This is the first research to investigate the vertical transmission of Lactobacillus kefiranofaciens subsp. kefiranofaciens, Lentilactobacillus kefiri, Lentilactobacillus parakefiri from mother to infant via consuming natural kefir. The mothers consumed kefir produced with kefir grains during 30th day. This was quantified by the qRT-PCR human milk and infant stool. L. kefiranofaciens subsp. kefiranofaciens, L. kefiri and L. parakefiri were not detected in human milk in the placebo group. The maternal who consume the kefir for 30 days had indeed transfer of those unique bacteria of kefir in the human milk and infant stool. L. kefiranofaciens, L. kefiri, and L. parakefiri in the milk of mothers who consumed kefir were quantified as 2.27 log cfu mL(-1), 1.64 log cfu mL(-1), 4.94 log cfu mL(-1) respectively, at the 30th day. These findings may contribute to rectifying deficiencies in human milk and neonatal gut microbiome development for healthy infants. (C) 2021 Elsevier Ltd. All rights reserved.