Progress 10/01/06 to 09/30/07
Outputs
Progress Report Objectives (from AD-416) 1) Evaluate biofilm formation by Salmonella serotypes on cantaloupe; 2) investigate survival, aggregation and biofilm development on disinfection efficacy to Salmonella serotypes on cantaloupe, honeydew, and watermelon; and 3) evaluate the impacts of interventions to disinfect whole and fresh cut melons on product quality, shelf-life or sensory attributes in coordinated cross-lab studies. Approach (from AD-416) Determine the role of cellulose and curli fimbriae production by salmonellae in biofilm formation using the glass adherence assay. Determine the ability of biofilm-deficient as well as biofilm-forming salmonellae to multiply and survive sanitation on melon surfaces. Determine efficacy of disinfection treatments including water at 76 degree C, 200 ppm chlorine solution, and chlorine dioxide gas in reducing populations of native microflora and human pathogens on cantaloupes, honeydew melons, and watermelons. Determine whether treatments shown to be effective in decontaminating melons have any adverse effects on visual or sensory quality or shelf-life. Significant Activities that Support Special Target Populations This report documents research conducted under a reimbursable cooperative agreement (58-1935-3-325) between ARS and the University of California, Davis. Biofilm formation by various isolates of Salmonella on cantaloupe rind surfaces during storage at 10 or 22C was demonstrated using SEM. Biofilm formation occurred rapidly, even at low inoculum concentrations, thus supporting the hypothesis that this may be responsible for decreased efficacy of aqueous sanitizers following storage of inoculated melons. In a screening of 53 Salmonella strains from various sources for biofilm formation by a crystal-violet microplate assay, little difference was observed between cantaloupe-related strains and the other isolates examined, but levels of biofilm produced by all isolates were highly variable. It is likely that all Salmonella spp. are able to make biofilm, but the conditions on cantaloupe surfaces stimulate increased production. A few 'high' and 'low' biofilm-formers were selected to test the hypothesis that increased biofilm formation is related to increased attachment strength and sanitizer resistance on cantaloupe surfaces. Results demonstrated a relationship between the ability of Salmonella to form biofilms on cantaloupe surfaces and the production of curli and cellulose. To further investigate the mechanism of attachment by Salmonella to abiotic surfaces, we received mutant strains deficient in curli and cellulose production from Dr. Carlos Gamazo (University of Navarra, Spain). Results indicated that cellulose deficient mutants were far less able to adhere to stainless steel, glass, and teflon coupons. Staining experiments further demonstrated that mutations in the bcsC and bcsE genes (cellulose production) greatly inhibited adherence. The inadequacy of aqueous sanitizers (currently practiced in produce industry) to inactivate and/or remove this human pathogen on cantaloupes could be due to biofilm formation and inaccessibility to microbial attachment sites by washing systems. The development of chlorine dioxide gas treatment capable of reaching and inactivating human pathogens within biofilms or attached to inaccessible sites on cantaloupe surfaces was carried-out. Artificially inoculated cantaloupes were fumigated with chlorine dioxide for up to 6 h in a closed chamber that was developed at ERRC, using two different technologies for generating the gas. We achieved more than 5 logs (99. 999%) reduction in Salmonella populations following treatments, regardless of the technology used for generating the gas. The research work showed that chlorine dioxide gas treatment of cantaloupes is able to inactivate Salmonella attached to inaccessible sites on the rind or within biofilms. This treatment also increased the shelf life of the whole cantaloupe by reducing spoilage microorganisms on the rind surface, and did not have apparent adverse effects on the quality of this commodity. This project should have terminated on August 31, 2006, however, awaiting Administrative Close-out.
Impacts
(N/A)
Publications
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Progress 10/01/05 to 09/30/06
Outputs
Progress Report 4d Progress report. This report serves to document research conducted under a reimbursable cooperative agreement (58-1935-3-325) between ARS and the University of California, Davis, in support of the parent project 1935-41420-011-00D, Intervention technologies for enhancing the safety and security of fresh and minimally processed produce and solid plant-derived foods. Previous research in our laboratory has documented the inadequacy of washing processes to inactivate and/or remove microorganisms on cantaloupes, including human pathogens, due to biofilm formation and inaccessibility of microbial attachment sites to washing systems. The development of chlorine dioxide gas treatment capable of reaching and inactivating human pathogens within biofilms or attached to inaccessible sites on cantaloupe surfaces was carried-out. Artificially inoculated cantaloupes were fumigated with chlorine dioxide for up to 6 h in a closed chamber that was developed at ERRC,
using two different technologies for generating the gas. We achieved more than 5 logs (99.999%) reduction in Salmonella populations following treatments, regardless of the technology used for generating the gas. The research work showed that chlorine dioxide gas treatment of cantaloupes is able to inactivate Salmonella attached to inaccessible sites on the rind or within biofilms. This treatment also increased the shelf life of the whole cantaloupe by reducing spoilage microorganism populations on the rind surface, and did not have apparent adverse effects on the quality of this commodity.
Impacts
(N/A)
Publications
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Progress 03/15/03 to 08/31/06
Outputs
Progress Report Objectives (from AD-416) 1) Evaluate biofilm formation by Salmonella serotypes on cantaloupe; 2) investigate survival, aggregation and biofilm development on disinfection efficacy to Salmonella serotypes on cantaloupe, honeydew, and watermelon; and 3) evaluate the impacts of interventions to disinfect whole and fresh cut melons on product quality, shelf-life or sensory attributes in coordinated cross-lab studies. Approach (from AD-416) Determine the role of cellulose and curli fimbriae production by salmonellae in biofilm formation using the glass adherence assay. Determine the ability of biofilm-deficient as well as biofilm-forming salmonellae to multiply and survive sanitation on melon surfaces. Determine efficacy of disinfection treatments including water at 76 degree C, 200 ppm chlorine solution, and chlorine dioxide gas in reducing populations of native microflora and human pathogens on cantaloupes, honeydew melons, and watermelons. Determine whether treatments shown to be effective in decontaminating melons have any adverse effects on visual or sensory quality or shelf-life. Significant Activities that Support Special Target Populations Biofilm formation by various isolates of Salmonella on cantaloupe rind surfaces during storage at 10 or 22C was demonstrated. Results indicated that biofilm formation occurred rapidly, even at low inoculum concentrations, thus supporting the hypothesis that this may be responsible for decreased efficacy of aqueous sanitizers following storage of inoculated melons. In a screening of 53 Salmonella strains from various sources for biofilm formation, little difference was observed between cantaloupe-related strains and the other isolates examined, but levels of biofilm produced by all isolates were highly variable. It is likely that all Salmonella spp. are able to make biofilm, but the conditions on cantaloupe surfaces stimulate increased production. The inadequacy of aqueous sanitizers (currently practiced in produce industry) to inactivate and/or remove this human pathogen on cantaloupes could be due to biofilm formation and inaccessibility to microbial attachment sites by washing systems. The development of chlorine dioxide gas treatment capable of reaching and inactivating human pathogens within biofilms or attached to inaccessible sites on cantaloupe surfaces was carried-out. Artificially inoculated cantaloupes were fumigated with chlorine dioxide for up to 6 h in a closed chamber that was developed at ERRC, using two different technologies for generating the gas. We achieved more than 5 logs (99.999%) reduction in Salmonella populations following treatments, regardless of the technology used for generating the gas. The research work showed that chlorine dioxide gas treatment of cantaloupes is able to inactivate Salmonella attached to inaccessible sites on the rind or within biofilms. This treatment also increased the shelf life of the whole cantaloupe by reducing spoilage microorganism populations on the rind surface, and did not have apparent adverse effects on the quality of this commodity.
Impacts
(N/A)
Publications
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Progress 10/01/04 to 09/30/05
Outputs
4d Progress report. This report serves to document research conducted under a reimbursable cooperative agreement between ARS and the University of California, Davis. Additional information regarding this research can be found in the parent project 1935-41420-007-00D, New Technologies for Decontamination of Fruits and Vegetables. A Research Associate, funded by the Agreement, investigated mechanism of attachment and biofilm formation by Salmonella on the surface of cantaloupe melons. Previous data demonstrated a relationship between the ability of Salmonella to form biofilms on cantaloupe surfaces and the production of curli and cellulose. To further investigate the mechanism of attachment by Salmonella to abiotic surfaces, we received mutant strains deficient in curli and cellulose production from the University of Navarra, Spain. Initial experiments indicated that cellulose deficient mutants were far less able to adhere to stainless steel, glass, and teflon coupons.
Staining experiments further demonstrated that mutations in the bcsC and bcsE genes (cellulose production) greatly inhibited adherence. The results of these studies will guide the development of improved interventions for disinfecting contaminated processing equipment.
Impacts
(N/A)
Publications
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Progress 10/01/03 to 09/30/04
Outputs
4. What were the most significant accomplishments this past year? D. Progress Report: This report serves to document research conducted under a reimbursable cooperative agreement between ARS and the University of California, Davis. Additional details of this research can be found in the parent project 1935-41420-007-00D, New Technologies for Decontamination of Fruits and Vegetables. A Research Associate, funded by the Agreement, investigated conditions under which bacteria on the surface of cantaloupe melons exist. Biofilm formation by various isolates of Salmonella on cantaloupe rind surfaces during storage at 10 or 22C was demonstrated using SEM. Biofilm formation occurred rapidly, even at lower inoculum concentrations, thus supporting the hypothesis that this may be responsible for decreased efficacy of aqueous sanitizers following storage of inoculated melons. In a screening of 53 Salmonella strains from various sources for biofilm formation by a crystal-violet
microplate assay, little difference was observed between cantaloupe-related strains and the other isolates examined, but levels of biofilm produced by all isolates were highly variable. It is likely that all Salmonella spp. are able to make biofilm, but the conditions on cantaloupe surfaces stimulate increased production. A few 'high' and 'low' biofilm-formers will be selected to test the hypothesis that increased biofilm formation is related to increased attachment strength and sanitizer resistance on cantaloupe surfaces. The results of these studies will guide the development of improved interventions for disinfecting contaminated melons during packing or fresh-cut processing.
Impacts
(N/A)
Publications
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