Pasteurized Donor Human Milk Maintains Microbiological Purity for 4 Days at 4°C

Background: Most protective components in human milk are stable during prolonged storage at 4ºC; however, pasteurization reduces some microbicidal activities responsible for suppressing microbial growth and protecting against infection. Donor milk used by neonatal intensive care units (NICUs) is frozen pasteurized donor human milk (PDHM) defrosted and stored at 4ºC. Current Human Milk Banking Association of North America (HMBANA) Best Practice guidelines recommend that milk be discarded 24 hours after being thawed, but experimental data on the duration of microbiological purity in thawed PDHM are sparse. Objective: This study evaluates microbiological purity of thawed PDHM during prolonged storage at 4ºC. Methods: A total of 42 independent, randomly selected PDHM samples were thawed at 4ºC. As is typical in NICUs, each bottle was opened at 3-hour intervals and 3 mL was withdrawn with a sterile syringe and transferred into a sterile tube. The 3 mL samples removed at 0, 24, 48, 72, 96 hours, and 9 days were tested for the presence of any microorganisms by a clinical laboratory that routinely screens PDHM for microbes. Results: No evidence of microbial growth was observed in cultured samples taken at 0 to 9 days after thawing of the milk samples. Conclusion: There was no evidence of microbes in PDHM as dispensed by HMBANA milk banks when defrosted and stored at 4ºC for up to 9 days. Extended storage of PDHM in the NICU could reduce waste of donor milk, thereby increasing availability of human milk to vulnerable neonatal patients.