[Influence of donor profile on pre and post-pasteurization bacteriology of donated human milk].

Introduction: breastfeeding is the gold standard for infant's nutrition. Human milk bank is an essential tool to guarantee availability and safety in those situations when breastfeeding is not an option. The manipulation during the extraction of the human milk by the donors is a critical point to ensure an adequate microbiological safety. Therefore, knowing the bacterial flora that prevails in donated milk is essential to draw conclusions that can lead to taking measures in the management of the bank. Objectives: to analyze the prevalence of microorganisms in milk samples donated to the milk bank and how the bacterial flora behaves according to the profile of the donors and the donor milk circuits. Methods: the present work is a retrospective descriptive observational study that analyzes characteristics and the positive microbiological results within our milk bank samples from June 1, 2016 to December 31, 2020. All milk bank donors voluntarily signed an informed consent that authorizes the use of data to investigation. Results: during the study period, a total of 1,587 liters of raw milk were donated by 266 women, highlighting that, despite the SARS-CoV-2 virus pandemic, 2020 has been the year in which more volume of milk has been dispensed. The results show that 221 batches had at least one positive microbiological isolation (149 of them were before and 46 after pasteurization). Pre and post-pasteurization rate varies over the years with a decrease in the pre-pasteurization discard rate (3,9%) and increase in the post-pasteurization rate (5,3%). The most frequently isolated germs found in pre-pasteurization cultures were gram positive cocci and Enterobacter and a decrease in the positivity to S. aureus after establishing an eradication protocol. In post-pasteurization cultures, the most commonly found germs are Bacillus. Regarding the donor's profile, it was found a non statistically significant way that those women with the highest donation volume and/or admission of their offspring in Neonatology were associated with higher frequency of positive cultures. Conclusions: bacteriological analysis of milk samples is an essential part of quality control for a milk bank. Our results reflect a good extraction system and transportation, as well as good training from the bank's professionals. Nevertheless, improvement of processes is necessary to reduce the rate of contamination and the amount of discarded milk.