The first comparative metagenomic analysis of diarrheal and non-diarrheal gut microbiome leading to the identification of prospective prognostic markers and probiotics to protect from diarrhea: A Brief Report

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Abstract

Introduction: Diarrhea is a leading contributor of mortality. Its disease burden can be assuaged using enhanced prognostics and therapeutics. A cross-sectional gut microbiome analysis  of  non-diarrheal  and   diarrheal  fecal  samples was conducted to meet the goals of the Global Action Plan for Pneumonia and Diarrhea. Hypothesis: Next-generation Sequencing as a tool for epidemiological surveillance helps in the comparison of structural diversity of the gut microbiome of diarrheal and non-diarrheal samples and can identify prognostic and therapeutic candidates. Aim: The pilot study was designed to identify taxa that are enriched in non-diarrheal samples and to predict gut microbial interactions. Methodology: 16SrRNA amplicon sequencing  and  analysis  were deployed for taxonomic  profiling  and  abundance  interpretation  of  OTUs (Operational Taxonomic Units). Results: The findings suggested significant  differences  in structural composition between  the  two  groups. Firmicutes was the  most  abundant  phylum in most samples. B/F ratio was consistently <1 in all diarrheal samples. Proteobacteria  was    more  abundant  in    diarrheal  samples.  Prevotellaceae  was  the  most  abundant  family  in  non-diarrheal  samples.  Streptococcaceae  was  the  most  abundant  family  in  60%  diarrheal  samples.Where  Streptococcaceae  was  suppressed,  Bacteroideaceae  and  Nocardeaceae  were  the  most  abundant.    In  non-diarrheal  samples  where  Bifidobacteriaceae  was  the  most  abundant  other  families  were significantly low.  A  negative  correlation  was  observed  between  Prevotellaceae  and  Bacteroideaceae  in    non-diarrheal  samples.  Prevotella  copri  was  the  most  abundant  species  in  70%  non-diarrheal  samples  and  was  significantly  suppressed  in  diarrheal  samples.  Proteus  mirabilis  was  identified  in  all  the  non-diarrheal  samples  and  were  absent in  diarrheal  samples.  Conclusion: The OTUs  associated  with  diarrheal  dysbiosis  can  serve  as  prognostic  markers.  This is the first report on the comparative analysis of diarrheal and non-diarrheal microbiome.  The study addressed  gut microbiome dysbiosis from the context that can lead to the development of prognostic markers and probiotics for protecting the endemic population from diarrhea and help in reaching Sustainable Development Goals 2 and 3.

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  1. Thank you for submitting your manuscript to Access Microbiology. It has now been reviewed by two experts in the field whose comments are attached at the bottom of this email. They both have important concerns on the structure, scope, literature references and interpretation of the results. Please address them carefully in a revised version of the manuscript. Please submit a revised version of the manuscript (including a tracked-changes document) along with a point-by-point response to the reviewer comments within 2 months.

  2. Comments to Author

    In the current manuscript, the authors compared the gut microbiome between diarrheal and non-diarrheal populations using metagenomic analysis. They found significant differences in structural composition between the two groups. However, the study populations were too small, especially for the diarrheal group (only 5). Moreover, the causative agent for diarrhea may be viruses (such as norovirus and rotavirus), parasites (such as Giardia lamblia and Entamoeba histolytica), or bacteria (such as Salmonella and Shigella). The authors did not distinguish viral diarrheal group from bacterial diarrheal group. The findings may be different under the circumstance of different pathogens.

    Please rate the manuscript for methodological rigour

    Poor

    Please rate the quality of the presentation and structure of the manuscript

    Satisfactory

    To what extent are the conclusions supported by the data?

    Not at all

    Do you have any concerns of possible image manipulation, plagiarism or any other unethical practices?

    No

    Is there a potential financial or other conflict of interest between yourself and the author(s)?

    No

    If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?

    Yes

  3. Comments to Author

    The MS by the authors described the microbiome analysis in diarrheal and non-diarrheal individuals using comparative 16S based metagenomic analysis. The study will be of importance to understand the dysbiosis and possible interventions. I append my comments as follows: General comment: 1. The MS has careless drafting errors and lack proofreading. Use of jargons is there. 2. Introduction lack enough literature survey. Not identifying the gaps in the literature. 3. There are literatures that need to be included in the background. Some eg. but not limited to are as follows. doi.org/10.1016/j.mib.2022.01.006 doi.org/10.1186/gb-2014-15-6-r76 doi.org/10.1080/19490976.2017.1361093 doi.org/10.1126/science.aad3503 4. Diarrhea is the disease of the low-income countries as described in the MS. How will the cost intensive metagenomics can be used for such resource poor settings? Methodology: 1. Sample size between diarrhea and non-diarrhea vary significantly. The results might be affected by the outliers particularly in diarrhea groups. 2. Ages of the individuals in diarrhea and non-diarrhea groups? 3. During the sample collection, did a comprehensive Q&A was carried out? This reviewer is interested in knowing if the individuals with diarrhea were on antibiotics before sample collection. Similarly, for non-diarrheal cases, did by any chance they have taken the antibiotics for non-related illness. If the information is available, this will aid the MS discussion. 4. How many days post onset of diarrhea, samples were collected? 5. What were the possible etiological agents in the 5 diarrheal cases? 6. Why 16S rRNA based metagenomic analysis was carried out when shotgun metagenomics can demonstrate higher level of phylotype resolution. Presentation of Results: 1. Although the submission of the MS is format neutral, still the authors should have considered preparing the tables in the basic publication format. 2. Same is for the figures. No need to separately describe the x-axis and y-axis. Rather, they should be in the axis itself. 3. In tables, decimal places are not unified and significant figures are not considered. 4. Core microbiome/conservation of OTUs in diarrhea cases should have been discussed with another study from the authors (Ref. 4) Referencing: Usage of full stops/periods is improper at multiple places. References are not unified. Other comments: Ln29: Add space after 'samples'. Ln56, 59: Add apace between numbers of the references. Ln63: Remove period after 'methods' Ln124: Add a space before 'correlation' Ln127: p=0.057914; p

    Please rate the manuscript for methodological rigour

    Poor

    Please rate the quality of the presentation and structure of the manuscript

    Satisfactory

    To what extent are the conclusions supported by the data?

    Strongly support

    Do you have any concerns of possible image manipulation, plagiarism or any other unethical practices?

    No

    Is there a potential financial or other conflict of interest between yourself and the author(s)?

    Yes: I have known one of the co-author through my meetings with them at conferences. Though I don't have any colloborative works, projects or publications with them.

    If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?

    Yes