Bacterial flora in human milk in health and disease

Abstract

Backgroundthe presence of bacteria in breast milk of lactating women was described more than 30 years ago and it was assumed that the cause was contamination of specimens from the mothers’ skin and infants’ mouths (Gavin & Ostovr 1977). A recent Swedish study showed that many healthy women harbour potential pathogens in their breast milk at similar concentrations to those with mastitis (Kvist et al, 2008). New methods of DNA sequencing of bacteria will revolutionize our understanding of the bacterial content of human milk. New knowledge must either be synthesized with the old or replace it.Aimto provide a synthesis and a comparison of findings from recent empirical research on microbial content of human breast milk in healthy women and women with mastitis in order to clarify present day knowledge.Methoda synthesis of the literature regarding bacterial content of breast milk from healthy women and women with mastitis, published between 1990 and 2010. This resulted in an analysis of milk from 844 healthy women and 624 women with mastitis.Findingsseven articles reported bacterial content in breast milk from healthy women, four reported findings from women with symptoms of mastitis and one study reported on bacterial content of milk from both groups. The isolate most commonly found in women with mastitis was S. epidermis (45.5%) and in healthy women the most common bacterial isolate was CNS (77.4%). S.aureus was reported in 5.1% of women with mastitis.Conclusionsa bacterial flora appears to exist in all breast milk. It is unclear why reports of sterile breast milk occur in the literature from time to time. The results of this synthesis challenge the conventional claim, that S. aureus is the most common cause of lactational mastitis.