Human milk storage conditions and bactericidal activity: An experimental study

Breast milk is crucial for neonatal nutrition and provides antimicrobial protection. While breastfeeding for at least 6 months is ideal, situations may arise where stored milk is necessary. This study examines how storage in polyethylene bags and Pyrex bottles affects breast milk's antimicrobial effectiveness against common neonatal pathogens: Escherichia coli, Staphylococcus aureus, and Streptococcus agalactiae.

Conducted from December 15, 2023, to March 15, 2024, the prospective study involved 30 term infants and their mothers, aged 18-40, at Gülhane Training and Research Hospital. Milk was manually expressed into both container types and stored at 4°C for 0, 24, and 48 h. Bactericidal activity was evaluated using standard strains of E. coli, S. aureus, and S. agalactiae, with colony counts analyzed after 24 h of cultivation.

No significant differences were found between storage types for overall colony counts. However, S. agalactiae showed a significant increase in colonies at 48 h in Pyrex bottles (p = 0.003), while S. aureus colonies increased significantly in polyethylene bags at 48 h (p = 0.036).

Bactericidal activity against S. agalactiae and S. aureus decreased significantly in stored milk after 24 and 48 h in the refrigerator. Short-term storage of human milk may compromise its antimicrobial properties depending on bacterial strain and container type, indicating the need for further research on optimal storage conditions.