We report the first documented case of a mycetoma caused by Nocardia yamanashiensis after the initial description of this species. The 16S-rRNA gene sequence analysis was used to identify the novel species, which showed a similarity of 99.9% to the gene sequence of the type strain. The case showed both clinical non-response and reduced susceptibility in vitro to amoxicillin plus clavulanate, and it was treated successfully with trimethoprim-sulfamethoxazole and doxycycline. Given antibiotic resistance concerns, we suggest that antimicrobial susceptibility testing should be done for the majority of Nocardia species without well-established resistance patterns.
