Biology subjects

Mil-Homens, D.

Publications and source records attributed to Mil-Homens, D..

4 recordsLinked to original sources

bioRxiv2026

Virulence studies of the human gut pathobiont Bilophila wadsworthia using Galleria mellonella as model host

Bilophila wadsworthia is a gut pathobiont implicated in dysbiosis-driven inflammation, yet its pathogenic mechanisms remain poorly investigated. Here, we evaluated the suitability of Galleria mellonella larvae as an in vivo model to study B. wadsworthia infection. Two infection routes were compared: oral inoculation to mimic gastrointestinal colonization and hemolymph injection to model systemic infection. Oral challenge had minimal impact on larval health, whereas hemolymph injection caused marked morbidity, including reduced mobility, impaired cocoon formation, and progressive melanization, indicating that access to the circulatory system is required for overt disease. Infection required live bacteria, with B. wadsworthia capable of intracellular replication within hemocytes, leading to transient depletion of circulating immune cells followed by compensatory hemocyte proliferation. These findings reveal tight coupling between bacterial proliferation and host immune dynamics. Comparison with other sulfidogenic bacteria suggests that Bilophila pathogenicity is likely to involve host-specific interactions. Overall, our results establish G. mellonella as a practical and ethically favorable model to investigate B. wadsworthia virulence, host-pathogen interactions, and mechanisms relevant to gut-associated infection.

microbiology↗

bioRxiv2026

A Nickel N-Heterocyclic Biscarbene Complex Derived from Caffeine Enhances Fluconazole Efficacy against Candida glabrata

Invasive infections caused by Candida spp. are associated with high morbidity and mortality, particularly in immunocompromised patients, and are increasingly difficult to treat due to rising antifungal resistance. Here, we further investigate the antifungal properties of a previously reported nickel N-heterocyclic biscarbene derived from caffeine (compound 5) and describe the synthesis of an analogous nickel N-heterocyclic biscarbene based on benzimidazole (compound 8), designed to evaluate the impact of the biscarbene and xanthine frameworks on activity and toxicity. Compound 5 displayed selective activity against Candida glabrata, inhibited biofilm formation and showed greater cellular accumulation in this species. In a Galleria mellonella infection model, 5 significantly reduced fungal burden while exhibiting lower cytotoxicity than the benzimidazole analogue 8. Importantly, although compound 5 and fluconazole are individually fungistatic, their combination was fungicidal against C. glabrata. In the presence of compound 5, the minimal inhibitory concentration of fluconazole decreased against both a fluconazole-resistant petite mutant and a respiratory-competent C. glabrata strain evolved in vitro to fluconazole resistance. Compound 5 increased the frequency of petite mutants, suggesting an effect on mitochondrial function; however, its retained activity against these mutants and its synergism with fluconazole in the petite background indicate an additional mechanism of action. These findings identify 5 as a promising antifungal adjuvant and support its potential use in combination therapy to enhance azole efficacy against C. glabrata. ImportanceInvasive infections caused by C. glabrata are increasingly hard to treat because this pathogen is often tolerant to azoles and is developing resistance to echinocandins, leaving clinicians with few effective options. Our work explores a nickel-caffeine complex that shows selective activity against C. glabrata and low toxicity, features that make it attractive as a potential therapeutic lead. Notably, this compound enhances the activity of fluconazole, turning a commonly used fungistatic drug into a fungicidal combination against both susceptible and resistant C. glabrata. By also affecting mitochondrial function yet remaining active in respiratory-deficient mutants, the compound appears to act through mechanisms distinct from existing antifungals. These properties suggest that metal-based xanthine complexes could be developed as adjuvants to restore or boost azole efficacy against difficult-to-treat C. glabrata infections, addressing an important priority identified for fungal pathogens.

microbiology↗

bioRxiv2024

Caspofungin binding to iron compromises its antifungal efficacy against Candida albicans

Echinocandin drugs, such as caspofungin, inhibit the synthesis of {beta}-1,3-D-glucans, which are essential components of the fungal cell wall. These drugs are often the preferred option for treating invasive fungal infections (IFIs) caused by Candida spp. due to their superior efficacy compared to other antifungal agents. Iron overload conditions, which exacerbate fungal burden, are well-documented as significant risk factors for the progression of IFIs. Recent in vitro studies have suggested that iron overload may also reduce the efficacy of cell wall-perturbing agents, such as echinocandins, against Candida albicans, by altering the composition of the fungal cell wall. Here, we show that iron loading conditions which do not interfere with the cell wall composition are still capable of recapitulating the caspofungin-resistant phenotype induced by iron in C. albicans. Spectroscopic analyses provided evidence that caspofungin binds to iron through its ethylenediamine moiety and two amide groups. Consistent with the in vitro activity of {beta}-1,3-D-glucan synthase, molecular dynamics simulations revealed that, when bound to iron, caspofungin undergoes conformational changes that may reduce its ability to inhibit the enzyme. Importantly, the in vivo antifungal efficacy of caspofungin is compromised in a Galleria mellonella model of IFI caused by C. albicans simulating a context of iron overload. This effect may extend beyond C. albicans infections, as the antagonism between iron and caspofungin was also observed in other medically important fungi causing IFIs.

microbiology↗

bioRxiv2021

RNase R, a new virulence determinant of Streptococcus pneumoniae

Pneumococcal infections have increasingly high mortality rates despite the availability of vaccines and antibiotics. The increase of bacterial resistance to antibiotics urges the discovery of new alternative therapeutics. Therefore, the identification of new virulence determinants, and the understanding of the molecular mechanisms behind pathogenesis and pneumococcal-host interactions has become of paramount importance in the search of new targets for drug development. The exoribonuclease RNase R has been involved in virulence in a growing number of pathogens. In this work, we have used Galleria mellonella as an infection model to demonstrate that the presence of ribonuclease R increases the pneumococcus virulence. Although the absence of RNase R does not affect exponential growth, the ability of the RNase R deleted strain to replicate in the hemolymph is compromised. Larvae infected with the RNase R mutant strain show an increased expression level of antimicrobial peptides, and have a lower bacterial load in the haemolymph in the later stages of infection, leading to a higher survival rate. Interestingly RNase R carrying pneumococci suffer a sudden drop in bacterial numbers immediately after infection, resembling the eclipse phase observed after intravenous inoculation in mice. Together our results suggest that RNase R might be involved in the ability of pneumococci to evade the host immune response, probably by interfering with internalisation and/or replication inside the larval hemocytes.

molecular biology↗