Abstract:

Because of low levels of Salmonella in food, a pre-enrichment step in PCR-based method for the detection of Salmonella is usually included. To investigate a simple and rapid pre-enrichment protocol, four strains of Salmonella in food were pre-enriched. The first step was to confirm whether shaking during pre-enrichment had any beneficial effects on the number increase of number of Salmonellae than not shaking. The second step was to examine whether MM broth would be superior to BPW broth in supporting the growth of Salmonella. The third step compared the enrichment effects at 6, 8, and 24 h of incubation in BPW broth. The results showed that shaking culture has no beneficial effect on the growth of Salmonella after 6 and 8 h of incubation (p ＞ 0.05). However, after incubation for 24 h the shaking effect is prominence (p ＜ 0.01). Similarly, there is no difference between MM and BPW broths after 6 and 8 h of incubation (p＞0.05), but after 24 h the effect of MM broth is very significantly increased (p＞0.01). During the incubation in BPW broth, the enrichment effect after 8 h is significantly higher than after 6 h (p＞0.01) and it after 24 h is also significantly higher than after 8 h (p＞0.01). In conclusion, shaking culture and MM broth are unable to promote the increase of Salmonella number, therefore the optimized protocol is to pre-rich Salmonella with still culture in BPW broth at 37 ℃ for 8 h.

Key words: Salmonella, PCR detection, pre-enrichment protocol