Evaluation of the Diagnostic Accuracy of the T2Resistance Panel (Research Use Only) in Patients With Possible Bacterial Bloodstream Infections.

BACKGROUND

Early identification and antimicrobial susceptibility testing (AST) of bloodstream pathogens are important for promptly determining the appropriate therapy. Currently, positive blood culture results (identification and AST) are reported in 2 to 4 days. The T2Resistance (T2R) Panel (T2 Biosystems, Inc) uses DNA amplification with magnetic resonance from 3 mL of whole blood for direct detection of 13 antibiotic resistance genes: , , , , , , AmpC , A/B, and A/C. We compared the accuracy of T2R testing to AST for positive blood cultures.

METHODS

This investigator-sponsored, single-center study prospectively enrolled 802 patients with a standard of care blood culture. Five hundred forty-seven patients had adequate blood for culture and T2R testing. Blood cultures with positive isolates were identified, and AST was performed. Blood samples with positive blood cultures were tested with the T2R Panel.

RESULTS

Blood cultures were positive for 58/547 (10.6%) patients. Contaminants (18/547 [3.3%]) were excluded. T2R testing results (n=31) showed 2 genes with 100% sensitivity; the remaining gram-negative resistance genes were not detected, so sensitivity could not accurately be determined. Specificity was 100% for the 16 gram-negative bacilli. Three enterococci and 2 showed 100% sensitivity/specificity. However, 10 coagulase-negative staphylococci showed 17% sensitivity/100% specificity. Antibiotic resistance genes identified were 2 , 2 A/C, and 1 A/B. T2R testing results were obtained in an average of 7 hours.

CONCLUSION

T2R testing is highly specific (100%) for the 13 antibiotic resistance genes on the panel. Sensitivity was 100% for the genes detected but was low (17%) for coagulase-negative staphylococci. T2R testing has the potential to diagnose certain antibiotic resistance genes from bacterial bloodstream infections in hours vs the days required for a positive blood culture with AST. Additional studies that include larger numbers of samples with antimicrobial resistance genes are needed.