title: Comparison of phenotypic methods and matrix-assisted laser desorption ionisation time-of-flight mass spectrometry for the identification of aero-tolerant Actinomyces spp. isolated from soft-tissue infections.
abstract: Aero-tolerant Actinomyces spp. are an under-recognised cause of cutaneous infections, in part because identification using conventional phenotypic methods is difficult and may be inaccurate. Matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) is a promising new technique for bacterial identification, but with limited data on the identification of aero-tolerant Actinomyces spp. This study evaluated the accuracy of a phenotypic biochemical kit, MALDI-TOF MS and genotypic identification methods for the identification of this problematic group of organisms. Thirty aero-tolerant Actinomyces spp. were isolated from soft-tissue infections over a 2-year period. Species identification was performed by 16 s rRNA sequencing and genotypic results were compared with results obtained by API Coryne and MALDI-TOF MS. There was poor agreement between API Coryne and genotypic identification, with only 33% of isolates correctly identified to the species level. MALDI-TOF MS correctly identified 97% of isolates to the species level, with 33% of identifications achieved with high confidence scores. MALDI-TOF MS is a promising new tool for the identification of aero-tolerant Actinomyces spp., but improvement of the database is required in order to increase the confidence level of identification.
authors.affiliation: Department of Laboratory Medicine, Changi General Hospital, 2 Simei Street 3, Singapore, Republic of Singapore.
authors.forename: L S Y
authors.initials: LS
authors.lastname: Ng
authors.forename: J H C
authors.initials: JH
authors.lastname: Sim
authors.forename: L C
authors.initials: LC
authors.lastname: Eng
authors.forename: S
authors.initials: S
authors.lastname: Menon
authors.forename: T Y
authors.initials: TY
authors.lastname: Tan
mesh_terms: D000190:Actinomyces / Q000737:chemistry / Q000145:classification* / Q000302:isolation & purification* / Q000502:physiology; D000196:Actinomycosis / Q000175:diagnosis* / Q000382:microbiology; D015373:Bacterial Typing Techniques; D001431:Bacteriological Techniques / Q000379:methods*; D020459:Genes, rRNA / Q000235:genetics; D006801:Humans; D058889:Molecular Typing; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012680:Sensitivity and Specificity; D018461:Soft Tissue Infections / Q000175:diagnosis* / Q000382:microbiology; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D012336:RNA, Ribosomal, 16S