1513. A New Method for Rapid Phenotypic Antimicrobial Susceptibility Testing Directly from Patient Samples

Abstract

BackgroundLife-threatening syndromic hospital infections including sepsis, ventilator acquired pneumonia, catheter-associated urinary tract infection (CAUTI), and surgical site infections are often caused by multidrug-resistant pathogens. Implementing the targeted narrow-spectrum antimicrobial therapy as rapidly as possible at the onset of infection is critical for lowering morbidity and mortality for these infections. We present the new MultiPath technology for rapid syndromic infection detection, pathogen identification, and phenotypic antimicrobial susceptibility testing (AST). Our feasibility data demonstrate the technology’s potential application as a rapid CAUTI diagnostic.MethodsThe MultiPath technology detects and counts cells in a 30-minute assay using nonmagnified digital imaging. For identification, target pathogen cells are labeled using fluorescent in situ hybridization (FISH) with rRNA-specific probes, tagged with magnetic nanoparticles, deposited on a surface, imaged, and quantified. For AST, samples are mixed with growth medium, incubated for 4 hours in the presence of serial dilutions of antibiotics, FISH-labeled, magnetically selected, and quantified by digital imaging. The MultiPath assays use a dye-cushion layer to optically sequester the sample and unbound fluorescent probes from the imaging surface, eliminating the need for sample preparation and wash steps.ResultsThe MultiPath ID method specifically detected a range of common CAUTI pathogens including E. coli, K. pneumonia, E. faecium, E. faecalis, and P. aeruginosa. The limit of detection for E. coli was 27 CFU in a 100 µL assay in 10% urine. We present data demonstrating target inclusivity, specificity, and dynamic range. Our AST feasibility study results show excellent correlation with the broth micro dilution reference test for 5 antibiotics. Variable inoculum levels had little impact on MICs in the study.ConclusionThe data presented demonstrate the potential of the rapid ID/AST technology to achieve excellent analytical and clinical performance. This, combined with the method’s simplicity, robustness to sample matrix, and ease-of-use may make the method valuable for rapid syndromic infection diagnostics.Disclosures All authors: No reported disclosures.