title: An evaluation of three processing methods and the effect of reduced culture times for faster direct identification of pathogens from BacT/ALERT blood cultures by MALDI-TOF MS.
abstract: Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) is a fast and reliable method for the identification of bacteria from agar media. Direct identification from positive blood cultures should decrease the time to obtaining the result. In this study, three different processing methods for the rapid direct identification of bacteria from positive blood culture bottles were compared. In total, 101 positive aerobe BacT/ALERT bottles were included in this study. Aliquots from all bottles were used for three bacterial processing methods, i.e. the commercially available Bruker's MALDI Sepsityper kit, the commercially available Molzym's MolYsis Basic5 kit and a centrifugation/washing method. In addition, the best method was used to evaluate the possibility of MALDI application after a reduced incubation time of 7 h of Staphylococcus aureus- and Escherichia coli-spiked (1,000, 100 and 10 colony-forming units [CFU]) aerobe BacT/ALERT blood cultures. Sixty-six (65%), 51 (50.5%) and 79 (78%) bottles were identified correctly at the species level when the centrifugation/washing method, MolYsis Basic 5 and Sepsityper were used, respectively. Incorrect identification was obtained in 35 (35%), 50 (49.5%) and 22 (22%) bottles, respectively. Gram-positive cocci were correctly identified in 33/52 (64%) of the cases. However, Gram-negative rods showed a correct identification in 45/47 (96%) of all bottles when the Sepsityper kit was used. Seven hours of pre-incubation of S. aureus- and E. coli-spiked aerobe BacT/ALERT blood cultures never resulted in reliable identification with MALDI-TOF MS. Sepsityper is superior for the direct identification of microorganisms from aerobe BacT/ALERT bottles. Gram-negative pathogens show better results compared to Gram-positive bacteria. Reduced incubation followed by MALDI-TOF MS did not result in faster reliable identification.
authors.affiliation: Department of Medical Microbiology, PAMM Laboratories, Veldhoven/Eindhoven, The Netherlands.
authors.forename: A J M
authors.initials: AJ
authors.lastname: Loonen
authors.forename: A R
authors.initials: AR
authors.lastname: Jansz
authors.forename: J
authors.initials: J
authors.lastname: Stalpers
authors.forename: P F G
authors.initials: PF
authors.lastname: Wolffs
authors.forename: A J C
authors.initials: AJ
authors.lastname: van den Brule
mesh_terms: D016470:Bacteremia / Q000175:diagnosis*; D001419:Bacteria / Q000145:classification* / Q000302:isolation & purification*; D001431:Bacteriological Techniques / Q000379:methods*; D001769:Blood / Q000382:microbiology*; D006801:Humans; D013048:Specimen Handling / Q000379:methods*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013997:Time Factors
references.citation: PLoS One. 2009 Nov 25;4(11):e8041
references.pmid: 19946369
references.citation: J Clin Microbiol. 2010 Apr;48(4):1481-3
references.pmid: 20164269
references.citation: J Clin Microbiol. 2006 Nov;44(11):4186-8
references.pmid: 17088371
references.citation: Vet Microbiol. 2009 Feb 16;134(1-2):45-54
references.pmid: 18986783
references.citation: J Clin Microbiol. 2010 Mar;48(3):900-7
references.pmid: 20053859
references.citation: J Clin Microbiol. 2011 Feb;49(2):693-6
references.pmid: 21106794
references.citation: J Clin Microbiol. 2010 May;48(5):1584-91
references.pmid: 20237093
references.citation: Eur J Clin Microbiol Infect Dis. 2011 Mar;30(3):337-42
references.pmid: 20972809
references.citation: Anal Bioanal Chem. 2011 Jun;400(7):1905-11
references.pmid: 21442367
references.citation: Chest. 2009 Nov;136(5):1237-1248
references.pmid: 19696123
references.citation: J Clin Microbiol. 2009 Aug;47(8):2629-31
references.pmid: 19535529
references.citation: Lancet Infect Dis. 2002 Nov;2(11):677-85
references.pmid: 12409048
references.citation: Clin Microbiol Infect. 2011 Feb;17(2):192-5
references.pmid: 20370799
references.citation: Clin Microbiol Infect. 2011 Apr;17(4):546-51
references.pmid: 20456452
references.citation: J Clin Microbiol. 2010 Feb;48(2):444-7
references.pmid: 19955282
references.citation: J Clin Microbiol. 2001 Oct;39(10):3446-51
references.pmid: 11574554
references.citation: Clin Microbiol Infect. 2010 Jun;16(6):774-9
references.pmid: 19689465
references.citation: Clin Microbiol Infect. 2010 Nov;16(11):1631-8
references.pmid: 20825442
references.citation: Crit Care Med. 2006 Jun;34(6):1589-96
references.pmid: 16625125
references.citation: J Clin Microbiol. 2009 Sep;47(9):2759-65
references.pmid: 19571030
references.citation: Eur J Clin Microbiol Infect Dis. 2010 Jan;29(1):89-95
references.pmid: 19902279
references.citation: J Clin Microbiol. 2010 May;48(5):1542-8
references.pmid: 20237092