Prenatal versus Postnatal Initial Colonization of Healthy Neonates' Colon Ecosystem by the Enterobacterium Escherichia coli.

The human colon is a microbial ecosystem whose initial bacterial colonization in neonates is an important step in establishing a beneficial microbiota for the body's health. This study investigated the occurrence of viable culturable Escherichia coli in first-day meconium versus subsequent days' stool to explore the prenatal versus postnatal initial colonization of the colon by E. coli in healthy neonates. E. coli occurrence was investigated on eosin-methylene blue (EMB) agar, followed by morphological and biochemical characterizations and phylogenetic analysis of 16S rRNA-encoding gene sequences. Viable culturable E. coli was not detected in meconium of healthy male or female neonates delivered either vaginally or by cesarean section. Neonates delivered surgically also showed no E. coli colonization on the second and third days, confirming postnatal colonization of the colon by this enterobacterium. E. coli's initial colonization in the colon of neonates delivered vaginally occurred on the second day, which can be attributed to inoculation from the vaginal canal during delivery and, in comparison to the colonization in neonates delivered surgically, leads to the inference that the bacterium is not originally found in meconium. This study suggests no viability of the meconium microbiome in healthy neonates, possibly due to antimicrobial action in the prenatal colon's meconium protecting babies' gut from infection during delivery. IMPORTANCE The results of this study suggest that the initial postnatal colonization of neonates' colon by beneficial bacteria is a naturally controlled process in which the prenatal colon's meconium might play a role in protecting against infection of the babies' gut during delivery.

Enterococcus faecalis Is a Better Competitor Than Other Lactic Acid Bacteria in the Initial Colonization of Colon of Healthy Newborn Babies at First Week of Their Life.

Initial colonization of human gut by bacteria is an important step in controlling its microbiota and health status. This study followed the initial colonization by lactic acid bacteria (LAB) in colon of new born babies through following its occurrence in their stool at first week of their life. The LAB occurrence in the neonates' stool was followed on MRS agar medium. The isolated LAB from male and female newborn babies of normal birth and cesarean section surgical delivery were molecular biologically identified by phylogenetic analysis of 16S rRNA gene sequence. From the 24 investigated newborn babies, three LAB taxa, Lactobacillaceae, Enterococcus, and Streptococcus, were detected in their stool at first week of their life. Lactobacillaceae represented 20.8% of total colonized LAB in newborn babies in the culture-dependent approach used in this study and included three species namely Limosilactobacillus reuteri (previously known as Lactobacillus reuteri), Lacticaseibacillus rhamnosus (previously known as Lactobacillus rhamnosus) and Ligilactobacillus agilis (previously known as Lactobacillus agilis). Enterococcus faecalis and E. faecium were detected where E. faecalis was the highest dominant, representing 62.5% of total LAB colonizing newborn babies. This result suggests that this bacterium has high potency for colonization and might be important for controlling the initial settlement of microbiota in healthy newborn babies. Only one species of Streptococcus namely Streptococcus agalactiae was detected in 8.33% total of the investigated newborn babies indicating high competency by other LAB for colonization and that this bacteria, in spite of its pathogenicity, is commensal in its low existence in healthy babies. The explored potency of natural initial colonization of the LAB species E. faecalis, E. faecium, L. reuteri, L. rhamnosus, and L. agilis of which many health beneficial strains were previously reported, would be important for future applications. Despite the controversy in evaluating its health benefits, E. faecalis as a potent competitor to other LAB refers to its importance in initial colonization of healthy babies colon at first week of their life. Further future studies, with more number of samples and characterization, would be of importance for evaluating the potential use of beneficial Enterococcus strains which could improve intestinal ecosystem.