Effects of Storage Process on the Bacterial Growth-Inhibiting Activity of Expressed Human Breast Milk on Common Neonatal Pathogens, Staphylococcus Aureus , Escherichia Coli and Klebsiella Pneumoniae

Storage of human breast milk is unavoidable especially among working mothers who need to report back to work soon after delivery. The aim of this study was to describe the effects of storage process on the bacterial growth-inhibiting activity of expressed human breast milk on common neonatal pathogens. Methods: This was an experimental study performed at the Ospital ng Makati on the breast milk of mothers who were without infection prior to delivery, did not take any medications, and spontaneously delivered their babies full term. Fifteen mothers expressed breast milk within the first seven days up to one month, postpartum. Each milk sample was stored and tested with the following time series: immediately after expression; thawed after being frozen for 24; and thawed after being frozen for 72 hours. Each of the broth medium containing Staphylococcus aureus, Escherichia coli or Klebsiella pneumonia was added to 1 ml of expressed breast milk. Tenfold dilutions were made. Each dilution was plated at zero and four hours and colony-forming units (CFU) were counted after 24 hours incubation. Same procedure was performed on a negative control. Results: The number of CFU for the three tested organisms (had lower nominal counts with the breast milk solution when compared to control solutions both at zero-hour and four-hour test samples. Breast milk exhibited bacteriostatic properties against most pathogens except for Escherichia coli after being frozen for 24 hours. For the breast milk that was frozen for 72 hours, most tests did not show significant lower counts when compared to control solutions, except still for Staphylococcus aureus and Escherichia coli both at 0 hour. Conclusion: Breast milk has bacterial inhibiting property against common neonatal pathogens. Bacteriostatic property of breast milk started to diminish after being frozen for 72 hours, but still exerted its inhibiting property.