The Toxicity Mechanisms of Staphylococcus aureus Exposure in Caenorhabditis elegans

Infectious diseases caused by pathogenic bacteria pose a critical threat to global public health security. However, existing research predominantly focuses on elucidating the acute virulence mechanisms of typical culturable (Wild-Type, WT) pathogenic bacteria, whereas studies on the host infection modes, virulence levels, and pathogenic mechanisms of viable but non-culturable (VBNC) state pathogens are notably lacking. Therefore, this study established a Staphylococcus aureus (S. aureus) (including VBNC state) -Caenorhabditis elegans (C. elegans) infection system. Following infection, S. aureus within exposed nematodes was released via lysis techniques to investigate bacterial state transitions, virulence protein secretion, and virulence gene expression patterns, aiming to elucidate infection mechanisms under distinct bacterial states. Findings of this research revealed that wild-type S. aureus exhibited accelerated proliferation and intestinal colonization in nematodes, accompanied by substantial virulence protein release, triggering acute infection. In contrast, VBNC-state S. aureus displayed significantly reduced reproductive and colonization capacities. Notably, VBNC-state S. aureus underwent resuscitation within the nematode host, achieving a resuscitation rate of 90.4%, representing a sixfold increase compared with natural resuscitation in vitro. Furthermore, wild-type S. aureus subverted host immune defenses through global upregulation of virulence gene expression. Conversely, VBNC-state S. aureus exhibited a distinct pathogenic pattern: delayed virulence gene expression, prioritized activation of biofilm formation-related genes to establish resuscitation conditions, followed by gradual restoration of virulence gene expression through stress response systems, ultimately re-establishing pathogenicity and inducing chronic infection. This unique virulence resuscitation mechanism facilitates VBNC-state S. aureus in maintaining long-term colonization under host immune pressure. Consequently, long-term monitoring of both typical pathogenic bacteria and their VBNC-state counterparts in environmental systems is imperative to prevent potential health risks.