Escherichia coli BarA-UvrY regulates the pks island and kills Staphylococci via the genotoxin colibactin during interspecies competition

Physiological drivers of pks+ E. coli in colorectal cancer

Colorectal cancer (CRC) is a significant global health challenge, with rising incidence, particularly among individuals under 50. Increasing evidence highlights the gut microbiota as key contributors to CRC development, with certain oncogenic bacteria influencing cancer initiation, progression, and therapy response. Among these is pks+ Escherichia coli, which produces colibactin, a genotoxic compound that induces DNA damage and leaves a distinct mutational signature in healthy individuals and CRC patients. While research has focused on its genotoxic effects, this review examines the kinetics of colibactin-induced mutations and the epithelial and environmental changes that promote E. coli expansion and colibactin exposure. We also explore the broader role of pks+ E. coli in cancer initiation and progression beyond genotoxicity, and discuss potential therapeutic approaches.

The deletion of the uvrY in Aeromonas veronii disrupted the BarA/UvrY two-component system, decreasing persister formation and bacterial resistance to multiple antibiotics

Antibiotic resistance (AR) is increasingly recognized as a critical global public health threat. Aeromonas species, widely distributed in aquatic environments, have emerged as potential foodborne pathogens. These bacteria are frequently detected in water sources and various ready-to-eat foods, posing a significant risk to food safety and human health. Two-component systems (TCSs) are key regulators of stress tolerance and adaptive behaviors, but the role of the BarA-UvrY TCS in AR is unclear. In our study, multidrug-resistant Aeromonas veronii (A. veronii) strains isolated from the grass carp intestinal contents were used to investigate the role of uvrY in AR, and mutant strain (Δ uvrY) was constructed using homologous recombination. The growth characteristics of wild-type (WT), Δ uvrY, and complemented strains (C-Δ uvrY) were evaluated under various stress conditions. Additionally, prokaryotic transcriptome analysis was performed to identify the downstream stress-factors in WT and Δ uvrY. The results indicated that the Δ uvrY strain exhibited reduced tolerance to osmotic and acid - base stress compared with the WT and C-Δ uvrY. Furthermore, the deletion of uvrY in A. veronii significantly impaired persister formation and decreased resistance to multiple antibiotics, particularly tetracyclines and chloramphenicol. The transcriptome analysis revealed that the increased susceptibility of Δ uvrY to tetracyclines was accompanied by a significant down-regulation of efflux pump genes and NADH dehydrogenase I. STRING network analysis further demonstrated that the BarA-UvrY TCS is associated with genes encoding NADH dehydrogenase I and efflux pump. Additionally, efflux experiments and respiratory rate assays confirmed that the Δ uvrY strain exhibited reduced efflux pump activity and a low respiratory rate, establishing a clear correlation between these two processes. Collectively, BarA-UvrY TCS play a crucial role in AR and persister formation by mediating energy-dependent efflux mechanisms. This study provides mechanistic insights into the regulatory functions of UvrY and offers a theoretical foundation for developing novel strategies to control A. veronii infections and enhance antimicrobial interventions.

Cross-talk between signal transduction systems and metabolic networks in antibiotic resistance and tolerance

The comprehensive antibiotic resistance of pathogens signifies the oneset of the "post-antibiotic era", and the myriad treatment challenges posed by "superbugs" have emerged as the primary threat to human health. Recent studies indicate that bacterial resistance and tolerance development are mediated at the metabolic level by various signalling networks (e.g., quorum sensing systems, second messenger systems, and two-component systems), resulting in metabolic rearrangements and alterations in bacterial community behaviour. This review focuses on current research, highlighting the intrinsic link between signalling and metabolic networks in bacterial resistance and tolerance.

Anti-Intracellular MRSA Activity of Antibiotic-Loaded Lipid-Polymer Hybrid Nanoparticles and Their Effectiveness in Murine Skin Wound Infection Models

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant concern for skin and soft tissue infections. Apart from biofilm formation, these bacteria can reside intracellularly in phagocytic and nonphagocytic mammalian cells, complicating treatment with conventional antibiotics. Lipid-polymer hybrid nanoparticle (LPN) systems, combining the advantages of polymeric nanoparticles and liposomes, represent a new generation of nanocarriers with the potential to address these therapeutic challenges. In this study, gentamicin (Gen) and vancomycin (Van) were encapsulated in LPNs and evaluated for their ability to eliminate intracellular MRSA in phagocytic macrophage RAW-Blue cells and nonphagocytic epithelial HaCaT cells. Compared to free antibiotics at 100 μg/mL, LPN formulations significantly reduced intracellular bacterial loads in both cell lines. Specifically, LPN-Van resulted in approximately 0.7 Log CFU/well reduction in RAW-Blue cells and 0.3 Log CFU/well reduction in HaCaT cells. LPN-Gen showed a more pronounced reduction, with approximately 1.26 Log CFU/well reduction in RAW-Blue cells and 0.45 Log CFU/well reduction in HaCaT cells. In vivo, LPN-Van at 500 μg/mL significantly reduced MRSA biofilm viability compared to untreated controls (p < 0.001), achieving 98% eradication based on median values. In comparison, free vancomycin achieved a nonstatistically significant 79.2% reduction in biofilm viability compared to control. Prophylactically, LPN-Van at 500 μg/mL decreased MRSA levels to the limit of detection, resulting in a ∼3.5 Log reduction in the median CFU/wound compared to free vancomycin. No acute dermal toxicity was observed for LPN-Van based on histological analysis. These data indicate that LPNs show promise as a drug delivery platform technology to address intracellular infections.

Investigating Polypyrrole/Silver-Based Composite for Biofilm Prevention on Silicone Surfaces for Urinary Catheter Applications

Catheter-associated urinary tract infections (CAUTIs) are among the most common healthcare-related infections caused by biofilm formation. This research investigated the efficacy of polypyrrole (PPy), silver nanoparticles (AgNPs), and their combination (PPy/AgNPs) as water-soluble additives applied in cleaning procedures for preventing the formation of Escherichia coli and Staphylococcus aureus (single and dual-species biofilms) on silicone. Ultraviolet-visible absorption assays, scanning electron microscopy (SEM) images, FTIR analysis, and dynamic light scattering experiments were conducted to evaluate the structure and physicochemical response of the antibiofilm compounds, with the biofilm prevention concentrations assessed by plate counting, flow cytometry, and SEM images. The composites proved to be dose-dependent agents preventing single- and dual-species biofilms from forming under simulated CAUTI conditions. Furthermore, cytotoxicity assays indicated that the materials are non-cytotoxic, supporting their suitability for biomedical applications. These findings pave the way for developing more effective, biocompatible catheter cleaning procedures, ultimately improving patient outcomes and addressing biofilms-related infections in clinical settings.

The chemical ecology and physiological functions of type I polyketide natural products: the emerging picture

Covering: up to 2024.For many years, the value of complex polyketides lay in their medical properties, including their antibiotic and antifungal activities, with little consideration paid to their native functions. However, more recent evidence gathered from the study of inter-organismal interactions has revealed the influence of these metabolites upon the ecological adaptation and distribution of their hosts, as well as their modes of communication. The increasing number of sequenced genomes and associated transcriptomes has also unveiled the widespread occurrence of the underlying biosynthetic enzymes across all kingdoms of life, and the important contributions they make to physiological events specific to each organism. This review depicts the diversity of roles fulfilled by type I polyketides, particularly in light of studies carried out during the last decade, providing an initial overall picture of their diverse functions.

Colibactin-induced damage in bacteria is cell contact independent

The bacterial toxin colibactin, produced primarily by the B2 phylogroup of Escherichia coli, underlies some cases of colorectal cancers. Colibactin crosslinks DNA and induces genotoxic damage in both mammalian and bacterial cells. While the mechanisms facilitating colibactin delivery remain unclear, results from multiple studies supported a delivery model that necessitates cell-cell contact. We directly tested this requirement in bacterial cultures by monitoring the spatiotemporal dynamics of the DNA damage response using a fluorescent transcriptional reporter. We found that in mixed-cell populations, DNA damage saturated within 12 hours and was detectable even in reporter cells separated from colibactin producers by hundreds of microns. Experiments with distinctly separated producer and reporter colonies revealed that the intensity of DNA damage decays similarly with distance regardless of colony contact. Our work reveals that cell contact is inconsequential for colibactin delivery in bacteria and suggests that contact dependence needs to be reexamined in mammalian cells as well.

IMPORTANCE

Colibactin is a bacteria-produced toxin that binds and damages DNA. It has been widely studied in mammalian cells due to its potential role in tumorigenesis. However, fundamental questions about its impact in bacteria remain underexplored. We used Escherichia coli as a model system to study colibactin toxicity in neighboring bacteria and directly tested if cell-cell contact is required for toxicity, as has previously been proposed. We found that colibactin can induce DNA damage in bacteria hundreds of microns away, and the intensity of DNA damage presents similarly regardless of cell-cell contact. Our work further suggests that the requirement for cell-cell contact for colibactin-induced toxicity also needs to be reevaluated in mammalian cells.

L-tryptophan and copper interactions linked to reduced colibactin genotoxicity in pks+ Escherichia coli

Colibactin, a nonribosomal peptide/polyketide produced by pks+ Enterobacteriaceae, is a virulence factor and putative carcinogen that damages DNA by interstrand crosslinking (ICL). While the clb genes for colibactin biosynthesis have been identified, studies are needed to elucidate the mechanisms regulating colibactin production and activity. Here we perform untargeted metabolomics of pks+ Escherichia coli cultures to identify L-tryptophan as a candidate repressor of colibactin activity. When pks+ E. coli is grown in a minimal medium supplemented with L-tryptophan in vitro ICL of plasmid DNA is reduced by >80%. L-tryptophan does not affect the transcription of clb genes but protects from copper toxicity and triggers the expression of genes to export copper to the periplasm where copper can directly inhibit the ClbP peptidase domain. Thus, L-tryptophan and copper interact and repress colibactin activity, potentially reducing its carcinogenic effects in the intestine.

IMPORTANCE

Colibactin is a small molecule produced by pks+ Enterobacteriaceae that damages DNA, leading to oncogenic mutations in human genomes. Colibactin-producing Escherichia coli (pks+) cells promote tumorigenesis in mouse models of colorectal cancer (CRC) and are elevated in abundance in CRC patient biopsies, making it important to identify the regulatory systems governing colibactin production. Here, we apply a systems biology approach to explore metabolite repression of colibactin production in pks+ E. coli. We identify L-tryptophan as a repressor of colibactin genotoxicity that stimulates the expression of genes to export copper to the periplasm where it can inhibit ClbP, the colibactin-activating peptidase. These results work toward an antibiotic-sparing, prophylactic strategy to inhibit colibactin genotoxicity and its tumorigenic effects in the intestine.

Colibactin leads to a bacteria-specific mutation pattern and self-inflicted DNA damage

Colibactin produced primarily by Escherichia coli strains of the B2 phylogroup cross-links DNA and can promote colon cancer in human hosts. Here, we investigate the toxin's impact on colibactin producers and on bacteria cocultured with producing cells. Using genome-wide genetic screens and mutation accumulation experiments, we uncover the cellular pathways that mitigate colibactin damage and reveal the specific mutations it induces. We discover that although colibactin targets A/T-rich motifs, as observed in human colon cells, it induces a bacteria-unique mutation pattern. Based on this pattern, we predict that long-term colibactin exposure will culminate in a genomic bias in trinucleotide composition. We test this prediction by analyzing thousands of E. coli genomes and find that colibactin-producing strains indeed show the predicted skewness in trinucleotide composition. Our work reveals a bacteria-specific mutation pattern and suggests that the resistance protein encoded on the colibactin pathogenicity island is insufficient in preventing self-inflicted DNA damage.

The wound microbiota: microbial mechanisms of impaired wound healing and infection

The skin barrier protects the human body from invasion by exogenous and pathogenic microorganisms. A breach in this barrier exposes the underlying tissue to microbial contamination, which can lead to infection, delayed healing, and further loss of tissue and organ integrity. Delayed wound healing and chronic wounds are associated with comorbidities, including diabetes, advanced age, immunosuppression and autoimmune disease. The wound microbiota can influence each stage of the multi-factorial repair process and influence the likelihood of an infection. Pathogens that commonly infect wounds, such as Staphylococcus aureus and Pseudomonas aeruginosa, express specialized virulence factors that facilitate adherence and invasion. Biofilm formation and other polymicrobial interactions contribute to host immunity evasion and resistance to antimicrobial therapies. Anaerobic organisms, fungal and viral pathogens, and emerging drug-resistant microorganisms present unique challenges for diagnosis and therapy. In this Review, we explore the current understanding of how microorganisms present in wounds impact the process of skin repair and lead to infection through their actions on the host and the other microbial wound inhabitants.

Colibactin-induced damage in bacteria is cell contact independent

The bacterial toxin colibactin, produced primarily by the B2 phylogroup of Escherichia coli, underlies some cases of colorectal cancers. Colibactin crosslinks DNA and induces genotoxic damage in both mammalian and bacterial cells. While the mechanisms facilitating colibactin delivery remain unclear, results from multiple studies supported a delivery model that necessitates cell-cell contact. We directly tested this requirement in bacterial cultures by monitoring the spatiotemporal dynamics of the DNA damage response using a fluorescent transcriptional reporter. We found that in mixed-cell populations, DNA damage saturated within twelve hours and was detectable even in reporter cells separated from colibactin producers by hundreds of microns. Experiments with distinctly separated producer and reporter colonies revealed that the intensity of DNA damage decays similarly with distance regardless of colony contact. Our work reveals that cell contact is inconsequential for colibactin delivery in bacteria and suggests that contact-dependence needs to be reexamined in mammalian cells as well.

Importance

Colibactin is a bacteria-produced toxin that binds and damages DNA. It has been widely studied in mammalian cells due to its potential role in tumorigenesis. However, fundamental questions about its impact in bacteria remain underexplored. We used E. coli as a model system to study colibactin toxicity in neighboring bacteria and directly tested if cell-cell contact is required for toxicity, as has previously been proposed. We found that colibactin can induce DNA damage in bacteria hundreds of microns away and that the intensity of DNA damage presents similarly regardless of cell-cell contact. Our work further suggests that the requirement for cell-cell contact for colibactin-induced toxicity also needs to be reevaluated in mammalian cells.

Prevalence and implications of pKs-positive Escherichia coli in colorectal cancer

Colorectal cancer (CRC) remains a significant global health concern, necessitating continuous investigation into its etiology and potential risk factors. Recent research has shed light on the potential role of pKs-positive Escherichia coli (pKs + E. coli) and colibactin in the development and progression of CRC. Therefore, this review aimed to provide an updated analysis of the prevalence and implications of pKs + E. coli in colorectal cancer. We conducted a literature review search in major scientific databases to identify relevant studies exploring the association between pKs + E. coli and CRC. The search strategy included studies published up to the present date, and articles were carefully selected based on predefined inclusion criteria. Thus, the present study encompasses scientific evidence from clinical and epidemiological studies supporting the presence of pKs + E. coli in CRC patients, demonstrating a consistent and significant association in multiple studies. Furthermore, we highlighted the potential mechanisms by which colibactin may promote tumorigenesis and cancer progression within the colorectal mucosa, including the production of genotoxic virulence factors. Additionally, we explored current diagnostic methods for detecting pKs + E. coli in clinical settings, emphasizing the importance of accurate identification. Moreover, we discussed future strategies that could utilize the presence of this strain as a biomarker for CRC diagnosis and treatment. In conclusion, this review consolidated existing evidence on the prevalence and implications of pKs + E. coli in colorectal cancer. The findings underscore the importance of further research to elucidate the precise mechanisms linking this strain to CRC pathogenesis and to explore its potential as a therapeutic target or diagnostic marker. Ultimately, a better understanding of the role of pKs + E. coli in CRC may pave the way for innovative strategies in CRC management and patient care.

pH-responsive on-demand release of eugenol from metal-organic frameworks for synergistic bacterial killing

Bacterial infections are a big challenge in clinical treatment, making it urgent to develop innovative antibacterial systems and therapies to combat bacterial infections. In this study, we developed a novel MOF-based synergistic antibacterial system (Eu@B-UiO-66/Zn) by loading a natural antibacterial substance (eugenol) with hierarchically porous MOF B-UiO-66 as a carrier and further complexing it with divalent zinc ions. Results indicate that the system achieved a controlled release of eugenol under pH responsive stimulation, with the complexation ability of eugenol and Zn2+ ions as a switch. Due to the destruction of a coordination bond between eugenol and Zn2+ ions by an acidic medium, the release of eugenol loaded in Eu@B-UiO-66/Zn reached 80% at pH 5.8, which was significantly higher than that under pH 8.0 (51%). Moreover, the inhibitory effect of Eu@B-UiO-66/Zn against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) after 24 h was 96.4% and 99.7%, respectively, owing to the synergistic antibacterial effect of eugenol and Zn2+ ions, which was significantly stronger than free eugenol and Eu@B-UiO-66. We hope that this strategy for constructing responsive MOF-based antibacterial carriers could have potential possibilities for the application of MOF materials in antibacterial fields.

Current understandings of colibactin regulation

The biosynthetic machinery for the production of colibactin is encoded by 19 genes (clbA - S) within the pks pathogenicity island harboured by many E. coli of the B2-phylogroup. Colibactin is a potent genotoxic metabolite which causes DNA-damage and which has potential roles in microbial competition and fitness of pks+ bacteria. Colibactin has also been strongly implicated in the development of colorectal cancer. Given the genotoxicity of colibactin and the metabolic cost of its synthesis, the regulatory system governing the clb cluster is accordingly highly complex, and many of the mechanisms remain to be elucidated. In this review we summarise the current understanding of regulation of colibactin biosynthesis by internal molecular components and how these factors are modulated by signals from the external environment.

Hypervirulent Klebsiella pneumoniae employs genomic island encoded toxins against bacterial competitors in the gut

The hypervirulent lineages of Klebsiella pneumoniae (HvKp) cause invasive infections such as Klebsiella-liver abscess. Invasive infection often occurs after initial colonization of the host gastrointestinal tract by HvKp. Over 80% of HvKp isolates belong to the clonal group 23 sublineage I that has acquired genomic islands (GIs) GIE492 and ICEKp10. Our analysis of 12 361 K. pneumoniae genomes revealed that GIs GIE492 and ICEKp10 are co-associated with the CG23-I and CG10118 HvKp lineages. GIE492 and ICEKp10 enable HvKp to make a functional bacteriocin microcin E492 (mccE492) and the genotoxin colibactin, respectively. We discovered that GIE492 and ICEKp10 play cooperative roles and enhance gastrointestinal colonization by HvKp. Colibactin is the primary driver of this effect, modifying gut microbiome diversity. Our in vitro assays demonstrate that colibactin and mccE492 kill or inhibit a range of Gram-negative Klebsiella species and Escherichia coli strains, including Gram-positive bacteria, sometimes cooperatively. Moreover, mccE492 and colibactin kill human anaerobic gut commensals that are similar to the taxa found altered by colibactin in the mouse intestines. Our findings suggest that GIs GIE492 and ICEKp10 enable HvKp to kill several commensal bacterial taxa during interspecies interactions in the gut. Thus, acquisition of GIE492 and ICEKp10 could enable better carriage in host populations and explain the dominance of the CG23-I HvKp lineage.

Microbiota-derived small molecule genotoxins: host interactions and ecological impact in the gut ecosystem

The human intestinal tract is densely colonized by a microbial community that is subject to intense competition. Bacteria in this complex habitat seek to outcompete their neighbors for nutrients and eliminate competitors with antibacterial toxins. Antagonism can be mediated by diverse effectors including toxic proteins and small molecule inhibitors that are released extracellularly or delivered by specialized secretion systems to targeted cells. Two prototypical microbiota-derived enterotoxins, colibactin and tilimycin, and the newly discovered family of indolimines represent an expanding group of non-proteinaceous small molecules which specifically target DNA. In addition to cell killing, they generate mutations and genome instability in intoxicated microbes and host cells alike. They have been studied in detail because of their direct toxicity to human cells and important etiological roles in intestinal pathologies. Increasing evidence, however, reveals that these commensal genotoxins are also mediators of interbacterial antagonism, which impacts gut microbial ecology. In this review, we illustrate the functional versatility of commensal genotoxins in the gut ecosystem.

Development of Composite Sponge Scaffolds Based on Carrageenan (CRG) and Cerium Oxide Nanoparticles (CeO2 NPs) for Hemostatic Applications

In this study, a novel absorbable hemostatic agent was developed using carrageenan (CRG) as a natural polymer and cerium oxide nanoparticles (CeO2 NPs). CRG-CeO2-0.5 and CRG-CeO2-1 composites were prepared by compositing CeO2 to CRG + CeO2 at a weight ratio of 0.5:100 and 1:100, respectively. The physicochemical and structural properties of these compounds were studied and compared with pristine CRG. Upon incorporation of CeO2 nanoparticles into the CRG matrix, significant reductions in hydrogel degradation were observed. In addition, it was noted that CRG-CeO2 exhibited better antibacterial and hemostatic properties than CRG hydrogel without CeO2 NPs. The biocompatibility of the materials was tested using the NIH 3T3 cell line, and all samples were found to be nontoxic. Particularly, CRG-CeO2-1 demonstrated superior hemostatic effects, biocompatibility, and a lower degradation rate since more CeO2 NPs were present in the CRG matrix. Therefore, CRG-CeO2-1 has the potential to be used as a hemostatic agent and wound dressing.

Staphylococcus aureus in Polymicrobial Skinand Soft Tissue Infections: Impact of Inter-Species Interactionsin Disease Outcome

Polymicrobial biofilms provide a complex environment where co-infecting microorganisms can behave antagonistically, additively, or synergistically to alter the disease outcome compared to monomicrobial infections. Staphylococcus aureus skin and soft tissue infections (Sa-SSTIs) are frequently reported in healthcare and community settings, and they can also involve other bacterial and fungal microorganisms. This polymicrobial aetiology is usually found in chronic wounds, such as diabetic foot ulcers, pressure ulcers, and burn wounds, where the establishment of multi-species biofilms in chronic wounds has been extensively described. This review article explores the recent updates on the microorganisms commonly found together with S. aureus in SSTIs, such as Pseudomonas aeruginosa, Escherichia coli, Enterococcus spp., Acinetobacter baumannii, and Candida albicans, among others. The molecular mechanisms behind these polymicrobial interactions in the context of infected wounds and their impact on pathogenesis and antimicrobial susceptibility are also revised.

Interspecies interactions in mixed-species biofilms formed by Enterococcus faecalis and gram-negative bacteria isolated from polymicrobial diabetic foot ulcers

Diabetic foot ulcers (DFU) are exacerbated by bacterial colonisation. Here, a high prevalence of Enterococcus faecalis was observed in DFU patients from an Argentinean hospital. E. faecalis was frequently co-isolated with Escherichia coli, Morganella morganii, and Pseudomonas aeruginosa. The effect of interspecies interactions on bacterial growth was investigated in mixed-species macrocolony biofilms developed in Lubbock-Glc-agar. Similar cell counts were found for E. faecalis and M. morganii growing in mixed and single-species biofilms. An E. faecalis strain showed 1 Log higher cell counts in mixed biofilms with E. coli. Remarkably, E. faecalis strains showed 2 to 4 Log higher cell counts in mixed biofilms with P. aeruginosa. This effect was not observed in planktonic growth or biofilms developed in tryptic soy agar. The present findings reveal bacterial interactions that benefit E. faecalis in mixed-species biofilms, mainly with P. aeruginosa, in a medium that partially mimics the nutrients found in DFU.

Current research on fungi in chronic wounds

The occurrence of chronic wounds is a major global health issue. These wounds are difficult to heal as a result of disordered healing mechanisms. The most common types of chronic wounds are diabetic ulcers, pressure ulcers, arterial/venous ulcers and nonhealing surgical wounds. Although bacteria are an important cause of chronic nonhealing wounds, fungi also play a substantial role in them. The fungal infection rate varies with different chronic wound types, but overall, the prevalence of fungi is extremely underestimated in the clinical treatment and management of chronic wounds. Wounds and ulcers can be colonized by host cutaneous, commensal or environmental fungi and evolve into local infections, causing fungemia as well as invasive fungal disease. Furthermore, the fungi involved in nonhealing wound-related infections help commensal bacteria resist antibiotics and the host immune response, forcing wounds to become reservoirs for multiresistant species, which are considered a potential key factor in the microbial bioburden of wounds and ulcers. Fungi can be recalcitrant to the healing process. Biofilm establishment is the predominant mechanism of fungal resistance or tolerance to antimicrobials in chronic nonhealing wounds. Candida albicans yeast and Trichophyton rubrum filamentous fungi are the main fungi involved in chronic wound infection. Fungal species diversity and drug resistance phenotypes in different chronic nonhealing wound types will be emphasized. In this review, we outline the latest research on fungi in chronic wounds and discuss challenges and future perspectives related to diagnosing and managing chronic wounds.