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

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CHAPTER 1: INTRODUCTION
20,009 cases and 821 deaths and V. cholerae continues to be an important cause of diarrhoea
in Vietnam (Dalsgaard et al., 1999b).
Cholera is caused by infection of the small intestine by Vibrio cholerae O1 and O139, and is
characterised by massive acute diarrhoea, vomiting, and dehydration. Other symptoms include
hypotension, nausea, and sometimes fever. The amount of fluid loss can be up to one or more
liter of per hour, resulting in severe dehydration and circulatory collapse if untreated, and
death can occur (Desmarchelier, 1997a; Farmer III et al., 2003). Gastroenteritis associated
with V. cholera non O1/non-O139 serogroup is nonbloody and occasionally bloody diarrhoea
with nausea, vomiting, and abdominal cramping (Oliver and Kaper, 2001). In the treatment of
cholera, replacing fluid and electrolytes is essential. Antibiotics such as tetracycline,
cotrimoxazole, erythromycin, doxycycline, chloramphenicol and furazolidone are useful
adjuncts in treatment of severe cases (WHO, 2000a). Cholera is transmitted from
contaminated water and food, direct person-to-person contact is rare (Guthmann, 1995; Kam
et al., 1995; Kaper et al., 1995; Rabbani and Greenough III, 1999; Oliver and Kaper, 2001).
Cholera is occasionally acquired from consumption of inadequately cooked crustaceans or
molluscan shellfish in many countries (Weber et al., 1994; Kam et al., 1995; Rabbani and
Greenough III, 1999; CDC, 2006c).
1.2. Virulence genes in foodborne bacteria
1.2.1. The virulence genes invA and spv in Salmonella spp.
Salmonella spp. are facultative intracellular pathogens which cause a variety of infectious
disease. The processes of invading, surviving, multiplying within diverse eukaryotic cell types