Expansion of MALDI-TOF MS database as a strategy for identification of species other than .

OBJECTIVES

This study aimed to evaluate an expanded matrix-assisted laser desorption-ionization-time of flight mass spectrometry (MALDI-TOF MS) database for the identification of species other than (Hi).

METHODS

A total of 144 species, cultured from respiratory samples from people (living) with cystic fibrosis, were identified with MALDI-TOF MS and 16S rRNA sequencing. Of these, 99 strains showed >99% similarity with the best matching strain in the National Center for Biotechnology Information (NCBI) database and were assigned to a single subspecies using both MALDI-TOF MS and 16S rRNA sequencing. The MS profiles of a subset of strains (n = 58/99) were added to the Bruker MALDI-TOF MS database. Subsequently, 270 different strains that were analyzed previously in a routine setting were re-analyzed.

RESULTS

16S rRNA sequencing reliably identified 99/144 strains (>99% similarity). 16S rRNA identification was suboptimal since only 3/21  strains attained a similarity of >99% with 16S rRNA sequence in the NCBI database. Expansion of the MALDI-TOF MS database improved the number of reliable identifications only moderately for , and (<10%). By contrast, improved identification was more outspoken for , , and (>85%).

CONCLUSION

16S rRNA sequencing is a valuable method for the identification of sp. other than Hi. Expansion of the MALDI-TOF MS database, based on 16S rRNA sequencing results, increased the proportion of reliable identifications and in this study resulted in an increase of 10% of sp. other than Hi strain identifications.