PWAT-D-24-00103

Reducing Water Quality Data Inequities: Improvements to a membrane filtration technique for the quantification of Escherichia coli in drinking water in low-resource contexts

PLOS Water

Dear Dr. Dorea,

Thank you for submitting your manuscript to PLOS Water. After careful consideration, we feel that it has merit but does not fully meet PLOS Water's publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Dec 13 2024 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at water@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pwat/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

We look forward to receiving your revised manuscript.

Kind regards,

Daniel Reddythota

Academic Editor

PLOS Water

Journal Requirements:

 1. We noticed you have some minor occurrence of overlapping text with the following previous publication(s), which needs to be addressed: Assessment of Decontamination and Reuse of Disposable Filter Funnels Used in Microbiological Water Quality Tests - https://doi.org/10.1177/1178630221101440 (Among others) In your revision ensure you cite all your sources (including your own works), and quote or rephrase any duplicated text outside the methods section. Further consideration is dependent on these concerns being addressed. 2. Please note that PLOS Water has specific guidelines on code sharing for submissions in which author-generated code underpins the findings in the manuscript. In these cases, we expect all author-generated code to be made available without restrictions upon publication of the work. Please review our guidelines at https://journals.plos.org/water/s/materials-and-software-sharing#loc-sharing-code and ensure that your code is shared in a way that follows best practice and facilitates reproducibility and reuse. 3. Please include a complete copy of PLOS’ questionnaire on inclusivity in global research in your revised manuscript. Our policy for research in this area aims to improve transparency in the reporting of research performed outside of researchers’ own country or community. The policy applies to researchers who have travelled to a different country to conduct research, research with Indigenous populations or their lands, and research on cultural artefacts. The questionnaire can also be requested at the journal’s discretion for any other submissions, even if these conditions are not met.  Please find more information on the policy and a link to download a blank copy of the questionnaire here: https://journals.plos.org/water/s/best-practices-in-research-reporting. Please upload a completed version of your questionnaire as Supporting Information when you resubmit your manuscript. 4. Please amend your detailed Financial Disclosure statement. This is published with the article. It must therefore be completed in full sentences and contain the exact wording you wish to be published. **Please only choose the relevant sentences from below** 1. Please clarify all sources of funding (financial or material support) for your study. List the grants (with grant number) or organizations (with url) that supported your study, including funding received from your institution. 2. State the initials, alongside each funding source, of each author to receive each grant.3. State what role the funders took in the study. If the funders had no role in your study, please state: “The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.”4. If any authors received a salary from any of your funders, please state which authors and which funders. If you did not receive any funding for this study, please simply state: “The authors received no specific funding for this work.” 5. In the online submission form, you indicated that "The Computer Aided Design (CAD) files for a version of the filter support unit which can be 3D printed are available on request from the authors. The data from this article can be requested via correspondence with the authors.".  All PLOS journals now require all data underlying the findings described in their manuscript to be freely available to other researchers, either 1. In a public repository, 2. Within the manuscript itself, or 3. Uploaded as supplementary information. This policy applies to all data except where public deposition would breach compliance with the protocol approved by your research ethics board. If your data cannot be made publicly available for ethical or legal reasons (e.g., public availability would compromise patient privacy), please explain your reasons by return email and your exemption request will be escalated to the editor for approval. Your exemption request will be handled independently and will not hold up the peer review process, but will need to be resolved should your manuscript be accepted for publication. One of the Editorial team will then be in touch if there are any issues. 6. Please provide separate figure files in .tif or .eps format. For more information about figure files please see our guidelines:   https://journals.plos.org/water/s/figures  https://journals.plos.org/water/s/figures#loc-file-requirements  7. We do not publish any copyright or trademark symbols that usually accompany proprietary names, eg (R), (C), or TM  (e.g. next to drug or reagent names). Please remove all instances of trademark/copyright symbols throughout the text, including SK Microfil® on page 8 and Mutaflor® on page 12. 8. "Figure 1" and "Graphical Abstract": Please confirm whether you drew the images / clip-art within the figure panels by hand. If you did not draw the images, please provide (a) a link to the source of the images or icons and their license / terms of use; or (b) written permission from the copyright holder to publish the images or icons under our CC-BY 4.0 license. Alternatively, you may replace the images with open source alternatives. See these open source resources you may use to replace images / clip-art:- https://commons.wikimedia.org- https://openclipart.org/"

Additional Editor Comments (if provided):

Author needs to revise his paper especially sampling is not clearly explained and these sampling results were not stated in the results and discussion section.

Methodology section should be more clear with sampling, incubation and SK & LCK.

In addition organization of methodology and results & discussion section need to be improved based on the two reviewers comments

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Does this manuscript meet PLOS Water’s publication criteria ? Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe methodologically and ethically rigorous research with conclusions that are appropriately drawn based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available (please refer to the Data Availability Statement at the start of the manuscript PDF file)?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception. The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: No

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS Water does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: I would suggest amending the manuscript title as the membrane filtration technique is more or less the same, but the equipment used for the analysis is more economical and so more attainable/realistic for widespread use in low resource contexts.

Another suggestion would be to clarify within the methods/results sections what occurred within the laboratories in Canada as part of field assessments in Malawi.

Line 58 - 60: Provide a reference for the statistics used within the sentence

Line 68: Include “such as” or “for example” prior to arsenic and fluoride, as they are not the only priority chemicals

Line 96 – 102: I understand that this information has been included within the introduction to provide context, but it reads as though it should be in the methods section. I would suggest rewording.

Line 112: Refer to figure 1.

Line 126: Refer to figure.

Line 126: Why was that feedback not included within this study?

Line 155 – 158: I would suggest rearranging the objectives to reflect the order that the results are presented.

Line 161 – 165: I would suggest rephrasing this section to be specific about what laboratory work was conducted in Canada and what was carried out in Malawi.

Line 177: Do you mean decontaminated or sterilised? And was this validated in preliminary testing prior to field work carried out in Malawi?

Line 192: Include that X-glucuronide is a differential agent to allow easy identification of E. coli.

Line 197: include that that “blue colonies” are a result of X-glucuronide.

Line 203 – 204: Would it be possible to include a map of the approximate sample sites in Malawi or context?

Line 213: Is there an example of the questionnaire used, and an overview of the outcomes/results.

Line 231 – 233: Were bottled water kept at an approximate temperature range and away from sunlight?

Line 233 – 238: Were drinking water bottles resealed after initial analysis? If so, how was contamination minimised?

Line 241: Italicise “E. coli” in heading.

Line 242 – 268: I would suggest breaking this section into methods that were used in Canada laboratories, and what methods were used as part of the field work in Malawi.

Line 244 - 246: Was the temperature monitored to assess the actual incubation temperature? If so, how?

Line 249 – 253: This information could potentially be included within the discussion section rather than methods.

Line 265: Was there any comparison carried out between the enumeration of E. coli between the SK and LCK, as well as conventional E. coli enumeration using gold-standard laboratory methods?

Line 268: How are the portable electric incubator powered, and how was the temperature monitored?

Line 323: Should this be SI Table S2, as it is the second SI table to be referred to.

Line 325: Italicise “E. coli”.

Line 326 – 341: Break up the results into Canada results and Malawi results.

Line 350: Who was the “positive informal feedback” from?

Line 367: Should this be referred to as SI Table 3?

Line 373 – 374: By how much did the LCK weigh in comparison to the SK?

Reviewer #2: Manuscript title: Reducing Water Quality Data Inequities: Improvements to a membrane filtration technique for the quantification of Escherichia coli in drinking water in low-resource contexts

This study assessed improvements to a cost-effective membrane filtration method (LCK) utilized in UNICEF’s MICS and other programmatic surveys, along with the evaluation of bottled water as negative controls (Blanks) across various countries. Additionally, laboratory and field testing were employed to investigate a reduction in incubation time from 24 to 18 hours. The findings indicated that the improved LCK method performed successfully in the field, offering the potential to reduce the cost of drinking water quality monitoring in low-resource settings. Furthermore, the study demonstrated that an 18-hour incubation period could be feasible, though there were limitations to these results. Bottled water was found to be an appropriate negative control in different countries.

This is original primary research that includes both laboratory and field data collection efforts. The development of cost-effective approaches for monitoring drinking water quality in low-resource settings is essential for collecting data to inform progress towards SDG 6.1. The paper is well-constructed, and I commend its clarity, which makes it accessible to a broader audience beyond the scientific community. The literature references are appropriate, and the conclusions are closely aligned with the study's findings. However, some clarifications are necessary.

Major comments:

1) Incubation at 37°C in Belt Incubators: How was it verified that samples reached and maintained a temperature of 37°C during incubation? Body surface temperature around the stomach, where belt incubators are positioned, may be lower than the core body temperature. Additionally, factors such as ambient air temperature and heat transfer mechanisms could result in uneven or lower sample temperatures. Has this been examined in other studies? If so, please reference these to enhance clarity.

2) Household Survey Results: What happened to the results from the 375 households surveyed? These findings appear absent from the results and discussion sections. If these data are not part of this manuscript, the methods section should be revised to avoid confusion.

3) Assessment of Blank Test Water: I recommend moving this section to the end of the methods/results section, as its placement disrupts the flow of the manuscript. The focus on a different study design, timeline, and locations (outside of Malawi and lab comparisons) creates confusion. Additionally, section 2.3 requires a clearer introduction to guide the reader on the intent of the assessment."

Minor comments:

• Pictures should be clearer.

• Lines 112 – 114: this should be in your methods/results/discussion, not your introduction as it’s repetitive.

• Line 141: Typo? “Secondly, it has not yet clear if the current practice…”

• Lines 211-212: Add the total number of LCK used for clarity.

• Line 344: “Results from the comparison of the novice and experienced counter” Where is this data shown?

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean? ). If published, this will include your full peer review and any attached files.

Do you want your identity to be public for this peer review? If you choose “no”, your identity will remain anonymous but your review may still be made public.

For information about this choice, including consent withdrawal, please see our Privacy Policy .

Reviewer #1: No

Reviewer #2: Yes:  Karina A. Chavarria

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Reducing Water Quality Data Inequities: A low-cost membrane filtration technique for the quantification of Escherichia coli in drinking water in low-resource contexts

PWAT-D-24-00103R1

Dear Dr. Dorea,

We are pleased to inform you that your manuscript 'Reducing Water Quality Data Inequities: A low-cost membrane filtration technique for the quantification of Escherichia coli in drinking water in low-resource contexts' has been provisionally accepted for publication in PLOS Water.

Before your manuscript can be formally accepted you will need to complete some formatting changes, which you will receive in a follow-up email from a member of our team. 

Please note that your manuscript will not be scheduled for publication until you have made the required changes, so a swift response is appreciated.

IMPORTANT: The editorial review process is now complete. PLOS will only permit corrections to spelling, formatting or significant scientific errors from this point onwards. Requests for major changes, or any which affect the scientific understanding of your work, will cause delays to the publication date of your manuscript.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they'll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact water@plos.org.

Thank you again for supporting Open Access publishing; we are looking forward to publishing your work in PLOS Water.

Best regards,

Daniel Reddythota

Academic Editor

PLOS Water

***********************************************************

Additional Editor Comments (if provided):

Accepted all your revisions

Reviewer Comments (if any, and for reference):

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

**********

2. Does this manuscript meet PLOS Water’s publication criteria ? Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe methodologically and ethically rigorous research with conclusions that are appropriately drawn based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available (please refer to the Data Availability Statement at the start of the manuscript PDF file)?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception. The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS Water does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

Reviewer #2: All my previous comments were adequately addressed and I don't have any further suggestions.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean? ). If published, this will include your full peer review and any attached files.

Do you want your identity to be public for this peer review? If you choose “no”, your identity will remain anonymous but your review may still be made public.

For information about this choice, including consent withdrawal, please see our Privacy Policy .

Reviewer #1: No

Reviewer #2: Yes:  Karina A. Chavarria

**********