For a study, the researchers looked into the possibility of isolating new probiotics from mothers and their babies. A selection of 21 isolates was tested for simulated GI transit survival, adhesion to Caco-2 cells, bacteriocin synthesis, and antibiotic resistance among 126 distinct bacteria from breast milk and newborn feces from 15 mother-infant pairs. A Lactobacillus crispatus isolate and 3 Lactobacillus gasseri isolates showed well in vitro GI transit tolerance profiles, and Caco-2 cell adhesion among the 21 isolates chosen. L. gasseri and Enterococcus faecalis isolates were the only ones that produced bacteriocin. Antibiotic resistance was common among newborn isolates, though not ubiquitous. From 5 infant-mother couples, highly similar isolates of Bifidobacterium longum subsp. infantis (1 match), Lactobacillus fermentum (2 games), Lactobacillus gasseri (6 games), and Enterococcus faecalis (1 round) were identified (≥97% similarity by barcode match). Antibiotic resistance profiles were similar among these isolate matches, except in one case where the L. gasseri isolate from the newborn had erythromycin and tetracycline resistance, which was not determined in the matching mother isolate. In the second case, the mother’s and infant’s L. gasseri isolates had different resistance levels to ampicillin, chloramphenicol, and vancomycin. The researchers isolated Gram-positive bacteria from mothers’ breast milk and their infants showed a wide range of GI transit survival and pathogen acid inhibition, but only a limited ability to manufacture bacteriocins. Probiotics can be identified in mothers and their infants. Nevertheless, healthy infants contained antibiotic-resistant isolates even in the early phases of development.