Abstract
Salmonella Typhimurium is a facultative, intracellular pathogen whose products range from self-limited gastroenteritis to systemic diseases. Food ingestion increases biomolecules’ concentration in the intestinal lumen, including amino acids such as cysteine, which is toxic in a concentration-dependent manner. When cysteine’s intracellular concentration reaches toxic levels, S. Typhimurium expresses a cysteine-inducible enzyme (CdsH), which converts cysteine into pyruvate, sulfide, and ammonia. Despite this evidence, the biological context of cdsH’s role is not completely clear, especially in the infective cycle. Since inside epithelial cells both cdsH and its positive regulator, ybaO, are overexpressed, we hypothesized a possible role of cdsH in the intestinal phase of the infection. To test this hypothesis, we used an in vitro model of HT-29 cell infection, adding extra cysteine to the culture medium during the infective process. We observed that, at 6 h post-invasion, the wild type S. Typhimurium proliferated 30% more than the ΔcdsH strain in the presence of extra cysteine. This result shows that cdsH contributes to the bacterial replication in the intracellular environment in increased concentrations of extracellular cysteine, strongly suggesting that cdsH participates by increasing the bacterial fitness in the intestinal phase of the S. Typhimurium infection.
Highlights
Salmonellosis corresponds to one of the most common food diseases, affecting an estimated ten million people annually, with more than 100.000 deaths worldwide
The infection begins with the consumption of contaminated food or water, where bacteria reach the distal ileum and induce their internalization into epithelial cells and M cells, among others, in the so-called intestinal phase of the infection [2]
Salmonella is an enteric pathogen that produces a wide variety of diseases, from self-limited gastroenteritis to systemic infections and death
Summary
Salmonellosis corresponds to one of the most common food diseases, affecting an estimated ten million people annually, with more than 100.000 deaths worldwide. The disease symptoms are noticeable between 6 and 72 h after consuming Salmonella, with a duration of 2–7 days [1]. Typhimurium) is one of the most relevant etiologic agents of salmonellosis. The infection begins with the consumption of contaminated food or water, where bacteria reach the distal ileum and induce their internalization into epithelial cells and M cells, among others, in the so-called intestinal phase of the infection [2]. S. Typhimurium produces self-limited gastroenteritis in healthy humans at this phase, whereas, in immunosuppressed individuals, children, and older adults, it can cause bacteriemia, or even a systemic infection in certain particular cases [3]
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