Abstract:

Objective To evaluate a method for determining pathogenic bacteria rapidly in midstream urine by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry （MALDI-TOF MS）combined with short-term culturing. Methods A total of 1 873 samples of midstream urine were collected. Each sample was divided equally into 2 parts. One was used for routine midstream urine culturing and identified by Vitek 2 Compact,the other was used for short-term culturing for 4 or 6 h after centrifugation,and then moss was collected and identified directly by MALDI-TOF MS. Identification by Vitek 2 Compact and quantitative culturing was considered as gold standard to evaluate the sensitivity and specificity of MALDI-TOF MS combined with short-term culturing for determining pathogenic bacteria in midstream urine. Results A total of 381 samples were determined with pathogenic bacteria in 1 873 samples,and the positive rate was 20.3%. Among them,346 cases （90.8%） had single species,27 cases （7.1%） had 2 species,and 8 cases （2.1%）had≥3 species. In samples with single species,the determination rate in 4 h culturing group was 80.1% （277/346）,and the determination rate in 6 h culturing group was 97.1% （336/346） by MALDI-TOF MS directly. The coincidence rate of MALDI-TOF MS combined with 6 h culturing compared with routine culturing was 100.0%,except Acinetobacter baumannii,Enterococcus faecium and Enterococcus faecalis（their coincidence rates were 81.4%,76.9% and 86.7%）. Conclusions The midstream urine samples are cultured for 4-6 h after centrifugation,then identified by MALDI-TOF MS directly. This method could effectively shorten both culturing time and turn-around time.

Key words: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, Short-term culturing, Rapid determination, Midstream urine