Evaluation of Probiotic Properties of Lactobacilli in Breast Milk and Their Inhibitory Effect on Pathogenic Bacteria of the Gastrointestinal Tracts

Background and Objective: Breast milk contains nutrients such as carbohydrates, essential fatty acids, proteins, vitamins, minerals, and a source of communal bacteria with probiotic potential that is very effective in the prevention and treatment of neonatal infections. The aim of this study was the evaluation of probiotic properties of lactobacilli in breast milk and their inhibitory effect on pathogenic bacteria of the gastrointestinal tracts. Materials and Methods: In a cross-sectional descriptive study, during 10 months from January to October 2018, 100 breast milk samples were collected by referring to health centers after isolation. Lactobacilli strains were evaluated based on morphological characteristics, catalase, and hot staining tests, survival tests in acidic conditions, and bile salt tolerance to evaluate probiotic properties. Antibiotic resistance of probiotic strains and ability to inhibit pathogenic bacteria was evaluated by well method and growth inhibition zone. Results: 122 lactobacilli belonging to 12 species were identified from 100 samples of breast milk by phototypical methods. The predominant species belonging to casei and other lactobacilli were Fermentum, Plantarum, and Gasseri, respectively.The highest antibiotic resistance was related to vancomycin (63.15%). The 3 isolates L4, L14 and L16 were able to strongly inhibit all the studied gastrointestinal pathogens. Conclusion: Breast milk is a rich source of beneficial probiotic lactobacilli, which can be useful in breast milk for infants who are not breastfed to prevent neonatal infections.