Abstract Rationale Nontuberculous mycobacteria (NTM) have emerged as clinically significant pathogens in cystic fibrosis (CF), associated with accelerated lung function decline and increased morbidity. Despite growing global concern, prospective data from low- and middle-income countries remain scarce. Understanding local epidemiology is essential to guide screening strategies and clinical management. Methods A prospective observational study was conducted at the adult CF clinic of Hospital de Clínicas de Porto Alegre, a national reference center in southern Brazil. Ninety-four adults (≥18 years) with confirmed CF were consecutively enrolled between 2023 and 2025. Clinical and demographic data were obtained from medical records. Spontaneous sputum samples were collected during outpatient visits and cultured for mycobacteria using both solid and liquid media, with species identification when positive. Exclusion criteria included lung transplantation, pregnancy, recent antibiotic use (7 days), or inability to provide sputum samples. Results Participants had a mean age of 28.9 years; 45.7% were female and 96.8% Caucasian. The mean age at CF diagnosis was 9 years, and the mean FEV1% predicted was 55.5%. Regarding genotype, 40.4% were F508del heterozygous and 21.2% homozygous. Pancreatic insufficiency occurred in 71.2%, CF-related diabetes in 21.2%, and liver disease in 40.4%. Chronic colonization was identified in 54.2% for Pseudomonas aeruginosa and 57.4% for Staphylococcus aureus. CFTR modulators were used by 69.1% of patients, predominantly Trikafta (61.7%). Mycobacterial cultures were positive in 4.2% of patients, consistent with international prevalence rates ranging from 3% to 13%. Conclusions This study provides partial results of the first prospective estimate of NTM prevalence among adults with CF in Brazil. The observed 4.2% rate parallels data from North American and European cohorts, suggesting similar epidemiologic patterns despite regional differences in resources and climate. These findings underscore the importance of systematic NTM surveillance in CF programs and support the inclusion of routine mycobacterial culture in national care guidelines. The widespread use of CFTR modulators may have contributed to the relatively low prevalence, highlighting their potential protective role in airway infection control. This abstract is funded by: none
Oliveira et al. (Fri,) studied this question.