Effect of holder pasteurization and storage of donor human milk on Bacillus cereus survival

Abstract

Human milk, which constitutes the best composed nutrition for infants, is not a sterile biofluid. Besides nutritional and bioactive components, many microorganisms have been found in human milk, including Bacillus cereus. Those pathogenic bacteria can be responsible for causing pneumonia or septicemia in neonates. Although Bacillus cereus infections are not common, they represent one of the increasing factors of a high mortality rate in the preterm infants group. Donor human milk (DHM) may be a significant source of this pathogen. Given the high ability of Bacillus cereus spores to survive under different thermal conditions, we tested the effect of the holder pasteurization and storage points (4 °C and −21 °C) on sporulation and vegetative forms’ survival in inoculated human milk samples by culture method and light microscopy. Studies confirmed that holder pasteurization is effective against vegetative forms of Bacillus cereus. Additionally, during storage endospores were observed in all analyzed inoculated donor milk samples, both the pasteurized and unpasteurized samples, thus possibly promoting the occurrence of Bacillus cereus in DHM. Bacillus cereus is considered a contamination in DHM and in the human milk banks’ (HMB) environment. There is a need to further develop methods of identifying, transmitting, and preventing bacteria forming spores, which could be applied in HMB.