T2 magnetic resonance for the diagnosis of bloodstream infections: charting a path forward

We discuss four studies in this issue of the Journal of Antimicrobial Chemotherapy that describe experience with T2 magnetic resonance (T2MR) nanodiagnostics for Candida and bacterial bloodstream infections, in the context of the T2MR literature. T2Candida and T2Bacteria panels use a dedicated instrument to detect amplified DNA from microbial cells directly in whole blood. T2Candida gives positive or negative results for C. albicans/C. tropicalis, C. glabrata/C. krusei, and C. parapsilosis. T2Bacteria detects Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Escherichia coli. In recent trials, T2Candida sensitivity and specificity for candidaemia were ∼90% and ∼98%, respectively. Two studies from Spanish hospitals now provide the first data on T2Candida as a prognostic tool. T2Candida was superior to cultures or serum β-d-glucan in identifying patients with complicated candidaemia, and in predicting the outcomes of empirical antifungal therapy for suspected candidiasis. In a retrospective study from US community hospitals, use of T2Candida was reported to reduce times to appropriate antifungal therapy, shorten courses of empirical therapy, and save an average of US$280 in antifungal costs per patient tested. Finally, a study from a hospital in Rome provides the first clinical data for T2Bacteria: sensitivity and specificity were 89% and 98%, respectively, among patients with positive blood cultures for bacteria detected by the panel, or fulfilling criteria for infection. We conclude that T2MR diagnostics are promising both for detecting bloodstream infections due to Candida and bacteria, and for providing prognostic information. More studies that present real-world performance data are needed.