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      Molecular characterization of Listeria monocytogenes isolated from fresh seafood samples in Iran

      1 , , 2
      Diagnostic Pathology
      BioMed Central
      Listeria spp, Listeria monocytogenes, Virulence factors, Serotypes, Seafood, Iran

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          Among all species of Listeria, Listeria monocytogenes ( L. monocytogenes) is a major pathogenic microorganism of humans and animals and L. ivanovii is rarely pathogenic for humans. The objective of this study was to isolate and characterize Listeria species and to determine the frequencies of virulence genes in L. monocytogenes serotypes in fresh fish, shrimp, crab and lobster in Isfahan and Shahrekord, Iran.


          From September 2010 to April 2011, a total of 300 marine food samples were purchased from supermarkets of Isfahan and Shahrekord cities, Iran. All samples were cultured and the positive samples for L. monocytogenes were analyzed for presence of serotypes and virulence genes.


          From the total 300 samples, 23 (10.45%) fresh fish and 1 (2.5%) shrimp samples were positive for Listeria spp., but there were no positive lobster and crab samples for Listeria species. Only L. monocytogenes was isolated from 17 fish (7.25%) and 1 shrimp (2.5%) samples while L. innocua, L. ivanovii and L. seeligeri only detected in fish samples (2 (0.9%), 3 (1.36%) and 1 (0.45%)), respectively. The plcA, prfA, actA, hlyA and iap virulence genes were detected in all of the 18  L. monocytogenes isolates. Totally, the 4b, 1/2a and 1/2b serotypes were detected in 66.66%, 5.55% and 27.77% bacterial isolates, respectively.


          Consumption of these sea foods, either raw or undercooked, may contribute to food-borne illness due to L. monocytogenes in Iran. The hygienic quality of sea food products should be observe.

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          Most cited references24

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          Methods for the isolation and identification of Listeria spp. and Listeria monocytogenes: a review.

          Listeria monocytogenes is an important food-borne pathogen and is widely tested for in food, environmental and clinical samples. Identification traditionally involved culture methods based on selective enrichment and plating followed by the characterization of Listeria spp. based on colony morphology, sugar fermentation and haemolytic properties. These methods are the gold standard; but they are lengthy and may not be suitable for testing of foods with short shelf lives. As a result more rapid tests were developed based on antibodies (ELISA) or molecular techniques (PCR or DNA hybridization). While these tests possess equal sensitivity, they are rapid and allow testing to be completed within 48 h. More recently, molecular methods were developed that target RNA rather than DNA, such as RT-PCR, real time PCR or nucleic acid based sequence amplification (NASBA). These tests not only provide a measure of cell viability but they can also be used for quantitative analysis. In addition, a variety of tests are available for sub-species characterization, which are particularly useful in epidemiological investigations. Early typing methods differentiated isolates based on phenotypic markers, such as multilocus enzyme electrophoresis, phage typing and serotyping. These phenotypic typing methods are being replaced by molecular tests, which reflect genetic relationships between isolates and are more accurate. These new methods are currently mainly used in research but their considerable potential for routine testing in the future cannot be overlooked.
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            Identification, subtyping and virulence determination of Listeria monocytogenes, an important foodborne pathogen.

            D. Liu (2006)
            Listeria monocytogenes is an opportunistic intracellular pathogen that has become an important cause of human foodborne infections worldwide. Given its close relationship to other Listeria species and its tendency to produce non-specific clinical symptoms, the availability of rapid, sensitive and specific diagnostic tests for the differentiation of L. monocytogenes from other Listeria species is helpful for selecting appropriate treatment regimens. In addition, with L. monocytogenes comprising a diversity of strains of varying pathogenicity, the ability to precisely track the strains involved in listeriosis outbreaks and speedily determine their pathogenic potential is critical for the control and prevention of further occurrences of this deadly disease. Extensive research in recent decades has revealed significant insights regarding the molecular mechanisms of L. monocytogenes infection. This in turn has facilitated the development of laboratory procedures for enhanced detection and identification of L. monocytogenes, and has also contributed to the implementation of improved control and prevention strategies against listeriosis. The purpose of this review is to summarize recent progress in the species-specific identification, subtyping and virulence determination of L. monocytogenes strains, and to discuss future research needs pertaining to these important areas of listeriosis.
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              A small-scale procedure for extracting nucleic acids from woody plants infected with various phytopathogens for PCR assay.

              The complexity of most nucleic acid extraction procedures limits the number of samples that can be easily processed for analysis by polymerase chain reaction (PCR). A simple, small-scale procedure was developed which can be carried out entirely in 1.5-ml microfuge tubes whereby the container and contents are frozen with liquid nitrogen, tissue is pulverized, and targeted nucleic acids are extracted. DNA of bacterial and phytoplasmal plant pathogens was extracted in hot CTAB buffer followed by chloroform clarification. Following centrifugation, the DNA in the aqueous fraction was precipitated with isopropanol and resuspended in water. RNA originating from viruses and viroids was extracted from triturated tissue using STE buffer and phenol. The nucleic acid fraction was purified using CF-11 cellulose. All purified preparations were used as PCR or RT-PCR templates to detect DNA or RNA, respectively. These procedures were used to detect Xylella fastidiosa, peach yellow leaf roll phytoplasma, sour cherry green ring mottle virus, and peach latent mosaic viroid by agarose gel electrophoresis.

                Author and article information

                Diagn Pathol
                Diagn Pathol
                Diagnostic Pathology
                BioMed Central
                13 September 2013
                : 8
                : 149
                [1 ]Department of Microbiology, College of Veterinary Medicine, ShahreKord Branch, Islamic Azad University, ShahreKord, Iran
                [2 ]Post graduated of Master of Science of Microbiology, Falavarjan Branch, Islamic Azad University, Falavarjan, Iran
                Copyright © 2013 Momtaz and Yadollahi; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                : 27 April 2013
                : 27 August 2013

                listeria spp,listeria monocytogenes,virulence factors,serotypes,seafood,iran
                listeria spp, listeria monocytogenes, virulence factors, serotypes, seafood, iran


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