Polymerase chain reaction (PCR)-based typing analysis of atypical isolatesof the fish pathogen Aeromonas salmonicida

Two hundred and five isolates of atypical Aeromonas salmonicida, recovered from a wide range of hosts and countries were characterized by polymerase c hain reaction (PCR) targeting four genes. The chosen genes were those encod ing the extracellular A-layer protein (AP), the serine protease (Sprot), th e glycerophospholipid:cholestrol acetyltransferase protein (GCAT), and the 16S rRNA (16S rDNA). All the atypical A. salmonicida isolates could be assi gned to 4 PCR groups. Group 1 comprised 45 strains which rested positive fo r PCR amplification, using the 16S rDNA, GCAT2, Sprot2, and AP primer-sets. Group 2 comprised 88 strains with produced PCR products using the 16S rDNA , GCAT2 and AP primer-sets. Group 3 comprised 21 strains which produced PCR products using 16S rDNA, GCAT2 and Sprot2 primer-sets, and group 4 compris ed 51 strains which produced PCR products using the 16S rDNA and GCAT2 prim er-sets only. A. salmonicida subsp. salmonicida isolates tested, belonged t o group 1. The PCR primer-sets separated A. salmonicida from other referenc e strains of Aeromonas species and related bacteria with the exception of A eromonas hydrophila. The results indicated that PCR typing is a useful fram ework for characterization of the increasing number of isolations of atypic al A. salmonicida.