Pulsed-field gel electrophoresis in the study of mesophilic and psychrophilic Aeromonas spp.

Pulsed-field gel electrophoresis (PFGE) was used to study the genetic diversity of mesophilic Aeromonas hybridization group (HG) 1, HG 2, HG 3, HG 4, HG 5, HG 6, HG 7, HG 8/10 and HG 11, psychrophilic Aeromonas salmonicida subsp. salmonicida and atypical Aerom. salmonicida strains. XbaI was chosen for restriction because it produced fragments whose numbers and size were appropriate for PFGE analysis of all studied HGs. All mesophilic Aeromonas strains within an HG had different banding patterns. No shared bands which could be used for identification of an HG were found. Pulsed-held gel electrophoresis analysis further confirmed the known genetic homogeneity of Aerom. salmonicida subsp. salmonicida. Pulsed-field gel electrophoresis pattern analysis suggested that the genomic size of Aerom. salmonicida subsp. salmonicida is smaller than that of mesophilic Aeromonas spp, or atypical Aerom. salmonicida. Aeromonas salmonicida subsp. salmonicida had only one large restriction fragment (310 kb) and lacked other large fragments (>160 kb). Although the PFGE patterns of atypical Aerom. salmonicida resembled the banding patterns of mesophilic Aeromonas spp. they had several small fragments (15-50 kb) shared with Aerom. salmonicida subsp. salmonicida suggesting genetic relatedness.