Characterization and probiotic properties of Lactobacilli from human breast milk

Abstract

Several studies have reported a complex microbial community in human breast milk. This community impacts the shape of the infant gut microbiota and consequently impacts host health. Lactobacillus is an important probiotic and has many applications in the functional food industry. This study isolated and evaluated the potential probiotic bacteria from human milk. Two Lactobacillus species, L. plantarum and L. pentosus, were isolated from the breast milk of Thai women. L. pentosus HM04-22, L. pentosus HM04-3, L. plantarum HM04-80, L. plantarum HM04-88 and L. plantarum HM01-1 showed good adhesion activity (> 55%) and resistance in gastric (pH 2) and bile (pH 8) conditions. Characterization of the probiotic properties indicated that all selected Lactobacillus isolates had anti-adhesion properties against Escherichia coli and Salmonella Typhimurium. Lactobacillus isolates protected Caco-2 cells from pathogen adhesion at 25-40%. In addition, the five selected strains presented anti-inflammatory properties by reducing interleukin (IL)-8 expression at 0.14 ± 0.16 to 0.52 ± 0.117-fold. However, the strains had no effect on the expression of tight junction genes, including zona occludens (ZO)-1, occludin and claudin-1. In conclusion, five selected Lactobacillus isolates from human milk were candidates for use as probiotics to promote health. However, more tests in animal models and clinical trials need to be performed.

Keywords: Adhesion; Human breast milk; Immune; Probiotic.

Fig. 1

Profiles of Gram-positive, acid-producing bacterial isolates from breast milk samples. Bacterial profiles defined by shape (a) and bacterial genera of rod isolates from three samples identified by MALDI–TOF–MS (b)

Fig. 2

Mucin adhesion ability of Lactobacillus isolates from human breast milk. Lactobacillus rhamnosus GG (LGG) was the standard control. The adhesion rate was calculated by estimating the percentage of adhesion with the number of CFUs attached to the mucin compared to the initial number of CFUs added. The adhesion rate was calculated from three replications

Fig. 3

Survival rate of Lactobacillus isolates from human breast milk in the simulated human gastrointestinal (GI) tract. The percent survival rate was calculated by estimating the number of living cells (CFUs) before and after incubation in GI conditions. The mean ± SD of three independent experiments are shown; *Represents a significant difference between tested isolates

Fig. 4

Inhibition rate of Lactobacillus isolates from human breast milk against S. Typhimurium (a) and E. coli (b) on Caco-2 cells. Percentage inhibition was calculated from the percentage of pathogen adhesion with and without Lactobacillus isolates. The inhibition rate was calculated from three replications

Fig. 5

Expression levels of ZO-1, occludin and claudin-1 protein from Caco-2 cells incubated with Lactobacillus isolates from human breast milk and pathogens. β-Actin was used as the reference gene. Data with different superscripts are significantly different at p ≤ 0.05

Fig. 6

Expression levels of IL-8 from Caco-2 cells incubated with Lactobacillus isolates from human breast milk and pathogens. β-Actin was used as the reference gene. Data with different superscripts are significantly different at p ≤ 0.05