Salmonella remains to be a major foodborne pathogen for animals and humans and is the
leading cause of foodborne infections and outbreaks in various countries. Salmonella Enteritidis
is one of the most frequently isolated serotypes in poultry and poultry products from human
food poisoning cases. It can cause mild to acute gastroenterititis as well as other common
food poisoning symptoms when infection takes place in human. Nucleic acid amplification
technologies such as Polymerase Chain Reaction (PCR) is a tool that is rapid and sensitive
for detection of bacterial pathogen. We report the successful detection of S. Enteritidis by
PCR in raw chicken meat artificially-contaminated with serial concentration of S. Enteritidis
using crude DNA extracts as DNA template. PCR primers, ENT-F and ENT-R targeted on sdfI
gene were used to amplify DNA region unique to S. Enteritidis with crude DNA extract of the
samples, yielded product with the size of 303 bp. These primers were specific to S. Enteritidis
when tested by in-silico simulation against genome database of targeted bacterial species and
confirmed in PCR as amplification bands were observed with S. Typhimurium, S. Polarum and
S. Gallinarum. The established PCR can detect as few as 9.4 X 101
CFU/ml of inoculated S.
Enteritidis concentration and proved that pre-enrichment effect have significant effect on PCR
detection by increasing 1000-fold of the sensitivity limit compared to the non pre-enriched
samples. The PCR technique indicated that it can be successfully coupled with pre-enrichment
step to offer advantage in routine screening and surveillance of bacterial contamination in food
samples.
The use of polyclonal antibody (IgG) has recently been applied to the detection of bacteria. We developed a lateral flow assay (LFA) strip using a specific IgG in combination with colloidal gold on a nitrocellulose membrane. A conjugate, gold-anti Escherichia coli (E. coli) O157:H7 IgG was developed in this study for the detection of E. coli O157:H7 in food. The 40 nm in size of colloidal gold nanoparticles was used to conjugate the anti-E. coli O157:H7 IgG. The optimal concentration, 12.0 µg/ml of the anti-E. coli O157:H7 IgG was determined by standard curve generated in titration method. The serially diluted of E. coli O157:H7 was detected and clearly visualized on the LFA strip as low as 106 CFU/ml (result not shown). The IgG raised in rabbit have shown specific binding capacity against E. coli O157:H7. No other genus of bacteria, including Salmonella typhimurium, Listeria monocytogenes and Campylobacter jejuni reacted to the IgG. The LFA strip could also detect E. coli O157:H7 in different food samples matrices after 18 h-enrichment and this result were in accordance with the results of the polymerase chain reaction (PCR) and colony count.