Identification of type strain-specific diagnostic peptides of the Bacillus cereus group

The Bacillus cereus group consists of eight very closely related species and comprises both harmless and human pathogenic species. Yet, methods to rapidly and accurately distinguish these species are currently lacking as we demonstrate that classical matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) biotyping did not achieve reliable identification of each type strain. We assigned type strain-specific diagnostic peptides to the B. cereus group based on comparisons of their proteome profiles. The number of diagnostic peptides varies remarkably in type strain-dependent manner. The state of the art of the reference database is crucial in the process of validating candidate diagnostic peptides and may lead to a noteworthy reduction of verified diagnostic peptides as putative diagnostic peptides might be found in other species as well.