Effects of human milk fortifier with iron on the bacteriostatic properties of breast milk

ObjectiveTo compare bacterial growth in pure colostrum versus colostrum with human milk fortifier (HMF) containing iron.MethodsThe growth of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa in 78 samples of pure colostrum or colostrum with added iron-containing HMF was compared. For qualitative analysis, filter paper discs were immersed in samples from each group and incubated for 48 hours with 10¹ colony forming units (CFUs)/mL of each strain. For quantitative assessment, 1 mL of each strain containing 10⁷ CFUs/mL was homogenized with 1 mL of either colostrum or colostrum with human milk fortifier, seeded into a Petri dish, and incubated at 37 °C. Twenty-four hours later, the number of CFUs was counted.ResultsThe qualitative analysis showed no difference in bacterial growth. In the quantitative evaluation, E. coli growth in the control group was 29.4 ± 9.7 × 10⁶ CFU/mL, while in the HMF group it was 31.2 ± 10.8 × 10⁶ CFU/mL. The difference between the average growth was 1.9 ± 4.9 × 10⁶ CFU/mL (p = 0.001). There were no differences in S. aureus and P. aeruginosa growth.ConclusionAddition of iron at this concentration reduces breast milk bacteriostatic action against E. coli.