Biology subjects

Horrocks, V.

Publications and source records attributed to Horrocks, V..

4 recordsLinked to original sources

bioRxiv2025

Metabolism of Lactobacillus and Gardnerella vaginalis in vaginal defined media

Lactobacilli and Gardnerella vaginalis are key bacteria within the vaginal microbiota, significantly impacting its chemical environment. Accurately reproducing vaginal bacteria metabolism in vitro is therefore critical in understanding how this may contribute to vaginal health and disease. Complex media such as brain heart infusion (BHI) support the growth of a wide variety of vaginal bacteria but may not accurately reproduce the conditions found in vivo leading to over- or under-representation of important metabolic processes. Here we use a 1H NMR approach to characterise the growth of Lactobacillus crispatus, L. jensenii and a panel of G. vaginalis isolates that differ in their metabolic strategy in a vaginal defined media (VDM). We find that both Lactobacillus species grow well in VDM, produce much more lactate, and consequently acidify the spent culture far more than when cultured in BHI. In contrast, G. vaginalis grows less well in VDM but differences in Bifidobacterium shunt and mixed acid fermentation, previously observed in BHI and evidenced by formate production, are preserved. Importantly neither species consume the available glucose but nevertheless conduct carbohydrate fermentation, implicating a preference for glycogen over glucose metabolism with glucose release evidence of glycogen breakdown. While further work is needed to develop media that can support the growth of a wider variety of vaginal bacteria species and recapitulate all features of their metabolism, VDM nevertheless accurately models the key aspects of the chemical environment when Lactobacillus dominate, and G. vaginalis is prevalent, in the microbiota.

microbiology↗

bioRxiv2024

Vancomycin-resistant Enterococcus colonise the antibiotic-treated intestine by occupying distinct nutrient- and metabolite-defined intestinal niches

Antibiotic treatment significantly disrupts the gut microbiome and promotes vancomycin-resistant enterococci (VRE) intestinal colonisation. These disruptions cause the intestine to act as a reservoir for VRE that seed difficult-to-treat infections. Patients would benefit from new treatments that prevent or treat VRE intestinal colonisation. However, the factors that drive VRE growth in the gut are poorly understood. We demonstrated that multiple antibiotics that promote VRE intestinal colonisation increased the concentration of a wide range of nutrients and decreased the concentration of a wide range of microbial metabolites. We found significant but incomplete suppression of VRE growth by individual short chain fatty acids that were decreased in antibiotic-treated faecal microbiomes. However, we showed that mixtures of short chain fatty acids provided complete or near complete suppression of VRE growth. We also showed that VRE could use most nutrients increased in antibiotic-treated faecal microbiomes as carbon or nitrogen sources to support their growth. Enterococcus faecium and Enterococcus faecalis had some common and some distinct preferences for use of specific nutrients that were enriched in antibiotic-treated faecal microbiomes. Finally, we showed that E. faecium and E. faecalis occupied overlapping but distinct nutrient-defined intestinal niches that promoted high growth when cultured with each other and when cultured with carbapenem-resistant Enterobacteriaceae (another group of multidrug-resistant pathogens). Our results demonstrated that VRE occupy distinct intestinal niches in the antibiotic-treated intestine, defined by their abilities to utilise specific enriched nutrients and their abilities to grow with reduced concentrations of inhibitory microbial metabolites.

microbiology↗

bioRxiv2023

Antibiotics promote intestinal growth of carbapenem-resistant Enterobacteriaceae by enriching nutrients and depleting microbial metabolites

The intestine is the primary colonisation site for carbapenem-resistant Enterobacteriaceae (CRE) and serves as a reservoir of CRE that cause invasive infections (e.g. bloodstream infections). Antibiotics disrupt colonisation resistance mediated by the gut microbiota, promoting the expansion of CRE within the intestine. We used ex vivo faecal cultures to measure the impact of antibiotics (that promote CRE intestinal colonisation) on the faecal microbiota from healthy human donors. We demonstrated that antibiotics decreased the abundance of gut commensals (including Bifidobacteriaceae and Bacteroidales) in human faecal microbiota, resulting in an enrichment of nutrients and a depletion of microbial metabolites. We measured the nutrient utilisation abilities, nutrient preferences, and metabolite inhibition susceptibilities of several carbapenem-resistant Enterobacteriaceae strains, including Escherichia coli, Klebsiella pneumoniae, and Enterobacter hormaechei. Nutrients (which were elevated with antibiotics) acted as carbon and nitrogen sources to support CRE growth, where CRE strains showed an ordered preference for specific nutrients. These nutrients were also increased in faeces from antibiotic-treated mice but decreased following intestinal colonisation with carbapenem-resistant E. coli. Microbial metabolites (which decreased with antibiotics) were inhibitory towards CRE growth in vitro. Carbapenem-resistant E. coli growth was decreased in faecal samples from mice treated with a mixture of inhibitory metabolites compared with PBS-treated mice. These findings demonstrated that killing gut commensals with antibiotics disrupts colonisation resistance by enriching nutrients that support CRE growth and depleting metabolites that inhibit CRE growth. These results support the development of new microbiome therapeutics to prevent CRE intestinal colonisation, which would also prevent the subsequent development of invasive CRE infections.

microbiology↗

bioRxiv2021

NMR metabolomics of symbioses between bacterial vaginosis associated bacteria

Bacterial vaginosis (BV) is a dysbiosis of the vaginal microbiome, characterised by low levels of lacto-bacilli and overgrowth of a diverse group of bacteria, and associated with higher risk of a variety of infections, surgical complications, cancer and spontaneous preterm birth (PTB). Despite the lack of a consistently applicable aetiology, Prevotella spp. are often associated with both BV and PTB and P. bivia has known symbiotic relationships with both Peptostreptococcus anaerobius and Gardnerella vaginalis. Higher risk of PTB can also be predicted by a composite of metabolites linked to bacterial metabolism but their specific bacterial source remains poorly understood. Here we characterise diversity of metabolic strategies among BV associated bacteria and lactobacilli and the symbiotic metabolic relationships between P. bivia and its partners and show how these influence the availability of metabolites associated with BV/PTB and/or pro- or anti-inflammatory immune responses. We confirm a commensal relationship between Pe. anaerobius and P. bivia, refining its mechanism; P. bivia supplies tyrosine, phenylalanine, methionine, uracil and proline, the last of which leads to a substantial increase in overall acetate production. In contrast, our data indicate the relationship between P. bivia and G. vaginalis strains, with sequence variant G2, is mutualistic with outcome dependent on the metabolic strategy of the G. vaginalis strain. Seven G. vaginalis strains could be separated according to whether they performed mixed acid fermentation (MAF) or bifid shunt (BS). In co-culture, P. bivia supplies all G. vaginalis strains with uracil and received substantial amounts of asparagine in return. Acetate production, which is lower in BS strains, then matched that of MAF strains while production of aspartate increased for the latter. Taken together, our data show how knowledge of inter- and intra-species metabolic diversity and the effects of symbiosis may refine our understanding of the mechanism and approach to risk prediction in BV and/or PTB.

microbiology↗