RESUMEN
Aeromonas sobria and A.hydrophila were isolated from infected fish in ratio of 3.5:1 during the outbreak of fish infections from December 1982 to February 1983, while isolates from human diarrheic stool was 1 :2. On the basis of IMVC reactions 138 isolates of motile aeromonads could be divided into 11 biogroups, with biogroup 4 showing statistically significant association with infections. Nine biogroups of aeromonads which were isolated from infected fish reflected that the outbreak was not caused by a single type of bacteria. There may have been some common factors which acted as predisposing causes. The possibility of zoonosis spreading of this epidemic infection of fish was low, because the majority of the infective agents in man and fish were different.