An outbreak of sepsis caused by Staphylococcus aureus has occurred in the newborn nursery. According to your knowledge of the normal flora, what is the most likely source of the bacteria?

• A. Colon
• B. Nose
• C. Throat
• D. Vagina

Answer: (B)

Staphylococcus aureus is a common inhabitant of the skin and mucous membranes, with the anterior nares (the inside of the nose) being the most important reservoir. Nasal carriage is relatively common and often persistent, and carriers can spread the bacteria to others via hands and contaminated surfaces. In a newborn nursery, that nasal reservoir among staff and caregivers is the most likely source of transmission leading to sepsis in neonates. While S. aureus can be found on skin, throat, or other sites, the nose stands out as the primary source of carriage. The vagina is more associated with other pathogens in neonatal infections, not the typical reservoir for S. aureus outbreaks.