Staphylococcus aureus enterotoxin production in raw, Holder-pasteurized, and ultraviolet-C-treated donated human milk

Document Type

Journal Article

Publication Title

Breastfeeding Medicine

PubMed ID



Mary Ann Liebert


School of Medical and Health Sciences




Funding information available at https://doi.org/10.1089/bfm.2018.0217


Almutawif, Y., Hartmann, B., Lloyd, M., Lai, C. T., Rea, A., & Geddes, D. (2019). Staphylococcus aureus enterotoxin production in raw, Holder-Pasteurized, and ultraviolet-C-treated donated human milk. Breastfeeding Medicine, 14(4), 262-270. Available here


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.