AUTHOR=Siala Mariam , Barbana Amina , Smaoui Salma , Hachicha Salma , Marouane Chema , Kammoun Sana , Gdoura Radhouane , Messadi-Akrout Férièle 

TITLE=Screening and Detecting Salmonella in Different Food Matrices in Southern Tunisia Using a Combined Enrichment/Real-Time PCR Method: Correlation with Conventional Culture Method

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.02416

DOI=10.3389/fmicb.2017.02416

ISSN=1664-302X

ABSTRACT=<p>A combined enrichment/ newly developed <italic>invA</italic> TaqMan<sup>®</sup> real-time PCR (qPCR) method as a screening assay to detect <italic>Salmonella</italic> spp. in 500 naturally food matrices is evaluated. DNA template for qPCR was extracted from an overnight pre-enriched sample in buffered peptone water using lysis–guanidine isothiocyanate method. Heterologous internal amplification control (IAC) was incorporated during qPCR assays and co-amplified with the <italic>invA</italic> gene of the target pathogen. <italic>InvA</italic> qPCR exhibited 100% specificity when testing 94 <italic>Salmonella</italic> strains (inclusivity) and 32 non-<italic>Salmonella</italic> strains (exclusivity). The qPCR showed a consistent detection of two copies of the <italic>invA</italic> gene/PCR reaction, a good intra- and inter-run reproducibility with a good PCR efficiency (89.6%). QPCR was sensitive and showed <italic>Salmonella</italic> detection at 8.5 × 10<sup>0</sup> CFU mL<sup>-1</sup> of artificially spiked poultry meat -BWP solution in less than 40 cycles. When analyzing 500 different food matrices and comparing the results with the ISO 6579:2002 conventional culture method, the sensitivity and specificity were 100 and 76.6%, respectively. QPCR showed <italic>Salmonella</italic> spp. DNA in raw poultry meat 27/45 (60%), milk 31/93 (33.3%), raw red meat 5/13 (38.5%), and fish 11/46 (23.9%) samples. The prevalence of <italic>Salmonella</italic> spp. in cakes, dairy, cooked meals, charcuterie products using qPCR was 11/14 (26.8%), 5/22 (22.7%), 32/150 (21.3%), and 5/20 (25%), respectively, compared to 0% as demonstrated by culture. <italic>S.</italic> Anatum was the most common serovar found associated with red meat compared to <italic>S.</italic> kentucky isolated from fish and poultry meat. In conclusion, our study is the first to use a combined enrichment/<italic>invA</italic> qPCR method as a screening assay to detect <italic>Salmonella</italic> DNA in different types of commercialized food in Southern Tunisia. QPCR results indicate that <italic>Salmonella</italic> contamination is common in milk and in other types of food samples.</p>