Lactation stage, gestational age and delivery mode all influence the composition of several bacteria inhabiting BM: Bifidobacterium, Lactobacillus, Staphylococcus, Streptococcus and Enterococcus spp., and, consequently, may affect the infant's early intestinal colonization.

Breast milk (BM) is considered as a reference for infant nutrition. The role of bioactive components, such as cytokines, hormones, growth factors (GFs) and fatty acids (FAs) is poorly known, but they might be implicated in immune response development. The aim of this study was to identify the lipid profile and the spectrum of cytokines and neuronal GF in BM samples and analyse the influence of gestational age and lactation time on these components. This study used a longitudinal prospective method for the characterization of cytokines, FAs and GFs global profiles in 120 BM samples from 40 healthy mothers (20 preterm and 20 term) collected as colostrum, transitional and mature milk. The cytokines were analysed by protein array (Ray Bio® Human Cytokine Array G6. Ray Biotech, Inc. Norcross, GA, USA) and the FAs were analysed by gas chromatography. The FA profile was similar between the term and the preterm BM samples. Omega-3-α-linoleic and docosahexaenoic acid (DHA) and omega-6-linoleic acid were the most abundant in the term and preterm samples during lactation. Omega-3 ETA and omega-3 EPA we observed exclusively in the preterm samples. The cytokine profile showed a different trend based on gestational age. A significantly higher expression of neurotrophic factors was found in the mature preterm milk samples as compared to the mature term samples. Our study is the first to identify the influence and interactions of perinatal factors on cytokine, GFs and FAs in human milk.

Genotype II.4 noroviruses (NoVs) are a leading cause of epidemic acute gastroenteritis in children and adults worldwide. The prevalence of different NoV genotypes causing outbreaks and sporadic cases of acute gastroenteritis in the region of Valencia, Spain, during a 4-year period (2008-11) was investigated. NoVs were detected in 42 out of 55 (76.3%) outbreaks and in 26 out of 332 (7.8%) sporadic cases of acute gastroenteritis. Genogroup GII strains were predominant in outbreaks and sporadic cases. Different genotype GII.4 variants were found (Yerseke_2006a, Den Haag_2006b, Apeldoorn_2007, and New Orleans_2009), with the latter variant detected most frequently (35.3%). A recombinant P domain of the NoV GII.4 Apeldoorn_2007 variant was produced in Escherichia coli and used as the coating antigen in an enzyme immunoassay to survey the IgG antibody seroprevalence against NoV GII.4 in a Spanish population. Baculovirus-expressed virus-like particles (VLPs) of NoV GII.4 Den Haag_2006b variant were also produced and used as antigen to compare seroreactivity. Of the 434 serum specimens analyzed, 429 (98.6%) had antibodies against the P domain. The comparison of reactivities of 30 serum samples to the NoV GII.4 P polypeptide and VLP showed reproducible results with a correlation coefficient of r = 0.794. Titers of antibodies to the P domain increased gradually and significantly with age, reaching the highest levels at the age group of 41-50 years. These results confirm the high prevalence of NoV GII.4 infections in Valencia from early childhood.

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