Host-microbe metatranscriptome reveals differences between acute and chronic infections in diabetes-related foot
Matthew Malone1,2, Michael Radzieta1,2, Timothy J Peters3,4
1South West Sydney Limb Preservation and Wound Research, South Western Sydney LHD, Sydney, NSW, Australia.
Abstract:
Virtually all diabetes-related foot ulcers (DRFUs) will become colonized by microorganisms that may increase the risk of developing an infection. The reasons why some ulcerations develop acute clinical infections (AI-DRFUs) whilst others develop chronic infection (CI-DRFUs) and the preceding host-microbe interactions in vivo remain largely unknown. Establishing that acute and chronic infections are distinct processes requires demonstrating that these are two different strategies employed by microbes when interacting with a host. In this study, dual-RNA seq was employed to differentiate the host-microbe metatranscriptome between DRFUs that had localized chronic infection or acute clinical infection. Comparison of the host metatranscriptome in AI-DRFUs relative to CI-DRFUs identified upregulated differentially expressed genes (DEGs) that functioned as regulators of vascular lymphatic inflammatory responses, T-cell signalling and olfactory receptors. Conversely, CI-DRFUs upregulated DEGs responsible for cellular homeostasis. Gene set enrichment analysis using Hallmark annotations revealed enrichment of immune and inflammatory profiles in CI-DRFUs relative to AI-DRFUs. Analysis of the microbial metatranscriptome identified the DEGs being enriched within AI-DRFUs relative to CI-DRFUs included several toxins, two-component systems, bacterial motility, secretion systems and genes encoding for energy metabolism. Functions relevant to DRFU pathology were further explored, including biofilm and bacterial pathogenesis. This identified that the expression of biofilm-associated genes was higher within CI-DRFUs compared to that of AI-DRFUs, with mucR being the most highly expressed gene. Collectively, these data provide insights into the host-microbe function in two clinically-distinct infective phenotypes that affect DRFUs. The data reveal that bacteria in acutely infected DRFUs prioritize motility over biofilm and demonstrate greater pathogenicity and mechanisms, which likely subvert host cellular and immune pathways to establish infection. Upregulation of genes for key vascular inflammatory mediators in acutely infected ulcers may contribute, in part, to the clinical picture of a red, hot, swollen foot, which differentiates an acutely infected ulcer from that of a chronic infection.
Insights
Microbes in diabetes-related foot ulcers (DRFUs) use different strategies for acute versus chronic infections. Acutely infected DRFUs show increased bacterial motility and pathogenicity, while chronic infections favor biofilm formation.
Area of Science:
- Microbiology and Immunology
- Diabetic Foot Complications
- Host-Pathogen Interactions
Background:
- Diabetes-related foot ulcers (DRFUs) are frequently colonized by microorganisms, increasing infection risk.
- The distinct host-microbe interactions driving acute clinical infections (AI-DRFUs) versus chronic infections (CI-DRFUs) in DRFUs are poorly understood.
- Differentiating acute and chronic infections requires understanding microbial strategies and host responses.
Purpose of the Study:
- To differentiate the host-microbe metatranscriptome between AI-DRFUs and CI-DRFUs.
- To elucidate the distinct host and microbial gene expression profiles associated with acute and chronic DRFU infections.
- To understand the functional differences in host-microbe interactions underlying these two infection types.
Main Methods:
- Dual-RNA sequencing was employed to analyze the metatranscriptome of host and microbial communities in DRFUs.
- Differential gene expression analysis was performed to compare AI-DRFUs and CI-DRFUs.
- Gene set enrichment analysis (using Hallmark annotations) and exploration of specific functions like biofilm formation were conducted.
Main Results:
- Host metatranscriptome analysis revealed upregulated immune and inflammatory genes in CI-DRFUs, and regulators of vascular/lymphatic responses and olfactory receptors in AI-DRFUs.
- Microbial metatranscriptome analysis showed enrichment of toxins, motility, secretion systems, and energy metabolism genes in AI-DRFUs.
- Biofilm-associated gene expression (e.g., mucR) was higher in CI-DRFUs, whereas AI-DRFUs showed prioritization of bacterial motility and pathogenicity.
Conclusions:
- Acute and chronic infections in DRFUs represent distinct microbial strategies and host responses.
- Bacteria in AI-DRFUs prioritize motility and pathogenicity, likely subverting host defenses, contributing to acute inflammatory symptoms.
- CI-DRFUs are characterized by higher biofilm gene expression and distinct host immune/inflammatory profiles, indicating a different pathogenic strategy.
