Use of restriction enzyme fragment length polymorphism (RFLP) of the 16S–23S rRNA internal transcribed spacer region (ITS) for identification of fish mycobacteria

PCR targeting the 16S–23S rRNA gene internally transcribed spacer (ITS) region has been proposed as a rapid and reliable method for the detection of Mycobacterium species in human clinical specimens. Because of variation in ITS sequences amongst Mycobacterium species, a single PCR amplification can be used to differentiate slowly growing and rapidly growing species within this genus. In the present study, analysis by ITS-PCR and ITS-restriction fragment length polymorphism (RFLP) was found to be a useful, simple and rapid method compared to current molecular and phenotypic techniques. The ITS was amplified from 13 reference strains and 59 fish isolated mycobacteria using a set of published PCR primers. After PCR, the banding patterns generated allowed slowly growing mycobacteria to be differentiated from all other rapidly growing species, with the exception of Mycobacterium conceptionense. HaeIII was selected as one of two restriction enzymes that, together with the knowledge about amplicon sizes, would produce an acceptable level of discrimination in the resulting RLFP patterns, especially in the rapidly growing group of mycobacteria. After digestion with Sau96I, the amplified products of most isolates of Mycobacterium fortuitum, including subtypes II and V and those 2 isolates with new patterns (220, 100bp), presented identical or very similar patterns as obtained by HaeIII digestion. All isolates of Mycobacterium marinum, Mycobacterium chelonae and Mycobacterium gordonae, whose PCR products were not digested with HaeIII, produced two well-defined fragments with the Sau96I restriction enzyme. •Rapid identification of myocobacteria is pivotal in control of fish mycobacteriosis.•Use of PCR–RFLP of the ITS region to identify fish mycobacteria was investigated.•Using this method, it is possible to differentiate slowly and rapidly growing mycobacteria.