SDS-PAGE for identification of species belonging to the Mycobacterium fortuitum complex

We performed a study to determine the usefulness of SDS-PAGE of whole cell proteins for the characterization of species of rapidly growing mycobacteria belonging to the Mycobacterium fortuitum complex. Strains included 37 M. fortuitum, 32 M. chelonae, 10 M. peregrinum, 5 M. abscessus, and 3 M. mucogenicum. Eight collection strains (including type strains of the five species) were also included in the study. All strains yielded between 44 and 58 bands in the electrophoretograms. Intraspecies similarity showed Dice coefficients higher than 95%, with only one strain of M. fortuitum having a six-band difference (Dice coefficient 87.75%). However, interspecies similarity was always below 75%, the similarity being higher between M. fortuitum and M. peregrinum (75.51%) and between M. chelonae and M. abscessus (54.9%). Visual examination of the electrophoretograms was sufficient for species characterization. SDS-PAGE of whole cell proteins is a useful technique for identification of isolates of the M. fortuitum complex, and is easy to perform without the need for complex or expensive equipment.