Background: It is difficult to permanently change the composition of the complex intestinal microflora of the adult. Orally administered probiotic bacteria produce only temporary colonization of the intestine in patients with a fully developed gut microflora. The gastrointestinal tract of a healthy fetus is sterile. During the birth process and rapidly thereafter, microbes from the mother and the surrounding environment colonize the gastrointestinal tract until a dense, complex microflora develops. Probiotic bacteria have been shown to beneficially influence the intestinal and systemic immune system and mediate protection against nosocomial infections affecting the neonate.
Objectives: The purpose of this study was to determine whether oral administration of the probiotic micro-organism Lactobacillus rhamnosus strain GG (L. GG) to the pregnant woman leads to colonization of the newborn infant.
Methods: The authors identified six women who were taking L. GG during late pregnancy. None of the children received L. GG after birth, and their mothers discontinued its consumption at the time of delivery. L. GG concentration in fecal samples was determined by colony morphology and molecular analysis.
Results: In all four children delivered vaginally and in one of two children delivered by cesarean section, L. GG was present in fecal samples at 1 and 6 months of age. Three children remained colonized for at least 12 months, and in two children L. GG was detected in fecal samples at 24 months of age. Three mothers were tested 1 month post partum and no L. GG was present in fecal samples. No L. GG was found in one of these women 24 months post partum. There was no L. GG detectable in stools of the siblings of two children at the 2-year and 3-years after birth of the index child. L. GG was not isolated from the stools of children whose mothers were not taking L. GG.
Conclusions: Temporary colonization of an infant with L. GG may be possible by colonizing the pregnant mother before delivery. Colonization is stable for as long as 6 months, and in unexplained circumstances may persist for as long as 24 months.
In recent years, the prevalence of chronic diseases such as atopy (1,2) and chronic intestinal inflammation (IBD) is increasing in the Western world (3). Although there is a strong hereditary component in the development of these diseases, heredity cannot entirely account for the recent increases seen (4). There is little consistent evidence that risk factors such as increased exposure to indoor allergens or pollution are solely responsible for the increase in atopic diseases. It has been suggested that a high turnover of the appropriate bacteria provides a potent, continuous immune stimulation necessary to prevent atopic diseases (5-10,44). It is interesting therefore to note that longitudinal studies of the gut microflora of Pakistani infants (low prevalence of allergies) and Swedish infants (higher prevalence of allergies) show that most infants in both countries harbor various Escherichia coli strains; however, Pakistani infants were colonized earlier and more frequently by new E. coli strains while the strains in the microflora of Swedish infants were stable for months and years (11-13). The influence of modern hygiene on IBD has been demonstrated by a clear connection between family size, the access to hot water, and an indoor toilet (3,14,15). Using animal models, the central role of the intestinal microflora in the development of IBD is even more evident. Experimental murine colitis does not occur in any of several mutant strains when they are maintained in a germ-free environment but develops rapidly when these mice are colonized by commensal bacteria (16). Although the immune system is functional at birth, it is thought that increased hygienic standards, by depriving the neonate of the immune stimulus of microbial infection, may produce an imbalance among the different components of the immune system and result in chronic inflammatory or atopic disorders (17-20,45).
The acquisition of the gut microflora by neonates has been studied thoroughly (21). During and shortly after birth, infants born vaginally are exposed mainly to microbes that originate from the mother (22-24). Infants delivered by cesarean section acquire intestinal flora mainly from the environment but also, as pointed out by Lennox-King et al. (25), from the fecal microbial strains of their mothers. The proximity of the birth canal and the anus, as well as intimate parental care of the neonate ensure transmission of microbes from mother to child.
Feeding type also influences infant gut colonization. Human milk is thought to create an environment favorable for the growth of bifidobacteria; however, study results are conflicting. Within the first month, bifidobacteria levels are equal in both breast milk and formula groups (26). However, the populations of bacteroides and lactobacilli do not appear to be influenced by feeding type (27). Furthermore, it has long been known that breastfeeding protects the infant against various infectious diseases (19,28,29).
The purpose of this study was to determine if oral administration of the probiotic micro-organism Lactobacillus rhamnosus strain GG (L. GG) colonizes the maternal gastrointestinal tract during late pregnancy and whether it results in colonization the infant.