The classification level of "aureus" for the organism *Staphylococcus aureus* is species.

Here's why:

* Staphylococcus is the genus name, a group of closely related bacteria.

* aureus is the species name, differentiating this specific type of staphylococcus from others like *Staphylococcus epidermidis*.

So, the full scientific name is *Staphylococcus aureus*, combining the genus and species names.