The first Saudi Arabian national inventory study revealed the upcoming challenges of highly diverse non-tuberculous mycobacterial diseases.

Background Incidences of nontuberculous mycobacteria (NTM) causing pulmonary and extrapulmonary diseases are reportedly increasing globally and the current epidemiologic situation in Saudi Arabia remains unclear. To study such trend, we carried out a nationwide systematic epidemiological study focusing on NTM diseases for the first time in the country. Methods/Principle findings A nationwide collection of NTM isolates with clinical and demographical data was conducted for a period of 24 months. Primary species identification was carried out by line probe assays followed by sequencing of 16S rRNA, 16S-23S ITS region, rpoB and hsp65 genes. The laboratory findings were comprehensively analysed against demographical and clinical data. A total of 527 isolates were enrolled with a higher proportion of Saudi citizens (76.5%), elderly (>60 years) patients (34.2%), and male gender (65.3%) respectively. Overall, 75.1% isolates were pulmonary origin with a proven clinical significance of 44.7%. In total, 34 NTM species including 17 rare species were identified, in addition to 8 'undefined' isolates. M. simiae (22.6%), M fortuitum (18.1%) and M.absc essus (17.8%) were predominant species. Interestingly, 27 new cases of clinically relevant M.riyadhense were also noticed (Primary data on emergence of rare NTM species and M.riyadhense has been recently reported). Results showed, rare clinical events such as mYmcobac teremia, cecum abscess, peritonitis and ascites caused by M. wolinskyi, M.holsaticum, M.duvaliiand M.monacence respectively. Diabetes mellitus (P value-0.04) and previous history of tuberculosis (P value- 0.001) were identified as independent risk factors associated with NTM diseases. Conclusions/Significance NTM disease spectrum and pathogen diversity is an emerging challenge to any nation, including Saudi Arabia. Therefore, more priorities will be given to NTM's with an immediate initiative to develop diagnostic infrastructures and disease management plans.