Anaphylaxis following the ingestion of flour contaminated by house dust mites--a report of two cases from Singapore.

This study presents two patients who developed anaphylaxis after eating mite-contaminated food, and also contains a survey of dust-mites contamination in flour samples from Singapore households. The clinical records of each patient was studied. Patient A developed anaphylaxis twenty minutes following the ingestion of home-made fried fish coated with Japanese flour, while Patient B developed similar life-threatening symptoms one hour after the ingestion of home baked scones. Both patients were NSAID-intolerant and had a history of allergic rhinitis. Skin prick tests showed a strong positive result for dust-mites and for extracts prepared from the ingested flour. Flour samples were also examined microscopically which revealed large numbers of live Dermatophagoides farinae dust-mites. A survey of 57 flour samples showed that 4 samples (7%) were contaminated with dust mites. The findings in the present study confirm that mite-contamination of flour exists in Singaporean households, and it may trigger anaphylaxis in susceptible individuals.

Pattern of sensitization to common environmental allergens amongst atopic Singapore children in the first 3 years of life.

This study was aimed to investigate the sensitization pattern to a range of common allergens in young Singaporean children. A cross-sectional study involving 75 children aged below 3 years was carried out. They presented between December 1995 and April 2000 with symptoms of asthma, rhinitis, eczema, or food allergy. Their levels of allergen-specific serum IgE to a panel of foods (egg white, milk, soy protein, shrimp, wheat and peanut), pet dander, dust mites and cockroaches were measured with Pharmacia CAP System radioallergosorbent test kits. Serum IgE levels greater than 0.35 kU/l represented a positive result. Four children could not be tested with the complete panel because of insufficient serum. The prevalence of sensitization was highest for cow's milk (45.9%) followed by egg white (38.7%), dust mites Dermatophagoides pteronyssinus (31.4%) and Blomia tropicalis (25.5%). Sensitization to ingested allergens was significantly more prevalent in children aged 1 year or younger than in the older children (70.4% of those below 1 year, and 50% of those aged 1-3 years; p < 0.02). Sensitization to inhaled allergens, such as dust mites, was more likely to manifest as respiratory symptoms (allergic rhinitis and asthma), while ingested allergens were associated with gastrointestinal symptoms and eczema (p < 0.001). It was concluded that infants and young children are at high risk of sensitization to common environmental substances. Allergen avoidance is therefore important even in the very young. The prevalence of sensitization to food allergens is higher compared to inhalant allergens in young children.

Utilization of healthcare resources for asthma in Singapore: demographic features and trends.

This study examined the healthcare utilization patterns for asthma in Singapore, a tropical island city-state, between 1986 and 1993. Asthma was ranked fifth among principal conditions with the highest number of discharges in Singapore (2.4 discharges per 1,000 population per annum). Among the 0-14 year-olds, asthma was ranked second, only after accidents and injuries, as the condition with the highest number of discharges (5.2 per 1,000). It was estimated that there were approximately 20,000 accident and emergency (A & E) room visits for asthma per annum (7.0 visits per 1,000 population per annum). There were, however, no significant changes in the number of hospitalized or emergency room cases for asthma over the period of analysis. In the primary healthcare setting, asthma ranked 6th among the leading conditions seen by the general practitioners and government polyclinics (15 visits per 100 population per annum). Among under 15 year olds, asthma (37 visits per 100 age-adjusted population per annum) ranked as the second leading condition behind upper respiratory tract infections. This study has shown that asthma causes a significant amount of morbidity in the Singapore community.

Food allergy in children-the Singapore story.

The study of food allergy in Singaporean children is still in its infancy. Confusion and misunderstanding is common among the public. Even so, we have found certain unique features regarding food allergy among Singaporean children. "Bird's nest" has been shown to be the most common cause of anaphylaxis requiring medical attention. This allergen has not been described before. Peanuts and tree nuts are extremely uncommon causes of anaphylaxis, unlike the West. However, the pattern of sensitization to foods in children as shown by skin prick test is similar to other Western populations. The reasons for the difference between the profile foods responsible for anaphylactic reactions in our population and those of the western population, despite the similarity in sensitization profiles, are still unclear.

Factors associated with increased respiratory symptoms among asthmatic children in Singapore.

Asthma is a common cause of childhood morbidity. The objective of the present study was to evaluate the factors associated with increased asthma morbidity among asthmatic children in Singapore. A cohort of primary school children (n = 6,404, aged 6-13 years) were evaluated using the American Thoracic Society and the Division of Lung Diseases of the National Heart, Lung and Blood Institute, USA (ATS-DLD) respiratory questionnaire. A total of 2,222 of 6,404 children (34.8%) was found to have reported symptoms of wheezing. Of these, 899/2,222 (40.5%) reported symptoms of "increased asthma morbidity". This was associated with the younger age group, male sex and higher socio-economic status. In addition, concurrent or past allergies were strongly associated with increased asthma morbidity, while premature birth and a history of prior childhood respiratory illnesses and Infections were predictive of greater asthma morbidity. No association was found between increased morbidity and presence of domestic pets, parental smoking, childcare attendance, and the season of birth.

Sensitization to Blomia tropicalis and dermatophagoides pteronyssinus-a comparative study between Singapore and Taiwan.

Blomia tropicalis (Bt) and Dermatophagoides pteronyssinus (Dp) are the predominant domestic mites species in Singapore and Taiwan. This study aims to characterize and compare the mite sensitization profiles in both countries. Skin prick tests were performed on 203 Singaporeans with Dp and Bt crude extracts. In vitro IgE and IgG4 reactivity to extracts and specific allergens (Der p 1, Der p 2 Der p 5 and Blo t 5) were determined by immunoassays. Approximately 91% of the tested Singaporeans were skin test positive for both Bt and Dp. Both populations share similar frequencies of in vitro IgE reactivity to all the allergens tested, but they differ in the pattern and magnitude of allergen sensitization. Although Der p 1, Der p 2 and Blo t5 are major sensitizing allergens in both countries, Blo t 5 is a more potent one in Singapore, probably reflecting the high level of exposure to Bt. The unique major Bt and Dp allergens should be included for precise diagnosis and effective immuno-therapeutic treatment of mite allergy in both countries.

Ethnic differences in genetic susceptibility to atopy and asthma.

The genetics of asthma and atopy is complex, but can be approached by studies of both candidate genes and mapping of susceptibility loci. Genetic factors conferring susceptibility to disease may vary among ethnic groups. We present our experience with some candidate gene studies for asthma and atopy and susceptibility locus mapping for linkage to chromosome 5q.

Culture of Blomia tropicalis and IgE immunoblot characterization of its allergenicity.

Blomia tropicalis is an important triggering factor for allergic diseases such as asthma, rhinitis and atopic dermatitis in tropical and subtropical regions, which climate favours the growth of this species. Our previous mite fauna study revealed that Blomia tropicalis is the most dominant species present in Singapore house dust The main objective of this study is to establish a mass culture of Blomia tropicalis for further characterization of the antigenic and molecular properties of this mite. Approximately one gram of mites could be obtained for every 300-gram of culture medium by culturing under natural condition with a mean annual temperature of 30 degrees C and a mean relative humidity of 80%, and harvested by modified Tullgren funnel. Allergen characterization by IgE immunoblot analysis with crude mite extracts showed some IgE reactivity differences between Blomia tropicalis mite extract from Singapore and Colombia. The possible reasons for these findings are the quality and source of the mite protein extracts used, or selective differences in the population under evaluation. Further, the atopic sera tested showed differences in the pattern and Intensity of IgE immunoblot reactivity to crude extracts of Blomia tropicalis and Dermatophagoides pteronyssinus, the other highly prevalent mite in Singapore. These data support the existence of species-specific allergens. In conclusion, we have been successful in setting up B. tropicalis mass cultures and have prepared extracts of high allergenicity.

Allergens of Bipolaris species.

Skin prick tests done previously revealed a significantly higher percentage of sensitization to an extract of Bipolaris sp. among atopic individuals (34/147, 23.1%) compared to non-atopic individuals. Bipolaris-specific IgE levels were quantified in sera from a representative group of 38 individuals using the Fluorescence Allergosorbent Test (FAST). Result obtained by FAST were found to be comparable to the skin prick test results (r2 = 0.60, p < 0.001 for IgE levels vs wheal sizes; r2 = 0.44, p < 0.001 for IgE levels vs erythema sizes). Characterisation of the extract's allergenic component by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) showed 28 protein bands with molecular weights (MW) ranging from 11 kDa to above 100 kDa. Immunoblotting with sera of 10 Bipolaris-sensitive (skin prick test, 3 +) individuals showed that Bipolaris spore extract contained at least 4 IgE binding proteins (MW 11-13 kDa, 16-17 kDa, 20-22 kDa and 36 kDa). All 10 sera reacted to the protein at MW 20-22 kDa, 2 sera with MW 11-13 kDa, 3 sera with 16-17 kDa and 6 sera with 36 kDa. This study has thus demonstrated that spores of Bipolaris sp. contain allergenic components which may elicit IgE-mediated reactions.

Detection of Mycobacterium tuberculosis in sputum, pleural and bronchoalveolar lavage fluid using DNA amplification of the MPB 64 protein coding gene and IS6110 insertion element.

Two gene sequences specific for Mycobacterium tuberculosis were evaluated for the diagnosis of pulmonary tuberculous (PTB) in pleural fluid (PF), bronchoalveolar lavage fluid (BAL) and sputum (Sp). The 240 bp sequence (nts 460-700) coding for the MPB 64 protein coding gene and the 123 bp IS6110 insertion element present in multiple copies in the mycobacterial genome were amplified using the polymerase chain reaction. Fifty-nine clinical specimens were studied. The diagnosis of PTB was confirmed by positive M. tuberculosis cultures in 14 specimens, and by the presence of characteristic histological features of granuloma and Langerhan's giant cells on pleural biopsy in 3 PF specimens through cultures for M. tuberculosis were negative. The remaining 42 specimens were obtained from patient's with non-tuberculosis pulmonary infections or malignancy, and these served as negative controls. Our results showed that the IS6110 insertion element and MPB 64 gene sequence were detected in all 14 culture positive PTB cases, although detection of the latter sequence required both DNA amplification and oligonucleotide hybridization. There was however one false positive specimen with the MPB 64 detection protocol. More importantly, both the MPB 64 sequence and IS6110 insertion element protocols were unable to detect M. tuberculosis DNA in the 3 PF samples diagnosed by histological characteristics on pleural biopsy and culture negative. We conclude that DNA amplification for M. tuberculosis-specific sequences is a useful method for rapid diagnosis of PTB in culture positive specimens. However, the false negative results with TB culture negative cases of tuberculosis pleurisy, limits its usefulness for the diagnosis of tuberculous pleurisy.

House dust mite allergen levels in a Singapore hospital.

House dust mite allergens constitute one of the most important allergens in house dust. In this study, the levels of two common dust mite allergens, Der p I and Der f I, in a general hospital in Singapore were evaluated. Our results showed that these allergens were detected in 42/74 (or 57%) of the dust samples. Der p I was found to be the predominant allergen detected (p < 0.001). The allergen levels were, however, low with only 1/74 having a Der p I concentration above 2 micrograms g-1 dust. None of the samples had Der f I concentrations above this level. Of the various niches studied (mattresses, pillows, sofas, carpets, blinds and floors), the blinds and floors had the lowest concentration of allergen (p < 0.05). These low levels in the hospital compared to homes were attributed to the vigorous cleaning schedule in the hospital, the use of plastic to encased mattresses and pillows, vinyl covered sofas and vinyl lined floors. These practices may be adopted in the home as a means to reduce mite allergen exposure.