Expressed human milk contains which of the following?

• A. A variety of pathogenic bacteria only
• B. A variety of normal skin flora
• C. No organisms due to rapid cooling
• D. Only human cells

Answer: (B)

Expressed human milk is not sterile; it contains a mix of cells and microbes that come from the mother's breast and skin. The nipple and surrounding skin contribute normal skin flora to the milk, so freshly expressed milk typically has a variety of commensal bacteria. Cooling or storing milk slows bacterial growth but does not eliminate all organisms, so milk can still contain microbes after cooling. It also isn’t made up only of human cells; bacteria are part of its composition too. Therefore, a variety of normal skin flora best explains what expressed human milk contains.