Utilization of Galleria mellonella larvae to characterize the development of Staphylococcus aureus infection.

Abstract

Staphylococcus aureus is a human opportunistic pathogen that causes a wide range of superficial and systemic infections in susceptible patients. Here we describe how an inoculum of S. aureus activates the cellular and humoral response of Galleria mellonella larvae while growing and disseminating throughout the host, forming nodules and ultimately killing the host. An inoculum of S. aureus (2×106 larva- 1 ) decreased larval viability at 24 (80±5.77\u200a%), 48 (55.93±5.55\u200a%) and 72 h (10.23±2.97\u200a%) and was accompanied by significant proliferation and dissemination of S. aureus between 6 and 48\u2009h and the formation of nodules in the host. The hemocyte (immune cell) densities increased between 4 and 24\u2009h and hemocytes isolated from larvae after 24\u2009h exposure to heat-killed S. aureus (2×106 larva- 1 ) showed altered killing kinetics as compared to those from control larvae. Alterations in the humoral immune response of larvae 6 and 24\u2009h post-infection were also determined by quantitative shotgun proteomics. The proteome of 6\u2009h-infected larvae was enriched for antimicrobial proteins, proteins of the prophenoloxidase cascade and a range of peptidoglycan recognition proteins. By 24\u2009h there was a significant increase in the abundance of a range of antimicrobial peptides with anti-staphylococcal activity and proteins associated with nodule formation. The results presented here indicate how S. aureus interacts with the larval immune response, induces the expression of a variety of immune-related peptides and also forms nodules which are a hallmark of soft tissue infections during human infection.