Biofilm is a community of bacteria embedded in the extracellular matrix that accounts for 80% of bacterial infections. Biofilm enables bacterial cells to provide particular conditions and produce virulence determinants in response to the unavailability of micronutrients and local oxygen, resulting in their resistance to various antibacterial agents. Besides, the human immune reactions are not completely competent in the elimination of biofilm. Most importantly, the growing body of evidence shows that some bacterial spp. use a variety of mechanisms by which hijack the host components to form biofilm. In this regard, host components, such as DNA, hyaluronan, collagen, fibronectin, mucin, oligosaccharide moieties, filamentous polymers (F-actin), plasma, platelets, keratin, sialic acid, laminin, vitronectin, C3- and C4- binding proteins, antibody, proteases, factor I, factor H, and acidic proline-rich proteins have been reviewed. Hence, the characterization of interactions between bacterial biofilm and the host would be critical to effectively address biofilm-associated infections. In this paper, we review the latest information on the hijacking of host factors by bacteria to form biofilm.

Introduction. Staphylococcus epidermidis is predominant in implant-associated infections due to its capability to form biofilms. It can deploy several strategies for biofilm development using either polysaccharide intercellular adhesin (PIA), extracellular DNA (eDNA) and/or proteins, such as the extracellular matrix-binding protein (Embp).Hypothesis/Gap Statement. We hypothesize that the dichotomic regulation of S. epidermidis adhesins is linked to whether it is inside a host or not, and that in vitro biofilm investigations in laboratory media may not reflect actual biofilms in vivo.Aim. We address the importance of PIA and Embp in biofilm grown in \'humanized\' media to understand if these components play different roles in biofilm formation under conditions where bacteria can incorporate host proteins in the biofilm matrix.Methodology. S. epidermidis 1585 WT (deficient in icaADBC), and derivative strains that either lack embp, express embp from an inducible promotor, or express icaADBC from a plasmid, were cultivated in standard laboratory media, or in media with human plasma or serum. The amount, structure, elasticity and antimicrobial penetration of biofilms was quantified to describe structural differences caused by the different matrix components and growth conditions. Finally, we quantified the initiation of biofilms as suspended aggregates in response to host factors to determine how quickly the cells aggregate in response to the host environment and reach a size that protects them from phagocytosis.Results. S. epidermidis 1585 required polysaccharides to form biofilm in laboratory media. However, these observations were not representative of the biofilm phenotype in the presence of human plasma. If human plasma were present, polysaccharides and Embp were redundant for biofilm formation. Biofilms formed in human plasma were loosely attached and existed mostly as suspended aggregates. Aggregation occurred after 2 h of exposing cells to plasma or serum. Despite stark differences in the amount and composition of biofilms formed by polysaccharide-producing and Embp-producing strains in different media, there were no differences in vancomycin penetration or susceptibility.Conclusion. We suggest that the assumed importance of polysaccharides for biofilm formation is an artefact from studying biofilms in laboratory media void of human matrix components. The cell-cell aggregation of S. epidermidis can be activated by host factors without relying on either of the major adhesins, PIA and Embp, indicating a need to revisit the basic question of how S. epidermidis deploys self-produced and host-derived matrix components to form antibiotic-tolerant biofilms in vivo.

Aloperine (1), a Chinese natural product with a unique endocyclic scaffold, was first identified to be a potent hepatitis C virus (HCV) inhibitor in our laboratory. Thirty-four new aloperine derivatives were designed, synthesized and evaluated for their anti-HCV activities taking 1 as the lead. Among them, compound 7f exhibited the potential potency with EC50 values in a micromolar range against both wild-type and direct-acting antiviral agents (DAAs)-resistant variants, and synergistically inhibited HCV replication with approved DAAs. Furthermore, it also owned a good oral pharmacokinetic and safety profile, suggesting a highly druglike nature. The primary mechanism showed that 7f might target host components, distinctly different from the DAAs currently used in clinic. Therefore, we consider aloperine derivatives to be a novel class of anti-HCV agents, and compound 7f has been selected as a promising antiviral candidate for further investigation.