Presented at the Neonatal Society 2015 Spring Meeting.
Przysiezna N1, Wijeyesakera AD2, Parkinson JR1, Hyde MJ1, Uthaya S1, Holmes E2, Modi N1
1 Section of Neonatal Medicine, Department of Medicine, Imperial College London, Chelsea & Westminster campus, 369 Fulham Road, London, UK
2 Computation Systems Medicine, Sir Alexander Fleming Building, Imperial College London, South Kensington, SW7 2AZ
Background: The composition of biofluids can provide useful information regarding health, physiology and may identify biomarkers of disease risk. Microbiota colonising the gut in early life may be a causal factor in long term health outcomes. Given their hospital environment it is to be expected that preterm babies will have a considerably different pattern of colonisation compared to term born infants. Here we used stool water metabonomics as a surrogate for gut microbiota activity, to answer the research question: Is there a time (post-natal age) dependant trend in the composition of stool water.
Methods: The study was conducted with Research Ethics Committee (09/H0707/88) approval as part of the NIHIR funded double-blind 2×2 factorial randomised trial of early nutrition (NEON). Weekly stool samples were collected from 160 infants and stored at -80°C until analysis (total number of samples = 1187). Stool water was extracted and analysed using one-dimensional 1H NMR spectroscopy at 300K on a Bruker LC-NMR 600 MHz spectrometer, using standard parameters and Bruker pre-processing algorithms. The spectra were phased, baseline corrected and referenced using an in-house script (MATLAB). We used probabilistic normalisation and analysed the spectra using Principal Component Analysis (PCA) and Orthogonal Partial Least Squares analysis (O-PLS).
Results: Analysing data from all babies (time points from 1 to 21 weeks postnatal age), we showed that the metabolic profile of stool samples from preterm infants altered over time (Fig 1). The PCA plot indicates that the variation in the metabolic profile of the faecal water decreases with increasing postnatal age. The greatest variation is seen during the first four weeks of postnatal life. The following metabolites increased with postnatal age: alanine, acetate, trimethylamine and tyramine. The source of acetate and trimethylamine is likely to be bacterial metabolism.
Figure 1: PCA scores scatter plot from NMR spectra of stool samples representing multiple time points for 160 premature infant. Samples coloured according to postnatal age (in weeks).
Conclusion: Indirect assessment of gut microbiota activity in preterm infants indicates that the variation observed in the first few weeks of life is reduced after a month. This overlaps with increasing amounts of enteral feeding and decreasing reliance on parenteral nutrition. Given the high exposure to breast milk in this cohort and that breast fed infants have lower microbial variability this may explain our findings. Infants are also likely to be commonly exposed to hospital specific bacteria.
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1. Parkinson JRC et al (2013) Pediatrics. 131:E1240