Antimicrobial capacity of human milk against Cronobacter sakazakii bacterium

Reviewed by Emily Henderson, B.Sc.Jul 14 2020

Much research has studied the antimicrobial capacity of human milk against some pathogens, but this ability had not yet been studied for the Cronobacter sakazakii bacterium, which causes neonatal infections with fatal consequences for newborns. Three researchers from Valencia's CEU Cardenal Herrera university have just published in the American Journal of Human Lactation the first study in the world that analyses this quality.

Professors Sandra Fernández Pastor, Mari Carmen López Mendoza, and Dolores Silvestre Castelló, from the Departments of Food Science and Technology and Pharmacy of the CEU UCH, are the authors of this research, which also establishes the optimum conditions for handling and storing human milk in order to decrease the risk of contamination by Cronobacter sakazakii.

It is increasingly common for mothers to have to extract the milk and store it in the fridge in order to continue feeding it to her children beyond the maternity leave period, which is why they have to keep it in the fridge or frozen. Human milk banks in hospitals have also increased, especially to feed premature babies with the milk of donor mothers, which is frozen so it may be preserved and then subjected to different treatments prior to being administered. In our research in this field, we analysed the optimum treatment conditions of human milk to avoid contamination risks and ensure that all its properties are preserved, including the antimicrobial ones."

Sandra Fernández Pastor, CEU UCH Professor

No more than three days in the fridge

In this last study, the research team of the CEU UCH has analyzed the properties of human milk against bacterium Cronobacter sakazakii, which had not yet been studied. As well as the optimum conditions for its handling and treatment, so that this quality is preserved following its extraction. "Recently there have been cases of infection by this bacterium in babies who had consumed previously-stored human milk. Hence the need to study the optimum handling and treatment conditions to prevent the risk of contamination from this bacterium, which we have also established in this same study," highlights professor Sandra Fernández Pastor.

The results reveal that storage in the fridge at 4ºC must not continue beyond 72 hours. And freezing between -18ºC and -20ºC must also be limited as much as possible to guarantee the properties of human milk against the studied bacterium. "These results can contribute to improving the storage protocols in human milk banks in hospitals around the world, as there remains a lack of an internationally-validated protocol. And it can also facilitate the appropriate handling on behalf of mothers in the breastfeeding period who have to extract the milk and store it to feed their babies," highlight the authors of the study.

Milk samples from donor mothers

The study has been conducted using samples of breast milk donated by 29 breastfeeding mothers from the Valencian Community and Murcia, in order to verify its antibacterial capacity against Cronobacter sakazakii before and after having been subjected to several treatments: stored in the fridge for 72 hours, stored frozen for one, two and three months, pasteurized and subjected to the global treatment of a human milk bank, which includes applying several treatments. In this last case, the analysis was conducted with and without the addition of a strengthener following the application of global treatment. The comparison of the bacterium in breast milk samples before and after being subjected to different storage conditions has led to the recommendations to better preserve its natural antimicrobial capacity.

The Human Nutrition and Food Safety for Health research group of the CEU UCH, headed by professors Mari Carmen López Mendoza, from the Degree in Veterinary Studies, and Dolores Silvestre, from the Degree in Pharmacy, and which researcher Sandra Fernández Pastor is a part of, studies the bio components and the effects on its properties when milk is donated and stored in human milk banks in hospitals, with the goal of contributing to an improvement of its treatment protocols.

The studies of this research group have been published in international scientific journals such as the International Dairy Journal, Maternal and Child Nutrition, or the Journal of Pediatric Gastroenterology and Nutrition.

A part of the research that has now been published in the Journal of Human Lactation was awarded at the X Spanish Breastfeeding Congress, held last year by the Association for the Promotion and Scientific and Cultural Research of Breastfeeding (APILAM), among the 173 research studies that were submitted.