ANALYSIS OF PLASMID PROFILES OF AEROMONAS-SALMONICIDA ISOLATES BY PULSED-FIELD GEL-ELECTROPHORESIS

Plasmid constitutions of Aeromonas salmonicida isolates were character ised by flat-bed and pulsed field gel electrophoresis. Resolution of p lasmids by pulsed field gel electrophoresis was greater and more consi stent than that achieved by flat-bed gel electrophoresis. The number o f plasmids separated by pulsed field gel electrophoresis varied betwee n A. salmonicida isolates, with five being the most common number pres ent in the isolates used in this study. Plasmid profiles were diverse and the reproducibility of the distances migrated facilitated the use of principal components analysis for the characterisation of the isola tes. Isolates were grouped according to the number of plasmids support ed. Further principal components analysis of groups of isolates suppor ting five and seven plasmids showed a spatial separation of plasmids b ased upon distance migrated. Principal components analysis of plasmid profiles and antimicrobial minimum inhibitory concentrations could not be correlated suggesting that resistance to antimicrobial agents is n ot associated with either one plasmid or a particular plasmid constitu tion.