A nasal swab tests positive for Staphylococcus aureus, but the patient shows no clinical signs of infection. What does this indicate?

• A. Colonization
• B. Contamination
• C. Latent infection
• D. Active infection

Answer: (A)

Carrying Staphylococcus aureus in the nose without any illness means the person is colonized with the organism. Colonization is when microbes are present on a body site but not causing disease or symptoms. The nose is a common site for S. aureus carriage, and carriers can still transmit the organism to others or potentially develop an infection later if the barrier is breached, but at this moment there are no signs of infection. This interpretation is distinct from contamination (a sampling error) and from latent infection or active infection (which would involve symptoms or disease).