Determination of virulence factors in strains of Aeromonas spp., isolated from fish

Objetive. The aim of this study was to determine the incidence of five phenotypic virulence markers in isolated strains of Aeromonas in fish being sold in Pamplona, Colombia. Materials and methods. A total of 47 strains previously identified were used. Haemolytic activity on blood agar, supplemented with 5% sheep erythrocytes, and blood agar supplemented with 5% human erythrocytes; proteolytic activity in Mueller-Hinton agar supplemented with 10% (w/v) skim milk; lipolytic activity on tributyrin agar and deoxyribonuclease (DNase) activity on DNAse agar plates were evaluated. Results. Strains of A. hydrophila, A. veronii GH 8, A. jandaei, A. veronii GH 10 and A. eucrenophila demonstrated haemolytic, proteolytic, lipolytic and nuclease capacities. All A. popoffii strains were β-haemolytic, proteolytic and with DNase activity on human blood agar. Strains of A. caviae, also were haemolytic and lipolytic, whereas the strain of A. schubertii presented haemolytic and DNase activity. Conclusions. The frequence of the virulence factors in the studied strains was: 87% of the isolates presented nuclease production, 83% were β-hemolytic on human erythrocytes, 68% presented lipase production, 63% were proteolytic, and 53% were found to be haemolytic on sheep erythrocytes, these data indicate the possible pathogenic potential of the strains. These results also suggest that the fish sold in Pamplona, could be an important source of Aeromonas species expressing factors associated with virulence in humans.