Roegner, M. | Search bioRxiv

bioRxiv2026

Rapid Phenotypic Antibiotic Susceptibility Determination Direct From Spiked Urine Samples Shows Strong Correlation with Gold Standard for Urinary Tract Infection

GeneCapture is developing a novel, point-of-care, rapid AST technique that, when fully automated, can accomplish AST within 2 hours directly from a raw sample, representing a significant advancement in diagnostic capabilities. For this study, a panel of uropathogen isolates was collected from clinical specimens positive for urinary tract infection from various laboratories in the southern US. A selection of these isolates were then spiked into fresh clean-catch urine samples to produce mock samples covering a variety of antibiotic responses. Testing was performed on 20 strains of Escherichia coli, the cause of over 80% of UTIs, and 6 strains each of Klebsiella pneumoniae and Proteus mirabilis, the next most common causes. Each strain was tested against the susceptible, intermediate and resistant (S-I-R) breakpoints of up to 5 appropriate antibiotics including Amoxicillin-Clavulanate, Cefpodoxime, Ciprofloxacin, Nitrofurantoin and Trimethoprim-Sulfamethoxazole. The new method uses a phenotypic assessment of bacterial growth, comparing responses from bacteria treated with antibiotics at S-I-R breakpoint concentrations to untreated controls as the metric for determining susceptibility. Exposure to the drugs for only 90 minutes gave a Categorical Agreement of 98% to gold standard culture results across the resulting 247 bacteria/antibiotic pairs. Testing on separate days of nine of these strains in triplicate gave a reproducibility of 97%. The sequential steps of this novel AST - sample processing, growth, labeling, and counting - can readily be performed on an automated cartridge that is currently under development. The presented work, which took place in a laboratory setting, demonstrates the efficacy of the assay.

microbiology↗

bioRxiv2025

PHOSPHATIDYLSERINE EXPOSURE AND EXTRACELLULAR ANNEXIN A5 WEAKEN THE ACTIN CORTEX IN OSTEOCLAST FUSION

Diverse cell-cell fusions involve intracellular Ca2+ signaling, non-apoptotic exposure of phosphatidylserine (PS) at the surface of fusion-committed cells and binding of extracellular Annexin A5 (Anx A5). Here we focus on the cell fusion stage of formation of bone-resorbing multinucleated osteoclasts and report that each of the listed hallmarks of cell fusion represents a step in a novel bidirectional signaling pathway. A rise in intracellular Ca{superscript 2} activates a lipid scramblase that translocates PS from the inner to the outer leaflet of the plasma membrane. This redistribution is enhanced by extracellular Anx A5 binding to cell surface PS. Depletion of PS in the inner leaflet weakens actin cortex-plasma membrane attachment mediated by ezrin/radixin/moesin (ERM) proteins, as evidenced by the preferential localization of cortex detachment areas within PS-enriched regions at the surface of the cells. Weakening of the cortex-membrane connection by Anx A5 or by adding an inhibitor of the ERM proteins promotes osteoclast fusion. We propose that this pathway facilitates osteoclast fusion and other cell-cell fusions by promoting membrane deformations required for formation of prefusion membrane contacts. Additionally, the elevated tension in the cortex detachment region of the membrane, suggested by our theoretical analysis, promotes fusion pore expansion.

cell biology↗