MSACL 2017 EU Abstract

Vaginal Swabs Analysis Using Desorption Electrospray Ionization (DESI) MS Permits Rapid Identification of Metabolic Signatures Associated with Preterm Birth

Holly Lewis (Presenter)
Imperial College London

Bio: Holly Lewis is an obstetrician and Clinical Research Fellow at Imperial College London. Her research interest is studying the relationship between the vaginal microbiome, host mucosa and associated metabolome in pregnancy and relating these findings to birth outcome.

Authorship: H Lewis, P Pruski, R Brown, L Kindinger, Y Lee, P Bennett, Z Takats, DA MacIntyre
Imperial College London

Short Abstract

Preterm birth (PTB) is the leading cause of death in children under 5 years. Approx. 30% of PTB are preceded by prelabour rupture of membranes (PPROM). We have recently described a method of medical swab analysis that permits rapid, direct assessment of the vaginal metabolome using Desorption Electrospray Ionization Mass Spectrometry (DESI-MS). In this study we show DESI-MS vaginal swab profiling can permit stratification of patients subsequently experiencing PPROM from healthy controls. Furthermore we can determine mucosal metabolic profiles for vaginal bacterial dysbiosis in women presenting with PPROM. This highlights the predictive and therapeutic potential of DESI-MS in high-risk pregnancies.

Long Abstract

Introduction

Preterm birth (PTB), defined as birth prior to 37 weeks gestation, is a major global health issue affecting 15 million births worldwide. It is the leading cause of death in children under five years and a high proportion of survivors will be faced with life-long health complications such as cerebral palsy, blindness and respiratory problems.

Despite decades of research, the rate of PTB has stayed largely the same. A major reason for this is our inability to reliably predict those women at risk of preterm birth, which is further complicated by the fact that PTB is a syndrome with multiple underlying aetiologies. In 30% of cases however, PTB is preceded by prelabour rupture of the membranes (PPROM), which is associated with ascending bacterial infection from the vagina. For this reason, prophylactic antibiotics are widely used as a frontline treatment strategy for PPROM. The ability to identify mothers at risk of PPROM, and those who could preferentially benefit from antibiotic treatment due to an infectious aetiology, would revolutionise medical management of these women.

We have recently described a method of medical swab analysis that permits rapid, direct assessment of the vaginal mucosal metabolome using Desorption Electrospray Ionization Mass Spectrometry (DESI-MS)1. In this study we aimed to firstly test if DESI-MS vaginal swab profiling can permit stratification of patients subsequently experiencing PPROM from healthy term pregnancy controls. Secondly, we aimed to determine if mucosal metabolic profiles can identify vaginal bacterial dysbiosis in women presenting with PPROM.

Methods

High vaginal swabs were prospectively collected from pregnant women with and without risk factors for PTB. Samples were taken from women that subsequently experienced PPROM and matched with controls of the similar gestation and ethnicity. Further vaginal swabs were taken following PPROM within 12 hours of the rupture of membranes, prior to antibiotic treatment.

Vaginal microbiota was assessed using MiSeq sequencing of the bacterial 16S rRNA genes (hypervariable regions V1-V2). Metabolic profiling was performed directly on swabs using an LTQ Orbitrap Discovery mass spectrometer connected to a DESI source. DESI was operated at 10 ┬ÁL/min flow rate, 4.3 kV high voltage settings with a MeOH:H20 solvent.

Spectral data was processed using customised scripts in R before being imported into SIMCA for multivariate analysis.

Results

High vaginal swabs were collected from 14 women who subsequently experienced PPROM (median gestation at delivery 35 wks + 4 days). Swabs were taken prior to the rupture event (median gestation at sampling 29 wks + 3 days) and compared with 30 gestational age-matched control women who delivered at term (median gestation at delivery 40 wks + 2 days).

Metabolic profiles of vaginal mucosa were obtained within 30 seconds and approximately 1500 spectral features collected in both negative and positive ion mode and used for multivariate modelling. High abundant analytes were tentatively identified by exact mass and MS/MS experiments as simple/complex lipids, peptides and bacterial secondary metabolites.

PPROM was significantly higher in women with Lactobacillus iners and Lactobacillus spp. deplete vaginal microbial communities compared with controls (79%; 11/14 vs 27%; 8/30; P=0.0025). The vaginal mucosa metabolome was robustly correlated with subsequent PPROM (R2Y: 0.916, Q2Y: 0.453). Discriminating metabolites were identified in both the PPROM and normal control groups.

Within 12 hours of PPROM and prior to erythromycin treatment, dysbiosis was found in 52% (15/29) of women. It was possible to discriminate between dysbiotic and Lactobacillus spp. dominant communities (R2Y: 0.912, Q2Y: 0.381) highlighting the potential of DESI-MS to identify groups that would benefit from targeted antibiotic therapy.

Conclusions & Discussion

Our results highlight the capacity of DESI-MS to rapidly detect differences in the vaginal metabolome associated with subsequent PPROM and thus improve spontaneous preterm birth prediction. Furthermore, following PPROM, DESI-MS has the potential to assist therapeutic decision-making, which may improve neonatal outcome.


References & Acknowledgements:

Pruski et al. Anal Chem. 2017 Feb 7; 89(3):1540-1550. doi: 10.1021/acs.analchem.6b03405.


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