Eterotoxin cytotoxic thermo stables produced by Aeromanas caviae isolated from diarrheic stools in children on the city of São Bento do Una - PE

Author(s)

Ana Carolina Amaral Lopes

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Ciências Médicas
• Defense date: 2009-08-06

Examining board members

Tomomasa Yano; Carlos Emilio Levy; Claudio Roberto Nobrega Amorim

• Advisor: Tomomasa Yano

Abstract

In this study we worked with 20 Aeromonas caviae samples isolated in the state of Pernambuco and associated to diarrheic stools. The samples were analysed for the production of virulence factors, as the bacterial isolates showed haemolytic activity when grown on blood agar plates, but when analyzed the culture supernatants, the presence of haemolysin wasn't detected. The presence of enterotoxins were observed among the samples by suckling mouse test and cytotoxins on Vero cells, HeLa and CaCo-2. The biological activities were kept after the heat treatment at 100ºC for 30 minutes, showing it to be thermo stable. Cell viability tests conducted with neutral red dye on Vero cells demonstrated a 50% reduction on cell viability after 6 hours of toxin exposure, what was confirmed by the MTT and LDH assays, where the cell viability reduction was presented after 4 and 2 hours respectively. The cytoskeleton disorders provoked by the enterotoxin were observed in trials where the fluorescein conjugated phalloidine (FITC) was used, showing that the culture supernatants caused contraction and lack of actin filaments. Tests to "aerolysin" gene detection were performed with the samples, but the amplification of this gene has not been verified. According to these results and by the fact that aerolysin is a thermo labile toxin, it shows that aerolysin and the thermo stable toxin produced by A. caviae are different. (AU)