Causes
Infectious pathogens commonly associated with mastitis are Staphylococcus aureus, streptococcus spp., gram negative bacilli such as Escherichia coli. Salmonella spp., mycobacteria, candida, and Cryptococcus have been identified in rare instances.
Recent research suggests that infectious pathogens play a much smaller role in the pathogenesis than was commonly assumed only a few years ago. Most detected pathogens are very common species that are natural part of the breast fauna and simple detection of their presence is not sufficient to prove a causative role. Furthermore treatment with antibiotics appears to have minimal impact.
The presence of cracks or sores on the nipples increases the likelihood of infection. Tight clothing or ill-fitting bras may also cause problems as they compress the breasts. There is a possibility that infants carrying infectious pathogens in their noses can infect their mothers; the clinical significance of this finding is still unknown.
Read more about this topic: Puerperal Mastitis