Toxicity-guided dose modification for disseminated Nocardia farcinica brain abscess in a patient with pneumoconiosis: a brief research report

Background Optimal antimicrobial strategies for disseminated nocardiosis with central nervous system (CNS) involvement remain poorly defined, particularly regarding trimethoprim-sulfamethoxazole (TMP-SMX) dosing in immunocompromised patients with severe drug intolerance. Methods This observational case study analyzed the clinical course and pharmacological management of a 55-year-old male gold miner with pneumoconiosis and chronic corticosteroid use who developed Nocardia farcinica brain abscess. Diagnosis was established via metagenomic next-generation sequencing (mNGS) and phenotypic culture. An individualized antimicrobial regimen was designed based on toxicity monitoring. Results Diagnosis of N. farcinica was confirmed by mNGS within 48 h. The patient initially failed empirical meropenem but responded to combination therapy with imipenem, amikacin, and TMP-SMX. Due to grade III gastrointestinal toxicity (CTCAE v5.0), TMP-SMX was de-escalated from 15 mg·kg −1 ·d −1 –11.25 mg·kg −1 ·d −1 , with maintenance at 7.5 mg·kg −1 ·d −1 . Clinical improvement was observed at Day 120, though durable cure remains unconfirmed. Conclusion In extreme circumstances of severe dose-limiting toxicity, temporary TMP-SMX dose reduction with intensive monitoring may be feasible as a bridge to complete guideline-concordant therapy, though this approach falls below current recommendations and requires robust therapeutic drug monitoring. Species-directed antimicrobial selection and early molecular diagnosis facilitated initial clinical resolution in this high-risk immunocompromised host.