Quantification of Listeria monocytogenes in minimally processed leafy vegetables using a combined method based on enrichment and 16S rRNA real-time PCR

Modern lifestyle markedly changed eating habits worldwide, with an increasing demand for ready-to-eat foods, such as minimally processed fruits and leafy greens. Packaging and storage conditions of those products may favor the growth of psychrotrophic bacteria, including the pathogen Listeria monocy...

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Bibliographic Details
Published in:	Food microbiology Vol. 27; no. 1; pp. 19 - 23
Main Authors:	Aparecida de Oliveira, Maria, Abeid Ribeiro, Eliana Guimarães, Morato Bergamini, Alzira Maria, Pereira De Martinis, Elaine Cristina
Format:	Journal Article
Language:	English
Published:	England Elsevier Ltd 01-02-2010
Subjects:	16S rRNA bacterial contamination Colony Count, Microbial DNA Primers - genetics DNA, Bacterial - genetics DNA, Ribosomal - genetics enrichment culture Food Handling food packaging food pathogens food safety food spoilage food storage fresh-cut foods fruits (food) genes green leafy vegetables isolation Listeria monocytogenes Listeria monocytogenes - genetics Listeria monocytogenes - growth & development Listeria monocytogenes - isolation & purification microbial detection Microbiological quality Minimally processed vegetables packaging materials polymerase chain reaction Polymerase Chain Reaction - methods predictive microbiology probabilistic models ready-to-eat foods Real-time PCR retail marketing RNA, Ribosomal, 16S - genetics storage temperature storage time Vegetables - microbiology virulence Brazil Listeria monocytogenes 16S rRNA Minimally processed vegetables Real-time PCR Microbiological quality
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Summary:	Modern lifestyle markedly changed eating habits worldwide, with an increasing demand for ready-to-eat foods, such as minimally processed fruits and leafy greens. Packaging and storage conditions of those products may favor the growth of psychrotrophic bacteria, including the pathogen Listeria monocytogenes. In this work, minimally processed leafy vegetables samples ( n = 162) from retail market from Ribeirão Preto, São Paulo, Brazil, were tested for the presence or absence of Listeria spp. by the immunoassay Listeria Rapid Test, Oxoid. Two L. monocytogenes positive and six artificially contaminated samples of minimally processed leafy vegetables were evaluated by the Most Probable Number (MPN) with detection by classical culture method and also culture method combined with real-time PCR (RTi-PCR) for 16S rRNA genes of L. monocytogenes. Positive MPN enrichment tubes were analyzed by RTi-PCR with primers specific for L. monocytogenes using the commercial preparation ABSOLUTE™ QPCR SYBR ® Green Mix (ABgene, UK). Real-time PCR assay presented good exclusivity and inclusivity results and no statistical significant difference was found in comparison with the conventional culture method ( p < 0.05). Moreover, RTi-PCR was fast and easy to perform, with MPN results obtained in ca. 48 h for RTi-PCR in comparison to 7 days for conventional method.
Bibliography:	http://dx.doi.org/10.1016/j.fm.2009.07.003 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 ObjectType-Article-2 ObjectType-Feature-1
ISSN:	0740-0020 1095-9998
DOI:	10.1016/j.fm.2009.07.003