Detection of Enteric Bacteria in Raw Food Samples from Vietnam ...

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CHAPTER 1: INTRODUCTION
Epidemiology studies have shown that contaminated food and water are the most common
vehicles for ETEC infection (Merson et al., 1976; Rosenberg et al., 1977; Taylor et al., 1982;
Wood et al., 1983; MacDonald et al., 1985; Mitsuda et al., 1998; Beatty et al., 2006). Oral
rehydration therapy is often lifesaving in infants and children with ETEC diarrhoea.
Administration of antibiotics such as fluoroquinolone for infected traveler’s diarrhoea can
shorten the duration of the episode (Nataro and Kaper, 1998a).
Enteroinvasive E. coli strains are related closely to Shigella spp. in biochemical, genetical,
and pathogenetical aspects. The strains normally produce a watery diarrhoea, occasionally
bloody diarrhoea occurs. The incidence of EIEC in developed countries is low, and is less
common than ETEC or EHEC in the developing world (Nataro and Kaper, 1998a; Bopp et al.,
2003). EIEC outbreaks are usually documented as foodborne or waterborne (Marier et al.,
1973; Tulloch et al., 1973; Snyder et al., 1984; Gordillo et al., 1992).
Enteroaggregative E. coli is defined by its distinctive aggregative pattern of adherence to
cultured human epithelial cells (Nataro et al., 1987). EAEC represents an emerging pathogen
that causes enteric and food-borne infectious diseases, causing acute and chronic diarrhoea
among children, adults and HIV-infected persons (Huang and DuPont, 2004; Huang et al.,
2006). EAEC associates mainly with diarrhoea in developing countries but recent studies have
recognized EAEC might be important agents of diarrhoea in developed countries, including
Europe, the UK, Switzerland and Japan (Nataro and Kaper, 1998a; Nataro et al., 1998b;
Huang et al., 2006). In 1993, a massive outbreak of diarrhoea due to EAEC occurred in Japan,
in which 2,697 children at 16 schools became ill after consuming contaminated school
lunches (Itoh et al., 1997). EAEC strains are the second most common cause of travelers’
diarrhoea after ETEC. It is transmitted by the faecal–oral route. Ingestion of contaminated
food and water, poor hygiene are risk factors for EAEC. The illness is usually self-limiting