Occupational asthma in bakeries caused by sensitivity to alpha-amylase

Occupational Exposures to Organic Dust in Irish Bakeries and a Pizzeria Restaurant

For decades, occupational exposure to flour dust has been linked to a range of respiratory diseases, including occupational asthma, thought to result from exposure to fungi present in the flour. Antifungal resistance is of increasing prevalence in clinical settings, and the role of occupational and environmental exposures, particularly for specific fungal species, is of concern. Occupational exposure to flour dust can occur in a range of occupational settings, however, few studies have focused on restaurant workers. The objective of this study was to measure occupational exposure to flour and microbial contamination, including azole resistance screening, in two small commercial bakeries and in a pizzeria. Personal full shift inhalable dust measurements were collected from workers, and were analyzed for inhalable dust and fungi, bacteria, azole resistance, and mycotoxins. Samples of settled dust were collected, and electrostatic dust cloths (EDC) were deployed and analyzed for microbial contamination, including azole resistance screening, and mycotoxins. Geometric mean exposures of 6.5 mg m-³ were calculated for inhalable dust, however, exposures of up to 18.30 mg m-³ were measured-70% of personal exposure measurements exceeded the occupational exposure limit for flour dust of 1.0 mg m-³. The air and EDC fungal counts were similar to those reported in previous studies for similar occupational environments. The fungi were dominated by Penicillium genera, however Aspergillus genera, including Fumigati and Flavi sections, were observed using culture-based methods, and the Fumigati section was also observed by molecular tools. Both Aspergillus sections were identified on the azole resistance screening. Mycotoxins were also detected in the settled dust samples, dominated by deoxynivalenol (DON). The role of environmental exposure in both the development of antimicrobial resistance and the total mycotoxin body burden is a growing concern; therefore, the presence of azole-resistant fungi and mycotoxin contamination, although low in magnitude, is of concern and warrants further investigation.

Assessment of occupational exposure to azole resistant fungi in 10 Portuguese bakeries

Occupational exposure to bioaerosols resulting from handling of flour dust and raw materials in bakeries is associated with health problems. The emergence of azole-resistant fungal species in the environment is thought to be related with the use of azole fungicides in cereal crops and prevention of postharvest spoilage. As raw materials used in bakeries are commonly exposed to azoles, we investigated the mycobiota and azole-resistant fungi prevalence in this occupational environment. Ten Portuguese bakeries were assessed through electrostatic dust cloth (EDC, n = 27), settled dust (n = 7), and raw material (n = 26) samples. Samples were inoculated in malt extract agar (2%) (MEA) with chloramphenicol (0.05 g/L) and in dichloran glycerol (DG18), and onto Saboraud screening media supplemented with 4 mg/L itraconazole, 1 mg/L voriconazole, or 0.5 mg/L posaconazole, and incubated for 3-5 days at 27 °C. Except for one out of the ten analyzed bakeries, Cladosporium sp., Penicillium sp., and Aspergillus sp. were the most prevalent fungi identified. Aspergillus sp. and Mucorales order were identified in raw materials with both media, whereas Penicillium sp. was identified in DG18 only. Azole-resistant species were identified in the environment (EDC) and, to a lower extent, in raw materials, including Aspergillus sp. and Mucorales. The presence of azole-resistant fungal species in bakeries represents an occupational risk for workers. This study proposes complementary sampling methods for the evaluation of occupational exposure to mycobiota, and highlights the importance of studying the prevalence of azole-resistant strains in specific occupational environments.

Sensitization to xylanolytic enzymes: an underestimated health hazard among bakers

BACKGROUND

The most important occupational allergens in baking include flour and enzymes, especially α-amylase. Although xylanolytic enzymes have previously been described as sensitizers, they may be overlooked during assessment of bakery workers with work-related symptoms.

AIMS

To report a case of a baker who suffered from work-related respiratory, ocular and skin symptoms as a consequence of sensitization to xylanolytic enzymes.

METHODS

Physical examination, chest X-ray, routine laboratory tests, skin prick tests (SPTs) with common and occupational allergens (wheat, pearl, rye, corn and oat flours, α-amylase, bakery adjuvants) and spirometric measurements, as well as assessments by a laryngologist, dermatologist and ophthalmologist were performed. Specific IgE (sIgE) to occupational agents were evaluated for flours, α-amylase, xylanase, cellulose and glucoamylase. Specific inhalation challenges (SICs) with flours and bakery adjuvants were carried out.

RESULTS

Hypersensitivity to Aspergillus moulds, flours and α-amylase was confirmed in SPTs; however, SIC with those agents gave a negative result. Further investigation revealed the presence of sIgE to xylanolytic enzymes. During SIC with bakery adjuvants, allergic skin, ocular and respiratory symptoms occurred and were confirmed by objective assessment.

CONCLUSIONS

In the assessment of work-related allergic symptoms in bakers, sensitization to xylanolytic enzymes should be considered. Completion of diagnostic procedures having excluded asthma and rhino-conjunctivitis related to flour hypersensitivity might result in a false-negative assessment.

Exposure to flour dust in the occupational environment

Exposure to flour dust can be found in the food industry and animal feed production. It may result in various adverse health outcomes from conjunctivitis to baker's asthma. In this paper, flour dust exposure in the above-mentioned occupational environments is characterized and its health effects are discussed. A peer-reviewed literature search was carried out and all available published materials were included if they provided information on the above-mentioned elements. The hitherto conducted studies show that different components of flour dust like enzymes, proteins and baker's additives can cause both non-allergic and allergic reactions among exposed workers. Moreover, the problem of exposure to cereal allergens present in flour dust can also be a concern for bakers' family members. Appreciating the importance of all these issues, the exposure assessment methods, hygienic standards and preventive measures are also addressed in this paper.

The 'take home' burden of workplace sensitizers: flour contamination in bakers' families

BACKGROUND

Exposure to flour/flour constituents is a leading cause of occupational asthma. Paternal occupational exposure to flour has been associated with increased likelihood of childhood asthma, raising the possibility of para-occupational exposure whereby family members are exposed to sensitizers 'taken home' on contaminated skin/clothing.

OBJECTIVE

To establish whether workplace contamination of skin/clothing with wheat flour allergen (WFA) and fungal α-amylase (FAA) is associated with increased levels of these allergens in bakers' homes.

METHODS

Bakeries in north-east Scotland were invited to participate. Control subjects were recruited from University of Aberdeen staff and students. Exposure assessment was carried out in bakeries, bakers' cars and the homes of bakers and controls using surface wipe and vacuum sampling; samples were analyzed for total protein, FAA and WFA.

RESULTS

164 wipe samples and 49 vacuum samples were collected from 38 bakers (from 5 bakeries) and 10 controls. Compared to non-bakers, bakers had higher median levels of WFA and FAA in house vacuum samples; the difference was statistically significant for WFA/total protein (515.8×10(-6) vs. 163.7×10(-6), p=0.031), FAA/total protein ratios (1.45×10(-6) vs. 0.04×10(-6), p<0.001) and FAA loading (median 1.2 pg/cm(2) vs. 0.1 pg/cm(2), p<0.001) with workplace exposure-home contamination relationships between bakers with higher and lower workplace contamination. We found positive correlations between WFA contamination of the bakers' foreheads and cars (r(s)0.57, p=0.028), foreheads and houses (r(s)0.46, p=0.025), shoes and houses (r(s)0.45, p=0.029); and between FAA contamination of shoes and houses (r(s)0.46, p=0.023), and cars and houses (r(s)0.70, p=0.008). There was no evidence of bakers using work-sourced flour for domestic baking.

CONCLUSIONS

This work demonstrates pathways for 'take home' exposure of occupationally sourced flour. Taken with our previous work, showing that bakers' children are more likely to have asthma, this supports the need for further investigation to establish whether 'take home' of occupationally sourced flour is widespread with health consequences.

Sensitization to wheat flour and enzymes and associated respiratory symptoms in British bakers

RATIONALE

Current literature suggests that flour exposed workers continue to be at risk of allergic sensitization to flour dust and respiratory ill health.

OBJECTIVES

A cross-sectional study of 225 workers currently potentially exposed to flour dust in British bakeries was performed to identify predictors of sensitization to wheat flour and enzymes.

RESULTS

Work-related nasal irritation was the most commonly reported symptom (28.9%) followed by eye irritation (13.3%) and work-related cough or chest tightness (both 10.2%). Work-related chest tightness was significantly associated (OR 7.9, 1.3-46.0) with co-sensitization to wheat flour and any added enzyme. Working at a bakery with inadequate control measures was not a risk factor for reporting work-related respiratory symptoms (OR 1.3, 0.4-3.7). Fifty-one workers were atopic and 23 (14%) were sensitized to workplace allergens. Atopy was the strongest predictive factor (OR 18.4, 5.3-64.3) determining sensitization. Current versus never smoking (OR 4.7, 1.1-20.8) was a significant risk factor for sensitization to wheat flour or enzymes in atopic workers only, corrected for current level and duration of exposure. This effect was not seen in non-atopic workers (OR 1.9, 0.2-17.9). Evidence of sensitization to less commonly encountered allergens was also seen to Aspergillus niger derived cellulase, hemicellulase and xylanase mix, in addition to glucose oxidase and amyloglucosidase mix.

CONCLUSIONS

The combination of health surveillance and exposure control in this population has been insufficient to prevent clinically significant workplace sensitization. Smoking may pose an additional risk factor for sensitization in atopic workers. Am. J. Ind. Med. 52:133-140, 2009.

Optimized methods for fungal ?-amylase airborne exposure assessment in bakeries and mills

BACKGROUND

In order to enable reproducible and comparable exposure measurements of fungal alpha-amylase (alpha-amylase) in different laboratories and countries, the entire procedure from sampling of airborne dust to measuring extracted samples (including standards and the used enzyme) immunoassays must be standardized. The aim of this study was to establish optimal elution and assay conditions.

METHODS

A parallel sampler was used for simultaneous collection of 10 samples of inhalable dust in bakeries and mills in Germany, England, the Netherlands and Spain. Three enzyme-immunoassays (EIAs) for detection of fungal alpha-amylase based on monoclonal antibodies or polyclonal antibodies were used for the measurement of the parallel-sampled filters (n=432) extracted using several methods. The results were analysed by regression analysis of variance. Additional filters (n=54) were extracted and analysed using two EIAs to investigate the storage stability of the extracts.

RESULTS

Although alpha-amylase concentrations correlated well (r> or =0.88), differences were found between the EIAs in the sensitivity and nominal values (up to a mean factor 5.8). The best elution medium for airborne filters (phosphate-buffered saline 'PBS' with 0.05% Tween-20) led to 1.2 to two times higher alpha-amylase allergen yields than extraction in PBS only, while higher Tween-20 concentrations decreased the extracted alpha-amylase yield. During storage of frozen dust/filter extracts for 3-4 months at -20 degrees C, a loss of approximately 40% of measurable alpha-amylase was observed, which could be partially prevented by addition of 0.1% casein to the medium directly after extraction.

CONCLUSION

Although the effects of only a few of many possible causes of variation were investigated, for these factors a clear choice could be made with regard to optimal elution conditions and the use of validated EIAs with calibrated standards, thus making significant progress towards a completely standardized procedure for airborne alpha-amylase measurements.

Interaction of environmental allergens with airway epithelium as a key component of asthma

Epithelial cells in the airway wall actively interact with environmental antigens/allergens, both in healthy individuals and patients with asthma. In patients with (allergic) asthma, the epithelium is abnormal, showing damaged structures and continuous activation similar to a repair phenotype cell. Epithelial cells bind allergens by a diversity of innate receptors, similar and in part identical to the Toll-like receptor family, which can induce the release of cytokines, chemokines, and growth factors. Protease-containing extracts (house dust mite, fungi) may additionally cause damage of the epithelial cell layer, thereby enhancing the repair phenotype of epithelial cells in patients with asthma. These interactions may result in facilitation of transport of allergens and enhanced presentation to the immune system (Th2-type response). The inflammatory response induces a second phase of Th2-type cytokines and cytotoxic products that will enhance growth factor-mediated airway remodeling, as is found in asthma. An understanding of the largely unknown innate responses of epithelial cells with environmental antigens/allergens may open new treatment modalities for asthma and other airway diseases.

Glucoamylase: another fungal enzyme associated with baker's asthma

BACKGROUND

Aspergillus-derived enzymes are widely used as dough additives in the baking industry. These enzymes may give rise to immunoglobulin (Ig)E-mediated sensitization and occupational asthma. Glucoamylase (or amyloglucosidase) is an important industrial enzyme obtained from Aspergillus niger and used to provide fermentable sugars for yeast to improve loaf volume and texture.

OBJECTIVE

The aim of our study was to investigate the potential allergenic role of glucoamylase in baker's asthma.

METHODS

We report four subjects with work-related allergic respiratory symptoms who were exposed to glucoamylase and other starch-cleaving enzymes used as baking additives. The causative role of glucoamylase in work-related asthma was investigated by immunologic tests and specific inhalation challenges (SIC). Glucoamylase allergenic components were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting.

RESULTS

Skin prick tests to glucoamylase (10 mg/mL) gave a positive response in all patients. Further, a positive skin prick test to alpha-amylase was obtained in the four patients and to hemicellulase in two of them. SIC to glucoamylase elicited isolated early asthmatic responses in the three patients tested, and SIC to alpha-amylase elicited early asthmatic responses in two patients and a dual asthmatic response in another patient. Immunoblotting with glucoamylase showed several IgE-binding bands with molecular masses between 33 and 96 kD. IgE-inhibition assays showed scarce to moderate allergenic cross-reactivity between glucoamylase and alpha-amylase.

CONCLUSIONS

These bakers had developed IgE-mediated occupational asthma to glucoamylase and alpha-amylase. Fungal glucoamylase is widely used as a baking additive and this enzyme may give rise to allergic respiratory reactions among exposed workers.

Development of a two-site enzyme-linked immunosorbent assay for alpha-amylase from Aspergillus oryzae based on monoclonal antibodies

A two-site monoclonal antibody ELISA was developed to quantify the allergen Asp o 2 (alpha-amylase from Aspergillus oryzae). Two mAbs recognizing distinct epitopes were selected, enriched by in vitro production in a modular minifermenter and affinity-purified. The first antibody was bound to microtiter plates which were then incubated with samples containing the allergen. Bound allergen was detected using a biotinylated second antibody and peroxidase-polymer-labelled streptavidin. The assay had a sensitivity of 0.6 ng/ml and did not react to high concentrations of wheat and rye flour or yeast proteins. The mAb ELISA will be useful in individual or epidemiological studies of baker's asthma to assess workplace allergen concentrations and the efficacy of allergen exposure prevention. It can be used as a standard assay for the quantification of alpha-amylase and the establishment and control of threshold limits in European bakeries.

Enzyme exposure and enzyme sensitisation in the baking industry

OBJECTIVES

To assess the exposure to enzymes and prevalence of enzyme sensitisation in the baking industry.

METHODS

A cross sectional study was conducted in four bakeries, one flour mill, and one crispbread factory. Sensitisation to enzymes, flours, and storage mites was examined by skin prick and radioallergosorbent (RAST) tests. 365 workers were tested. The workers were interviewed for work related respiratory and skin symptoms. Total dust concentrations were measured by a gravimetric method, and the concentration of alpha-amylase in air was measured by a catalytic method. An immunochemical method was used for measuring cellulase and xylanase in air.

RESULTS

Total measured dust concentrations were from 0.1 to 18 mg/m3, with highest values in dough making areas of bakeries. The alpha-amylase concentrations generally followed the total dust concentrations and reached the highest values < 6.6 micrograms/m3 in the same areas. Cellulase and xylanase varied with concentrations < 180 ng/m3 and < 40 ng/m3, respectively, in the flour mill and the crispbread factory. No cellulase, but concentrations of 1-200 ng/m3 xylanase, were found in the bakeries, probably indicating the natural xylanase activity of wheat. 12 workers (8%) in the bakeries, three (5%) in the flour mill, and four (3%) in the crispbread factory were skin prick positive to enzymes. The corresponding percentages of positive reactions to flours were 12%, 5%, and 8%.

CONCLUSIONS

The study confirmed that industrial enzymes in baking used as additives in a powdered form pose a risk of sensitisation. The no effect air concentrations for industrial enzymes are not known. Based on present knowledge, however, lowering exposures and eliminating short and high peaks by technical measures would lower the risk of sensitisation. This would be most effectively accomplished by shifting to non-dusty products.

Baker's asthma related to soybean lecithin exposure

We report two cases of soybean-lecithin-induced asthma in bakers. The patients experienced clinical symptoms in relation to an occupational exposure to this additive. Skin tests were positive with soybean lecithin, RAST showed a sensitization to soybean, and bronchial challenge tests were positive for a dilution of 10(-3) with this allergen. The same tests remained negative among healthy and asthmatic controls. Soybean lecithin, a common additive in bakery, must be added to the list of numerous aeroallergens involved in baker's asthma.

[Occupational asthma caused by organic substances]

Occupational asthma (OA) to organic substances is frequently related to IgE-dependent hypersensitivity. New etiological agents are latex and vegetal gums, in health care personnel as in carpet-making manufactures. Bakers are exposed to numerous allergens: wheat and cereal flours, sesame and other seed proteins, alpha-amylase and other enzymes. Alpha-amylase extracted from Aspergillus orizae is a potent allergen. Plant derived materials have been identified as allergens in the floral industry (Ficus, Ginseng, Gypsophila, etc). The accurate diagnosis relies upon a thorough history, completed by measurements of peak expiratory flows during the work. Sensitization can be confirmed by prick tests and immuno assays for IgE antibodies. Bronchial provocation tests documenting OA are advisable. The early detection of OA might be evaluated by skin tests to occupational allergens repeated yearly. The prevention of OA relies on air sampling technologies controlling the allergenic density of the atmosphere and removing asthmatics from exposed areas. There are no scientific grounds for discarding atopics from occupations at risk for OA.

alpha-Amylase, a flour additive: an important cause of protein contact dermatitis in bakers

BACKGROUND

alpha-Amylase, an enzyme commonly used in flour additives, has been reported to be an important cause of rhinitis and asthma in bakers.

OBJECTIVE

Our purpose was to determine whether this enzyme could also cause dermatitis. We tested it routinely in bakers with hand eczema.

METHODS

Patch tests were administered with the International Contact Dermatitis Research Group standard series and a bakery series and scratch-chamber or prick tests were performed with the bakers' own material and with alpha-amylase powder.

RESULTS

Of 32 bakers tested, seven had an immediate wheal-and-flare reaction and two also had a delayed eczematous reaction. High dilutions of the alpha-amylase powder still gave strong reactions.

CONCLUSION

alpha-Amylase is an important cause of skin reactions in bakers and should be tested routinely if a contact allergy is suspected.

Respiratory allergy to Aspergillus-derived enzymes in bakers' asthma

Baking and food industry workers are exposed to several powdered Aspergillus-derived enzymes with carbohydrate-cleaving activity that are commonly used to enhance baked products. We describe a retrospective study of sensitization to fungal alpha-amylase and cellulase on bakers. Five bakers in whom respiratory allergy symptoms developed when they were exposed to bread "improvers" that contained fungal alpha-amylase and cellulase were investigated by in vivo and in vitro tests. Type I hypersensitivity to these enzymes was demonstrated in the five patients by means of skin testing, histamine release test, positive reverse enzyme-immunoassay for specific IgE antibodies, and bronchial provocation test response to alpha-amylase or cellulase or both. Isolated immediate and dual responses to the bronchial challenge tests with these enzymes were observed. Immunoblot analysis with use of a pooled serum identified IgE-binding components in both enzymes. In the reverse-enzyme immunoassay-inhibition assays cross-reactivity between alpha-amylase and cellulase was not found, but some degree of cross-reactivity between alpha-amylase and A. oryzae, and between cellulase and A. niger was demonstrated. Four of the patients were also sensitized to cereal flour. Aspergillus-derived enzymes used as flour additives can elicit IgE-mediated respiratory allergy, and this fact has to be considered in the diagnosis and clinical management of bakers' asthma.