Biology subjects

Fatsis-Kavalopoulos, N.

Publications and source records attributed to Fatsis-Kavalopoulos, N..

4 recordsLinked to original sources

bioRxiv2025

Sublethal Interaction Factor (SIF), a growth-based method to analyse antibiotic combinations at sub-inhibitory concentrations.

Antibiotic resistance is a global concern with significant implications for healthcare, food production and the environment. Therapies involving antibiotic combinations are frequently employed as a strategy to overcome antibiotic resistance. When present in combination, the efficacy of antibiotics may be enhanced or weakened, and as antibiotic interactions are a priori generally unpredictable they need to be experimentally determined. Though antibiotics are regularly present at sublethal concentrations (for example in patients with suboptimal dosing regimens and in the environment), effects of antibiotic combinations are generally studied at lethal dosages. To address this, we developed the Sublethal Interaction Factor (SIF) assay, based on the Bliss Independence model, to quantify antibiotic combination effects at sublethal concentrations. SIF assay uses the whole growth curve, instead of only the growth rate, and determines reliably the outcome of the interaction between two antibiotics at sub-lethal concentrations. The SIF method was validated against checkerboards and CombiANT assays and showed high sensitivity and specificity, attesting to its usability.

microbiology↗

bioRxiv2024

A Novel Method for Testing Antifungal Interactions: Assessing Synergy and Antagonism in Candida albicans Clinical Isolates.

The rise in antifungal resistance has limited treatment options for serious fungal infections, emphasizing the need for effective combination therapies. However, low-cost and rapid systems to evaluate synergy and antagonism in antifungal combinations are lacking. Here, we introduce a novel in vitro testing method for assessing antifungal interactions in C. albicans, enabling the simultaneous testing of three antifungal agents in a single agar plate with overnight results. This method, validated against the checkerboard assay, provides consistent fractional inhibitory concentration (FICi) measurements with reduced variability and workload. We applied this method in a comprehensive screen of 92 clinical C. albicans isolates for three antifungals--amphotericin B, fluconazole, and anidulafungin--yielding assessments of a total of 276 distinct combinations of antifungals and isolates. Results revealed isolate-specific interaction patterns, with amphotericin B and fluconazole showing synergy in 1% of isolates, anidulafungin and fluconazole in 19.5%, and amphotericin B and anidulafungin in 23.9%. These findings underscore the need for isolate-specific testing in clinical settings, which this scalable, high-throughput assay can facilitate effectively.

microbiology↗

bioRxiv2020

Piezo1 activation attenuates thrombin-induced blebbing in breast cancer cells

Cancer cells exploit a variety of migration modes to leave primary tumors and establish metastases, including amoeboid cell migration facilitated by bleb formation. Here we demonstrate that thrombin induces dynamic blebbing in the MDA-MB-231 breast cancer cell line, and confirm that PAR2 activation is sufficient to induce this effect. Cell confinement has been implicated as a driving force in bleb-based migration. Unexpectedly, we find that gentle contact compression, exerted using a "Cell Press" to mechanically stimulate cells, attenuated thrombin-induced blebbing with an associated increase in cytosolic calcium. Thrombin-induced blebbing was similarly attenuated using Yoda1, an agonist of the mechanosensitive calcium channel Piezo1, and its capacity to attenuate blebbing was impaired in Piezo1 depleted cells. Additionally, Piezo1 activation suppressed and reversed the thrombin-induced phosphorylation of ERM proteins, which are implicated in the blebbing process, and this activity was in part mediated through activation of the PP1A/PP2A family of serine/threonine phosphatases. Our results provide mechanistic insights into Piezo1 activation as a suppressor of dynamic blebbing, specifically that which is induced by thrombin.

cell biology↗

bioRxiv2019

A high-throughput fluidic chip for rapid phenotypic antibiotic susceptibility testing

Many patients with severe infections receive inappropriate empirical treatment and rapid detection of bacterial antibiotic susceptibility can in this context improve clinical outcome and reduce mortality. We have to this end developed a high-throughput fluidic chip for rapid phenotypic antibiotic susceptibility testing of bacteria. A total of 21 clinical isolates of Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus were acquired from the EUCAST Development Laboratory and tested against amikacin, ceftazidime and meropenem (Gramnegative bacteria) or gentamicin, ofloxacin and tetracycline (Gram-positive bacteria). The bacterial samples were mixed with agarose and loaded in 8 separate growth chambers in the fluidic chip. The chip was thereafter connected to a reservoir lid containing different antibiotics and a pump used to draw growth media with or without antibiotics into the chip for generation of diffusion-limited antibiotic gradients in the growth chambers. Bacterial microcolony growth was monitored using darkfield time-lapse microscopy and quantified using a cluster image analysis algorithm. Minimum inhibitory concentration (MIC) values were automatically obtained by tracking the growth rates of individual microcolonies in different regions of antibiotic gradients. Stable MIC values were obtained within 2-4 hours and the results showed categorical agreement to reference MIC values as determined with broth microdilution in 86% of the cases.\n\nImportancePrompt and effective antimicrobial therapy is crucial for the management of patients with severe bacterial infections but is becoming increasingly difficult to provide due to emerging antibiotic resistance. The traditional methods for antibiotic susceptibility testing (AST) used in most clinical laboratories are reliable but slow with turnaround times of 2-3 days, which necessitates the use of empirical therapy with broad-spectrum antibiotics. There is a great need for fast and reliable AST methods that enable start of targeted treatment within a few hours to improve patient outcome and reduce overuse of broad-spectrum antibiotics. The high-throughput fluidic chip for phenotypic AST described in the present study enables data on antimicrobial resistance within 2-4 hours allowing for an early initiation of appropriate antibiotic therapy.

microbiology↗