Fecal Volatile Metabolomics Predict Gram-Negative Late-Onset Sepsis in Preterm Infants: A Nationwide Case-Control Study

Abstract

Early detection of late-onset sepsis (LOS) in preterm infants is crucial since timely treatment initiation is a key prognostic factor. We hypothesized that fecal volatile organic compounds (VOCs), reflecting microbiota composition and function, could serve as a non-invasive biomarker for preclinical pathogen-specific LOS detection. Fecal samples and clinical data of all preterm infants (≤30 weeks' gestation) admitted at nine neonatal intensive care units in the Netherlands and Belgium were collected daily. Samples from one to three days before LOS onset were analyzed by gas chromatography-ion mobility spectrometry (GC-IMS), a technique based on pattern recognition, and gas chromatography-time of flight-mass spectrometry (GC-TOF-MS), to identify unique metabolites. Fecal VOC profiles and metabolites from infants with LOS were compared with matched controls. Samples from 121 LOS infants and 121 matched controls were analyzed using GC-IMS, and from 34 LOS infants and 34 matched controls using GC-TOF-MS. Differences in fecal VOCs were most profound one and two days preceding Escherichia coli LOS (Area Under Curve; p-value: 0.73; p = 0.02, 0.83; p < 0.002, respectively) and two and three days before gram-negative LOS (0.81; p < 0.001, 0.85; p < 0.001, respectively). GC-TOF-MS identified pathogen-specific discriminative metabolites for LOS. This study underlines the potential for VOCs as a non-invasive preclinical diagnostic LOS biomarker.

Keywords: fecal biomarker; gas chromatography—ion mobility spectrometry; gas chromatography—time of flight—mass spectrometry; microbiota; neonatology; volatile organic compounds.

Figure 1

Flow diagram of included preterm infants. A total of 121 LOS cases was included for analysis and matched to 121 controls. Subsequently, 34 LOS cases and controls were eligible for GC-TOF-MS analysis. Abbreviations: GC-IMS, gas chromatography—ion mobility spectrometry; GC-TOF-MS, gas chromatography—time of flight—mass spectrometry; LOS, late-onset sepsis; NEC, necrotizing enterocolitis; SIP, spontaneous intestinal perforation.

Figure 2

Discriminatory metabolites identified using GC-TOF-MS. The log2(FC) of the median peak height intensities is depicted for every significant comparison, indicating an increase (orange) or decrease (blue) in metabolite abundance in LOS cases. White indicates that the metabolite was not considered discriminatory for that subgroup. Gram-positive LOS is not depicted since there were no significant comparisons. Abbreviations: log2(FC), log2(fold change); LOS, late-onset sepsis.