Many bacteria are resistant to antibiotics, so the sooner an infection’s antibiotic susceptibility can be determined, the sooner an effective treatment can be devised. But current clinical methods for determining antibiotic susceptibility involve bacterial culture and can take more than a day. To accelerate the process, Mohamed N. Seleem of Purdue University, Ji-Xin Cheng of Boston University, and coworkers used stimulated Raman scattering (SRS) microscopy of carbon-deuterium bonds to monitor glucose metabolism of Enterococcus faecalis at the single-bacterium level (Anal. Chem. 2018, DOI: 10.1021/acs.analchem.7b03382). By using so-called hyperspectral SRS, they can acquire a complete spectrum at each pixel. The Raman spectrum changes in response to the metabolic activity of the bacteria. When the researchers treated susceptible and resistant E. faecalis with vancomycin and fed the bacteria deuterated glucose, differences in the bugs’ incorporation of glucose in proteins and lipids were apparent within a half hour of treatment. That’s fast enough to determine antibiotic susceptibility within a single bacterial cell cycle. The researchers also showed that the method is applicable to other types of bacteria and antibiotics.