RESUMEN
Nocardia cyriacigeorgica is a well-known agent of human nocardiosis and is considered an emerging pathogen, however, its identification to the species level is complex for many clinical laboratories. Available data on the clinical significance of N. cyriacigeorgica in veterinary medicine are sparse and mainly concern isolated reports of pyogranulomatous lesions in domestic animals. We report a case of severe bovine mastitis caused by N. cyriacigeorgica that did not respond to conventional antimicrobial therapy in a small holding in Bosnia and Herzegovina. After isolation of the pathogen, further identification by routine microbiological methods was not possible. Susceptibility to antimicrobials was tested using the disc diffusion method according to published recommendations. The sample was also tested by MALDI-ToF MS with inconclusive results. In addition, 16S rRNA sequence analysis, verified by multilocus sequence analysis (MLSA) using the gyrB, 16S rRNA, secA1, and hsp65 sequences, confirmed the species N. cyriacigeorgica. To our knowledge, this is the first report of isolation of N. cyriacigeorgica from a clinical case of bovine mastitis in a European dairy farm and the first MLSA method approach to distinguish a Nocardia spp. strain isolated from animals.