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Updated: May 24, 2026

Individualized Reconstitution of Human Milk Microbiota: A Feasible Approach in Real-World Settings
Published on: February 7, 2025
Cultures of Holder-pasteurized donor human milk after use in a neonatal intensive care unit
Ronald S Cohen1, Chien-Fang Riva Huang, Sean C Xiong
1Neonatal and Developmental Medicine, Stanford University School of Medicine, Palo Alto, California 94304, USA. rscohen@stanford.edu
Objective:
Current guidelines state that human milk, once thawed, should be kept in a refrigerator for only 24 hours. We cultured Holder-pasteurized donor human milk (DHM) after thawing and refrigeration under clinical conditions.
Study Design:
Bottles of pasteurized DHM were thawed and used in a regional level 3 neonatal intensive care unit (NICU) in standard clinical fashion and kept refrigerated when not in use. Once no longer needed clinically, aliquots were cultured for bacteria.
Results:
In total, 30 bottles were returned for culture; six were excluded from analysis because human milk fortifier had been added, and two had been left out of the refrigerator. The remaining 22 bottles were culture-negative after having been thawed for 7-122 hours.
Conclusions:
DHM without additives was culture-negative for 24 hours or longer after thawing and routine NICU handling. These data indicate that unfortified Holder-pasteurized DHM handled appropriately and refrigerated remains sterile for 24 hours after thawing and perhaps longer. Further study is needed to confirm this.

