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

## TL;DR

This study examines eight cases of skin infections caused by Nocardia brasiliensis, focusing on diagnosis and treatment challenges.

## Contribution

The study provides insights into diagnosing primary cutaneous nocardiosis using various techniques and drug susceptibility testing.

## Key findings

- Primary cutaneous nocardiosis can manifest as localized nodular lesions.
- Conventional diagnostic methods may be insufficient without MALDI-TOF MS.
- Molecular identification and drug susceptibility testing are crucial for accurate diagnosis.

## Abstract

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.