Bacteroides fragilis and related species are important human pathogens involved in mixed infections of different origins. The B. fragilis group isolates are phenotypically very similar, grow more slowly than aerobic bacteria and, accordingly, are frequently misidentifed with classical or automated phenotypical identification methods. Recent taxonomic changes and new species accepted as members of the Bacteroides genus are not included in the different databases of commercially available identification kits. The use of matrix-assisted laser-desorption/ ionization time-of-flight mass spectrometry (MALDI-TOF MS) was therefore evaluated for the species identification of 277 clinical isolates of the Bacteroides genus. Species identification was carried out with MALDI Bruker Daltonik Biotyper software (Bruker Daltonik GmbH, Bremen, Germany) by comparing the mass spectrum of each strain with the mass spectra of the 3260 reference strains currently available. The results of conventional phenotypical identification of the isolates were used as a reference. 16S rRNA gene sequencing was performed for a selection of the strains that gave discrepant results and for all those inconclusively identified by MALDI-TOF MS; 270 isolates (97.5%) were unequivocally identified [log(score) =2.0] by comparison with the reference strains present in the MALDI Biotyper database. Of the 23 isolates for which the MALDI-TOF MS species identification differed from the conventional phenotypical identification, 11 were sequenced. The sequencing data confirmed the MALDI-TOF MS result in ten cases and, for the remaining isolate, the sequencing data did not lead to the determination of the species, but only to that of the genus (Bacteroides sp.). The discriminating power and identification accuracy of MALDI-TOF MS proved to be superior to that of biochemical testing for Bacteroides thetaiotaomicron , Bacteroides ovatus and Bacteroides uniformis. © 2009 The Authors Journal compilation © 2009 European Society of Clinical Microbiology and Infectious Diseases.

Species identification of clinical isolates of Bacteroides by matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry

MAZZARIOL, Annarita;
2009

Abstract

Bacteroides fragilis and related species are important human pathogens involved in mixed infections of different origins. The B. fragilis group isolates are phenotypically very similar, grow more slowly than aerobic bacteria and, accordingly, are frequently misidentifed with classical or automated phenotypical identification methods. Recent taxonomic changes and new species accepted as members of the Bacteroides genus are not included in the different databases of commercially available identification kits. The use of matrix-assisted laser-desorption/ ionization time-of-flight mass spectrometry (MALDI-TOF MS) was therefore evaluated for the species identification of 277 clinical isolates of the Bacteroides genus. Species identification was carried out with MALDI Bruker Daltonik Biotyper software (Bruker Daltonik GmbH, Bremen, Germany) by comparing the mass spectrum of each strain with the mass spectra of the 3260 reference strains currently available. The results of conventional phenotypical identification of the isolates were used as a reference. 16S rRNA gene sequencing was performed for a selection of the strains that gave discrepant results and for all those inconclusively identified by MALDI-TOF MS; 270 isolates (97.5%) were unequivocally identified [log(score) =2.0] by comparison with the reference strains present in the MALDI Biotyper database. Of the 23 isolates for which the MALDI-TOF MS species identification differed from the conventional phenotypical identification, 11 were sequenced. The sequencing data confirmed the MALDI-TOF MS result in ten cases and, for the remaining isolate, the sequencing data did not lead to the determination of the species, but only to that of the genus (Bacteroides sp.). The discriminating power and identification accuracy of MALDI-TOF MS proved to be superior to that of biochemical testing for Bacteroides thetaiotaomicron , Bacteroides ovatus and Bacteroides uniformis. © 2009 The Authors Journal compilation © 2009 European Society of Clinical Microbiology and Infectious Diseases.
Bacteroides; Clinical isolates; Identification; MALDI-TOF MS; Sequencing; accuracy; article; bacterial strain; bacterium identification; bacterium isolate; Bacteroides ovatus; Bacteroides thetaiotaomicron; Bacteroides uniformis; chemical analysis; controlled study; genus; intermethod comparison; matrix assisted laser desorption ionization time of flight mass spectrometry; nonhuman; optical resolution phenotype; priority journal; sequence analysis; species identification; spectrophotometer; strain difference; Bacteroides fragilis; Bacteroides sp.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11562/338929
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