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RESULTS MATERIAL and METHODS Experimental assessment of disinfection procedures for eradication of Aspergillus fumigatus in food L. Noussair 1, A. Bouakline.

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Presentation on theme: "RESULTS MATERIAL and METHODS Experimental assessment of disinfection procedures for eradication of Aspergillus fumigatus in food L. Noussair 1, A. Bouakline."— Presentation transcript:

1 RESULTS MATERIAL and METHODS Experimental assessment of disinfection procedures for eradication of Aspergillus fumigatus in food L. Noussair 1, A. Bouakline 1, N. Roux 2, C. Lacroix 1, F. Derouin 1* and J.P. Gangneux 1,3 1 Laboratory of Parasitology-Mycology, 2 Saint-Louis Hospital, Paris - 3 Laboratory of Parasitology-Mycology, CHU de Rennes, France. 41th Interscience Conference on Antimicrobial Agents and Chemotherapy Chicago, (IL), USA. September 22-25, 2001 A sufficient duration of exposure to a temperature of at least 100°C is necessary to eradicate A. fumigatus spores from an experimental suspension. Chemical disinfection using ethanol 70% was highly effective to decontaminate dry surfaces inoculated with spores. Experiment performed on naturally or artificially contaminated food confirmed the experimental evaluation. Since chemical procedures are difficult to consider for dry or dehydrated foods and that MW is not efficient, oven heating allowing to reach a boiling temperature after reconstitution is the only efficient method to decontaminate. For dry food that are not reconstituted with water like black pepper for example, the thermic procedure was efficient but resulted in a great loss of flavour. For fruits and individual wrappings of foods, washing with water followed by an exposure to ethanol 70% gives the best results. CONCLUSIONS 265 Invasive aspergillosis is a major opportunistic fungal infection in patients with prolonged neutropenia. Previous studies showed that food is a potential source of fungal exposure. In particular, black pepper, regular and herbal tea, but also fruits, freeze-dried soup and individual wrappings. Objective In this study, we examined the efficacy of several thermic procedures such as oven heating, microwave irradiation (MW), or hot water (60°C and 100°C), and chemical procedures such as ethanol 70% or soap, that can be applied on foods and wrappings for the eradication of A. fumigatus (A.f.) contamination. INTRODUCTION Background: Since food is considered as a potential source of fungal exposure for neutropenic patients, we examined the efficacy of several procedures that can be applied on food samples for the eradication of A. fumigatus (A.f.) contamination. Material-Methods : A spore suspension of A.f. ( /ml) was exposed to oven heating (5', 10', 15' at 150 or 220°C), microwave irradiation (MW) (800 W, 1' and 2'), hot water (60 and 100°C). Similar processes and treatment with ethanol 70° were also applied on a dry surface experimentally inoculated with of A.f. spores. The most efficient methods were then applied on food samples either naturally (black pepper, infused tea) or experimentally contaminated by A.f. (apple and orange skin, freeze- dried soup). Quantification of spores was performed by subculture using a microtitration method. Results : Thermic and MW processes resulted in a complete decontamination of the spore suspension only when the suspension was boiling. On dry surface inoculated with A.f. spores, MW, hot water and short-time heat exposure (<15' at 220°C) resulted in 10 to 90% reduction of contamination. A complete eradication was only obtained with ethanol 70° or heating at 220°C for 15'. Dry pepper was decontaminated when heated 15' at 220°C but not by MW. Soup and infused tea were only decontaminated by boiling (MW or oven heat) ; the addition of hot water (60 or 100°C) was not efficient. For food that could not be exposed to high temperature or MW (apple or orange), treatment with ethanol 70° was only partially effective. Conclusion : A sufficient duration of exposure to a temperature >100°C is necessary to eradicate A.f. spores from food. For food that cannot be exposed to high temperature or MW, treatment with ethanol reduces the level of surface contamination but does not guarantee a total eradication of A.f., especially for fruits. Study design : The effect of several disinfectant procedures was assessed on a spore suspension of A.f. ( / ml) and on a dry surface experimentally inoculated with A.f. spores ( spores). Thereafter, the most efficient methods were applied on food samples either naturally or experimentally contaminated by A.f - Fruits experimentally contaminated by immersion in a spore suspension of A.f. ( / ml), - Black pepper naturally contaminated by A.f. spores, - Infused tea from tea bags naturally contaminated by A.f. spores, - Reconsituted freeze-dried soup experimentally contaminated with A.f. spores ( /ml). Assessment of the disinfectant procedures : The quantification of spores was performed by subculturing using a microtitration method in 96-well plates. Statistical analysis : ANOVA was performed to compare the efficacy of disinfectant methods. A p value < 0.05 was considered statistically significant from the control. Assessment of decontamination on naturally contaminated food (Figures 3 to 6) : Dry pepper was decontaminated when heated 15' at 220°C but not by MW. Reconstituted soup and infused tea were decontaminated after boiling ; exposure to hot water (60°C) was not efficient. For foods that could not be exposed to high temperature or MW (i.e. apple or orange), exposure to ethanol 70% was only partially effective. Experimental studies (Figures 1 and 2) : Spore suspension: Thermic and microwave processes resulted in a complete decontamination on only when a boiling temperature was reached. Freezing and exposure to hot water did not decrease significantly the fungal load of the suspension. Dry surface : hot water and short-time heat exposure (<15' at 220°C) resulted in a 10 to 90% reduction of contamination. A complete eradication was only obtained with ethanol 70% or heating at 220°C. Contact information: F. DEROUIN. Parasitology-Mycology lab., St-Louis hospital, Paris. Figure 5.Percentage of samples with a positive culture before and after decontamination of 100 ml of tea infusion done with tea powder naturally contaminated by A. fumigatus Figure 6 : Fungal load after different protocols of decontamination on 100 ml of reconstituted dried soup contaminated by A. fumigatus Figure 1. Fungal load after different protocols of decontamination on a 10 ml suspension containing spores of A. fumigatus/ml. Figure 2. Fungal load after different protocols of decontamination on a dried surface contaminated with spores of A. fumigatus Figure 4. Fungal load after different protocols of decontamination on pepper naturally contaminated by A. fumigatus. Figure 3. Fungal load after different protocols of decontamination on fruits contaminated by a suspension containing spores of A. fumigatus/ml


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