Background: The microbiota of human plays an important role in the health improvement, and found abundant in the
gastrointestinal tract. In recent years, probiotics have been increasingly used in prevention of certain intestinal diseases. The
most important population to study the microbiome is probably in the healthy newborns.
Objective: The preliminary study aimed to isolate and identify the gut microbiota of newborns for the assessment of prevalent
Lactic Acid Bacteria (LAB) distribution.
Material and Method: Thirty eight Thai newborns, 0-5 days old of both sexes were subjected for fecal samples collection.
Isolated bacteria were cultivated on the MRS selective media and further phenotypically characterized by conventional
methods including Gram stain, catalase, and lactic acid production. Genotypic identification was completed by 16S rRNA
gene sequencing and phylogenetic analysis.
Results: Forty five isolates of LAB and non-LAB bacteria were obtained from feces of newborns. The most prevalence LAB
found in this population were 45% Enterococcus faecalis, 14% E. faecium, 11% E. hirae, 11% Lactobacillus paracasei, and 2% L. gasseri. Unusually, Gram-negative bacteria including Klebsiella pneumoniae, Enterobacter hormaechei, Escherichia
fergusonii, Leclercia adecarboxylata, and Shigella flexneri were isolated among LAB strains on the selective MRS media.
Conclusion: The gut microbiota was a great resource of beneficial LAB which was remarkably distributed among this
population of Thai newborns. Further study on individual LAB isolates for the effective probiotics development would be
essentially investigated for future alternative treatment of gastrointestinal diseases.

Keywords: Enterococcus, Lactobacillus, Lactic acid bacteria, 16S rRNA gene, Newborn, Probiotics