UC Irvine

Introduction. The alarming rise in urinary tract infection (UTI) antimicrobial resistance has resulted from a combination of high prevalence, low specificity and the lack of a rapid, point-of-care (POC) antibiotic susceptibility test (AST), which has led to the overuse/inappropriate use of antibiotics.Aim. This study aimed to evaluate the performance of a rapid POC phenotypic AST device in reporting susceptibility information within 2 h.Methodology. Instrument calibration was performed with model bacteria and fluorescent microbeads to determine the dynamic range and limit of detection for quantifying concentrations of bacteria and demonstrate the ability to rapidly differentiate susceptible and resistant model bacteria. We then evaluated 30 presumptive UTI-positive patient urine samples in a clinical pilot study using a panel of 5 common UTI antibiotics plus a growth control and compared our results to the hospital standard of care AST.Results. Our device was able to robustly detect and quantify bacteria concentrations from 50 to 10⁵ colony-forming units (c.f.u.) ml^-1. The high sensitivity of this measurement technique enabled the device to differentiate between susceptible and resistant model bacteria with 100 % specificity over a 2 h growth period. In the clinical pilot study, an overall categorical agreement (CA) of 90.7 % was observed (sensitivity=91.4 %, specificity=88.9 %, n=97) with performance for individual drugs ranging from 85 % CA (ceftazidime) to 100 % (nitrofurantoin).Conclusions. By reducing the typical timeframe for susceptibility testing from 2-3 days to 2 h, our POC phenotypic AST can provide critical information to clinicians prior to the administration of antibiotic therapy.