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Review of 'Flow Cytometry for Rapid Detection of Salmonella spp. in Seed Sprouts'

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5
The article has significant implication in its specific field particularly food safely issues.
Average rating:
    Rated 4.5 of 5.
Level of importance:
    Rated 5 of 5.
Level of validity:
    Rated 5 of 5.
Level of completeness:
    Rated 4 of 5.
Level of comprehensibility:
    Rated 4 of 5.
Competing interests:
None

Reviewed article

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  • Article: found
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Flow Cytometry for Rapid Detection of Salmonella spp. in Seed Sprouts

 Byron Brehm-Stecher (corresponding) ,  Bledar Bisha (2014)
Seed sprouts (alfalfa, mung bean, radish, etc.) have been implicated in several recent national and international outbreaks of salmonellosis. Conditions used for sprouting are also conducive to the growth of Salmonella. As a result, this pathogen can quickly grow to very high cell densities during sprouting without any detectable organoleptic impact. Seed sprouts typically also support heavy growth (~108 CFU g-1) of a heterogeneous microbiota consisting of various bacterial, yeast and mold species, often dominated by non-pathogenic members of the family Enterobacteriaceae. This heavy background may present challenges to the detection of Salmonella, especially if this pathogen is present in relatively low numbers. We combined DNA-based fluorescence in situ hybridization (FISH) with flow cytometry (FCM) for the rapid molecular detection of Salmonella enterica Ser. Typhimurium in artificially contaminated alfalfa and other seed sprouts. Components of the assay included a set of cooperatively binding probes, a chemical blocking treatment intended to reduce non-specific background and sample concentration via tangential flow filtration (TFF). We were able to detect S. Typhimurium in sprout wash at levels as low as 103 CFU ml-1 sprout wash (104 CFU g-1 sprouts) against high microbial backgrounds (~108 CFU g-1 sprouts). Hybridization times were typically 30 min, with additional washing, but we ultimately found that S. Typhimurium could be readily detected using hybridization times as short as 2 min, without a wash step. These results clearly demonstrate the potential of combined DNA-FISH and FCM for rapid detection of Salmonella in this challenging food matrix and provides industry with a useful tool for compliance with sprout production standards proposed in the Food Safety Modernization Act (FSMA).
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    Review information

    10.14293/S2199-1006.1.SOR-LIFE.AJ19WR.v1.RFFSLN

    This work has been published open access under Creative Commons Attribution License CC BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at www.scienceopen.com.

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    Review text

    Salmonella enterica is one of the most important bacterial pathogens causing gastrointestinal disorders in humans and contaminated seed sprouts (alfalfa, mung bean, radish, etc.) act as important source of human salmonellosis. Here, a combined DNA-based fluorescence in situ hybridization (FISH) with flow cytometry (FCM) approach is introduced for the rapid molecular detection of Salmonella enterica ser. Typhimurium in contaminated seed sprouts. Therefore, the results of the present study have significant implication in its specific field particularly in food safely issues.



    However, this reviewer has few minor comments on the manuscript that the authors may consider in revision:



    1. Cooperative binding of Sal3 and Salm-63 described in Fig 1 is interesting. However, it might be better to shorten figure legends. Authors made their hypothesis and described how they tested their hypothesis within figure legends. It is better to exclude those points from figure legends. Authors may include those points in result section, not within figure legend.



    2. Results described under the subheading “Cultural and molecular characterization of endogenous sprout microbiota” are not presented either in Table or Figure. This reviewer thinks that at least molecular survey results of endogenous sprout microbiota (though the results may not reflect the true prevalence of each microbial type) needs to be shown as supplementary data in the form of table or figure.



    3. Page 4: Subheading: Pre-analytical sample preparation: …… were aliquoted into in 1.5 ml polypropylene microcentrifuge…….>> …..were aliquoted into 1.5 ml polypropylene microcentrifuge……



    4. Page 8: Subheading: Impact of TTF on detection sensitivity>> Is it TTF or TFF? It might be better to spelled out the acronym in subheading for a broader readership.

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