The rapid evaluation of bacterial growth and antibiotic susceptibility in blood cultures by selected ion flow tube mass spectrometry

We have measured the production of volatile organic compounds (VOCs) by selected ion flow tube mass spectrometry (SIFT-MS) in the headspaces of conventional BacT/ALERT blood culture bottles (Biomerieux, Durham, NC) artificially infected with 5 bacterial strains. Uninfected blood samples were inoculated with Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli, and Neisseria meningitidis. Growth and species identification were determined at 6 h by measuring a panel of 9 VOC products. Two species, E. coli and S. aureus, were also incubated in the presence of gentamicin or flucloxacillin, respectively, above or below their demonstrated MIC. The concentration-dependent antibiotic susceptibility of both strains was demonstrated by the inhibition of VOC production at 22 h (P < .05). These results suggest incorporating SIFT-MS detection of microbial VOCs as a sensitive method for bacterial detection, identification, and determination of antibiotic susceptibility in a conventional blood culture system.