A multicentre study investigating parameters which influence direct bacterial identification from urine

Area of Science:

• Clinical Microbiology
• Diagnostic Technology
• Infectious Diseases

Background:

• Rapid bacterial identification is crucial for effective patient management and combating antibiotic resistance.
• Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-ToF-MS) is a promising technique for microbial identification.

Purpose of the Study:

• To investigate parameters influencing reliable bacterial identification in urine using a combination of flow cytometry and MALDI-ToF-MS.
• To assess the accuracy and concordance of direct MALDI-ToF-MS identification in various urine sample types.

Main Methods:

• A multicenter study involving 1,050 urine samples across nine hospitals in Spain.
• Bacterial identification using direct MALDI-ToF-MS, with flow cytometry used to assess sample parameters.
• Analysis of factors affecting identification success, including bacterial counts, cell counts, species, morphology, and patient setting.

Main Results:

• Direct MALDI-ToF-MS achieved valid identification in 72.8% of all samples, with 80.3% concordance in culture-positive samples.
• High bacterial counts, presence of Escherichia coli, and rod-shaped bacteria (from flow cytometry) correlated with successful identification.
• High epithelial cell (EC) and white blood cell (WBC) counts, and samples from in-patients were associated with identification failures.

Conclusions:

• Direct MALDI-ToF-MS is a useful and accurate method for bacterial identification in urine samples.
• Evaluating parameters beyond bacterial count, such as EC/WBC counts, bacterial characteristics, and clinical context, is vital for sample suitability.
• Optimizing sample selection based on these parameters can enhance the efficiency and reliability of direct MALDI-ToF-MS diagnostics.