Detecção de genes do Sistema de Secreção do Tipo III em Aeromonas hydrophila e sua relação com a virulência em tilápia do Nilo

Abstract

Aeromonas hydrophila is a bacterium which can cause diseases in several hosts such as humans and fish The type three secretion system (T3SS) has been reported as one of major virulence factor in Gram negative bacteria including the fish pathogen A hydrophila The aims of this study were to develop PCR systems to detect ascV and aopB genes from the T3SS to evaluate their frequency in A. hydrophila strains isolated from diseased fish and aquaculture environment and the relation between T3SS presence and virulence to Nile tilapia The PCR developed here was useful to detect the target genes showing three different profiles among the strains ascV+/aopB+ ascV+/aopB- e ascV-/aopB- Higher frequency of ascV+/aopB+ was verified in isolates from diseased fish than aquaculture environment (P < 005) Among 64 isolates from diseased fish ascV+/aopB+ (62.5%) was the most frequent profile (P < 005) and promoted more intensive mortality rates Environmental strains with ascV+/aopB+ profile were less virulent than isolates from clinical cases This result suggests that the presence of functional T3SS probably improves the A hydrophila virulence The PCR assay showed to be a specific and efficient tool for detection of T3SS and this technique can be used for typing A. hydrophila isolates