Search Results (163)

Background: There is an urgent need for novel treatment options for Neisseria gonorrhoeae. Methenamine is an interesting urinary antiseptic with a very low propensity to induce antimicrobial resistance. Methods: We assessed the MICs of methenamine-hippurate for 18 N. gonorrhoeae isolates. We then assessed the in vivo efficacy of methenamine-hippurate against N. gonorrhoeae using the Galleria mellonella infection model. Results: We found that all the gonococcal isolates had a methenamine-hippurate MIC of 300 mg/L. This MIC was not higher in isolates with higher ceftriaxone MICs. No toxicity of methenamine at the doses tested was found, and doses as low as 200 mg/kg were effective in the G. mellonella model. Conclusions: Further studies in mice and humans are required to assess if methenamine-hippurate could be used to treat gonococcal urethritis alone or in combination with other agents such as ceftriaxone. Full article

Staphylococcus saprophyticus (S. saprophyticus) is an opportunistic coagulase-negative staphylococcus (CoNS) known to cause urinary tract infections in humans and is increasingly recognized in veterinary medicine. The aim of this study was to provide an epidemiological characterization of S. saprophyticus strains and to identify potential virulence factors that may contribute to interspecies transmission. This research is particularly important, as companion animals represent an understudied reservoir of this microorganism, and their role in the spread of resistant pathogens remains insufficiently understood. A total of 61 S. saprophyticus strains isolated from humans, dogs, and cats were analyzed. Identification was performed using MALDI-TOF MS and confirmed by PCR targeting the hrcA gene. Antimicrobial susceptibility was assessed using the disk diffusion and broth microdilution methods, while resistance genes were detected by PCR. The blaZ and mecA genes were present in all strains; additionally, the majority harbored the resistance genes ermA, ermB, tetM, and tetK. Multidrug resistance (MDR) was identified in 21/61 strains (34.4%). Biofilm-forming capacity was temperature-dependent, with the strongest biofilm production observed at 37 °C (70.5%). At 38 °C and 39 °C, the proportion of strong biofilm producers decreased to 50.8% and 52.5%, respectively. All tested strains demonstrated pathogenic potential in the Galleria mellonella larvae infection model, with the highest mortality recorded for selected feline and canine strains. These findings indicate that S. saprophyticus strains from both humans and companion animals possess notable virulence and multidrug resistance. The detection of genotypically and phenotypically resistant strains in animals highlights their potential role as reservoir for zoonotic transmission. Full article

The Steinernema carpocapsae nematode is known to release several excretory/secretory products (ESPs) in its venom upon contact and during the parasitic infection process of insect hosts. A recurrent family of proteins found in this nematode’s venom is the CAP (cysteine-rich secretory protein/antigen 5/pathogenesis-related 1) protein, but the functional role of these proteins remains unknown. To elucidate the biological function, this study focused on characterising the secreted protein, first identified in the venom of the nematode’s parasitic stage, and the sequence retrieved from transcriptomic analysis. The structural comparisons of the Sc-CAP protein model, as determined by AlphaFold2, revealed related structures from other parasitic nematodes of vertebrates. Some of these closely related proteins are reported to have sterol-binding ability. The Sc-CAP recombinant protein was successfully produced in Escherichia coli in conjunction with a chaperone protein. The results showed that the Sc-CAP protein binds to cholesterol, and docking analyses of sterols on the protein revealed potential molecular interactions. Immunoassays performed in Galleria mellonella larvae revealed that this venom protein has an inhibitory effect against phenoloxidase and the antimicrobial response of insects. This suggests that the venom protein has an immunomodulatory function against insects, emphasising its importance during the parasite–host interaction. Full article

Daptomycin (DAP) is a therapeutic option for vancomycin-resistant Enterococcus faecium (VRE) infections, but DAP resistance may occur during treatment. Previously, we identified a mutation within the E. faecium lafB gene that induces hypersusceptibility to DAP. The lafB gene encodes a glycosyltransferase involved in lipoteichoic acid anchor synthesis, which makes it a promising target for enhancing DAP efficacy. In this study, we characterized E. faecium LafB protein (EfLafB) biophysical properties, used AlphaFold3 to predict LafB in silico three-dimensional structure, and determined lafB gene mutation’s role in virulence, comparing E. faecium HBSJRP18 (DAP-hypersusceptible) and a lafB revertant, HBSJRP18_2.7, and analyzing bacterial growth kinetics, biofilm formation ability, and virulence in a Galleria mellonella model. After gene cloning and expressing and purifying EfLafB, circular dichroism and SEC-MALS assays revealed its monomeric nature under in vitro conditions, with approximately a 40 kDa molecular mass and a melting temperature of 50 °C. In silico prediction indicated that LafB is an αβ-type protein with two domains conforming to the GT-4 family glycosyltransferases. These results are further supported by the highly conserved amino acids (E257, D91, R184, and K185), likely involved in UDP-Glc binding. The studied lafB gene mutation resulted in a significant decrease in bacterial growth and virulence in the invertebrate model. Full article

The pleuromutilin derivative, the compound PL-W, was synthesized by introducing a 4-fluorophenyl group at the C21 position and selected for comprehensive antibacterial evaluation. PL-W demonstrated notable antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), with a minimum inhibitory concentration (MIC) of 0.03125 µg/mL, which is significantly lower than that of tiamulin (0.5 µg/mL). Crystal violet (CV) staining revealed that it inhibited MRSA biofilm formation and electron microscopy revealed that it disrupted bacterial cell division and, possibly, the synthesis of essential cell wall proteins. In both in vivo models, PL-W exhibited excellent performance. In the Galleria mellonella infection model, treatment with different concentrations of PL-W increased the survival rate from 20% to 90% and significantly reduced the bacterial load. In the mouse model of MRSA pneumonia, a 10 mg/kg dose of PL-W increased the survival rate to 70%, decreased the bacterial load in the lungs, and alleviated inflammatory damage. Molecular docking studies indicated that PL-W had a similar docking pose and comparable binding affinity to that of lefamulin, with hydrogen bond interactions that are crucial for binding to the peptidyl transferase center (PTC). Moreover, it demonstrated no significant reduction in cell viability in HepG2 and HEK293 cells, even at high concentrations (≤50 µg/mL). Overall, PL-W shows significant potential as a novel anti-MRSA agent owing to its potent in vitro and in vivo activities and low cytotoxicity. Full article

Citrobacter braakii can colonize the intestinal tract of humans and animals and occasionally act as opportunistic pathogen. Although isolated from food and the environment, its potential as a foodborne pathogen remains uncertain. Twenty C. braakii isolates were previously collected from salami and soft cheese artisanal productions. In the present study, the potentialities of C. braakii as a food safety hazard were explored by a genomic comparison of C. braakii newly sequenced genomes with publicly available genomes, including those of clinical relevance, and a pathogenicity assessment in Galleria mellonella as an in vivo infection model. Phylogenomic reconstruction revealed that one salami clone and two C. braakii genomes of the soft cheese production were closely related (from 11 to 28 core SNP differences) to C. braakii publicly available clinical genomes. All genomes carried the chromosomally located bla_CMY and/or qnrB genes and were resistant to cephalosporins and/or had reduced susceptibility to ciprofloxacin. G. mellonella larvae showed 90% mortality after challenge with C. braakii strains carrying the vex and tvi operons coding for the capsular polysaccharide (Vi antigen), in comparison to 40% of strains lacking these two operons. The high mortality rate of vex- and tvi-positive C. braakii isolated from food processing plants suggests C. braakii to be a possible foodborne hazard. Full article

The novel pathogen Candida auris has rapidly become a major health threat due to its high virulence, resistance to multiple antifungal agents, and remarkable environmental persistence. This study evaluated the influence of phenotypic traits and antifungal minimum inhibitory concentrations (MICs) on C. auris virulence using a Galleria mellonella infection model. Ten clinical strains, categorized as aggregative or non-aggregative, were analyzed for antifungal susceptibility and survival outcomes. All strains exhibited fluconazole resistance, with variable susceptibilities to other antifungals. Survival analysis revealed that the non-aggregative phenotype was independently associated with reduced survival in G. mellonella (HR = 2.418, p = 0.015), while antifungal MICs and invasive origin were not significant independent predictors of mortality in an elastic net-adjusted multivariable model. Strong correlations were observed between certain antifungal MICs, suggesting potential cross-resistance patterns; however, no independent association with virulence was identified. These results suggest that C. auris possesses not only an enhanced ability to develop antifungal resistance but also the capacity to do so without incurring fitness costs that could attenuate its virulence. Full article

Trichosporon austroamericanum is a recently described yeast species related to Trichosporon inkin and exclusively isolated from clinical specimens. However, its genomic features and pathogenic potential remain poorly understood. In this study, we performed whole-genome sequencing on three blood-derived isolates from patients with invasive fungal infections and comparative analyses with 13 related Trichosporon species. The three isolates yielded high-quality assemblies of 9–10 scaffolds (~21 Mb), facilitating reliable comparisons. While most species had comparable genome sizes, Trichosporon ovoides, Trichosporon coremiiforme, and Cutaneotrichosporon mucoides displayed large, fragmented genomes, suggestive of polyploidy. ANI analysis and phylogenetic trees based on ANI and single-copy orthologs supported the classification of T. austroamericanum as a distinct clade with moderate intraspecific divergence. Using the Galleria mellonella, a model for fungal pathogenicity, all T. austroamericanum strains reduced larval survival, and NIIDF 0077300 exhibited virulence comparable to T. asahii and greater than T. inkin. To explore the gene-level differences associated with pathogenicity, we performed ortholog analysis based on single-copy genes. This revealed a unique Zn(II)₂Cys₆-type transcription factor gene (OG0010545) present only in NIIDF 0077300 and T. asahii. These findings highlight the genomic diversity and infection-associated traits of T. austroamericanum, providing a framework for future functional studies. Full article

Increasing antifungal resistance and side effects of existing drugs demand alternative approaches for treating Candida (C.) infections. This study aimed to comprehensively evaluate the antifungal efficacy of myricetin (MYR), a natural flavonoid, against both fluconazole (FLC)-resistant and susceptible clinical Candida strains, with a particular focus on its inhibitory effects on C. albicans biofilms. Antifungal susceptibility was evaluated on Candida spp. by the broth microdilution method, and the impact of myricetin on C. albicans biofilms was determined using the Cell Counting Kit-8 (CCK-8) assay. To understand the molecular mechanisms underlying the antibiofilm properties of myricetin, expression analysis of genes in the RAS1/cAMP/EFG1 pathway (ALS3, HWP1, ECE1, UME6, HGC1) and cAMP-dependent protein kinase regulation (RAS1, CYR1, EFG1) involved in the transition from yeast to hyphae was performed. Field emission scanning electron microscopy (FESEM) was used to study the ultrastructural changes and morphological dynamics of Candida biofilms after exposure to MYR and FLC. The in vivo toxicity of myricetin was evaluated by survival analysis using the Galleria mellonella model. Myricetin significantly suppressed key genes related to hyphae development (RAS1, CYR1, EFG1, UME6, and HGC1) and adhesion (ALS3 and HWP1) in both clinical and reference Candida strains at a concentration of 640 µg/mL. FESEM analysis revealed that myricetin inhibited hyphae growth and elongation in C. albicans. This study highlights the promising antibiofilm potential of myricetin through a significant inhibition of biofilm formation and hyphal morphogenesis. Full article

Fungal infections, including skin ones, due to resistant strains combined with the gap in discovering new antifungal compounds have presented great medical importance; thus, we evaluated the antifungal properties of Plinia cauliflora, a Brazilian plant known as jabuticabeira, as its fruits have been used in traditional medicine, which has been scientifically proved. The differential in this study was the use of leaves to obtain the ethanolic extract and its fractions and with incorporation in microemulsions that can increase the activity, promoting greater availability of active components in therapeutic targets. Candida glabrata has been very prominent in nosocomial infections and our results were very promising, showing a minimum inhibitory concentration of 4.88 μg/mL for the extract and about a 4-fold decrease with its microemulsion reaching 1.22 μg/mL; for the dermatophytic fungus Trichophyton rubrum, this decreased 2-fold, from 156.25 μg/mL to 78.12 μg/mL. The antioxidant activity was also studied, showing the best results for the extract at 25.6 μg/mL and lastly, the samples were not toxic when the Galleria mellonella model was used. Thus, the results demonstrate the activity of the extract, and that the incorporation was able to increase the antifungal activity in a safe, non-toxic manner, making it possible to provide a therapeutic option for these fluconazole-resistant microorganisms. Full article

Background: Fungal infections pose an increasingly predominant threat to human and animal health. Modified compounds derived from chemo-diverse natural products offer enhanced therapeutic efficacies and promising approaches to combat life-threatening fungal pathogens. Methods: We performed biosynthetic gene clusters analysis of 2,4-diacetylchloroglucoside (DAPG) in 4292 shotgun metagenomes samples from the healthy and diseased skin. Then, we assessed the antifungal activity of DAPG and the derivative 2,4-diproylphloroglucinol (DPPG) against pathogenic fungi by minimum inhibitory concentrations. The inhibitory effects of DPPG were measured using hyphal growth assay and spore germination assay. Concurrently, the mechanism of DPPG on Aspergillus fumigatus was investigated in membrane permeability and fluidity. The therapeutic efficacy was evaluated in a Galleria mellonella infection model. Results: We observed a significantly higher abundance of bacteria harboring DAPG biosynthetic clusters on healthy skin compared to diseased skin. Further, we designed and synthesized a series of phloroglucinol derivatives based on DAPG and obtained an antifungal candidate DPPG. DPPG not only exhibited robust antifungal activity against Aspergillus spp. and Candida spp. but also impaired hyphal growth and spore germination of A. fumigatus in vitro. A mechanism study showed that DPPG reduced membrane fluidity and increased the leakage of cellular contents, resulting in membrane perturbation and fungal death. Lastly, the therapeutic efficacy of DPPG was confirmed in a G. mellonella infection model. Conclusions: Our study demonstrates that DPPG is a potent scaffold to combat invasive fungal infections. Full article

Lactic acid bacteria (LAB) are gaining increasing attention as functional ingredients in the cosmetic industry, particularly those derived from natural plant sources. Although various LAB strains have been widely applied in cosmetic formulations, studies investigating the effects of naturally derived LAB on the skin remain limited. In this study, we isolated an LAB strain from ginseng and evaluated its potential as a functional cosmetic ingredient. The antimicrobial activity of the strain was assessed against skin-associated pathogens Staphylococcus aureus and Staphylococcus epidermidis, while cytotoxicity was evaluated using HaCaT and Caco-2 cells. Considering the limitations of vertebrate animal testing, infection and survival assays were conducted using Galleria mellonella larvae as an alternative in vivo model. The ginseng-derived strain exhibited 99.93% similarity to Pediococcus pentosaceus and was designated P. pentosaceus THG-219. It exhibited an MIC of 0.625 mg/mL and 1.25 mg/mL against S. aureus KCTC 3881 and S. epidermidis KCTC 1917, respectively. Its antimicrobial activity was further enhanced following ethyl acetate fractionation. P. pentosaceus THG-219 showed no toxicity in G. mellonella larvae and exerted antibacterial effects in this model. No cytotoxicity was observed in HaCaT and Caco-2 cells. Furthermore, P. pentosaceus THG-219 promoted host cell adhesion while inhibiting pathogen adhesion. It also exhibited excellent acid, bile, and heat tolerance, suggesting strong survivability under harsh conditions. Collectively, these results indicate that P. pentosaceus THG-219, isolated from ginseng, is a promising, safe, and stable candidate for development as a functional cosmetic ingredient. Full article

Background/Objectives: Diabetic foot infections (DFIs) are commonly associated with frequent hospitalizations, limb amputations, and premature death due to the profile of the bacteria infecting foot ulcers. DFIs are generally colonized by a polymicrobial net of bacteria that grows in biofilms, developing an increased antimicrobial resistance to multiple antibiotics. DFI treatment is a hurdle, and the need to develop new therapies that do not promote resistance is urgent. Therefore, the antibacterial efficacy of Nisin Z (antimicrobial peptide), a core–shell polycationic polyurea pharmadendrimer (PURE_G4OEI₄₈) (antimicrobial polymer), and amlodipine (antihypertensive drug) was evaluated against S. aureus and P. aeruginosa isolated from a DFI and previously characterized. Methods: The antibacterial activity was analyzed in vitro by determining the minimal inhibitory concentration (MIC) and in vivo in a Galleria mellonella model by assessing the larvae survival and health index. Results: The results indicate that Nisin Z exhibited antibacterial activity against S. aureus in vivo, allowing larvae full survival, and no antibacterial activity against P. aeruginosa. Nisin Z may have reduced the antibacterial effectiveness of both PURE_G4OEI₄₈ and amlodipine. PURE_G4OEI₄₈ significantly increased the survival of the larvae infected with P. aeruginosa, while amlodipine showed no activity against both bacteria in vivo. Conclusions: These findings suggest that both Nisin Z and PURE_G4OEI₄₈ could potentially be used individually as adjunct treatments for mild DFIs. However, further studies are needed to confirm these findings and assess the potential toxicity and efficacy of PURE_G4OEI₄₈ in more complex models. Full article

Background/Objectives: Wounds from burns are susceptible to infections, allowing multidrug-resistant microorganisms to complicate treatments and patient recovery. This highlights the development of new strategies to control these microorganisms. This work evaluated the antibacterial activity of hydrogels containing biogenic silver nanoparticles (bio-AgNP) and Origanum vulgare essential oil (OEO) against multidrug-resistant bacteria. Methods: The formulations were subjected to organoleptic, pharmacotechnical, and stability characterization and antimicrobial activity assessment by time–kill tests and alternative methods, an ex vivo model using porcine skin, and an in vivo model using Galleria mellonella. Results: All hydrogels maintained their stability after the thermal stress. The hydrogel containing bio-AgNP + OEO 1% (HAgNP + OEO1) presented bactericidal effectiveness, within 2 h, against both Gram-positive and Gram-negative multidrug-resistant bacteria in the time–kill test. For alternative testing, HAgNP + OEO1 was compared with 1% silver sulfadiazine (SS) and the base formulation. In the ex vivo test, both HAgNP + OEO1 and SS treatments showed a similar reduction in superficial washing of the burn for S. aureus 999, while for P. aeruginosa, the reduction was more expressive for SS treatment. In the burn tissue, HAgNP + OEO1 treatment was more effective against S. aureus 999, while for P. aeruginosa 1461, both formulations were similarly effective. In the Galleria mellonella test, survival rates after 48 h were 84% for the control group (base) and 50% for both HAgNP + OEO1 and SS treatment groups. Conclusions: This study demonstrates that the hydrogel combining antimicrobials is effective against multidrug-resistant microorganisms, offering a promising alternative for the treatment of infected burns. Full article

Background/Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) presents a major public health challenge due to its multidrug resistance and high virulence. Developing representative model strains is crucial for systematically assessing pathogenesis and antimicrobial therapies. Methods: The highly virulent MRSA strain T144, isolated from pigs, was characterized through whole-genome sequencing and antimicrobial susceptibility testing. Infection models were successfully established in Galleria mellonella and mice to evaluate virulence. A mouse lung infection model was specifically developed to assess bacterial load dynamics, immune responses, and the efficacy of vancomycin treatment. Results: MRSA T144 demonstrated broad-spectrum antibiotic resistance and high mortality rates in both Galleria mellonella and mouse models. Whole-genome sequencing identified multiple virulence-associated genes, including hemolysins and enterotoxins. The concentration of 7 × 10⁸ CFUs was optimized for establishing the mouse lung infection model. In the mouse lung infection model, MRSA T144 demonstrated rapid bacterial proliferation within the first 24 h, followed by a slower growth rate. Significant changes in immune markers were observed, with elevated levels of pro-inflammatory cytokines (IL-1β, IL-6, IL-8, IL-17a, TNF-α) and decreased IL-10 levels. Vancomycin treatment significantly improved survival rates and reduced bacterial load, confirming the model’s utility for antimicrobial efficacy studies. Conclusions: The successful establishment of MRSA T144 infection models provides a robust platform for investigating bacterial dynamics, immune responses, and antimicrobial efficacy against highly virulent MRSA strains. These findings highlight the potential of MRSA T144 as a valuable model for developing novel therapeutic strategies. Full article