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Care of Pumped Breast Milk

Liza Green Golan Mackintosh, MD and Michael Cosimini, MD

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Liza and Mike discuss a case of Cronobacter sakazakii infection from contaminated breast milk in preterm infant and new CDC recommendations for safe expression of human breast milk.



  • While rare, sepsis can occur in premature infants from contaminated expressed breast milk.

  • The Centers for Disease Control has new guidelines to help mothers safely express breast milk.  


Case 1

On day of life 21 an ex-29-week premature, 1400 grams neonate developed sepsis, meningitis, and liquefactive necrosis. This lead to a very bad outcome including cerebral palsy, gastrostomy tube dependence,  and need for ventriculoperitoneal shunt. The causative organism is Cronobacter sakazakii. The local health department and Centers for Disease Control(CDC) are involved in the case as this pathogen has been reported in contaminated infant formula. This patient had received human milk fortifier in addition to expressed breast milk from mom and donor breast milk. The pathogen is found valves of the pump at home, the sink at home, and the breast milk that was brought in from home.

  • Bowen A, et al. Notes from the Field: Cronobacter sakazakii Infection Associated with Feeding Extrinsically Contaminated Expressed Human Milk to a Premature Infant - Pennsylvania, 2016. MMWR Morb Mortal Wkly Rep. 2017 Jul 21;66(28):761-762. PMID 28727679

  • Is infection from expressed breast milk common? This is not common but this is not the first case of sepsis from contaminated expressed breast milk. Other cases including pseudomonas, e coli, klebsiella and staphylococcus have been reported. These are typically patients that are premature or in the neonatal intensive care unit.

  • How was the milk expressed and handled in this case?  The mother was taking the pumping parts and soaking them in soapy water for a few hours, rinsing, air drying, and storing them in a Ziploc bag. She was not scrubbing the parts.

  • How should the milk be expressed? CDC has some guidelines for how to express breast milk with a pump. How to Keep Your Breast Pump Kit Clean: The Essentials

    • Start by washing hands with soap and water. Inspect and assemble the pumping kit. Than clean the pump, the knobs on the pump, the surface that is being used with sanitizing wipes.

      • This could be somewhat difficult to implement for parents because of all the different locations that mothers may be pumping and that it may be difficult to clean surfaces.

    • After expressing the milk into the bottles they should be capped, labeled and put in the fridge. The pumping areas should be cleaned again and the pump should be disassembled and all the parts should be rinsed right away and washed as soon as possible.

    • The washing should be done in a dedicated basin just for the pumping parts. The parts are washed and scrubbed in soap and hot water, rinsed and the allowed to air dry.

      • In another reported case of sepsis from contaminated breast milk the pumping parts were dried with paper towels and put in bags immediately without air drying. Another way mothers may stray from these recommendations is when they refrigerate parts between sessions but use the same parts to pump multiple times in a day.

    • They also recommend sanitizing once a week either with boiling water or the dishwasher on sanitize settings. This is more important for parents of infants less than three months old, those born prematurely, those with a weak immune system, or under medical treatment for some other reason.

  • Once the milk is pumped how should it be stored?

    • Once the milk has been pumped, it can stay out on the counter or in room air for up to about four hours (six to eight if expressed in an extremely clean environment).

    • Milk should be dated and stored in the back of the refrigerator preferably for four days but for up to eight days.

    • In a typical freezer (again, in the back) it can be stored for nine months and in a deep freezer for 12 months.

    • To thaw the milk can be put in the refrigerator overnight or  can be thawed under warm water but should not be microwaved.

    • Thawing and refrigerating breast milk.

  • What do you know about informal sharing of breast milk? Donor human milk can be a very positive thing when done correctly. There are about 20 certified human milk banks in the United States. What these milk banks is do is they screen all the milk for different bacteria, viruses, drugs. They pasteurize milk and then they distribute it, mostly to NICUs.

    • There is a lot of unregulated human milk sharing. This goes back to wet nurses. The official recommendation is against this because you do not know how that milk was expressed and stored. The milk has not been pasteurized or screened for bacteria, viruses, or drugs.

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