Identification of urinary tract pathogens after 3-hours urine culture by MALDI-TOF mass spectrometry

•Rapid (4–6 h) identification of urinary tract pathogens by MALDI-TOF MS•Urine was incubated on chocolate agar (3 h) and analyzed by MALDI-TOF MS.•Method is called U-si-MALDI-TOF and has minimal hands-on time.•Gram-negative urinary tract pathogens can be reliably identified with U-si-MALDI-TOF.

Complicated urinary tract infections, such as pyelonephritis, may lead to sepsis. Rapid diagnosis is needed to identify the causative urinary pathogen and to verify the appropriate empirical antimicrobial therapy. We describe here a rapid identification method for urinary pathogens: urine is incubated on chocolate agar for 3 h at 35 °C with 5% CO2 and subjected to MALDI-TOF MS analysis by VITEK MS. Overall 207 screened clinical urine samples were tested in parallel with conventional urine culture. The method, called U-si-MALDI-TOF (urine short incubation MALDI-TOF), showed correct identification for 86% of Gram-negative urinary tract pathogens (Escherichia coli, Klebsiella pneumoniae, and other Enterobacteriaceae), when present at > 105 cfu/ml in culture (n = 107), compared with conventional culture method. However, Gram-positive bacteria (n = 28) were not successfully identified by U-si-MALDI-TOF. This method is especially suitable for rapid identification of E. coli, the most common cause of urinary tract infections and urosepsis. Turnaround time for identification using U-si-MALDI-TOF compared with conventional urine culture was improved from 24 h to 4–6 h.

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