Clinical relevance of Mycobacterium szulgai in The Netherlands

The clinical relevance of Mycobacterium szulgai isolates is unknown, and available literature focuses on case reports of M. szulgai disease. We assessed the clinical relevance of M. szulgai isolated from patients in The Netherlands.

We reviewed medical files for all 21 patients in The Netherlands from whom M. szulgai was isolated during 1999-2006, applying the diagnostic criteria of the American Thoracic Society for nontuberculous mycobacterial infection. Random amplified polymorphic DNA genotyping was performed using IS986, OPA-2, and OPA-18 as primers.

Of the 21 patients, 16 (76%) met the American Thoracic Society diagnostic criteria and were thus likely to have M. szulgai disease. Pulmonary M. szulgai disease was the most common presentation, with extrapulmonary disease restricted to patients with an impaired systemic immunity. Although treatment regimens varied in content and duration, the outcomes were mostly favorable. Both overtreatment and undertreatment were noticed. Random amplified polymorphic DNA genotyping revealed a higher degree of interpatient variability, with limited intrapatient variability, suggesting persisting monoclonal infection and good reproducibility. No genotype was associated with clinical relevance.

Clinical isolation of M. szulgai generally represents true disease and demands careful follow-up. Extrapulmonary disease occurs in patients with impaired immunity. Adherence to diagnostic guidelines can be improved.