Primary cutaneous nocardiosis caused by Nocardia brasiliensis: isolation, susceptibility, and molecular identification in eight consecutive cases from a tertiary hospital

Nocardiosis is caused by Gram-positive aerobic bacteria of the genus Nocardia , which are soil-dwelling saprophytes. Infection may also occur via direct inoculation, leading to primary infections of the skin and subcutaneous tissues that often manifest as localized nodular lesions. Diagnostic identification can be challenging or even unfeasible using conventional laboratory techniques, particularly when Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) is not available. We conducted a retrospective analysis of eight cases of primary cutaneous nocardiosis diagnosed in the dermatology department of our hospital between 2022 and 2025, aiming to provide diagnostic insights with regard to culture, staining, mass spectrometry, 16S rRNA sequencing, and drug susceptibility testing, as well as to delineate the epidemiological characteristics of this condition.