A Solution to Antifolate Resistance in Group B Streptococcus: Untargeted Metabolomics Identifies Human Milk Oligosaccharide-Induced Perturbations That Result in Potentiation of Trimethoprim.

Schuyler A Chambers,Simona G Codreanu,John A Mclean,Kelly M Craft,Stacy D Sherrod,Rebecca E Moore,Harrison C Thomas,Jennifer A Gaddy,David M Aronoff,Shannon D Manning,Steven D Townsend,Rishub Das,Jimmy D Ballard

doi:10.1128/mbio.00076-20

Schuyler A Chambers, Simona G Codreanu + Show 11 more

Open Access

https://doi.org/10.1128/mbio.00076-20

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Abstract

Adjuvants can be used to potentiate the function of antibiotics whose efficacy has been reduced by acquired or intrinsic resistance. In the present study, we discovered that human milk oligosaccharides (HMOs) sensitize strains of group B Streptococcus (GBS) to trimethoprim (TMP), an antibiotic to which GBS is intrinsically resistant. Reductions in the MIC of TMP reached as high as 512-fold across a diverse panel of isolates. To better understand HMOs' mechanism of action, we characterized the metabolic response of GBS to HMO treatment using ultrahigh-performance liquid chromatography-high-resolution tandem mass spectrometry (UPLC-HRMS/MS) analysis. These data showed that when challenged by HMOs, GBS undergoes significant perturbations in metabolic pathways related to the biosynthesis and incorporation of macromolecules involved in membrane construction. This study represents reports the metabolic characterization of a cell that is perturbed by HMOs.IMPORTANCE Group B Streptococcus is an important human pathogen that causes serious infections during pregnancy which can lead to chorioamnionitis, funisitis, premature rupture of gestational membranes, preterm birth, neonatal sepsis, and death. GBS is evolving antimicrobial resistance mechanisms, and the work presented in this paper provides evidence that prebiotics such as human milk oligosaccharides can act as adjuvants to restore the utility of antibiotics.

Highlights

In addition to structure-activity relationship (SAR) studies, we found that human milk oligosaccharides (HMOs) potentiate the activity of select intracellular targeting antibiotics [32]
HMOs were assayed against five strains of group B Streptococcus (GBS) of various serotypes to determine the strain specificity of antibiotic potentiation
GBS strains are divided into 10 serotypes (1a, 1b, and II to IX) based on a serological reaction against their capsular polysaccharides [55]

Summary

Introduction

At their 50% inhibitory concentration (IC50), HMO extracts reduced the MICs of certain intracellular targeting antibiotics up to 32-fold (Table 1). Based on their ability to increase cellular permeability, a second-generation combination study was initiated to further characterize HMO enhancement of intracellular targeting antibiotics in the GBS model. The MIC of the HMOs and TMP were determined separately in each strain of GBS grown in Todd-Hewitt broth (THB) using a broth microdilution assay (Table 2).

Results

Conclusion