| Congresso Brasileiro de Microbiologia 2023 | Resumo: 643-1 | ||||
Resumo:Salmonella enterica represents a pathogen of great global importance for public health. In recent years, outbreaks involving S. enterica in coconut products have attracted the attention of authorities. However, there is a lack of information in the literature related to physiological state of S. enterica in dehydrated coconut-flakes during storage. The purpose of work was to measure DNA damage and membrane integrity of S. enterica in conventionally and osmotically dehydrated coconut-flakes stored at 25 °C using flow cytometry. A five-strain cocktail of S. enterica serovars (S. Muenster, S. Bredeney, S. Agona, S. Enteritidis and S. Typhimurium; ~7.0 log CFU/g) was inoculated in coconut-flakes (4 x 1 mm) and subsequently submitted to conventional (55 °C/6h) or osmotic (40% sucrose/50 °C/3h followed by 55 °C/6h) dehydration. Dehydrated coconut-flakes samples were packed in biaxially oriented polypropylene bags and storage in a desiccator at 25 °C with a saturated magnesium chloride salt solution (aw 0.34) for 120-days. 1-day after dehydration and after 120 days, cells were harvested (4500 g x 10 min, 4 °C), washed twice and re-suspended in PBS and double-labeled with propidium iodide (PI) and thiazole orange (TO). Damaged subpopulations were measured using flow cytometry. Statistical significance was considered for p values <0.05. The 120-days-storage of coconut-flakes (conventionally dehydrated) caused an increase (p < 0.05) of 6.1% in the population of cells with DNA damage (from 72 to 78.1%) and 1 % in cells with permeabilized membrane and DNA damage (from 1 to 2%). In contrast, after 120-days-storage of coconut-flakes (osmotically dehydrated) an increase (p < 0.05) of 10% in the population of cells with DNA damage (from 81.1 to 91.1%) was observed while the population of permeabilized cells with DNA damage did not change (p > 0.05). Exposure of a cell population to stress conditions can cause the appearance of different cell populations and, in particular, of sub-lethally compromised cells. The higher population of non-permeabilized cells with DNA damage identified after osmotic-dehydration compared to conventional-dehydration may be associated with more severe stress conditions. The data demonstrate that osmotic-dehydration is the method that causes the greatest damage to the S. enterica cells during storage. Palavras-chave: Salmonella enterica, coconut flakes, flow cytometry, damaged subpopulations | |||||