Abstract Background Staphylococcus aureusstrains with distinct genetic backgrounds have shown different virulence in animal models as well as associations with different clinical outcomes, such as causing infection in the hospital or the community. With S. aureusstrains carrying diverse genetic backgrounds that have been demonstrated by gene typing and genomic sequences, it is difficult to compare these strains using mammalian models. Invertebrate host models provide a useful alternative approach for studying bacterial pathogenesis in mammals since they have conserved innate immune systems of biological defense. Here, we employed Drosophila melanogasteras a host model for studying the virulence of S. aureusstrains. Results
S. aureus(CA-MRSA) strains USA300, USA400 and CMRSA2 were more virulent than a hospital-associated (HA)-MRSA strain (CMRSA6) and a colonization strain (M92) in the D. melanogastermodel. These results correlate with bacterial virulence in the Caenorhabditis eleganshost model as well as human clinical data. Moreover, MRSA killing activities in the D. melanogastermodel are associated with bacterial replication within the flies. Different MRSA strains induced similar host responses in D. melanogaster, but demonstrated differential expression of common bacterial virulence factors, which may account for the different killing activities in the model. In addition, hemolysin α, an important virulence factor produced by S. aureusin human infections is postulated to play a role in the fly killing. Conclusions
Our results demonstrate that the
D. melanogastermodel is potentially useful for studying S. aureuspathogenicity. Different MRSA strains demonstrated diverse virulence in the D. melanogastermodel, which may be the result of differing expression of bacterial virulence factors in vivo.