Pretreatment of Urine Samples with SDS Improves Direct Identification of Urinary Tract Pathogens with Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

We pretreated with SDS 71 urine samples with bacterial counts of>105 CFU/ml and matrix-assisted laser desorption ioniza-tion–time of flight (MALDI-TOF) identification scores of<2, in order to minimize failure rates. Identification improved in 46.5 % of samples, remained unchanged in 49.3%, and worsened in 4.2%. The improvement was more evident for Gram-negative (54.3%) than for Gram-positive (32%) bacteria. Urinary tract infections (UTIs) are among the most common hu-man bacterial infections (1).Tests developed for UTI screening include urine dipstick testing, urinalysis, and Gram staining. The urine culture remains the “gold standard, ” but the use of this method, without any previous screening procedure, is time-consuming and expensive, because of the high cost of unnecessary testing of negative samples (2). Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) has been shown as a fast and reli-able method for bacterial identification both from culture plates (3, 4) and from blood cultures vials (5, 6), and also from some other sam-ples, such as infected urine, especially when Gram-negative bacteri