Available online xxxx Keywords: Iran Mycobacterium fortuitum RGM Soil Water A B S T R A C T Objective/Background: Nontuberculosis mycobacteria (NTM) are a diverse group of microorganisms that cause a variety of diseases in humans including skin, respiratory, and gastrointestinal tract infection. Generally, NTM are classified into two categories: rapid (<7 days) and slow growing (>7 days). In this study, we aimed to investigate NTM frequency and prevalence in environmental samples. Additionally,

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... we tried to identify various subtypes of isolated rapid growing mycobacteria (RGM). Methods: Through a prospective descriptive cross-sectional study, water and soil samples were gathered from four neighboring towns around Tehran, the capital of Iran, at different geographic directions. Every 100 m 2 of the studied areas gave one sample containing 6 g of soil in 3-5 cm depth deposited in 50 mL sterile water as sampling media. After digestion and decontamination, DNA from culture-positive specimens (RGM) were extracted using phenol-chloroform methods. Then the molecular identification of species and subspecies were performed using 16s-23s rRNA and hsp65 gene. Results: In total, 341 RGM were found, out of which 322 (94.4%) were identified and 20 (5.8%) could not be identified. The most frequent RGM was, Mycobacterium fortuitum (72; 22%), Mycobacterium senegalense (58; 17.7%), Mycobacterium parafortuitum (44; 13.4%) and Mycobacterium conceptionense type 1 (24; 7.2%), and Mycobacterium cheloni type 1 (20; 6.0%). As shown in Table 1 , M. fortuitum had more subtypes (8), and the frequency of subtypes 1 (27.7%), 4 (16.6%), and 5 (13.8%) were higher. Among subtypes of M. senegalense, subtype 1 had a higher frequency (70.4%) in comparison to subtype 2 (29.5%). M. cheloni had just one subtype. http://dx.