Abstract
Salmonella can resist various stresses and survive during food processing, storage, and distribution, resulting in potential health risks to consumers. Therefore, evaluation of bacterial survival profiles under various environmental stresses is necessary. In this study, the resistance profiles of five Salmonella isolates [serotypes with Agona, Infantis, Typhimurium, Enteritidis, and a standard strain (ATCC 13076, Enteritidis serotype)] to acidic, hyperosmotic, and oxidative stresses were examined, and the relative expressions of non-coding small RNAs were also evaluated, including CyaR, MicC, MicA, InvR, RybB, and DsrA, induced by specific stresses. The results indicated that although all tested strains displayed a certain resistance to stresses, there was great diversity in stress resistance among the strains. According to the reduction numbers of cells exposed to stress for 3 h, S. Enteritidis showed the highest resistance to acidic and hyperosmotic stresses, whereas ATCC 13076 showed the greatest resistance to oxidative stress, with less than 0.1 Log CFU/ml of cell reduction. Greater resistance of cells to acidic, hyperosmotic, and oxidative stresses was observed within 1 h, after 2 h, and from 1 to 2 h, respectively. The relative expression of sRNAs depended on the isolate for each stress; acidic exposure for the tested isolates induced high expression levels of DsrA, MicC, InvR, RybB, MicA, and CyaR. The sRNA RybB, associated with sigma E and outer membrane protein in bacteria, showed a fold change of greater than 7 in S. Enteritidis exposed to the tested stresses. CyaR and InvR involved in general stress responses and stress adaptation were also induced to show high expression levels of Salmonella exposed to hyperosmotic stress. Overall, these findings demonstrated that the behaviors of Salmonella under specific stresses varied according to strain and were likely not related to other profiles. The finding also provided insights into the survival of Salmonella subjected to short-term stresses and for controlling Salmonella in the food industry.
Highlights
IntroductionMainly caused by ingestion of water and food contaminated by microorganisms, have become a global health concern
Foodborne diseases, mainly caused by ingestion of water and food contaminated by microorganisms, have become a global health concern
Salmonella can cause a wide range of human diseases, including gastroenteritis and septicemia, and is the leading cause of food poisoning associated with foodborne pathogens, resulting in millions of recalls and outbreaks
Summary
Mainly caused by ingestion of water and food contaminated by microorganisms, have become a global health concern. Many strategies and disinfectants, such as good hygiene and handling practices, chlorite-based sanitizers, and salt-cured processes, have been applied to avoid and/or reduce bacterial contamination in the food industry (Khan et al, 2017; Yoon and Lee, 2018); these harsh conditions represent serious stresses to microorganisms surviving in the corresponding surroundings. When encountering these stresses, most bacteria are rapidly injured and killed, whereas some of the cells survive by triggering adaptive cell responses to specific environmental stresses; when bacteria are not inactivated by environmental stresses, they may adapt in response to various environmental challenges or stresses, and become more persistent strains. Besides the numbers of survival cells, the intracellular profiles were altered by the stresses (Begley and Hill, 2015; Wang et al, 2016; Pradhan and Negi, 2019)
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