Melting temperature mapping method in children: Rapid identification of pathogenic microbes

Introduction: The melting temperature (T_m) mapping method (TM) identifies bacterial species by intrinsic patterns of T_m values in the 16S ribosomal RNA gene (16S rDNA) extracted directly from whole blood. We examined potential clinical application of TM in children with bloodstream infection (BSI). Methods: This was a prospective observational study at a children's hospital in Japan from 2018 to 2021. In patients with diagnosed or suspected BSI, we investigated the match rates of pathogenic bacteria identified by TM and blood culture (BC), the inspection time to identification of TM, and the amount of bacterial DNA in blood samples. Results: The median age of 81 patients (93 samples) was 3.6 years. Of 23 samples identified by TM, 11 samples matched the bacterial species with BC (positive-match rate, 48 %). Of 64 TM-negative samples, 62 samples were negative for BC (negative-match rate, 97 %). Six samples, including one containing two pathogenic bacterial species, were not suitable for TM identification. In total, the matched samples were 73 of 93 samples (match rate, 78 %). There were seven samples identified by TM in BC-negative samples from blood collected after antibiotic therapy. Interestingly, the bacteria were matched with BC before antibiotic administration. These TM samples contained as many 16S rDNA copies as the BC-positive samples. The median inspection time to identification using TM was 4.7 h. Conclusions: In children with BSI, TM had high negative-match rates with BC, the potential to identify the pathogenic bacteria even in patients on antibiotic therapy, and more rapid identification compared to BC. Registering clinical trials: UMIN000041359https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000047220.