Effects of human milk fortifier on the antimicrobial properties of human milk

ABM Clinical Protocol #29: Iron, Zinc, and Vitamin D Supplementation During Breastfeeding

A central goal of The Academy of Breastfeeding Medicine is the development of clinical protocols, free from commercial interest or influence, for managing common medical problems that may impact breastfeeding success. These protocols serve only as guidelines for the care of breastfeeding mothers and infants and do not delineate an exclusive course of treatment or serve as standards of medical care. Variations in treatment may be appropriate according to the needs of an individual patient.

Investigation into the antimicrobial action and mechanism of a novel endogenous peptide β-casein 197 from human milk

A novel endogenous peptide cleaved from 197–213 AA of β-casein, named β-casein 197, was identified by tandem mass spectrometry. β-casein 197 constituted a significant proportion of the peptide content in preterm milk. This study investigated the antibacterial effects and mechanisms against common pathogenic bacteria. Six bacterial strains were selected for this study: Escherichia coli, Staphylococcus aureus, Yersinia enterocolitica, Listeria monocytogenes, Klebsiella pneumonia and Bacillus subtilis. After synthesis, serial twofold dilutions of β-casein 197 were added to select for sensitive bacteria. The disk diffusion method and analysis of bacterial staining were used to identify antibacterial effect, while DNA-binding, scanning electron microscopy and transmission electron microscopy were used to explore antimicrobial mechanisms. Disk diffusion showed that E. coli, S. aureus and Y. enterocolitica were sensitive to the β-casein 197. In addition, live/dead fluorescent staining also confirmed antibacterial effects. Scanning electron and transmission electron microscopy revealed affected extracellular and intracellular structure for three species of bacteria, while a DNA-binding assay showed that the antimicrobial activity did not occur through DNA binding. This study suggests that β-casein 197 has antimicrobial activity against common pathogenic bacteria in newborns with infection. The peptide induced membrane permeabilization but did not bind to genomic DNA. Based on our findings, β-casein 197 has potential clinical value for preventing infections of premature infants.

The effect of UV-C pasteurization on bacteriostatic properties and immunological proteins of donor human milk

Background

Human milk possesses bacteriostatic properties, largely due to the presence of immunological proteins. Heat treatments such as Holder pasteurization reduce the concentration of immunological proteins in human milk and consequently increase the bacterial growth rate. This study investigated the bacterial growth rate and the immunological protein concentration of ultraviolet (UV-C) irradiated, Holder pasteurized and untreated human milk.

Methods

Samples (n=10) of untreated, Holder pasteurized and UV-C irradiated human milk were inoculated with E. coli and S. aureus and the growth rate over 2 hours incubation time at 37°C was observed. Additionally, the concentration of sIgA, lactoferrin and lysozyme of untreated and treated human milk was analyzed.

Results

The bacterial growth rate of untreated and UV-C irradiated human milk was not significantly different. The bacterial growth rate of Holder pasteurized human milk was double compared to untreated human milk (p<0.001). The retention of sIgA, lactoferrin and lysozyme after UV-C irradiation was 89%, 87%, and 75% respectively, which were higher than Holder treated with 49%, 9%, and 41% respectively.

Conclusion

UV-C irradiation of human milk preserves significantly higher levels of immunological proteins than Holder pasteurization, resulting in bacteriostatic properties similar to those of untreated human milk.

Human milk and the premature infant

Human milk is the preferred feeding for both term and preterm infants. While being considered optimal for term infants, human milk, even from mothers delivering preterm infants, is lacking in protein, energy, sodium, calcium, and phosphorus, resulting in poorer growth and nutrient deficiencies when compared to formulas designed for these high-risk infants. Further, the lack of growth is associated with long-term adverse consequences. Since human milk has unique properties in promoting gastrointestinal maturation and immunological benefits, it is prudent to implement strategies to fortify it appropriately to realize its benefits which include reduced rates of necrotizing enterocolitis, fewer episodes of sepsis and urinary tract infections, and improved visual and neurocognitive development. Donor human milk is being widely used when mothers' own milk is not available or is in short supply. While it retains some of the biological properties and clinical benefits of mothers' own milk, it requires additional care in fortification, especially if the donor milk is from a pool of term human milk. As nutritional strategies improve, the ultimate goal is to minimize extrauterine growth restriction and promote appropriate growth after regaining birth weight.

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

OBJECTIVE

To compare bacterial growth in pure colostrum versus colostrum with human milk fortifier (HMF) containing iron.

METHODS

The 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 10(1) colony forming units (CFUs)/mL of each strain. For quantitative assessment, 1 mL of each strain containing 10(7) 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.

RESULTS

The qualitative analysis showed no difference in bacterial growth. In the quantitative evaluation, E. coli growth in the control group was 29.4±9.7×10(6)CFU/mL, while in the HMF group it was 31.2±10.8×10(6)CFU/mL. The difference between the average growth was 1.9±4.9×10(6)CFU/mL (p=0.001). There were no differences in S. aureus and P. aeruginosa growth.

CONCLUSION

Addition of iron at this concentration reduces breast milk bacteriostatic action against E. coli.

Cultures of Holder-pasteurized donor human milk after use in a neonatal intensive care unit

OBJECTIVE

Current guidelines state that human milk, once thawed, should be kept in a refrigerator for only 24 hours. We cultured Holder-pasteurized donor human milk (DHM) after thawing and refrigeration under clinical conditions.

STUDY DESIGN

Bottles of pasteurized DHM were thawed and used in a regional level 3 neonatal intensive care unit (NICU) in standard clinical fashion and kept refrigerated when not in use. Once no longer needed clinically, aliquots were cultured for bacteria.

RESULTS

In total, 30 bottles were returned for culture; six were excluded from analysis because human milk fortifier had been added, and two had been left out of the refrigerator. The remaining 22 bottles were culture-negative after having been thawed for 7-122 hours.

CONCLUSIONS

DHM without additives was culture-negative for 24 hours or longer after thawing and routine NICU handling. These data indicate that unfortified Holder-pasteurized DHM handled appropriately and refrigerated remains sterile for 24 hours after thawing and perhaps longer. Further study is needed to confirm this.

Effect of pasteurization on the bactericidal capacity of human milk

The use of human milk in milk banks requires thermal processing to eliminate microbiological hazards. An evaluation is made of the stability of overall human milk bactericidal capacity following 2 modalities of thermal pasteurization: 63 degrees C/30 minutes and 75 degrees C/15 seconds. Ten milk samples (mature milk) were analyzed. In each sample, the effect of both thermal treatments on bactericidal capacity against Escherichia coli was evaluated in relation to the capacity of fresh milk (control). All the samples analyzed possessed bactericidal capacity. Human milk pasteurization induced a significant loss of this capacity that was more pronounced after high-temperature treatment than after low-temperature processing. Untreated milk, low-pasteurized milk, and high-pasteurized milk yielded a reduction in E. coli growth of 70.10%, 52.27%, and 36.39%, respectively. In conclusion, human milk possesses antimicrobial activity that is lost in part as a result of thermal processing. Such bactericidal capacity is, moreover, better preserved by low-temperature, long-time pasteurization.

Effects of a human milk-derived human milk fortifier on the antibacterial actions of human milk

OBJECTIVES

To compare the effects of a human breastmilk-derived fortifier on the antibacterial activity of milk obtained from lactating mothers delivering prematurely with the effects of a powdered fortifier on the same milk.

STUDY DESIGN

Human milk samples were obtained after the first week of postnatal life from 10 lactating mothers, who had delivered prematurely. A bovine milk-based powdered fortifier and a human breastmilk-based frozen fortifier were evaluated. All mothers were healthy and they were not on any medications, although they were taking prenatal vitamins during lactation. The effects of each fortifier on the antimicrobial activity of milk toward Enterobacter sakazaki (ES), Escherichia coli, Clostridium difficile (CD), and Shigella soneii (SS) were evaluated by both the filter paper method and the growth inhibition method.

RESULTS

Human milk inhibited the growth of all of the test organisms. This antibacterial activity was almost totally inhibited by the addition of the bovine protein-based human milk fortifier, while it remained unaffected by the addition of the human breastmilk-based fortifier.

CONCLUSIONS

Breastmilk from women who have delivered preterm has antibacterial activity that can be affected by the addition of bovine-based fortifier, but not by the addition of a human breastmilk-based fortifier.