Correct characterization and reliable identification of the members of the genus Avibacterium still represent a major challenge in diagnostic laboratories with misidentifications as a frequent and a serious problem. The present investigation based on Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) reports a new approach to analyse Avibacterium species. For this purpose a well characterized strain collection (n=33) of Avibacterium species was investigated. The robustness of the currently available reference database (Bruker Biotyper 3.0) was tested to determine the degree of identification of these strains. A reproducible signal pattern was obtained from all 33 Avibacterium strains investigated by MALDI-TOF MS. Signal patterns obtained were compared with data in the Bruker Biotyper reference database version 3. Reliable identification at genus level was demonstrated for 25 strains (76%). Identification at species level was only possible for six strains (18%), all of which were identified as Av. endocarditidis.
To improve the Avibacterium species identification by MALDI/Biotyper six reference strains were included in the reference database and identification was again performed. Based on this all the strains were reliable identified to species level except for one strain which was identified only to the genus level.
To determine the relationship between the 33 Avibacterium strains a score oriented MSP dendrogram was generated. Based on a distance level of 500 two clusters were present, revealing that only Av. paragallinarum represents a well-defined species. This finding was also supported by the organism’s best and second best match MALDI-TOF MS values based on the enhanced reference database.
In conclusion, MALDI-TOF MS was shown to represent a fast and reliable method for identification and separation of the Av. paragallinarum complex. But, further taxonomic investigations including whole genome comparisons are needed to solve the diagnostic and taxonomic problems associated with the genus Avibacterium.