2180. Novel Method for Determining Rapid E.coli Antibiotic Susceptibility (AST) Results for Urinary Tract Infections

Abstract

BackgroundMeasuring changes in phase noise from bacteria on a quartz crystal resonator has been shown to effectively distinguish viable from non-viable E. coli. We report using this method to rapidly perform AST for E. coli isolated from a leftover clinical urinary tract infection (UTI) specimen.MethodsAn experimental system was designed to sense changes in bacterial mechanics through changes in phase noise generated by bacterial cells (Figure 1). The system includes a quartz-crystal resonator with thin-film gold electrodes on opposite surfaces housed within a module. The module provides electrical contact to the crystal’s electrodes, and incorporates channels through which fluids can be pumped (Figure 2). E. coli was isolated from a leftover positive urine culture specimen, cultured overnight and resuspended in phosphate-buffered saline (PBS). The suspension was run through the experimental system. E.coli cells were adhered to the surface of the quartz resonant crystal coated with a cationic polymer. After a growth phase, the cells were exposed to antibiotic (ampicillin). Phase noise was monitored throughout the test. The power spectral density of the noise was averaged each 5 minutes. E.coli was classified as ampicillin susceptible if the spectral power of the added phase noise was at least 50% lower compared with controls. Controls were in growth media only (Figure 3). Automated microscopy was utilized to monitor cell growth.ResultsThe method correctly classified the E.coli as ampicillin susceptible. Power spectral density increased in untreated cells and dropped or stayed steady in cells treated with Ampicillin. Corresponding loss of E. coli viability was confirmed microscopically. Results were compared with standard of care antibiotic susceptibility testing.ConclusionThe phase noise measurement method correctly identified ampicillin susceptible E.coli isolated from a leftover patient urine sample in three and one half hours. It shows promise for providing rapid AST results to treat UTIs. Disclosures All authors: No reported disclosures.