited. The mite specific IgE of all allergic subjects were higher compared with
healthy subjetcs despite being not statistically significant except for D. farinae and G.
malaysiensis. The mean serum IgE levels against HDM and SM for allergic subjects were
significantly higher compared with those in healthy subjects. They were mainly sensitized to
Dermatophagoides farinae (35%) and Glycycometus malaysiensis (37%). Immunoblots revealed
not all allergic subjects showed positive immuno-reactivity against the mites tested. Single or
multiple bands were observed for different species. The subjects were commonly sensitized
to Group 2 (9-12 kDa), 10 (38 kDa) and 18 (40-48 kDa) allergens. Twenty-one out of 60 allergic
subjects were sensitized to either one or more species. The majority of them (71%) were
sensitized to single species. The allergic subjects were mainly sensitized to D. pteronyssinus,
followed by Tyrophagus putrecentiae and Aleuroglyphus ovatus. Seven were solely sensitized
to HDM while 10 were solely sensitized to SM. Four subjects were sensitized to both. Preadsorption
study revealed no cross-reactivity. There was difference between the prevalence
and reactivity to allergens of HDM and SM in these subjects. Both ELISA and immunoblot did
not correlate well but can complement each other in improving the detection of mite allergens
to the species level.
4.Morphology of Glycycometus malaysiensis, a domestic mite in Malaysia
Ling, S.J. ; Wong, S.F. ; Mak, J.W. ; Ho, T.M.
Tropical Biomedicine 2019;36(1):263-273
Glycycometus malaysiensis is an allergenic domestic mite found in houses. G.
malaysiensis is known to be highly similar to and is often mistaken as Blomia tropicalis, one
of the major house dust mite species that causes asthma and allergic diseases in many
tropical and subtropical regions. It was also suggested that these mites cross-react with each
other and that the prevalence of G. malaysiensis might be higher than previous reports. A
review on the taxonomic keys as well as light and scanning electron micrographs of G.
malaysiensis are presented to appreciate the fine morphological structures of G. malaysiensis.
The mouth, setae, legs (trochanter, femur, genu, tibia and tarsus) and the sexual organs
(genital openings, genital setae and genital suckers) of G. malaysiensis are outlined. The
morphology of G. malaysiensis is also compared with that of B. tropicalis to delineate the
key features for the differentiation between these two mite species.
5.In vitro adhesion and invasion by Cladosporium sphaerospermum in human bronchial epithelial cells (BEAS-2B) and human pulmonary alveolar epithelial cells (HPAEpiC)
Lo, S.G. ; Wong, S.F ; Mak, J.W. ; Choo, K.K. ; Ng, K.P.
Tropical Biomedicine 2019;36(4):958-971
Cladosporium spores are ubiquitous in indoor and outdoor environment and may
potentially trigger allergic responses upon inhalation. To date, there is limited investigation
on the fate of Cladosporium spores after being inhaled into the respiratory tract. This study
was conducted to investigate the interaction of Cladosporium sphaerospermum with Human
Bronchial Epithelial Cells (BEAS-2B) and Human Pulmonary Alveolar Epithelial Cells
(HPAEpiC). C. sphaerospermum conidia were harvested and co-cultured with BEAS-2B or
HPAEpiC cells for 72 hours. At each time point (30 minutes, 2, 4, 24, 48 and 72 hours),
adherence and invasion of the cells by C. sphaerospermum conidia (and hyphae) were
investigated by immunofluorescence staining. This study demonstrated the adherence and
internalization of C. sphaerospermum conidia within these epithelial cells. In addition, the
conidia were able to germinate and invade the epithelial cells. The ability of the fungal
conidia to adhere, internalize, germinate and invade both the bronchial and alveolar epithelial
cells of the respiratory tract in vitro might contribute to the understanding of the pathogenesis
of Cladosporium in respiratory infection and allergy in vivo.
INTRODUCTION
Cladosporium species is a member of the
phylum Ascomycota. The common species
include C. herbarum, C. cladosporioides
and C. sphaerospermum. This genus has
worldwide distribution. Aerobiological
studies reported that majority of fungal
spores in outdoor air is from the phyla
Ascomycota and Basidiomycota, while
Cladosporium is one of the most studied
allergenic Ascomycetes fungi (Knutsen et
al., 2012). Cladosporium spores are found
abundantly in indoors and outdoors at
approximately 18/m3 and 141/m3 respectively
(Codina et al., 2008).
As an imperfect dematiaceous fungus,
Cladosporium species causes opportunistic
infections such
6.Parasites in soil samples from Signy island, Antarctica
Lim, P.K.C. ; Lee, X.C ; Mohd Nazmi, N.M.A. ; Tang, Y.Y. ; Wong, S.F ; Mak, J.W ; Convey, P.
Tropical Biomedicine 2018;35(4):1007-1016
Studies on parasite populations in Antarctic soils are scarce and thus little is
known about the threat of these parasites towards either the natural fauna or human
visitors. However, human presence in Antarctica, mainly through research and tourism,
keeps increasing over time, potentially exposing visitors to zoonotic infections from
Antarctic wildlife and environment. Most available literature to date has focused on faecal
samples from Antarctic vertebrates. Therefore, this study addressed the possible presence
of parasites in Antarctic soil that may be infectious to humans. Soil samples were obtained
from five locations on Signy Island (South Orkney Islands, maritime Antarctic), namely
North Point and Gourlay Peninsula (penguin rookeries), Pumphouse (relic coal-powered
pump house), Jane Col (barren high altitude fellfield) and Berntsen Point (low altitude
vegetated fellfield close to current research station). Approximately 10% of the soil samples
(14/135) from 3 out of the 5 study sites had parasites which included Diphyllobotridae spp.
eggs, Cryptosporidium sp., an apicomplexan protozoa (gregarine), Toxoplasma gondii,
helminths (a cestode, Tetrabothrius sp., and a nematode larva) and mites. The presence of
parasites in the 3 sites are most likely due to the presence of animal and human activities
as two of these sites are penguin rookeries (North Point and Gourlay Peninsula) while the
third site (Pumphouse Lake) has human activity. While some of the parasite species found
in the soil samples appear to be distinctive, there were also parasites such as
Cryptosporidium and Toxoplasma gondii that have a global distribution and are potentially
pathogenic.