• Adhesion of Staphylococcus aureus to Candida albicans During Co-Infection Promotes Bacterial Dissemination Through the Host Immune Response

      Van Dyck, K.; Viela, F.; Mathelié-Guinlet, M.; Demuyser, L.; Hauben, E.; Jabra-Rizk, M.A.; Vande Velde, G.; Dufrêne, Y.F.; Krom, B.P.; Van Dijck, P. (Frontiers Media S.A., 2021-02-02)
      Interspecies interactions greatly influence the virulence, drug tolerance and ultimately the outcome of polymicrobial biofilm infections. A synergistic interaction is observed between the fungus Candida albicans and the bacterium Staphylococcus aureus. These species are both normal commensals of most healthy humans and co-exist in several niches of the host. However, under certain circumstances, they can cause hospital-acquired infections with high morbidity and mortality rates. Using a mouse model of oral co-infection, we previously showed that an oral infection with C. albicans predisposes to a secondary systemic infection with S. aureus. Here, we unraveled this intriguing mechanism of bacterial dissemination. Using static and dynamic adhesion assays in combination with single-cell force spectroscopy, we identified C. albicans Als1 and Als3 adhesins as the molecular players involved in the interaction with S. aureus and in subsequent bacterial dissemination. Remarkably, we identified the host immune response as a key element required for bacterial dissemination. We found that the level of immunosuppression of the host plays a critical yet paradoxical role in this process. In addition, secretion of candidalysin, the C. albicans peptide responsible for immune activation and cell damage, is required for C. albicans colonization and subsequent bacterial dissemination. The physical interaction with C. albicans enhances bacterial uptake by phagocytic immune cells, thereby enabling an opportunity to disseminate. Copyright 2021 Van Dyck, Viela, Mathelié-Guinlet, Demuyser, Hauben, Jabra-Rizk, Vande Velde, Dufrêne, Krom and Van Dijck.
    • Therapeutic implications of C. albicans-S. aureus mixed biofilm in a murine subcutaneous catheter model of polymicrobial infection

      Vila, T.; Kong, E.F.; Montelongo-Jauregui, D.; Van Dijck, P.; Shetty, A.C.; McCracken, C.; Bruno, V.M.; Jabra-Rizk, M.A. (Bellwether Publishing, Ltd., 2021-03-08)
      Biofilm-associated polymicrobial infections tend to be challenging to treat. Candida albicans and Staphylococcus aureus are leading pathogens due to their ability to form biofilms on medical devices. However, the therapeutic implications of their interactions in a host is largely unexplored. In this study, we used a mouse subcutaneous catheter model for in vivo-grown polymicrobial biofilms to validate our in vitro findings on C. albicans-mediated enhanced S. aureus tolerance to vancomycin in vivo. Comparative assessment of S. aureus recovery from catheters with single- or mixed-species infection demonstrated failure of vancomycin against S. aureus in mice with co-infected catheters. To provide some mechanistic insights, RNA-seq analysis was performed on catheter biofilms to delineate transcriptional modulations during polymicrobial infections. C. albicans induced the activation of the S. aureus biofilm formation network via down-regulation of the lrg operon, repressor of autolysis, and up-regulation of the ica operon and production of polysaccharide intercellular adhesin (PIA), indicating an increase in eDNA production, and extracellular polysaccharide matrix, respectively. Interestingly, virulence factors important for disseminated infections, and superantigen-like proteins were down-regulated during mixed-species infection, whereas capsular polysaccharide genes were up-regulated, signifying a strategy favoring survival, persistence and host immune evasion. In vitro follow-up experiments using DNA enzymatic digestion, lrg operon mutant strains, and confocal scanning microscopy confirmed the role of C. albicans-mediated enhanced eDNA production in mixed-biofilms on S. aureus tolerance to vancomycin. Combined, these findings provide mechanistic insights into the therapeutic implications of interspecies interactions, underscoring the need for novel strategies to overcome limitations of current therapies. Copyright 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.