Relation between probiotic properties of isolates isolated from breast milk and infants’ stools

Breast milk has been hypothesized to be a source of bacteria for the infant gut. This paper aims to search for probiotic bacteria among 415 isolates belonging to the Enterococcus, Lactobacillus, Streptococcus and Bifidobacterium genera recovered from breast milk of 50 lactating mothers and their respective infant stools, and then, determine whether their levels in stools vary with different modalities of breast feeding.

To prove that the isolates were probable probiotics, subtractive screening was done using three major selection criteria, namely, resistance to low pH, tolerance against bile salts and testing for their antimicrobial activity.

The three criteria were fulfilled by 31.7 and 31 per cent of the isolates recovered from mothers’ breast milk and infants’ stool specimens, respectively. The majority of probiotic strains, isolated from milk and infants’ stools were phenotypically identical, suggesting breast milk as their probable source. Moreover, there was a positive correlation between exclusive breast milk feeding and the number of probiotics in the infants’ stools.

Viable bacteria could be retrieved from breast milk of healthy women, not suffering from mastitis, by using different types of media and different cultivation conditions. Up to five different species belonging to the same genus could be isolated in the same specimen of whether milk or stools. Breast milk could be a source of probiotic bacteria for intestinal microflora of infants, which help improvement of infants’ gut and growth.