Aeromonas species isolated from pintado fish (Pseudoplatystoma SP): virulence factors and drug susceptibility

RESUMO

Aeromas has been described as an emergent foodborne pathogen of increasing importance. In this study, we report that 48(per cent) of 50 Pintado fish samples collected at the retail market of São Paulo city were positive for Aeromas sp, as detected by the direct plating method. When the presence/absence method was used, the positivity was 42(per cent). A caviae was the most frequent species, followed by A. hydrophila and A. sobria. Production of cytotoxic enterotoxin, observed in suckling mouse assay, was detected in 67(per cent) of A sobria strains, in 60(per cent) of A. hydrophila strains and in 40(per cent) of A. caviae strains. In vitro tests, performed with HEp-2 cells, showed that 88(per cent) of A. hydrophila, 27(per cent) of A. sobria and 13(per cent) of A. caviae strains were positive for this toxin. The in vivo production of cytotonic enterotoxin, tested after heating the filtrates at 56degreeC for 20 minutes, was detected in 17(per cent) of A. sobria, in 10(per cent) of A. caviae and in none of A. hydrophila strains in vivo. All analyzed strains did not alter HEp-2 cells. 20(per cent) and 16(per cent) of A. sobria and A. caviae isolates, respectively, presented capacity to adhere to HEp-2 cells. In counterpart, invasion of HEp-2 cells was not observed in any isolate. The Aeromonas isolates were sensitive to the majority of the antimicrobiol agents tested.