Corynebacterium durum and possibilities of its identification.

Corynebaterium (C.) durum is a part of the resident human oral microbiota. Its role in the aetiology of infectious diseases is ambiguous. With the increasing number of immunocompromised patients, it must be considered a potential opportunistic pathogen. It is isolated from the sputum, bronchoalveolar-lavage fluid, as well as blood, especially from immunocompromised patients with pneumonia. In that case, the critical steps involve a correct identification of Corynebacterium to the species level and right interpretation of the findings. The previously widely used commercial test for the identification of Corynebacteria (API Coryne, BioMerieux) is not suitable for all species, including C. durum, as its biotype number is not included in the database. But the obtained result can be compared with the available literature data. Chemotaxonomic and proteomic analysis (matrix-assisted laser desorption/ ionization - time of flight, MALDI-TOF MS) or 16S rRNA sequencing allow for accurate differentiation from the other Corynebacteria species. Nevertheless, these methods are not routinely used in clinical laboratories. A polyphasic approach to the taxonomy based on the data from combined laboratory tests is crucial.