Human breast milk is considered to be of primary importance for the optimal health, growth and development of the infant (1). Aside from its nutritional value, it also contains several bioactive factors that may enhance the infant’s defences (1,2) and protect it against colonizing pathogens (3,4). It has been suggested that commensal and potential probiotic bacterial components present in breast milk may also be involved in the development of the infant’s gastrointestinal mucosal tissues and its acquisition of a healthy gut microbiota (2,5). Mother’s milk is a consistent source of microorgan- isms for the neonatal gut during several weeks after birth, and it is only after the introduction of solid food that the gut microbiota becomes more diverse and begins to resemble that of adults (5). The bacterial species generally found in healthy human breast milk belong to the genera Staphylococcus, Streptococcus, Lactobacillus, Micrococcus, Enterococcus and Bifidobacterium (4, 6). Some of these genera originate from the surface of the nipple and the surrounding skin and may be adapted to survival in the milk ducts in the breast (1,5).
Lactobacilli make up an important part of the healthy human intestinal microbiota and are thought to be involved in the control and maintenance of the microbiota (7). L. reuteri is an indigenous colonizer of the gastrointestinal (GI) tract of humans and animals (7,8). L. reuteri has been demonstrated to have probiotic properties (7, 12) and has previously been found in breast milk of Finnish women (8,13). Growing evidence that lactobacilli colonization at a very early age may protect the infant from develop- ing atopic allergy (14) points to a possible role for a natural supply of lactobacilli in the breast milk as a beneficial factor for the suckling infant.
Little information is available in the literature concerning the presence of lactobacilli, including L. reuteri, in human breast milk. The present study was undertaken to investigate (i) the occurrence of L. reuteri in human breast milk, and (ii) the possible links between the presence of L. reuteri and the mothers’ geographic areas of residence.