Hi, I had gone through your question and understand your concerns. You should be worried but not too much. This bacteria is a natural inhabitant of the skin, nose, throat, intestine. Sometimes it overgrows (for lack of hygiene, decrease in the natural defense of the body, or having a more agressive mutation of the bacteria) and it produces infection. Most commonly these infections are in the skin but it can affect almost every organ (bone, heart, blood infections, ect), it can cause allergic dermatitis, bronchial asthma. Moderate growth indicates that he has overgrowth and bacterial sinusitis. If I were your treating Doctor for this case of staphylococcus aureus infection , I would come up with three possibilities, these include: 1.The first possibility is of antibiotic therapy according to sensitivity. Try to perform nose and throat culture and sensitivity to antibiotics. The most sensitive are Ciprofloxacin drops 3 times in the nose or 1% Chloramphenicol can be applied in nose cavity. 2.The second possibility is of Staphylococcal bacteriophage 20 ml orally twice a day for 10 days, you can drop it in his nose. 3.The last possibility is of antistaphylococcal immunoglobulin 1 injection intramuscular every alternative day ,3 injections enough. I suggest you to discuss it with his ENT doctor. Hope this answers your question. If you have additional questions or follow up questions then please do not hesitate in writing to us. I will be happy to answer your questions. Wishing you and your son good health.