Salmonella is one of the most important pathogenic genera implicated in food-borne bacterial outbreaks and diseases (Gouws et al. 1998). Over the last few years, Salmonella enterica serotype enteritidis has appeared to be the most common serovar of Salmonella spp. in many countries (Usera et al. 1994; Landeras et al. 1996; Baylis et al. 2000). Most cases of salmonellosis occurred sporadically or as limited family or community outbreaks. However, some hospital- and nursing home-associated outbreaks have also been reported previously (Landeras et al. 1996). In addition, Salm. enteritidis has frequently been observed as a contaminant in foods such as eggs and poultry products (Cohen et al. 1994; Fadl et al. 1995; Landeras et al. 1996).
Traditional detection methods for Salmonella were based on cultures using selective media and followed by a series of biochemical and/or serological tests. As long as 5–7 d are generally required to confirm the presence of Salmonella species (Food and Drug Administration 1995). This time delay has led to the development of several alternative methods for the rapid detection of the presence of Salmonella sp., some of which have been commercialized (Gouws et al. 1998). Among these procedures, a series of DNA-based methods for the detection and identification of either all type serovars (Lin et al. 1996; Gouws et al. 1998; Tsen and Jian 1998) or specific species of Salmonella, such as typhimurium (Soumet et al. 1999a, 1999b), typhi (Song et al. 1993; Liu et al. 1995) and enteritidis (Cohen et al. 1994; Fadl et al. 1995; Frech and Schwarz 2000) have already been established recently. Various polymerase chain reaction (PCR)-based methods have also been published for the detection of enteritidis. For example, an arbitrarily primed PCR was developed to analyse the genomic DNA of enteritidis isolated from human outbreaks and an avian source (Fadl et al. 1995). However, enteritidis was detected in faeces from hens by using a PCR process. It was shown that these primers were specific to all members of the genus Salmonella, but not only exclusively to Salm. enteritidis (Cohen et al. 1994). A Multiplex PCR-based assay method with three sets of primers has been developed for the simultaneous detection of Salm. enteritidis, Salm. typhimurium and all Salmonella spp. (Soumet et al. 1999a, 1999b). However, unfortunately only relatively few serovars of Salmonella have been used to test the specificities of these primers.
In this study, two sets of novel PCR primers were developed based on their insertion element (IE) gene sequence; these primers demonstrate the ability to be used for the specific detection of Salm. enteritidis. The nucleotide sequences of these two primers appear to be characteristically different from other primers previously reported (Cohen et al. 1994; Soumet et al. 1999a, 1999b). In this paper, the approach to the design of new primers and the application of these primers in the PCR detection of Salm. enteritidis contamination in foods and faecal samples is described. For comparison, some of these samples were preinoculated with cultured bacterial cells of Salm. enteritidis.