i believe the answer is commensalistic symbiosis
The presence of stapylococcus aureus in skin as normal flora doesn't give the human host any benefit, while stapylococcus aureus could find food on the human skin. Since only one side has got the profit, the symbiosis would be called commensalistic symbiosis. It was different for the normal flora inside the intestine because the host got some benefit, thus it was mutualistic symbiosis.