Biology subjects

Sandstrom, S.

Publications and source records attributed to Sandstrom, S..

8 recordsLinked to original sources

bioRxiv2025

Establishing an ex vivo porcine skin model to investigate the effects of broad spectrum antiseptic on viable skin microbial communities

Incomplete antiseptic efficacy against potentially pathogenic microbial taxa places some patients at disproportionate risk for developing a surgical site infection. Laboratory models capable of interrogating the effects of antiseptics on the skin and its complex microbial communities are desperately needed to improve and better tailor antiseptic formulations. This work aims to establish an ex vivo porcine skin model to explore the impact of topical antiseptics on complex skin microbial communities and superficial skin lipids. Microbiome samples were treated with propidium-monoazide to selectively evaluate DNA from viable microorganisms. Bacterial abundances were assessed via viability-qPCR and quantitative culture. Viable community populations were evaluated with 16S rRNA gene sequencing. Epidermal biopsies were collected at multiple timepoints for lipidomic assessment via LC/MS. The ex vivo environment promoted shifts in porcine skin lipid composition and microbial communities over the experiments duration. Compared to water treated control skin, skin treated with the antiseptic chlorhexidine gluconate had significantly lower culturable and bioburden determined by viability-qPCR. Compared to water treated skin, viable microbial communities on CHG treated skin displayed greater relative abundance of several gut associated and Gram-negative bacterial taxa, including SMB53, Turicibacter, Pseudomonas and Proteus. Collectively these findings highlight the utility of an ex vivo porcine skin system for interrogating the impacts of antimicrobial disruption to complex microbial ecosystems, and ultimately for the future testing and development of improved antiseptic formulations.

microbiology↗

bioRxiv2024

Large-scale investigation for antimicrobial activity reveals novel defensive species across the healthy skin microbiome

The human skin microbiome constitutes a dynamic barrier that can impede pathogen invasion by producing antimicrobial natural products. Gene clusters encoding for production of secondary metabolites, biosynthetic gene clusters (BGCs), that are enriched in the human skin microbiome relative to other ecological settings, position this niche as a promising source for new natural product mining. Here, we introduce a new human microbiome isolate collection, the EPithelial Isolate Collection (EPIC). It includes a large phylogenetically diverse set of human skin-derived bacterial strains from eight body sites. This skin collection, consisting of 980 strains is larger and more diverse than existing resources, includes hundreds of rare and low-abundance strains, and hundreds of unique BGCs. Using a large-scale co-culture screen to assess 8,756 pairwise interactions between skin-associated bacteria and potential pathogens, we reveal broad antifungal activity by skin microbiome members. Integrating 287 whole isolate genomes and 268 metagenomes from sampling sites demonstrates that while the distribution of BGC types is stable across body sites, specific gene cluster families (GCFs), each predicted to encode for a distinct secondary metabolite, can substantially vary. Sites that are dry or rarely moist harbor the greatest potential for discovery of novel bioactive metabolites. Among our discoveries are four novel bacterial species, three of which exert significant and broad-spectrum antifungal activity. This comprehensive isolate collection advances our understanding of the skin microbiomes biosynthetic capabilities and pathogen-fighting mechanisms, opening new avenues towards antimicrobial drug discovery and microbiome engineering.

microbiology↗

bioRxiv2024

Altered oral microbiota of drug-resistant organism carriers exhibit impaired gram-negative pathogen inhibition

The oral microbiome has been understudied as a reservoir for clinical pathogens, including drug-resistant strains. Understanding how alterations in microbiome functioning render this site vulnerable to colonization is essential, as multidrug-resistant organisms (MDRO) carriage is a major risk factor for developing serious infections. To advance our knowledge of oral MDRO carriage and protection against pathogen colonization conferred by native microbiota, we examined microbiomes from individuals colonized by MDROs (n=33) and non-colonized age-matched controls (n=30). Shotgun metagenomic analyses of oral swabs from study participants revealed significant differences in microbial communities with depletion of Streptococcus spp. among those colonized by multidrug-resistant gram-negative bacilli (RGNB), compared to non-carriers. We utilized metagenomic sequencing to characterize the oral resistome and find antimicrobial resistance genes are present in higher abundance among RNGB carriers versus non-carriers. High-throughput co-culture screening revealed oral bacteria isolated from MDRO non-carriers demonstrate greater inhibition of gram-negative pathogens, compared to isolates from carriers. Moreover, biosynthetic gene clusters from streptococci are found in higher abundance from non-carrier microbiomes, compared to RGNB carrier microbiomes. Bioactivity-guided fractionation of extracts from Streptococcus isolate SID2657 demonstrated evidence of strong E. coli and A. baumannii inhibition in a murine model of infection. Together, this provides evidence that oral microbiota shape this dynamic microbial community and may serve as an untapped source for much-needed antimicrobial small-molecules.

microbiology↗

bioRxiv2024

Still Not Sterile: Chlorhexidine gluconate treatment does not completely reduce skin microbial bioburden and promotes pathogen overabundance in patients undergoing elective surgeries.

Surgical site infections (SSI) continue to occur despite widespread adoption of surgical antiseptics. The effects of chlorhexidine gluconate (CHG)-based antiseptics on the skin microbiome also remains undefined due to confounding effects of CHG persistence on skin. Patients undergoing elective surgery were enrolled to characterize the immediate and long-term impact of pre-surgical preparation with CHG antiseptic on skin microbial communities. Due to the broad-spectrum antimicrobial activity of CHG and its propensity to bind extracellular DNA, methods to selectively identify live microorganisms are critical to this process and to fully elucidate the effectiveness of pre-surgical protocols and potential disruptions to the healthy skin microbiome. Swabs of the surgical site skin microbiome were collected at multiple timepoints before and after surgery. Microbial bioburden and community compositions were evaluated with viability qPCR and 16S ribosomal RNA gene profiling. Pre-operative CHG induced a measurable reduction in the viable microbial bioburden at the surgical site. On the day of surgery, surgical sites displayed a significant increase in the relative abundance of several SSI associated bacterial genera, including, Acinetobacter, Bacillus, Escherichia-Shigella, and Pseudomonas, compared to baseline. Bacillus species isolated from subjects at baseline showed resistance to CHG with MICs exceeding 1000 {micro}g/ml. Despite major shifts in the skin microbiome upon exposure to CHG, they were transient in the majority of individuals. Skin microbial community structure recovered by the post-surgical follow-up. In short, this study shows that pre-surgical application of CHG can significantly reduce viable skin microbial bioburden, however, complete sterility is not achieved. While CHG induces temporary shifts in the skin microbiome, including enrichment for potentially pathogenic taxa, the skin microbiome recovers back to near baseline. Collectively, these findings identify tangible avenues for improving antiseptic formulations and offer further support that the skin microbiome is viable, stable, and resilient to chemical perturbation.

microbiology↗

bioRxiv2024

Upper respiratory microbial communities of healthy populations are shaped by niche and age

BackgroundAlterations in upper respiratory microbiomes have been implicated in shaping host health trajectories, including by limiting mucosal pathogen colonization. However, limited comparative studies of respiratory microbiome development and functioning across age groups have been performed. Herein, we perform shotgun metagenomic sequencing paired with pathogen inhibition assays to elucidate differences in nasal and oral microbiome composition and functioning across healthy 24-month-old infant (n=229) and adult (n=100) populations. ResultsWe find that beta diversity of nasal and oral microbiomes varies with age, with nasal microbiomes showing greater population-level variation compared to oral microbiomes. Infant microbiome alpha diversity was significantly lower across nasal samples and higher in oral samples, relative to adults. Accordingly, we demonstrate significant differences in genus- and species-level composition of microbiomes between sites and age groups. Antimicrobial resistome patterns likewise varied across body sites, with oral microbiomes showing higher resistance gene abundance compared to nasal microbiomes. Biosynthetic gene clusters encoding specialized metabolite production were found in higher abundance across infant oral microbiomes, relative to adults. Investigation of pathogen inhibition revealed greater inhibition of gram-negative and gram-positive bacteria by oral commensals, while nasal isolates had higher antifungal activity. ConclusionsIn summary, we identify significant differences in the microbial communities inhabiting nasal and oral cavities of healthy infants relative to adults. These findings inform our understanding of the interactions impacting respiratory microbiome composition and functioning, with important implications for host health across the lifespan.

microbiology↗

bioRxiv2024

The Porcine Skin Microbiome Exhibits Broad Fungal Antagonism

The skin and its microbiome function to protect the host from pathogen colonization and environmental stressors. In this study, using the Wisconsin Miniature Swine model, we characterize the porcine skin fungal and bacterial microbiomes, identify bacterial isolates displaying antifungal activity, and use whole-genome sequencing to identify biosynthetic gene clusters encoding for secondary metabolites that may be responsible for the antagonistic effects on fungi. Through this comprehensive approach of paired microbiome sequencing with culturomics, we report the discovery of novel species of Corynebacterium and Rothia. Further, this study represents the first comprehensive evaluation of the porcine skin mycobiome and the evaluation of bacterial-fungal interactions on this surface. Several diverse bacterial isolates exhibit potent antifungal properties against fungal pathogens in vitro. Genomic analysis of inhibitory species revealed a diverse repertoire of uncharacterized biosynthetic gene clusters suggesting a reservoir of novel chemical and biological diversity. Collectively, the porcine skin microbiome represents a potential unique source of novel antifungals. HighlightsO_LIPorcine skin bacterial communities are consistent with previous reports on porcine and human skin. C_LIO_LIFungal community composition resembles mycobiomes from other mammalian skin, but not human skin. C_LIO_LIBacteria isolated from porcine skin have antimicrobial and particularly strong antifungal activity in vitro. C_LIO_LIDiscovered three new Corynebacterium species and one new Rothia species. C_LI

microbiology↗

bioRxiv2022

Sweat and sebum preferences of the human skin microbiota

The microorganisms that inhabit human skin, collectively termed the skin microbiome, must overcome numerous challenges that typically impede microbial growth, including low pH, osmotic pressure, and low nutrient availability. Yet, the skin microbiota thrive on the skin and have adapted to these stressful conditions. Limited skin nutrients are available for microbial use in this unique niche, including those from host-derived sweat, sebum, and corneocytes. Here, we have developed physiologically-relevant, skin-like growth media that is composed of compounds present in human sweat and sebum. We find that skin-associated bacterial species exhibit unique growth profiles in different concentrations of sweat and sebum. The majority of strains evaluated demonstrate a preference for high sweat concentrations, while sebum preference is highly variable, suggesting that the capacity for sebum utilization may be an important driver of skin microbial community structure. Furthermore, these findings provide experimental rationale for why different skin microenvironments harbor distinct microbiome communities. In all, our study further emphasizes the importance of studying microorganisms in an ecologically-relevant context, which is critical for our understanding of their physiology, ecology, and function on the skin.

microbiology↗

bioRxiv2022

lsaBGC provides a comprehensive framework for evolutionary analysis of biosynthetic gene clusters within focal taxa

We developed lsaBGC, a bioinformatics suite that introduces several new methods to expand on the available infrastructure for genomic and metagenomic-based comparative and evolutionary investigation of biosynthetic gene clusters (BGCs). Through application of the suite to four genera commonly found in skin microbiomes, we uncover multiple novel findings on the evolution and diversity of their BGCs. We show that the virulence associated carotenoid staphyloxanthin in Staphylococcus aureus is ubiquitous across the Staphylococcus genus but has largely been lost in the skin-commensal species Staphylococcus epidermidis. We further identify thousands of novel single nucleotide variants (SNVs) within BGCs from the Corynebacterium tuberculostearicum sp. complex, which we describe here to be a narrow, multi-species clade that features the most prevalent Corynebacterium in healthy skin microbiomes. Although novel SNVs were approximately ten times as likely to correspond to synonymous changes when located in the top five percentile of conserved sites, lsaBGC identified SNVs which defied this trend and are predicted to underlie amino acid changes within functionally key enzymatic domains. Ultimately, beyond supporting evolutionary investigations, lsaBGC provides important functionalities to aid efforts for the discovery or synthesis of natural products.

microbiology↗