Molecular Surveillance of Plasmodium vivax and Plasmodium falciparum Drug Resistance Genes in the Republic of Korea: 2022–2025

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Manuscript Title: Molecular Surveillance of Plasmodium vivax and Plasmodium falciparum Drug Resistance Genes in the Republic of Korea: 2022–2025

 

General Assessment

This manuscript presents a multi-year molecular surveillance study of antimalarial drug resistance markers in Plasmodium vivax and P. falciparum in the Republic of Korea (ROK). The topic is timely and relevant, particularly given the unique epidemiological context of malaria in the ROK, including the role of military populations and imported falciparum cases. The dataset spanning 2022–2025 is valuable, and the identification of key mutations, such as the high prevalence of multiple Pvmdr-1 mutations and the detection of Pfmdr-1 D1246Y and PfK13 A675V, has potential implications for surveillance and treatment policy.

However, the manuscript is largely descriptive and would benefit from additional analytical depth, clearer articulation of novelty, and more cautious interpretation of findings. Substantial revisions are required to strengthen the scientific rigor and clarity of the work.

Recommendation: Major Revision

 

Major Comments

1. Lack of Statistical Analysis
   The study relies primarily on descriptive reporting of mutation frequencies. Statistical analyses comparing mutation prevalence across groups (soldiers vs. civilians vs. imported cases) and across years are needed to support the conclusions. Inclusion of appropriate tests (chi-square or Fisher’s exact test) and confidence intervals would significantly strengthen the manuscript.
2. Unclear Novelty and Contribution
   The manuscript does not clearly define how this study advances beyond previous surveillance efforts (including prior KDCA reports). The authors should explicitly state the novel contributions of this work, such as new mutation detections, temporal trends, or unique population insights.
3. Interpretation of Drug Resistance
   The discussion occasionally overinterprets the clinical implications of detected mutations. Molecular markers do not necessarily equate to phenotypic resistance or treatment failure. The authors should temper their conclusions and clearly distinguish between genetic markers and confirmed clinical resistance.
4. Sampling Bias and Representativeness
   The study focuses on high-risk groups (soldiers receiving chemoprophylaxis, relapse patients, and imported cases), which may not represent the broader malaria population in the ROK. This limitation should be explicitly acknowledged and discussed.
5. Limited Depth in Discussion of Key Mutations
   Some important findings, such as the absence of Y976F in pvmdr-1 and the detection of PfK13 A675V, are not sufficiently contextualized. The authors should expand discussion on the epidemiological and mechanistic significance of these mutations, including comparison with regional and global data.
6. Figures and Data Presentation
   Figures (particularly Figures 1 and 2) are difficult to interpret due to visual complexity and dense labeling. Simplification and improved formatting are recommended to enhance clarity. Consider focusing on key mutations and moving detailed data to supplementary materials.

 

Minor Comments

1. Language and Style

Reduce repetitive phrasing (“identified in 100% of cases”).

Improve sentence flow and concision, particularly in the Results and Discussion sections.

2. Typographical Errors

Correct minor errors such as “P. knwolesi” → P. knowlesi.

3. Consistency in Terminology

Ensure consistent formatting of mutation names (T529 vs. “T529 mutation”).

4. Abstract

Strengthen by emphasizing key implications and clearly stating the novelty of the findings.

5. Introduction

Clarify the research gap and rationale for this study more explicitly.

6. Methods

Provide additional details on inclusion criteria and clarify whether any statistical methods were considered.

7. Discussion Structure

Streamline to reduce repetition of results and emphasize key take-home messages.

8. Conclusion

Consider adding a concise, standalone conclusion summarizing the main findings and their implications.

 

Summary

This manuscript addresses an important topic and provides valuable surveillance data. With the addition of statistical analysis, clearer framing of novelty, improved interpretation, and enhanced presentation, the study could make a meaningful contribution to the field.

Comments on the Quality of English Language

The English is generally clear and understandable, and the manuscript can be followed without major difficulty. However, minor revisions are recommended to improve clarity, conciseness, and overall readability. In particular, some sentences are repetitive or overly long, and certain phrases could be streamlined. There are also a few minor typographical errors and inconsistencies in terminology. Careful language editing would further enhance the quality of presentation.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The Molecular Surveillance of Plasmodium vivax and Plasmodium falciparum Drug Resistance Genes in the Republic of Korea: 2022–2025' offers valuable insights, but the following revisions are recommended to improve it.

The authors found drug resistance genes for P. vivax and P. falciparum in South Korea; are these findings entirely new?

Please check if the references format follows the Journal's instructions.

Abstract

Line 18 and 20: The abbreviations P. vivax and P. falciparum should be placed in parentheses after full terms’ Plasmodium vivax and Plasmodium falciparum upon their first appearance; use these abbreviations for all subsequent references.

Introduction

Line 39-40: The abbreviations P. vivax, P. falciparum, P. malariae, P. ovale, and P. knowlesi should be placed in parentheses after full terms upon their first appearance; use these abbreviations for all subsequent references.

Material and Methods

The manuscript does not provide the total number of patients for P. vivax or P. falciparum, nor the numbers within each subgroup. Please include this information in the Materials and Methods section, preferably supported by a flow diagram illustrating the methodology.

Line 89-90: The authors mentioned ‘Herein, we selected patients with vivax malaria in the ROK who were considered a high risk of drug resistance.’ What factors led you to consider these patients hight-risk?

Line 101: Please add the URL for the manufacturer’s protocol for easy reader access.

Table 1: Primers used in the study are best place in the supplementary data.

Results

Table 3: A legend allows the reader to interpret the table without referring to the main text; therefore, authors should include detailed legend with the table.

Figure 1: The authors should include additional detailed legend for the figure. Please specify the ratio and the percentage labeled on the Y-axis.

Table 4: Please ensure the table title is placed above the table, and the legends (keys) are placed below.

Figure 2: Same as figure 1

Limitation: The authors should add a section on the limitation of the review.

Abbreviations: Ensure all abbreviations are listed in an orderly manner.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors,

Your manuscript “Molecular Surveillance of Plasmodium vivax and Plasmodium falciparum Drug Resistance Genes in the Republic of Korea: 2022–2025” describes a surveillance study of drug resistance genes of Plasmodium vivax and Plasmodium falciparum isolates collected in the Republic of Korea between 2022 and 2025.

The manuscript is written well, contains all necessary parts. The introduction provides the necessary information about the object of research and allows the reader, unfamiliar with the subject, to understand the essence of the problem being studied. The study logic and methodology are clear. The results and discussion are logical and leave no doubt.

However, in current form the manuscript needs revision.

The abstract section requires text correction. For example, you refer to malaria as a disease, but you do not indicate that the species mentioned are its causative agents. It is unclear what is Pvmdr-1, vivax malaria, etc… “D1246Y mutation was first identified in a patient” – but the mutation was identified in pathogen from patient, not in the patient. Please check all abstract text and correct where necessary.

 

L46 – “vivax malaria” – maybe it should better to explain what is it, to make the text clear.

 

Section 2.1. Ethics statement.

L80 – “IRB” – please give the full name of the abbreviation for the first time. It would also be useful if it were possible to provide a reference to the relevant document. Moreover, I am not sure that even in the case of anonymous samples, their collection (blood) does not require informed consent from patients to participate in research, which in turn must be approved by an ethics committee.

 

Section 2.2. Sample collection and malaria diagnosis.

L93-94 “For falciparum malaria” – please explain what is it.

L99 – “identical subtypes” – no information given about the subtypes, it should be provided in the Introduction section.

 

Section 2.3. Drug resistance gene amplification.

Table 1 – 1) Please change “Size” (as it is not a size of primer) to “PCR-fragment size”

2) Primers “mdr-3F” and “mdr-3F” correspond to different sequences but have the same names. Please correct. 3) What do “1st” and “2nd” mean? Should be stated here.

 

Section 2.4. Sequence analysis

L115 – “commercial sequencing service” – the appropriate reference (company or facility, etc..) should be given.

 

Results section.

L130-131 – “were rarely identified only in military patients, they appear to be related to prophylactic chemotherapy” - What is this assumption based on? Without explanation, it seems somewhat speculative.

Table 3 - Sample sizes vary considerably across years and groups (e.g., only 1 imported case in 2022, 4 in 2023, etc.). The authors should discuss whether statistical comparisons were performed and, if not, why.

Figure 1 - the x- and y-axis are not labeled. The figure legend does not explain what the bars represent (percentage of isolates with each mutation?). Please correct.

 

Discussion section.

L176-177 – “This indicates that the Korean malarial strain is a transboundary gene pool” – please correct, as “starin” cannot be a “gene pool”.

Suggestion for improving the section: the manuscript repeatedly emphasizes the need for "continued surveillance" but does not propose specific sampling strategies, target sample sizes, or a timeline for future monitoring. A more concrete recommendation would improve the paper's impact.

 

References section.

Some references contain no DOI, or link to online source, etc…please carefully check.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for the careful revision of your manuscript. The revised version shows clear improvement in both scientific rigor and clarity of presentation.

The inclusion of statistical analyses (chi-square/Fisher’s exact tests and regression approaches) significantly strengthens the validity of the comparisons across groups and over time. The interpretation of drug resistance markers has also been appropriately moderated, with a clearer distinction between molecular markers and confirmed clinical resistance. In addition, the manuscript now better acknowledges limitations related to sampling bias and representativeness, which improves transparency.

The discussion has been expanded and is better contextualized within the existing literature. The revisions to figures and overall language have also improved readability.

That said, a few minor points remain that could further strengthen the manuscript:

1. Novelty and Contribution
   While improved, the statement of novelty could be presented more concisely and explicitly, particularly in the final paragraph of the Introduction or Discussion.
2. Discussion Depth and Implications
   The Discussion would benefit from a slightly stronger emphasis on the broader implications of these findings for regional or global malaria control and surveillance strategies.
3. Concluding Summary
   A brief, clearly articulated concluding paragraph summarizing the key take-home messages would enhance the overall impact (even if a separate Conclusion section is not required by the journal).

Overall, the manuscript has improved substantially and is close to being suitable for publication.

Comments on the Quality of English Language

The English is generally clear and understandable, and the manuscript can be followed without major difficulty. However, minor revisions are recommended to improve clarity, conciseness, and overall readability. In particular, some sentences are repetitive or overly long, and certain phrases could be streamlined. There are also a few minor typographical errors and inconsistencies in terminology. Careful language editing would further enhance the quality of presentation.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors,

Your manuscript “Molecular Surveillance of Plasmodium vivax and Plasmodium falciparum Drug Resistance Genes in the Republic of Korea: 2022–2025” describes a surveillance study of drug resistance genes of Plasmodium vivax and Plasmodium falciparum isolates collected in the Republic of Korea between 2022 and 2025.

The manuscript is written well, contains all necessary parts. The introduction provides the necessary information about the object of research and allows the reader, unfamiliar with the subject, to understand the essence of the problem being studied. The study logic and methodology are clear. The results and discussion are logical and leave no doubt.

All issues contained in the previous version of the manuscript were resolved, thank you!

I have only one little remark:

Table 1 – “PCR-Fragment – please change to “PCR-fgrament”

Author Response

Please see the attachment.

Author Response File: Author Response.pdf