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

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CHAPTER 1: INTRODUCTION
The genus Salmonella appears to be limited to the digestive tract of humans and animals. Its
present in the environmental, food and water sources is normally from faecal contamination.
While most serotypes have a broad host-spectrum, several serotypes have a limited to a single
host species such as S. Typhi in human; S. Dublin in cattle; and S. Choleraesuis in pigs
(Selander et al., 1992; Jay et al., 1997; WHO, 2005b).
1.1.4.1.2. Salmonella epidemiology and transmission
Nontyphoidal Salmonella spp. always causes a higher proportion of food-related deaths
annually than any other bacterial pathogen in many countries (Adak et al., 2002; Kennedy et
al., 2004; Vaillant et al., 2005; The OzFoodNet Working Group, 2006; Hughes et al., 2007).
It is estimated that 800,000 to 4,000,000 human cases of salmonellosis occur in the US
annually and estimated to cost of $0.5-$3.2 billion per annum (Kennedy et al., 2004; Voetsch
et al., 2004). The worldwide incidence of non-typhoidal salmonellosis is estimated at 1.3
billion cases and 3 million deaths annually (Tassios et al., 1997).
Although all Salmonella are considered potentially pathogenic, the majority of human cases
of non-typhoidal salmonellosis are caused by only a few serotypes, such as S. Enteriditis,
S. Typhimurium, S. Anatum, S. Derby, S. Hadar, S. Rissen, S. Braenderup, S. Virchow,
S. Javiana, Weltevreden, S. Infantis, S. Newport, S. Heidelberg etc. (Fisher, 2000;
Bangtrakulnonth et al., 2004; Galanis et al., 2006; Poppe et al., 2006). S. Enteriditis and
S. Typhimurium are the two most important serotypes for human salmonellosis (Czerwinrski,
2006; Galanis et al., 2006; Lynch et al., 2006; The OzFoodNet Working Group, 2006;
Hughes et al., 2007). These two particular strains with epidemic potential will continue to be
the dominant serotypes worldwide in the foreseeable future (WHO, 2005b).