The use of a two-gene sequencing approach to accurately distinguish between the species within the Mycobacterium abscessus complex and Mycobacterium chelonae.

Mycobacterium abscessus [M. abscessus (sensu lato) or M. abscessus complex] comprises three closely related species: M. abscessus (sensu stricto), hereafter referred to as M. abscessus, M. bolletii and M. massiliense. We describe here an accurate and robust method for distinguishing M. chelonae from M. abscessus, M. bolletii and M. massiliense, using polymerase chain reaction (PCR) and the sequencing of house-keeping gene targets (hsp65 and rpoB). Sequencing of the sodA gene is of little additional value in discriminating between species, but M. massiliense can be rapidly identified by amplification of the truncated erm(41) gene without the need for amplicon sequencing. We have applied the method to 81 isolates from 40 patients from two hospitals, the majority of whom were cystic fibrosis (CF) patients. Of these patients, 21 had previously been identified as M. chelonae and 59 as M. abscessus complex using commercial line probe assays. We identified these as 46 M. abscessus isolates, 20 M. massiliense isolates, five M. bolletii isolates and nine M. chelonae isolates and confirmed the one M. fortuitum isolate. This is the first study that has identified the individual members of the M. abscessus complex in a UK cohort of mainly CF patients.