Rapid Antimicrobial Susceptibility Testing Directly from Blood culture Broth by Surface-enhanced Raman Scattering of Spectral Biomarkers

Background: As effective management of sepsis requires timely administration of appropriate antibiotics, a reliable and rapid antimicrobial susceptibility testing (AST) is crucial. To meet clinical needs, we developed a novel AST, referred to as SERS-AST, based on the surface-enhanced Raman Scattering (SERS) technology. SERS-AST determines antibiotic susceptibility of bacteria based on variations in bacterial SERS signals derived from secreted purines and their derivatives. Methods SERS-AST was applied to blood culture samples of patients with bacteremia. Eight common causative organisms, including Staphylococcus aureus , Staphylococcus epidermidis , Enterococcus faecalis , Enterococcus faecium, Escherichia coli , Enterobacter cloacae, Klebsiella pneumoniae , and Acinetobacter baumannii and seven most prescribed antibiotics, including oxacillin, levofloxacin, vancomycin, ampicillin, cefotaxime, ceftazidime, levofloxacin, and imipenem were tested. Receiver operating characteristic analysis was performed to obtain the optimal cutoff SERS signal value to determine the susceptibility of tested bacteria. The results of SERS-AST were compared with those of VITEK 2. Results A total of 164 bacterial isolates from blood samples were examined, and the agreement rates between SERS-AST and VITEK 2 results were 96% for Gram-positive bacteria and 97% for Gram-negative bacteria. Conclusions By directly assaying positive blood cultures without additional subcultures, SERS-AST can be completed within 4 hours with high accuracy. It can be an alternative AST method to provide critical information to clinicians for timely administration of appropriate antibiotics to treat patients with blood stream infections.