Application of MALDI-TOF MS for identification of clinical isolates of bacteria from humans and animals

Abstract

Routinely used diagnostic methods are insufficient to identify the microorganisms with unusual biochemical properties or less commonly occurring, including zoonotic microorganisms. During our study the possibility of identification of different bacteria isolated from humans and from breeding birds using MALDI-TOF MS (Matrix Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry) and biochemical methods was compared. The material for the study were 6 reference strains from ATCC, 30 isolates selected from healthy people (throat and nasal swabs) and 16 isolates selected from birds breeding (throat swabs from the vicinity of throat of asymptomatic birds and biopsies from the heart of the dead birds). Isolates were identified based on their biochemical properties (biochemical microtests and panels for biochemical analyzer Vitek 2) or based on a protein profile using MALDI-TOF MS technique. Biochemical methods were sufficient to identify the most common and relevant to human pathology pathogens such as e.g. Escherichia coli and Staphylococcus aureus; these results were consistent with the data obtained using MALDI-TOF MS. Identification of less common bacteria required the use of MALDI-TOF MS, because some bacteria isolated from humans or breeding birds could not be classified by their biochemical properties. The biggest differences were observed in the case of bacteria from the Pasteurellaceae family, which on the basis of biochemical properties were classified mainly as Haemophilus spp., whereas in accordance to the results obtained from the protein profile as Avibacterium endocarditidis. Identification of microorganisms using MALDI-TOF MS has proved to be more useful in the diagnosis of micro-organisms rarely isolated or problematic in routine diagnostics.