Deletion of impairs biofilm formation, generation of viable but non-culturable cells and stimulates cytokine production in human macrophages.

biofilms are one of the major causes of bloodstream infections related to the use of medical devices. The diagnosis of these infections is challenging, delaying their treatment and resulting in increased morbidity and mortality rates. As such, it is urgent to characterize the mechanisms employed by this bacterium to endure antibiotic treatments and the response of the host immune system, to develop more effective therapeutic strategies. In several bacterial species, the gene was shown to encode a protein that regulates the expression of genes involved in biofilm formation and immune evasion. Additionally, in a previous study, our group generated evidence indicating that is involved in the emergence of viable but non-culturable (VBNC) cells in . As such, we hypothesized that the gene codY has have an important role in this bacterium virulence. This study aimed to assess, for the first time, the impact of the deletion of the gene in virulence, namely, in antibiotic susceptibility, biofilm formation, VBNC state emergence and host immune system response. Using an allelic replacement strategy, we constructed and then characterized an strain lacking in regards to biofilm and VBNC cell formation, susceptibility to antibiotics as well as their role in the interaction with human blood and plasma. Additionally, we investigate whether the gene can impact the activation of innate immune cells by evaluating the production of both pro- and anti-inflammatory cytokines by THP-1 macrophages. We demonstrated that the deletion of the gene resulted in biofilms with less c.f.u. counts and fewer VBNC cells. Furthermore, we show that although WT and mutant cells were similarly internalized by human macrophages, a stronger cytokine response was elicited by the mutant in a toll-like receptor 4-dependent manner. Our results indicate that contributes to virulence, which in turn may have an impact on our ability to manage the biofilm-associated infections caused by this bacterium.