Biology subjects

Gardner, S. E.

Publications and source records attributed to Gardner, S. E..

3 recordsLinked to original sources

bioRxiv2023

Wound microbiota-mediated correction of matrix metalloproteinase expression promotes re-epithelialization of diabetic wounds

Chronic wounds are a common and costly complication of diabetes, where multifactorial defects contribute to dysregulated skin repair, inflammation, tissue damage, and infection. We previously showed that aspects of the diabetic foot ulcer microbiota were correlated with poor healing outcomes, but many microbial species recovered remain uninvestigated with respect to wound healing. Here we focused on Alcaligenes faecalis, a Gram-negative bacterium that is frequently recovered from chronic wounds but rarely causes infection. Treatment of diabetic wounds with A. faecalis accelerated healing during early stages. We investigated the underlying mechanisms and found that A. faecalis treatment promotes re-epithelialization of diabetic keratinocytes, a process which is necessary for healing but deficient in chronic wounds. Overexpression of matrix metalloproteinases in diabetes contributes to failed epithelialization, and we found that A. faecalis treatment balances this overexpression to allow proper healing. This work uncovers a mechanism of bacterial-driven wound repair and provides a foundation for the development of microbiota-based wound interventions.

microbiology↗

bioRxiv2022

Staphyloxanthin production by Staphylococcus aureus promotes resistance to oxidative stress to delay diabetic wound healing

Diabetic foot ulcers (DFU) are a serious complication of diabetes mellitus that burden patients and health care systems. Staphylococcus aureus is prevalent and abundant in the DFU microbiome, and strain-level differences in S. aureus may drive clinical outcomes. To identify mechanisms underlying strain-specific outcomes in DFU with S. aureus, we performed high-throughput phenotyping screens on a collection of 221 S. aureus cultured isolates from clinically uninfected DFU. Of the 4 phenotypes examined (in vitro biofilm formation and production of staphylokinase, staphyloxanthin, and siderophores), we discovered that isolates from non-healing wounds produced more staphyloxanthin, a carotenoid cell membrane pigment. In a murine diabetic wound healing model, staphyloxanthin-producing isolates delayed wound closure significantly compared to staphyloxanthin-deficient isolates. Staphyloxanthin promoted resistance to oxidative stress in vitro and enhanced bacterial survival in human neutrophils. Comparative genomic and transcriptomic analysis of genetically similar clinical isolates with disparate staphyloxanthin phenotypes revealed a mutation in the Sigma B regulatory pathway that resulted in marked differences in stress response gene expression. Our findings suggest that staphyloxanthin production delays wound healing by protecting S. aureus from neutrophil-mediated oxidative stress, and may provide a target for therapeutic intervention in S. aureus-positive wounds.

microbiology↗

bioRxiv2018

The microbial basis of impaired wound healing: differential roles for pathogens, \"bystanders\", and strain-level diversification in clinical outcomes

Chronic, non-healing wounds are a major complication of diabetes associated with high morbidity and health care expenditures estimated at $9-13 billion annually in the US. Though microbial infection and critical colonization is hypothesized to impair healing and contribute to severe outcomes such as amputation, antimicrobial therapy is inefficacious and the role of microbes in tissue repair, regeneration, and healing remains unclear. Here, in a longitudinal prospective cohort study of 100 subjects with non-infected neuropathic diabetic foot ulcer (DFU), we performed metagenomic shotgun sequencing to elucidate microbial temporal dynamics at strain-level resolution, to investigate pathogenicity and virulence of the DFU microbiome with respect to outcomes, and to determine the influence of therapeutic intervention on the DFU microbiota. Slow healing DFUs were associated with signatures of biofilm formation, host invasion, and virulence. Though antibiotic resistance was widespread at the genetic level, debridement, rather than antibiotic treatment, significantly shifted the DFU microbiome in patients with more favorable outcomes. Primary clinical isolates of S. aureus, C. striatum, and A. faecalis induced differential biological responses in keratinocytes and in a murine model of diabetic wound healing, with the S. aureus strain associated with non-healing wounds eliciting the most severe phenotype. Together these findings implicate strain-level diversification of the wound pathogen S. aureus in chronic wound outcomes, while revealing potential contributions from skin commensals and other previously underappreciated constituents of the wound microbiota.

genomics↗