Sulfonamide resistance in a disseminated infection caused by Nocardia wallacei: a case report

INTRODUCTION: Nocardial infections, although rare, are challenging for clinicians to treat. Recent contradictory reports of sulfonamide resistance have raised concerns about using this drug to treat nocardial infections. CASE PRESENTATION: A 62-year-old immunocompetent Caucasian woman showed disseminated pulmonary nodules and a brain abscess by chest computed tomography and brain magnetic resonance imaging, respectively. Multidrug-resistant Nocardia wallacei was cultured from a stereotactic brain biopsy and confirmed by 16S ribosomal ribonucleic acid gene sequencing. After the first-line treatment failed, a long course of trimethoprim-sulfamethoxazole was prescribed with no evidence of recurrence. To the best of our knowledge, this is the first report of a Nocardia wallacei disseminated infection in an immunocompetent patient, and it is the first detailed description of successful treatment with trimethoprim-sulfamethoxazole despite the resistance observed in vitro. CONCLUSION: Species identification of clinical isolates is critical for diagnosis, a prediction of antimicrobial susceptibility and epidemiological tracking. In the case of Nocardia wallacei, the clinical outcome suggests that sulfonamides can be used for treatment despite ambiguous results from in vitro susceptibility tests.