Biology subjects

Kolenda, C.

Publications and source records attributed to Kolenda, C..

3 recordsLinked to original sources

bioRxiv2025

Exploring Phage-Staphylococcus aureus Host Dynamics Through Innovative In Vitro Experiment and Pharmacokinetic/pharmacodynamic Modeling

BackgroundPhage therapy is a promising approach against multidrug-resistant Staphylococcus aureus, but its clinical development is limited by gaps in pharmacokinetic/pharmacodynamic (PK/PD) understanding, especially concerning phage self-replication and resistance dynamics. MethodsWe combined in vitro time-kill assays with PK/PD modeling to study three anti-staphylococcal phages (V1SA019, V1SA020, V1SA022) against two S. aureus strains (SH1000 and USA300). A system of differential equations captured the co-dynamics of susceptible, resistant and infected bacteria and free phages. Nonlinear mixed-effect modeling quantified parameter variability. Resistance emergence was monitored through phenotyping and whole-genome sequencing of resistant clones. ResultsPhage-bacteria interactions followed a predator-prey pattern, with early bacterial growth, rapid phage amplification, and subsequent bacterial collapse. However, resistant subpopulations emerged, regrew over time, in a multiplicity of infection (MOI) dependent way. The model accurately described bacterial and phage dynamics and estimated kinetic parameters including adsorption and burst size. Proliferation and inundation thresholds varied by strain and phage. All resistant clones harbored mutations in genes involved in teichoic acid biosynthesis, with associated growth defects. Simulations demonstrated that only phage doses exceeding both susceptible and resistant bacterial inundation thresholds fully suppressed regrowth. ConclusionThis study provides a quantitative framework for understanding phage-S. aureus co-dynamics and resistance emergence. It emphasizes the importance of considering both proliferation and inundation thresholds when designing phage dosing regimens. These findings inform the rational development of phage therapy and support translation toward in vivo and clinical applications.

pharmacology and toxicology↗

bioRxiv2025

Membrane curvature regulates Ups1 dependent phosphatidic acid transfer across lipid bilayers

Mitochondria are essential organelles in eukaryotic cells, enclosed by two membranes with distinct compositions and functions. In addition to the endoplasmic reticulum, mitochondria are major sites of cellular lipid production. Cardiolipin, for example, is exclusively synthesized in the mitochondrial inner membrane. This requires the precursor lipid phosphatidic acid to be imported from the endoplasmic reticulum to the mitochondrial outer membrane. Subsequently phosphatidic acid is transferred to the inner membrane by the lipid transfer protein Ups1/PRELID1. The regulation of this process, the role of membrane physico-chemical properties, and the mechanisms by which energy barriers are overcome during lipid extraction and insertion remain poorly understood. Here, we demonstrate that Ups1 exhibits a strong preference for binding to positively curved membrane regions. Our findings reveal that phosphatidic acid extraction is energetically favored at these membrane domains, leading to enhanced lipid transfer between membranes with high positive curvature and we show that events at the donor membrane are rate limiting for the transfer cycle. Our data suggest that Ups1 membrane binding is modulated by pH, lipid composition, and membrane morphology, pointing to a complex, multipartite regulatory network underlying intra-mitochondrial lipid transfer.

biochemistry↗

bioRxiv2024

Acquisition of daptomycin resistance in patients results in decreased virulence in Drosophila

Staphylococcus aureus can acquire antimicrobial resistance which in turn may affect its pathogenic potential. Using a panel of paired clinical isolates collected before and after daptomycin resistance acquisition, most frequently through single mprF mutation, we show a relationship between increasing daptomycin minimum inhibitory concentration and reduced virulence in a Drosophila systemic infection model. Analysing toxin production, in vitro bacterial growth characteristics, and cell surface properties, we failed to link daptomycin resistance-related attenuated virulence to either reduced virulence factor production, reduced fitness or to any of the cell surface characteristics investigated. Competition assays in Drosophila also did not support any altered ability in immune evasion. Instead, using a panel of mutant flies defective for various immune components, we show that this daptomycin resistance-related attenuated virulence is mostly explained by greater susceptibility to activity of Drosophila prophenoloxidase, a tyrosinase involved in melanization, but not to antimicrobial peptides or to Bomanin antimicrobial effectors. Further investigation could not link daptomycin resistance-related attenuation of virulence to a differential susceptibility to reactive oxygen species or to quinones prominently associated with phenoloxidase bacterial-killing activity. Taken together, it appears that daptomycin resistance attenuates Staphylococcus aureus virulence through an enhanced sensitivity to phenoloxidase based on a complex mechanism. Our study provides new insights in the understanding of the crosstalk between antimicrobial resistance, escape from immune killing, and virulence. Author summaryAcquiring antimicrobial resistance can increase or decrease bacterial virulence. However, the mechanisms causing these resistance-virulence linked effects are unclear. Here, we bring new insights on the crosstalk between antimicrobial resistance and virulence. We characterized a panel of Staphylococcus aureus strains isolated from patients before and after resistance acquisition to the antibiotic daptomycin. Relative to the parental strain, resistant isolates most often varied by one single mutation, in a gene involved in the composition of the bacterial membrane, and these strains were much less virulent when fruit-flies were infected. Our results indicate that the difference of virulence is unrelated to changes in bacterial toxin production, bacterial growth, immune evasion or cell surface properties. Instead, resistant strains were more vulnerable to a host proenzyme involved in the antibacterial melanization response, an important response deployed throughout the arthropods. We predict that daptomycin resistance forces staphylococci to alter the composition of their cell surface. This alteration causes the bacteria to become more vulnerable to killing by melanization. Our results contribute to our understanding of the link between antimicrobial resistance and pathogenicity.

microbiology↗