title: Comparing the identification of Clostridium spp. by two Matrix-Assisted Laser Desorption Ionization-Time of Flight (MALDI-TOF) mass spectrometry platforms to 16S rRNA PCR sequencing as a reference standard: a detailed analysis of age of culture and sample preparation.
abstract: We compared the identification of Clostridium species using mass spectrometry by two different Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) platforms (Bruker MS and Vitek MS) against 16S rRNA sequencing as the reference standard. We then examined the impact of different sample preparations and (on one of those platforms) age of bacterial colonial growth on the performance of the MALDI-TOF MS systems. We identified 10 different species amongst the 52 isolates by 16S rRNA sequencing, with Clostridium perfringens the most prevalent (n=30). Spectrometric analysis using Vitek MS correctly speciated 47/52 (90.4%) isolates and was not affected by the sample preparation used. Performance of the Bruker MS was dependent on sample preparation with correct speciation obtained for 36 of 52 (69.2%) isolates tested using the Direct Transfer [DT] protocol, but all 52 (100%) isolates were correctly speciated using either an Extended Direct Transfer [EDT] or a Full Formic Extraction [EX] protocol. We then examined the effect of bacterial colonial growth age on the performance of Bruker MS and found substantial agreement in speciation using DT (Kappa=0.62, 95% CI: 0.46-0.75), almost perfect agreement for EDT (Kappa=0.94, 95% CI: 0.86-1.00) and exact agreement for EX (Kappa=1.00) between different days.
authors.affiliation: Microbiology Department, Royal Melbourne Hospital, Melbourne, Victoria, Australia. Electronic address: royale168@hotmail.com.
authors.forename: Roy
authors.initials: R
authors.lastname: Chean
authors.affiliation: Monash Infectious Disease, Monash Health, Australia.
authors.forename: Despina
authors.initials: D
authors.lastname: Kotsanas
authors.affiliation: Microbiology Department, Monash Health, Australia.
authors.forename: Michelle J
authors.initials: MJ
authors.lastname: Francis
authors.affiliation: Department of Chemistry and Biotechnology, Swinburne University of Technology, Australia.
authors.forename: Enzo A
authors.initials: EA
authors.lastname: Palombo
authors.affiliation: Department of Chemistry and Biotechnology, Swinburne University of Technology, Australia.
authors.forename: Snehal R
authors.initials: SR
authors.lastname: Jadhav
authors.affiliation: Department of Microbiology, Monash University, Australia.
authors.forename: Milena M
authors.initials: MM
authors.lastname: Awad
authors.affiliation: Department of Microbiology, Monash University, Australia.
authors.forename: Dena
authors.initials: D
authors.lastname: Lyras
authors.affiliation: Monash Infectious Disease, Monash Health, Australia; Microbiology Department, Monash Health, Australia; Department of Medicine, Monash University, Australia.
authors.forename: Tony M
authors.initials: TM
authors.lastname: Korman
authors.affiliation: Monash Infectious Disease, Monash Health, Australia.
authors.forename: Grant A
authors.initials: GA
authors.lastname: Jenkin
mesh_terms: D016470:Bacteremia / Q000175:diagnosis / Q000382:microbiology; D001431:Bacteriological Techniques / Q000379:methods*; D003013:Clostridium / Q000737:chemistry / Q000145:classification* / Q000302:isolation & purification*; D003015:Clostridium Infections / Q000175:diagnosis / Q000382:microbiology*; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012015:Reference Standards; D017422:Sequence Analysis, DNA; D013048:Specimen Handling / Q000379:methods; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S
keywords: Age of culture; Clostridium; MALDI-TOF; Nucleic acid sequencing; Sample preparation