Characterisation of Aeromonas strains and species by pulsed field gel electrophoresis and principal components analysis

Aeromonas genomes were investigated by restriction digesting chromosomal DN A with the endonuclease XbaI, separation of restriction fragments by pulsed field gel electrophoresis (PFGE) and principal components analysis (PCA) o f resulting separation patterns. A. salmonicida salmonicida were unique amo ngst the isolates investigated. Separation profiles of these isolates were similar and all characterised by a distinct absence of bands in the 250kb r egion. Principal components analysis represented these strains as a clearly defined homogeneous group separated by insignificant Euclidian distances. However, A. salmonicida dchromogenes isolates in common with those of A, hy drophila and A. sobria were shown by principal components analysis to be mo re heterogeneous in nature. Fragments from these isolates were more uniform in size distribution but as demonstrated by the Euclidian distances attain ed through PCA potentially characteristic of each strain. Furthermore passa ging of Aeromonas isolates through an appropriate host did not greatly modi fy fragment separation profiles, indicative of the genomic stability of tes t aeromonads and the potential of restriction digesting/PFGE/PCA in Aeromon as typing.