Role of the LytSR Two-Component Regulatory System in Staphylococcus lugdunensis Biofilm Formation and Pathogenesis

Abstract

Staphylococcus lugdunensis is a coagulase negative Staphylococcus recognized as a virulent pathogen. It is responsible for a wide variety of infections, some of which are associated with biofilm production, such as implanted medical device infections or endocarditis. However, little is known about S. lugdunensis regulation of virulence factor expression. Two-component regulatory systems (TCS) play a critical role in bacterial adaptation, survival, and virulence. Among them, LytSR is widely conserved but has variable roles in different organisms, all connected to metabolism or cell death and lysis occurring during biofilm development. Therefore, we investigated here the functions of LytSR in S. lugdunensis pathogenesis. Deletion of lytSR in S. lugdunensis DSM 4804 strain did not alter either susceptibility to Triton X-100 induced autolysis or death induced by antibiotics targeting cell wall synthesis. Interestingly, ΔlytSR biofilm was characterized by a lower biomass, a lack of tower structures, and a higher rate of dead cells compared to the wild-type strain. Virulence toward Caenorhabditis elegans using a slow-killing assay was significantly reduced for the mutant compared to the wild-type strain. By contrast, the deletion of lytSR had no effect on the cytotoxicity of S. lugdunensis toward the human keratinocyte cell line HaCaT. Transcriptional analyses conducted at mid-and late-exponential phases showed that lytSR deletion affected the expression of 286 genes. Most of them were involved in basic functions such as the metabolism of amino acids, carbohydrates, and nucleotides. Furthermore, LytSR appeared to be involved in the regulation of genes encoding known or putative virulence and colonization factors, including the fibrinogen-binding protein Fbl, the major autolysin AtlL, and the type VII secretion system. Overall, our data suggest that the LytSR TCS is implicated in S. lugdunensis pathogenesis, through its involvement in biofilm formation and potentially by the control of genes encoding putative virulence factors.

Application of Conventional Techniques for the Diagnosis of <i>Staphylococcus lugdunensis </i>in Clinical Microbiology

“…[2][3][4] Regarding the characteristics of the culture, it should be noted that Staphylococcus lugdunensis usually manifests as a generally heterogeneous culture, with different colony sizes, and different expression of β-hemolysis; the extension of the incubation time to 48-72 h allows to observe much more homogeneous colonies that present a more typical appearance; these colonies are yellowish-white, creamy, and with a small halo of β-hemolysis (unlike the broader βhemolysis of S. aureus). [9][10][11][12][13] Related to the production of biofilms, the authors agree with what was obtained by other researchers, [11,12] since there was a biofilm production within 6 h after culture and highly consistent not appreciated in other staphylococci. Concerning biofilm production it should be noted, bacteria can respond rapidly to unfavorable or stressful environmental conditions by reducing their metabolic activity, altering their gene expression or inducing changes, entering a state of torpor.…”

“…However, it should be noted that the reaction produced by S. lugdunensis is later and weaker than that produced by S. aureus. [8][9][10][11][12][13][14] Although the sensitivity of coagulase-negative staphylococci to antibiotics is unpredictable, and depends mainly on the species and the origin of the isolated strain (hospital or out-ofhospital environment). The usual, to date, in S. lugdunensis is its sensitivity to all groups of antibiotics used in the treatment of staphylococcal infections, including penicillins, which is consistent with the literature consulted, [8][9][10][11][12] Since similar results were obtained in this study, as the production of βlactamase was negative, the isolated strains were sensitive to most of the antimicrobials used, including penicillins.…”

Inactivation of the Response Regulator AgrA Has a Pleiotropic Effect on Biofilm Formation, Pathogenesis and Stress Response in Staphylococcus lugdunensis

“…In this context, the regulation of immune system evasion and stress response mechanisms orchestrated by transcriptional regulators constitutes the keys to explain the ambivalence of this species. LytSR is the only regulatory system that has been experimentally studied in S. lugdunensis ( 18 ). This two-component system appeared implicated in pathogenesis likely due to its involvement in biofilm formation and the control of the transcription of virulence factors such as fibrinogen-binding protein (Fbl), autolysin (Atl), and the type VII secretion system ( 18 ).…”

“…LytSR is the only regulatory system that has been experimentally studied in S. lugdunensis ( 18 ). This two-component system appeared implicated in pathogenesis likely due to its involvement in biofilm formation and the control of the transcription of virulence factors such as fibrinogen-binding protein (Fbl), autolysin (Atl), and the type VII secretion system ( 18 ). The agr locus of S. lugdunensis has a genomic organization similar to that of S. aureus , with 63% sequence homology, and with a highly conserved intergenic region comprising the P2 and P3 promoters ( 19 ).…”

Phenotypic and proteomic approaches of the response to iron-limited condition in Staphylococcus lugdunensis

“…However, the ability to adapt and to cope with stresses are important for the virulence of opportunistic pathogens. In response to environmental stimuli, regulatory cascades leads to a fine-tuning of metabolic and virulence genes expression [ 9 , 10 ]. Among Omics technologies, proteomics occupies a strategic place because it deals with enzymes which are the true effectors of the cellular physiology.…”