Transcriptional profiling of Salmonella enterica serovar Enteritidis exposed to ethanolic extract of organic cranberry pomace

Abstract

Non-typhoidal Salmonella enterica serovars continue to be an important food safety issue worldwide. Cranberry ( Vaccinium macrocarpon Ait ) fruits possess antimicrobial properties due to their various acids and phenolic compounds; however, the underlying mechanism of actions is poorly understood. We evaluated the effects of cranberry extracts on the growth rate of Salmonella enterica serovars Typhimurium, Enteritidis and Heidelberg and on the transcriptomic profile of Salmonella Enteritidis to gain insight into phenotypic and transcriptional changes induced by cranberry extracts on this pathogen. An ethanolic extract from cranberry pomaces (KCOH) and two of its sub-fractions, anthocyanins (CRFa20) and non-anthocyanin polyphenols (CRFp85), were used. The minimum inhibitory (MICs) and bactericidal (MBCs) concentrations of these fractions against tested pathogens were obtained using the broth micro-dilution method according to the Clinical Laboratory Standard Institute’s guidelines. Transcriptional profiles of S . Enteritidis grown in cation-adjusted Mueller-Hinton broth supplemented with or without 2 or 4 mg/ml of KCOH were compared by RNASeq to reveal gene modulations serving as markers for biological activity. The MIC and MBC values of KCOH were 8 and 16 mg/mL, respectively, against all tested S . enterica isolates. The MIC value was 4 mg/mL for both CRFa20 and CRFp85 sub-fractions, and a reduced MBC value was obtained for CRFp85 (4 mg/ml). Treatment of S . Enteritidis with KCOH revealed a concentration-dependent transcriptional signature. Compared to the control, 2 mg/ml of KCOH exposure resulted in 89 differentially expressed genes (DEGs), of which 53 and 36 were downregulated and upregulated, respectively. The upregulated genes included those involved in citrate metabolism, enterobactin synthesis and transport, and virulence. Exposure to 4 mg/ml KCOH led to the modulated expression of 376 genes, of which 233 were downregulated and 143 upregulated, which is 4.2 times more DEGs than from exposure to 2 mg/ml KCOH. The downregulated genes were related to flagellar motility, Salmonella Pathogenicity Island-1 (SPI-1), cell wall/membrane biogenesis, and transcription. Moreover, genes involved in energy production and conversion, carbohydrate transport and metabolism, and coenzyme transport and metabolism were upregulated during exposure to 4 mg/ml KCOH. Overall, 57 genes were differentially expressed (48 downregulated and 9 upregulated) in response to both concentrations. Both concentrations of KCOH downregulated expression of hilA , which is a major SPI-1 transcriptional regulator. This study provides information on the response of Salmonella exposed to cranberry extracts, which could be used in the control of this important foodborne pathogen.

Alginate-, Carboxymethyl Cellulose-, and κ-Carrageenan-Based Microparticles as Storage Vehicles for Cranberry Extract

“…Fruits of large cranberry and their preserves (juices, infusions, teas, and pomace) are readily consumed as functional food due to their broad spectrum of properties that are beneficial for health, such as reduced risk of cancers [ 11 ] and cardiovascular diseases [ 12 ], general antimicrobial activity [ 13 ], and specific antimicrobial activity towards pathogens in the urinal tract (inhibits bacterial adhesion) [ 14 ], as well as antimutagenic, anti-inflammatory, and anti-hypercholesterolemic activities [ 15 ]. Additionally, large cranberry fruit juice has been used to treat digestive tract disorders [ 11 ].…”

Transcriptomic Analysis, Motility and Biofilm Formation Characteristics of Salmonella typhimurium Exposed to Benzyl Isothiocyanate Treatment

“…With the development of genome technologies, the study of S. typhimurium by transcriptome analysis is increasing. Das et al studied transcriptome changes of S. typhimurium after treatment with cranberry extract and found that the expression of several pathogenicity-related genes, including ssaT on virulence island II, were significantly downregulated [22]. SPI2, which encodes T3SS2, plays an important role in the survival and pathogenicity of S. typhimurium in host cells [31][32][33].…”

“…For example, the effects of cranberry extract and antimicrobial proteins on the growth rates and transcriptomics of S. typhimurium were investigated. The expressions of related genes, such as those involved in iron acquisition, flagella, energy metabolism, pathogenicity, virulence islands and the cell membrane, were significantly downregulated after bacteriostatic treatment in S. typhimurium [22,23]. According to Song et al and Wang et al [24,25], the transcriptome was used to explore the mechanism of antibacterial activity of BITC on Vibrio parahaemolyticus and Staphylococcus aureus.…”

Oligosaccharides and Complex Carbohydrates: A New Paradigm for Cranberry Bioactivity

“…Unless the material used in any given study was fully purified and structurally characterized by NMR spectroscopy, it must be assumed that multiple components beyond those discussed by the researchers could be contributing to the observed biological effects, including oligosaccharides and other compounds. In spite of this, many studies continue to attribute observed biological effects primarily to polyphenols, flavonoids, and other phenolic compounds [132,149,155,288,308]. Some studies have even directly reported carbohydrate contents as high as 95% for their materials and yet still discuss their results in the context of the more readily detectable and more frequently characterized anthocyanins, flavonols, organic acids, and PACs [308].…”

“…In spite of this, many studies continue to attribute observed biological effects primarily to polyphenols, flavonoids, and other phenolic compounds [132,149,155,288,308]. Some studies have even directly reported carbohydrate contents as high as 95% for their materials and yet still discuss their results in the context of the more readily detectable and more frequently characterized anthocyanins, flavonols, organic acids, and PACs [308]. This type of bias towards flavonoids and polyphenolic compounds as the primary significant biological components of cranberries may predispose other researchers to avoid considering additional possible explanations for their results and further delay overall progress for future investigations of cranberry bioactivity.…”