Antibacterial defences in preterm breast milk and their role in protecting the preterm infant from late-onset neonatal sepsis

    Research output: ThesisDoctoral Thesis

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    Abstract

    [Truncated] Preterm infants are extremely susceptible to late-onset sepsis (LOS), caused by infection with commensal microorganisms. Such infections may translocate from the gut, and consequently, preterm infants who consume sufficient doses of breast milk are less likely to suffer from LOS. Despite this protective association, the immunological composition of breast milk, particularly in preterm mothers, remains poorly defined. It is unclear how milk protects infants against LOS, and which components of the many soluble or cellular immune factors in milk may be protective. If identified, these critical protective factors could be used to fortify formula, breast milk with low immune content, or pasteurised donor human milk to reduce the incidence of preterm infant infections.

    A major preliminary aim of this thesis was to develop assays to measure the levels of innate antimicrobial, cellular and immune modulating factors for use with breast milk, a complex fluid of unusual light scattering, protein binding, and physical properties. In Chapter 2, enzyme-linked immunosorbent assays were developed to measure the levels of antimicrobial proteins and peptides (AMPs) in breast milk, and bacterial growth inhibition assays were developed to measure the activity of milk and AMPs against sepsis-causing pathogens. Using these methods, we were able to investigate the research hypotheses presented in the thesis.

    In Chapter 3, we aimed to determine the levels of a range of innate immune factors in preterm mothers’ milk, in comparison to term mothers’ milk. We found that there was no evidence of deficiencies of soluble immune molecules in preterm breast milk. In fact, extremely preterm mothers’ milk contained higher concentrations of antimicrobial peptides and soluble pattern recognition receptors than term mothers’ milk.

    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2015

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