Evaluation of susceptibility profile of bacteria isolated from conventional and organic fresh produce to disinfectants

• Grant number: 19/07378-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2019
• End date: July 31, 2020
• Field of knowledge: Agronomical Sciences - Food Science and Technology - Food Science
• Principal Investigator: Andrezza Maria Fernandes
• Grantee: Tatiana Yumi Tamanaha
• Host Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil

Abstract

Organic foods are those that are produced without any kind of synthetic input, so issues related to microbiological contamination, nutritional value and sales price are matters still discussed by experts. The microbiological quality of organic foods and the factors influencing it, such as the susceptibility of bacteria to disinfectants, should be investigated so that, if the risks are greater when compared to conventional foods, measures can be developed and applied while ensuring consumer safety. Thus, the objective of this research is to compare the susceptibility profile of bacterial isolates from conventional and organic fresh produce to disinfectants. Three-hundred samples of lettuce and/or arugula will be collected, including 100 conventional, 100 certified and labeled organic, and 100 called organic, but without label. The samples of produce will be purchased at points of sale in the state of São Paulo, including the capital and the countryside. The samplings will be carried out over a period of 10 months. Samples will be subjected to the isolation of Salmonella and E. coli. For each bacterium, three random colonies from each positive sample will be used for the disinfectants susceptibility tests. These colonies will be transferred to tubes containing nutrient broth for the sequence of analysis. If there is a large number of positive samples for both bacteria, the random colonies will be selected from the positive samples, limiting the selection to 20% of the total number of samples (total n 300, maximum n = 60), distributed among the three groups of produce to be sampled, adding up to a maximum of 360 colonies evaluated. The isolated bacteria will be tested for susceptibility to sanitizing agents. Two disinfectants will be evaluated: peracetic acid solution and sodium hypochlorite. For the determination of the susceptibility profile of the isolates to the disinfectants, the minimum inhibitory concentration (MIC) technique will be used. The MIC will be determined as the lowest concentration of a disinfectant agent that prevented the visible growth of the microorganisms. Kaplan-Meier survival curves will be based on three incubation periods (24, 48 and 72 h) for disinfectants. There are no studies investigating the susceptibility profile of bacterial isolates to disinfectants, comparing conventional and organic produce. Thus, this study will help in the knowledge of possible differences between these products.