title: Direct Identification of Urinary Tract Pathogens From Urine Samples Using the Vitek MS System Based on Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry.
abstract: BACKGROUND
  We evaluated the coincidence rate between Vitek MS system (bioMérieux, France) and Vitek 2 in identifying uropathogens directly from urine specimens.
  
  
  METHODS
  Urine specimens submitted to our microbiology laboratory between July and September 2013 for Gram staining and bacterial culture were analyzed. Bacterial identification was performed by using the conventional method. Urine specimens showing a single morphotype by Gram staining were processed by culturing and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Of 2,370 urine specimens, 251 showed a single morphotype on Gram staining, and among them, 202 were available for MALDI-TOF MS.
  
  
  RESULTS
  In these 202 specimens, colony growth was observed in 189 specimens, and 145 specimens had significant growth of single-colony morphotype in culture. One hundred and ten (75.9%) of them had colony counts of ≥10(5) colony-forming units (CFU)/mL and included 71 enteric gram-negative bacteria (GNB), 5 glucose-non-fermenting GNB, 9 gram-positive cocci (GPC), and 25 yeasts. Furthermore, 70 (98.6%), 3 (60.0%), 4 (44.4%), and 5 (20.0%), respectively, of these were correctly identified by Vitek MS. Thirty-one specimens (21.4%; 11 GNB, 7 GPC, 12 yeasts, and 1 gram-positive bacillus) had colony counts of 10(4)-10(5) CFU/mL. Four specimens (2.8%) yielded colony counts of 10(3)-10(4) CFU/mL.
  
  
  CONCLUSIONS
  Vitek MS showed high rate of accuracy for the identification of GNB in urine specimens (≥10(5) CFU/mL). This could become a rapid and accurate diagnostic method for urinary tract infection caused by GNB. However, for the identification of GPC and yeasts, further studies on appropriate pre-treatment are warranted.
authors.affiliation: Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Yeongsic
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Kang Gyun
authors.initials: KG
authors.lastname: Park
authors.affiliation: Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Kyungwon
authors.initials: K
authors.lastname: Lee
authors.affiliation: Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Yeon-Joon
authors.initials: YJ
authors.lastname: Park
mesh_terms: D005840:Gentian Violet / Q000737:chemistry; D006090:Gram-Negative Bacteria / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006095:Gram-Positive Cocci / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D010619:Phenazines / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D016482:Urinalysis; D014552:Urinary Tract Infections / Q000175:diagnosis / Q000382:microbiology* / Q000652:urine; D014556:Urine / Q000382:microbiology*
chemical_list: C035863:Gram's stain; D010619:Phenazines; D005840:Gentian Violet
keywords: MALDI-TOF MS; UTI; Urinary tract pathogens; Vitek MS