Author(s):
Guerreiro, Suse Cristina Alves 
Date: 2012
Persistent ID: http://hdl.handle.net/10400.5/5357
Origin: Repositório da UTL
Subject(s): Escherichia coli; cytotoxicity; Vero cells; virulence factors; multiplex PCR; ready-to-eat food
Description
Mestrado em Engenharia Alimentar - Qualidade e Segurança Alimentar - Instituto Superior de Agronomia The bacteria Escherichia coli diarrheagenic (DEC) are an important cause of gastrointestinal
diseases. The DEC are classified into: enteropathogenic, enterohaemorrhagic,
enterotoxigenic, enteroaggregative, enteroinvasive and diffusely adherent, due to the
presence of certain virulence factors. The toxins LT, ST, EAST1 and VT are encoded by the
genes lt, st, astA and stx, respectively. The intimin, encoded by the gene eae, causes the
A/E lesions (attaching and effacing), which favors the adherence of bacteria to the intestine,
being also an important factor of pathogenicity.
This study was aimed to evaluate the virulence of 36 isolates of E. coli from ready-to-eat
(RTE) food, by investigating the presence of the stx, lt, st, astA and eae genes (Multiplex
PCR) and by measuring the activity of the enzyme lactate dehydrogenase (LDH) from Vero
cells and microscopic observation (phase contrast and DAPI) of these cells, exposed to
bacterial toxins. Five isolates showed the stx gene, one of which also amplified the eae, four
isolates, the lt gene and three, the st. Cytotoxicity tests and microscopic analysis of exposed
Vero cells validate the results obtained by multiplex PCR, being that the isolates stx+ induced
higher release (p ≤ 0.05) of LDH (19.9 a 32%) than the isolates stx- (4.6 a 9.1%), having the
first ones caused extensive cytopathic effects.
Document Type
Master Thesis
Language
Portuguese
Advisor(s)
Brito, Maria Luísa de Castro; Machado, Jorge Pinheiro da Costa
