Contamination of human milk with aerobic flora: Evaluation of losses for a human milk bank

Introduction. In France, human milk banks pasteurize milk for the mother's own hospitalized baby (personalized milk) and for donation. There is specific legislation regulating the activity of human milk banks with bacterial screening of donor milk before and after pasteurization. Milk should be tested for Staphylococcus aureus and total aerobic flora. Any sample of milk positive for aerobic flora and/or S. aureus before and/or after pasteurization should be discarded. The real pathogenicity of the total aerobic flora is actually debated as well as the usefulness of systematic postpasteurization screening. The aim of this study was to quantify milk losses related to prepasteurization contamination by total aerobic flora in a regional milk bank, to identify losses due to contamination with S. aureus or aerobic flora, and to analyze differences between centers. Methods. This was a prospective observational study conducted in the regional human milk bank of the Nord-Pas-de-Calais area in France. Data were collected from six major centers providing 80% of the milk collected between June 2011 and June 2012. Variables were the volumes of personalized milk collected by each center, volumes of contaminated milk, and the type of bacteria identified. Results. During the study period, the regional human milk bank treated 4715 L (liters) of personalized milk and 508 L (10.8%) were discarded due to bacteriological screening. Among these 508 L, 43% were discarded because of a prepasteurization contamination with aerobic flora, 55% because of a prepasteurization contamination with S. aureus, and 2% because of other pathogenic bacteria. Postpasteurization tests were positive in 25 samples (0.5%). Only five of these 25 samples were positive before pasteurization and in all cases with S. aureus. A total of 218 L were destroyed because of prepasteurization contamination with total aerobic flora, while the postpasteurization culture was sterile. There was a great difference between centets in the percentage of discarded milk and the type of contamination. The percentage of discarded milk varied from 4 to 16% (P < 0.001) and the percentage of prepasteurization positive samples with aerobic flora from 0 to 70% (P < 0.001). Costing 80 (sic)/L in France, this represented an economic loss of (sic) 17,440. Conclusion. A significant volume of milk is discarded because of contamination with total aerobic flora found only in prepasteurization tests. Reassessment of the French regulations with regard to microbiological safety could save human milk to cover the needs of a larger group of preterm babies. 2015 Published by Elsevier Masson SAS.