Antimicrobial Activity Versus Virulence Potential of Hyaluronic Acid: Balancing Advantages and Disadvantages.

Hyaluronic acid (HA) is a ubiquitous glycosaminoglycan essential for maintaining tissue hydration, structural integrity, and immunological homeostasis in vertebrates. Although traditionally regarded as a host-derived molecule, HA is also produced by a range of microorganisms, most notably Streptococcus spp., through specialized hyaluronan synthases (HAS). Microbial HA and host-derived HA fragments play key roles not only in tissue physiology but also in infection biology, influencing microbial virulence, biofilm formation, and immune evasion. In bacteria, HA-rich capsules promote adhesion, shield pathogens from complement-mediated opsonization and phagocytosis, and facilitate dissemination through host tissues. Conversely, HA-degrading enzymes and reactive oxygen species generate low-molecular-weight HA fragments that amplify inflammation by activating-toll-like receptor 2 (TLR2)/toll-like receptor 4 (TLR4) signaling, contributing to chronic inflammatory states. Furthermore, microbial HA modulates biofilm organization in both bacterial and fungal pathogens, enhancing persistence and antimicrobial tolerance. Clinically, widespread use of HA-based dermal fillers has generated increasing concern over delayed biofilm-associated infections, diagnostic challenges, and complications arising from microbial contamination and host-microbe interactions. Recent advances in HA engineering, including anti-microbial HA conjugates and receptor-targeted biomaterials, offer promising strategies to mitigate infection risk while expanding therapeutic applications. This review synthesizes current knowledge on HA biosynthesis across biological kingdoms, its dualistic role in health and disease, and its emerging relevance at the interface of microbiology, immunology, and biomedical applications.