Staphylococcus xylosus is a species of bacteria belonging to the genus Staphylococcus. It is a Gram-positive bacterium that forms clusters of cells. Like most staphylococcal species, it is coagulase-negative and exists as a commensal on the skin of humans and animals and in the environment. It appears to be far more common in animals than in humans.
An unpublished case report in Italy claimed to have found a cluster of a chronic fatigue syndrome-like illness in dogs. They tests positive for two vancomycin-resistant strains of Staphylococcus xylosus. Treatment with thiacetarsamide sodium, an arsenic-based heartworm treatment, resulted in complete remission.