Mycobacterium aquaticum sp. nov., a rapidly growing species isolated from haemodialysis water.

The characterization of five Iranian isolates, four from hospital haemodialysis water and one from the sputum of a patient, led to the detection of a novel mycobacterium species. The strains were characterized by mucoid colonies developing in 3-5 days at temperatures ranging from 25 to 37 °C. The biochemical test pattern was unremarkable while the HPLC profile of mycolic acids resembled that of Mycobacterium fortuitum. The sequences of three major housekeeping genes (16S rRNA, hsp65 and rpoB) were unique and differed from those of any other mycobacterium. Mycobacterium brisbanense, which is the species that shared the highest 16S rRNA gene sequence similarity (99.03 %), was distinct, as shown by the average nucleotide identity and by the genome to genome distance values (91.05 and 43.10 %, respectively). The strains are thus considered to represent a novel species of the genus Mycobacterium, for which the name Mycobacterium aquaticum sp. nov. is proposed. The type strain is RW6T (=DSM 104277T=CIP111198T).