Rapid in vitro identification of the pathogenic bacteria in actual urine samples by proton transfer reaction mass spectrometry

The speed of bacterial identification is crucial for the treatment efficiency of patients with infections. However, the clinical method typically requires more than 24 h to obtain identification results. Recent studies have revealed that bacteria can emit or absorb characteristic volatile organic compounds (VOCs) in the early stage of cultivation. Based on this discovery, our study tried to develop a rapid identification method using these bacteria-derived VOCs. The studied subjects are five common urinary tract infection (UTI) bacteria: Klebsiella pneumoniae ( Kpn ), Escherichia coli ( Eco ), Pseudomonas aeruginosa ( Pae ), Enterococcus faecalis ( Efs ) and Enterococcus faecium ( Efm ). Within six hours of cultivation, characteristic VOCs specific to these bacteria emerged and were detected by a proton transfer reaction mass spectrometry (PTR-MS). Using a hierarchical classification tree method, we constructed several discriminant models based on different combinations of these VOCs, all achieving 100 % accuracy. To validate the clinical applicability of this method, we collected and analyzed 119 actual urine samples. A classification model utilizing VOCs with m/z values of 63, 65, and 71 achieved 95.0 % accuracy. These three VOCs were identified as dimethyl sulfide, ethanol, and 3-methyl-1-butanol, respectively, using gas chromatography-proton transfer reaction mass spectrometry (GC-PTR-MS). Our results demonstrate that this novel method can rapidly and accurately identify UTI bacteria, requiring only one-fourth of the time compared to clinical method. This method has the potential to help promptly formulate antibiotic treatment plans, which could shorten the treatment process and enhance therapeutic effects.