Staphylococcus aureus enterotoxin production in raw and pasteurized milk: The effect of selected different storage durations and temperatures
Mary Ann Liebert
School of Medical and Health Sciences
Introduction: S. aureus is one of the most prevalent potential pathogenic bacteria found in DHM. Some strains produce heat stable enterotoxins that are able to survive pasteurization. These enterotoxins have been associated with gastritis and potentially necrotizing enterocolitis in preterm infants. The aim of this study is to assess the impact of different storage temperatures on Staphylococcus aureus growth and enterotoxin A and B production in raw and Holder pasteurized donor human milk (DHM).
Materials and Methods: Raw and pasteurized DHM were inoculated with enterotoxin A and B producing S. aureus. Samples were incubated at 4°C (10 days), 21°C, and 37°C (18 hours). Bacterial growth and enterotoxin A and B were quantified.
Results: S. aureus count increased in pasteurized DHM. Bacterial count decreased in the raw milk when incubated at 21°C and 4°C and slightly increased when incubated at 37°C. Enterotoxins A and B were only detected in pasteurized DHM at 37°C from 9 hours onward.
Conclusion: This study showed that raw milk is capable of suppressing S. aureus growth compared to pasteurized DHM. It also provides a measure of assurance of the safety of raw and pasteurized DHM when refrigerated or left at room temperature for a few hours.