The nurse knows that which of the following is not a cause of mastitis?

Choice A rationale Infrequent, inconsistent feedings can lead to milk stasis within the mammary ducts. This stasis provides an ideal environment for bacterial proliferation, typically *Staphylococcus aureus*, which can then ascend the milk ducts from the nipple opening, leading to inflammation and infection of the breast tissue. Choice B rationale Engorgement results from an oversupply of milk that is not effectively removed, causing milk stasis. This creates a warm, nutrient-rich environment for bacteria, often skin flora, to multiply within the stagnant milk, subsequently ascending through the ducts and initiating an inflammatory response, culminating in mastitis. Choice C rationale Cracks or fissures on the nipples compromise the integrity of the skin barrier, allowing for the entry of bacteria, predominantly *Staphylococcus aureus* from the mother's skin or the infant's nasopharynx, directly into the underlying breast tissue. This direct inoculation bypasses the normal protective skin defenses, predisposing to infection. Choice D rationale Gradual weaning allows for a slow reduction in milk production, preventing significant milk stasis. This physiological adaptation minimizes the likelihood of milk accumulation and subsequent bacterial overgrowth, thereby reducing the risk of inflammation and infection in the mammary glands.