1 Presence of virulence markers on clinical and environmental isolates of

We have investigated the presence of four virulence genes, i.e. alt, ast, aerolysin/hemolysin and lafA in 32 isolates of A. jandaei from clinical, environmental and animal origins. The lafA gene was the most widely distributed (61.5% of the isolates), followed by the aerolysin/hemolysin (42.3%), alt (11.5%) and ast (3.8%) genes. Only one human diarrhoeal isolate presented the ast gene in combination with alt and lafA. Simultaneous presence of the lafA gene and aerolysin/hemolysin was observed in 34.7% of the isolates regardless of their origin. A total of 72.2% of the clinical isolates presented any of the studied virulence genes, while only 40% of the environmental isolates did. Since 18 of the 32 isolates were obtained from different authors, all the isolates were typed with the PCR amplification of the enterobacterial repetitive intergenic consensus (ERIC) obtaining specific profiles for only 26 isolates. This indicated that the rest were duplicates. 1.Introduction The genus Aeromonas includes 15 species (Figueras et al., 2000b; Pidiyar et al., 2002), A. veronii bt sobria, A. caviae and A. hydrophila being the most prevalent in clinical samples, although other species such as A. jandaei are also isolated (Carnahan et al., 1991; Joseph et al., 1991; Gonzalez et al., 2001; Overman et al., 1999; Figueras et al., 2000a; Carson et al., 2001; Janda & Abbott, 1998; Valera & Esteve, 2002; Sarma, 2002). The incidence of A. jandaei in our studies using genetic identification methods was 2.6% of intestinal and 5.6% of extraintestinal isolates (unpublished data). This species has caused septicemia and intestinal diseases in humans (Janda & Abbott, 1998) and has showed more resistance to antibiotics than other clinical species such as A. schubertii, A. trota and A. veronii biotype veronii (Overman et al., 1999).