Staphylococcus aureus Enterotoxin Production in Raw, Holder-Pasteurized, and Ultraviolet-C-Treated Donated Human Milk

Breastfeed Med. 2019 May;14(4):262-270. doi: 10.1089/bfm.2018.0217. Epub 2019 Feb 28.


Background: Some strains of Staphylococcus aureus can produce heat-stable enterotoxins that have been associated with gastritis and potentially necrotizing enterocolitis in preterm infants. Objectives/Hypothesis: To assess the impact of different storage temperatures on S. aureus growth and enterotoxin production in raw, Holder-pasteurized (HP) and ultraviolet-C (UV-C)-treated donated human milk (DHM). Materials and Methods: The milk samples from individual donors were pooled and divided into four equal portions. One portion was HP, the second was UV-C treated, the third was not treated, and the fourth was UV-C treated after being spiked with S. aureus. All samples were incubated at 37°C (18 hours) and 4°C (14 days). Bacterial colony count, enterotoxin A and B, and immune proteins were quantified. Results: At 37°C, the colony count increased in HP DHM and decreased in raw and UV-C-treated DHM. At 4°C, colony counts in HP DHM reduced and were not detected in raw and UV-C-treated DHM from day 8 of incubation. No bacteria were detected in samples that were inoculated before UV-C treatment. Enterotoxin A was only detected in HP-DHM at 37°C from the 9th hour onward. Enterotoxin B was detected in one sample at the 15th hour. Immune protein concentrations were similar in raw and UV-C DHM, and were reduced in the HP DHM. Conclusion: UV-C-treated milk reduces S. aureus growth with similar kinetics to raw milk making it a promising emerging technique to eliminate bacteria while retaining essential immune proteins in DHM.

Keywords: Holder pasteurization; UV-C treatment; donated human milk; enterotoxin.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Enterotoxins / analysis
  • Female
  • Food Irradiation / methods
  • Humans
  • Immunoglobulin A, Secretory / analysis
  • Lactoferrin / analysis
  • Linear Models
  • Milk, Human / microbiology*
  • Milk, Human / radiation effects*
  • Pasteurization / methods*
  • Staphylococcus aureus / growth & development
  • Staphylococcus aureus / isolation & purification*
  • Staphylococcus aureus / radiation effects
  • Ultraviolet Rays*


  • Enterotoxins
  • Immunoglobulin A, Secretory
  • Lactoferrin