655. Detection of Antibiotic Resistance Genes in Clinical Samples using T2 Magnetic Resonance

Abstract

BackgroundAntibiotic-resistant bacteria are spread through selective pressure from the use of broad-spectrum empirical therapies, mobile genetic elements that pass resistance genes between species, and the inability to rapidly and appropriately respond to their presence. Resistance gene identification is often performed with post culture molecular diagnostic tests. The T2Resistance Panel, which detects methicillin resistance genes mecA/C; vancomycin resistance genes vanA/B; carbapenemases blaKPC, blaOXA-48,blaNDM, blaVIM, and blaIMP; AmpC β-lactamases blaCMY and blaDHA; and extended-spectrum β-lactamases blaCTX-M directly from patient blood samples, is based on T2 magnetic resonance (T2MR), an FDA-cleared technology with demonstrated high sensitivity and specificity for culture-independent bacterial and fungal species identification. Here we report the clinical performance of T2MR detection of resistance genes directly from patient blood samples.MethodsPatients with a clinical diagnosis of sepsis and an order for blood culture (BC) were enrolled in the study at two sites. BCs were managed using standard procedures and MALDI-TOF for species identification. Resistance testing with the T2MR assay was performed on a direct patient draw and compared with diagnostic test results from concurrent BC specimen and BC specimen taken at other points in time. The potential impact on therapy was evaluated through patient chart review.ResultsT2MR detected the same resistance genes as detected by post culture diagnostics in 100% of samples from concurrent blood draws. Discordant results occurred when T2MR was taken ≥48 hours after BC for patients on antimicrobial therapy. The average time to positive result was 5.9 hours with T2MR vs. 30.6 hours with post-culture molecular testing.ConclusionThe T2Resistance Panel detected antibiotic resistance genes in clinical samples and displayed agreement with post culture genetic testing. T2MR results were achieved faster than culture-dependent diagnostic testing results and may allow for an earlier change from empiric to directed therapy. The use of culture-independent diagnostics like T2MR could enable a quicker response to antibiotic-resistant organisms for individual patients and developing outbreaks.Disclosures All authors: No reported disclosures.