Potential Environmental Reservoirs of Candida auris: A Systematic Review

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The primary objectives of Silva et al.’s study were to identify and analyze potential environmental sources and reservoirs of Candida auris that contribute to its spread and persistence. Through a well conducted systematic review of existing literature, the authors aimed to consolidate knowledge regarding the ecological niches of this pathogen and its interactions with environmental factors. The main results highlighted the varied nature of these reservoirs, emphasizing the complexity and global relevance of managing C. auris in healthcare and community settings.

I thoroughly enjoyed reading and analyzing this work. It addresses a crucial and yet often overlooked aspect of infectious disease management—environmental surveillance and control, which is essential for a comprehensive understanding of pathogens like C. auris. The topic undeniably warrants ongoing research and vigilance due to the organism's resilience, rapid spread, and the increasing incidence of outbreaks worldwide. The methodology of the study was commendably rigorous, employing a well-structured systematic approach to gather and synthesize available data, which provides a solid foundation for the conclusions drawn. The tables are well organized and clear.

However, while the research is well-executed, it does contain minor flaws that should be addressed to enhance the clarity and impact of the findings. Refining some methodological details, expanding the search strategy for more comprehensive analysis, and improving stylistic elements will strengthen the paper, increasing its publication suitability and ensuring that this important topic is presented with the necessary quality and precision.

1.       A significant lacuna in the understanding of C. auris involves its capacity to thrive in non-human animal hosts and its potential for zoonotic or zooanthroponotic transmission. Notably, a pivotal study documenting a dog in a Kansas shelter colonized with C. auris is missing from the analysis. This landmark study is the first to report the presence of C. auris in a pet and a non-human mammal in the United States, as well as the first to identify an isolate of C. auris in Kansas. This study should be cited and discussed for its critical insights. (White TC, Esquivel BD, Rouse Salcido EM, et al.  C. auris detected in the oral cavity of a dog in Kansas. mBio. 2024;15(2):e0308023. doi: 10.1128/mbio.03080-23.)

2.       The review is predominantly based on literature collected from only three databases. Expanding the search to include additional databases and grey literature would likely capture a broader spectrum of studies, thus minimizing potential publication bias. Additionally, when referring to the fifth clade in line 59, the emergence of a possible novel sixth clade should be briefly discussed to maintain the review’s current relevance. (https://www.medrxiv.org/content/10.1101/2024.04.12.24305665v2, https://www.medrxiv.org/content/10.1101/2023.08.01.23293435v1)

3.       In line 64, the review presents global data on antifungal resistance from 2017 and 2018. Updating this information is crucial as the antifungal susceptibility profiles may have shifted, potentially showing greater resistance than previously documented.

4.       The tables are well-designed and provide comprehensive information. However, considering the critical role of drug resistance in this pathogen, it would be beneficial for at least one column in Table 3 to indicate whether susceptibility testing was performed and, if so, by which technique. The methodology used for MIC determination, such as disk diffusion, dilution, commercial kits like SENSITITRE, or manual microdilution testing, should also be discussed in section 3.4 to aid in interpreting the results.

5.       In section 3.4, lines 222-224, it would be insightful to discuss the findings from the study by Arora, where the strain exhibiting lower thermoresistance and drug resistance was discovered in a more pristine, less human-impacted ecosystem compared to other isolates found in beach areas that resembled clinical isolates.

6.       The review utilizes the NIH tool for assessing the risk of bias but fails to provide detailed insights into these assessments. Enhancing transparency regarding how biases were managed and their impact on the study’s overall findings could bolster the credibility of the review. A robust analysis of the risk of bias is particularly necessary for environmental studies, where more standardized techniques are urgently needed.

7.       It has been demonstrated that aggregative and non-aggregative phenotypes of C. auris exhibit differing levels of virulence, with non-aggregative phenotypes being significantly more virulent. The review should clarify whether some of the included studies analyzed these phenotypes.

8.       In section 4.6, line 335, while echinocandin treatment is recommended as the first-line option, the review could also mention the frequent need for combined treatments and the often poor therapeutic responses compared to other Candida species.

9.       In section 4.9, line 378, the preferred method suggested is swabbing surfaces and inoculating them in Salt Sabouraud Enrichment Broth, followed by PCR analysis. However, earlier in the review, MALDI-TOF is mentioned as a useful and faster technique. It would be valuable to also suggest MALDI-TOF identification as an alternative to PCR.

10.   Formal errors such as spacing, punctuation in references, and the use of italics for species names need correction throughout the document to enhance its professional presentation and readability:

- Many errors in spacing or punctuation in references: line 41, line 75, line 86, line 122, “Yadav,22” in Table 1, ln 203, 208, 219, 237

- Italics for species: legend in figure 1, line 162 and Irinyi in table 1, line 280, line 328.

Comments on the Quality of English Language

The English quality is high, with no notable errors or issues in grammar or syntax. However, there are some errors in scientific notation or references. At most, some sentences could be somehow simplified for conciseness.

Author Response

Responses to Reviewer 1 Comments to the Authors:

The primary objectives of Silva et al.’s study were to identify and analyze potential environmental sources and reservoirs of Candida auris that contribute to its spread and persistence. Through a well conducted systematic review of existing literature, the authors aimed to consolidate knowledge regarding the ecological niches of this pathogen and its interactions with environmental factors. The main results highlighted the varied nature of these reservoirs, emphasizing the complexity and global relevance of managing C. auris in healthcare and community settings.

I thoroughly enjoyed reading and analyzing this work. It addresses a crucial and yet often overlooked aspect of infectious disease management—environmental surveillance and control, which is essential for a comprehensive understanding of pathogens like C. auris. The topic undeniably warrants ongoing research and vigilance due to the organism's resilience, rapid spread, and the increasing incidence of outbreaks worldwide. The methodology of the study was commendably rigorous, employing a well-structured systematic approach to gather and synthesize available data, which provides a solid foundation for the conclusions drawn. The tables are well organized and clear.

However, while the research is well-executed, it does contain minor flaws that should be addressed to enhance the clarity and impact of the findings. Refining some methodological details, expanding the search strategy for more comprehensive analysis, and improving stylistic elements will strengthen the paper, increasing its publication suitability and ensuring that this important topic is presented with the necessary quality and precision.

1. A significant lacuna in the understanding of  aurisinvolves its capacity to thrive in non-human animal hosts and its potential for zoonotic or zooanthroponotic transmission. Notably, a pivotal study documenting a dog in a Kansas shelter colonized with C. auris is missing from the analysis. This landmark study is the first to report the presence of C. auris in a pet and a non-human mammal in the United States, as well as the first to identify an isolate of C. auris in Kansas. This study should be cited and discussed for its critical insights. (White TC, Esquivel BD, Rouse Salcido EM, et al.  C. auris detected in the oral cavity of a dog in Kansas. mBio. 2024;15(2):e0308023. doi: 10.1128/mbio.03080-23.)

R: The authors would like to thank the Reviewer for the comments. The article in question was published in January 2024, after our systematic literature review concluded in October 2023. Although we recognize the importance of this article, it is pertinent to mention that our review had already identified two studies detailing C. auris infection and colonization in domestic dogs in Spain (reference 43) and India (reference 39), and we had discussed the implications of potential zoonotic transmission in our discussion section.

2. The review is predominantly based on literature collected from only three databases. Expanding the search to include additional databases and grey literature would likely capture a broader spectrum of studies, thus minimizing potential publication bias.

R: The authors intended that with Pubmed, SCOPUS and Web of Science a wide range of scientific fields would be covered. Regarding grey, it was excluded from the review because of the scarce scientific information provided. For this reason, this was a criterion for exclusion.  

3. Additionally, when referring to the fifth clade in line 59, the emergence of a possible novel sixth clade should be briefly discussed to maintain the review’s current relevance. (https://www.medrxiv.org/content/10.1101/2024.04.12.24305665v2, https://www.medrxiv.org/content/10.1101/2023.08.01.23293435v1)

R: This sentence has been rewritten and a reference has been added (references 23 and 24 and line 63-66).

4. In line 64, the review presents global data on antifungal resistance from 2017 and 2018. Updating this information is crucial as the antifungal susceptibility profiles may have shifted, potentially showing greater resistance than previously documented.

R: We believe that keeping the reference would be useful since this was the only meta-analysis on global antifungal susceptibility published on C.auris. However, we added a more updated reference, only reporting antifungal susceptibility data in United States (reference 26)

5. The tables are well-designed and provide comprehensive information. However, considering the critical role of drug resistance in this pathogen, it would be beneficial for at least one column in Table 3 to indicate whether susceptibility testing was performed and, if so, by which technique. The methodology used for MIC determination, such as disk diffusion, dilution, commercial kits like SENSITITRE, or manual microdilution testing, should also be discussed in section 3.4 to aid in interpreting the results.

R: The authors agree with the Reviewer suggestion, however to avoid cluttering the table, we have chosen to include detailed information regarding susceptibility testing methodology in section 3.4. The majority of the studies employed broth microdilution assay for MIC determination.

6. In section 3.4, lines 222-224, it would be insightful to discuss the findings from the study by Arora, where the strain exhibiting lower thermoresistance and drug resistance was discovered in a more pristine, less human-impacted ecosystem compared to other isolates found in beach areas that resembled clinical isolates.

R: Information has been added in discussion section (line 338-343)

7. The review utilizes the NIH tool for assessing the risk of bias but fails to provide detailed insights into these assessments. Enhancing transparency regarding how biases were managed and their impact on the study’s overall findings could bolster the credibility of the review. A robust analysis of the risk of bias is particularly necessary for environmental studies, where more standardized techniques are urgently needed.

R: Given the complexity and variability of environmental studies, standardizing bias assessment techniques could improve the reliability of conclusions drawn across different studies. Implementing more uniform methods could help compare results more effectively. However, the environmental studies included in the review were highly heterogeneous, disabling the risk analysis. A table (S2) with detailed insights into the risk of bias has been added to the supplementary material section.

7. It has been demonstrated that aggregative and non-aggregative phenotypes of C. auris exhibit differing levels of virulence, with non-aggregative phenotypes being significantly more virulent. The review should clarify whether some of the included studies analyzed these phenotypes.

R: The information regarding the aggregative phenotype and other virulence attributes would definitely enrich this systematic review. Unfortunately, none of the included studies have studied these phenotypes of C. auris.

8. In section 4.6, line 335, while echinocandin treatment is recommended as the first-line option, the review could also mention the frequent need for combined treatments and the often poor therapeutic responses compared to other Candida species.

R: Information was added as suggested (line 389-394).

9. In section 4.9, line 378, the preferred method suggested is swabbing surfaces and inoculating them in Salt Sabouraud Enrichment Broth, followed by PCR analysis. However, earlier in the review, MALDI-TOF is mentioned as a useful and faster technique. It would be valuable to also suggest MALDI-TOF identification as an alternative to PCR.

R: Changes were made accordingly (line 437).

10. Formal errors such as spacing, punctuation in references, and the use of italics for species names need correction throughout the document to enhance its professional presentation and readability:

- Many errors in spacing or punctuation in references: line 41, line 75, line 86, line 122, “Yadav,22” in Table 1, ln 203, 208, 219, 237

- Italics for species: legend in figure 1, line 162 and Irinyi in table 1, line 280, line 328.

R: Changes were made as suggested

Reviewer 2 Report

Comments and Suggestions for Authors

This paper provides a useful and moderately well written summary of published environmental sampling for C. auris. It could benefit from greater revision and clarity of the writing.

I strongly suggest that the authors be clearer in what they are trying to accomplish beyond general platitudes about comprehending pathogen transmission leading to more effective control strategies. Specifically, the authors could be much clearer about the possible directionality between C. auris in the natural environment compared with urban and healthcare environments, as currently this distinction is minimally discussed. For example, it is well documented that C. auris spreads readily between patients in certain healthcare facilities likely through the immediate healthcare environment. Numerous examples exist of a patient arriving at a new healthcare facility and spreading C. auris to other patients. This means that C. auris in healthcare environments is extremely likely to represent a very different situation than in other locations, especially natural environments. The authors could also clearly discuss the potential sources and implications of C. auris in wastewater. Finally, the authors could more cogently discuss the implications of finding C. auris in multiple aquatic environments and what such detections might mean about its origins. I would suggest the authors read “On the Origins of a Species: What Might Explain the Rise of Candida auris,” published in 2019 for more ideas.

I am also concerned, as described below, that the authors are too quick to assume that climate change is driving the emergence and spread of C. auris. This is an interesting hypothesis, but it is little more than that at this point.

·        Line 15: Suggest “review” instead of “revise”

·        Abstract: It would be helpful to include more information summarizing the locations of detection in natural habitats and any inferences that can be drawn.

·        Line 36: Suggest “cause” not “catalyser,” since C. auris is the cause of infections and not just a catalyst.

·        Line 52: Suggest noting that premature birth history is only a risk factor for C. auris infection among infants unless there is evidence that it is also a risk factor for adults as well.

·        Line 57: Suggest first listing clades by Roman numeral, followed by the locations from which they were first detected. Although it is likely that each clade originated from those locations, it is not confirmed. Also, the clades have spread well beyond the locations from which they were first detected.

·        Line 64: Reference 24 providing proportion of C. auris isolates susceptible to various antifungal classes is six years old. Suggest a more recent reference. Also suggest noting dramatic differences in susceptibility by clade.

·        Lines 64-66: This sentence overstates the evidence for combination antifungal treatment. The reference describes lack of antagonism in vitro and is not a clinical trial. For most C. auris infections, an echinocandin will be effective, which is why CDC recommends it as primary therapy. https://www.cdc.gov/fungal/candida-auris/c-auris-treatment.html. CDC’s sentence on combination therapy underscores the lack of data: “Combination antifungal treatment yielded promising results in laboratory testing but has not been evaluated in clinical settings.” This is an important point since the sentence in the manuscript may inappropriately influence clinical care.

·        Line 77: This sentence is not accurate as written, “Nonetheless, in the face of escalating global temperatures, certain species, including C. auris, appear to have evolved to prosper in warmer climates [30].” Reference 30 involves speculation that global heating from climate change has prompted evolution of C. auris to survive in warmer temperatures, but it does not include evidence to support this speculation. The sentence from the manuscript under review overstates this link. It is quite possible, and even likely, that C. auris has been able to survive and thrive at temperatures 37-40 degrees C independent of climate change. Climate change or other environmental factors may have increased the prevalence of C. auris in the environment by expanding its niche, but this is speculation as well. The following paper addresses this issue extensively: PubMed ID (PMID): 31284576. Given that the main focus of the paper under review is the environmental detection of C. auris, the existing language must be corrected.

·        Line 85: Suggest “importance” instead of “significance.” The latter term should be reserved for statistical significance and does not convey the correct message.

·        Lines 114-116: Eligibility criteria should include non-natural, non-healthcare environments, as described in the abstract.

·        Line 155: Missing the full name of the National Center for Biotechnology Information.

·        Line 162: Scientific names should be italicized

·        Table 2: Suggest renaming the title of this table. Finding C. auris in certain locations within healthcare settings simply indicates the fungus is present in that location, not necessarily a reservoir. The title notes they are “potential” reservoirs, but I see no need to make such an extrapolation. Recommend calling them “sites of detection” or something like that. C. auris can be identified in a multitude of locations within healthcare settings, largely dependent on where shedding from colonized patients occurs.

·        Line 216: Suggest removing the contraction “there’s” in this scientific manuscript

·        Line 224: Please specify which samples that “these samples” refer to. Sand/beach or salt marsh?

·        Line 250: Suggest commenting on detection bias. It is highly likely that the locations where C. auris has been detected are highly dependent on where certain investigators have chosen to sample. The samples from the natural environment underscore that we are sampling only the tiniest tip of the environmental C. auris iceberg.

·        Discussion: I think the link between this systematic review and helping with prevention and management may be overstated. This review is a worthwhile endeavor, but I would suggest being more circumspect about its direct impacts.

·        Line 263: “Lack of agreement” seems a strange term for the diversity of sampling methods, as does the word “disparities.” Suggest alternate phrasing.

·        Lines 278-280: Please confirm that the FDA-approved libraries are no longer as effective at identifying C. auris as RUO libraries. I suspect this may have changed since the referenced papers were published. Also, FDA and RUO should be defined.

·        Line 280: C. auris is more often misidentified with C. duobushaemulonii than C. haemulonii in this study. Identification of Candida auris by Use of the Updated Vitek 2 Yeast Identification System, Version 8.01: a Multilaboratory Evaluation Study - PubMed (nih.gov). Also, C. haemulonii should be italicized.

·        Line 290: Why use the term “distinct” to describe these countries? Aren’t countries distinct from each other by their very nature? It may be more helpful to note that they were on two different continents.

·        Line 299: Suggest noting that, “In humans, most Candida infections are caused by colonizing strains.” As written, it sounds as if most C. auris infections.

·        Line 301: The “moreover” here seems out of place, and the flow of sentences and logic should be improved.

·        Line 304: It is a stretch to use reference 79 to imply that C. auris on apples may pose a risk of exposure and infection. The possibility exists, but it may be remote. Suggest rephrasing with more tempered language.

·        Lines 320-323: This paper is rife with speculation but becomes oddly cautious when saying that correlations between colonized patients are not clearly linked to C. auris in the healthcare environment. I suggest re-reviewing the papers on healthcare colonization, many of which have shown that environmental contamination is closely correlated with presence of a colonized patient. Note for example the title of this paper: Positive Correlation Between Candida auris Skin-Colonization Burden and Environmental Contamination at a Ventilator-Capable Skilled Nursing Facility in Chicago | Clinical Infectious Diseases | Oxford Academic (oup.com).

·        Line 326: Sporicidal disinfectants are not always needed for C. auris. The US EPA now has a specific C. auris claim distinct from, and less stringent than, sporicidal. EPA’s Registered Antimicrobial Products Effective Against Candida auris [List P] | US EPA

·        Line 335: Referring to echinocandins as first line (correctly) conflicts with statements from the introduction about combination therapy.

·        Lines 354-368: This section, while containing useful information and hypotheses/speculation, is not well tied to the findings of the paper. I think the speculation that climate change may lead to more fungal infections is very interesting and persuasive, but the actual data behind it are scant, at best.

·        Lines 370-376: These are accurate statements but not areas for future research, so do not align well with the section title. Also, this section fails to note the importance of hand hygiene for healthcare staff as a key element in spread of C. auris throughout the healthcare environment, which the authors describe above.

·        Lines 377-381: This overly simplistic statement about optimal method is not well supported by the results of the paper, which do not specifically evaluate performance of different sampling and testing methods. The salt Sabouraud enrichment broth is a useful technique, but it has its limitations (e.g., time consuming) and may not be required for all C. auris environmental sampling. This section could benefit from a more nuanced but still brief description of the strengths and weaknesses of the various methods and a call for research on more head-to-head comparisons for optimal results in various settings.

·        Section 4.9 (Limitations): Perhaps the biggest limitation is sampling bias. That is, very few researchers have performed environmental sampling for C. auris, and so detections outside of healthcare environments are limited to those areas where they thought to test, often in relatively close proximity to their laboratories. We are seeing only the tiniest sliver of where C. auris exists in the world. This is a far, far greater limitation than the minor differences in sampling methods.

Comments on the Quality of English Language

Quality of English language writing is generally very good. I have flagged a few word choice issues that could be improved.

Author Response

Responses to Reviewer 2 Comments to the Authors:

This paper provides a useful and moderately well written summary of published environmental sampling for C. auris. It could benefit from greater revision and clarity of the writing.

I strongly suggest that the authors be clearer in what they are trying to accomplish beyond general platitudes about comprehending pathogen transmission leading to more effective control strategies. Specifically, the authors could be much clearer about the possible directionality between C. auris in the natural environment compared with urban and healthcare environments, as currently this distinction is minimally discussed. For example, it is well documented that C. auris spreads readily between patients in certain healthcare facilities likely through the immediate healthcare environment. Numerous examples exist of a patient arriving at a new healthcare facility and spreading C. auris to other patients. This means that C. auris in healthcare environments is extremely likely to represent a very different situation than in other locations, especially natural environments.

R: The authors would like to thank the Reviewer for the comments. The manuscript has been improved in accordance with the Reviewer suggestions.

The authors could also clearly discuss the potential sources and implications of C. auris in wastewater.

R: The sources and implications of C. auris in wastewater where added as suggested (line339-352).

Finally, the authors could more cogently discuss the implications of finding C. auris in multiple aquatic environments and what such detections might mean about its origins. I would suggest the authors read “On the Origins of a Species: What Might Explain the Rise of Candida auris,” published in 2019 for more ideas.

R: Information has been added in discussion section (line 338-343).

I am also concerned, as described below, that the authors are too quick to assume that climate change is driving the emergence and spread of C. auris. This is an interesting hypothesis, but it is little more than that at this point.

R: We have tried to use more tempered language when speaking about the hypothesis.

• Line 15: Suggest “review” instead of “revise”

R: Correction was made as suggested.

Abstract: It would be helpful to include more information summarizing the locations of detection in natural habitats and any inferences that can be drawn.

R: Information was included as suggested (line 20-22).

• Line 36: Suggest “cause” not “catalyser,” since C. auris is the cause of infections and not just a catalyst.

R: Correction was made as suggested.

• Line 52: Suggest noting that premature birth history is only a risk factor for C. auris infection among infants unless there is evidence that it is also a risk factor for adults as well.

R: According to current knowledge, premature birth history seems to be the only risk factor for infants. This issue has been clarified.

• Line 57: Suggest first listing clades by Roman numeral, followed by the locations from which they were first detected. Although it is likely that each clade originated from those locations, it is not confirmed. Also, the clades have spread well beyond the locations from which they were first detected.

R: We made the changes according to the suggestion and removed the phrase with the countries where they were first identified to avoid confusion about whether they would be circumscribed to this geographical area.

• Line 64: Reference 24 providing proportion of C. auris isolates susceptible to various antifungal classes is six years old. Suggest a more recent reference. Also suggest noting dramatic differences in susceptibility by clade.

R: We believe that keeping the reference would be useful since this was the only meta-analysis on global antifungal susceptibility published on C.auris. However, we added a more updated reference, only reporting antifungal susceptibility data in United States (reference 26).

Regarding clade differences in susceptibility, I would like to point out that this issue is already addressed in the discussion section of our paper. We believe that the depth and detail with which we treat this subject in that section provide an adequate understanding of the topic.

• Lines 64-66: This sentence overstates the evidence for combination antifungal treatment. The reference describes lack of antagonism in vitro and is not a clinical trial. For most C. auris infections, an echinocandin will be effective, which is why CDC recommends it as primary therapy. https://www.cdc.gov/fungal/candida-auris/c-auris-treatment.html. CDC’s sentence on combination therapy underscores the lack of data: “Combination antifungal treatment yielded promising results in laboratory testing but has not been evaluated in clinical settings.” This is an important point since the sentence in the manuscript may inappropriately influence clinical care.

R: We agree with the Reviewer and we have deleted the sentence from the introduction section. This information is more clear in the discussion section (lines 383-387).

• Line 77: This sentence is not accurate as written, “Nonetheless, in the face of escalating global temperatures, certain species, including C. auris, appear to have evolved to prosper in warmer climates [30].” Reference 30 involves speculation that global heating from climate change has prompted evolution of C. auris to survive in warmer temperatures, but it does not include evidence to support this speculation. The sentence from the manuscript under review overstates this link. It is quite possible, and even likely, that C. auris has been able to survive and thrive at temperatures 37-40 degrees C independent of climate change. Climate change or other environmental factors may have increased the prevalence of C. auris in the environment by expanding its niche, but this is speculation as well. The following paper addresses this issue extensively: PubMed ID (PMID): 31284576. Given that the main focus of the paper under review is the environmental detection of C. auris, the existing language must be corrected.

R: We have tried to use more tempered language to clarify that this is a mere hypothesis and not a certainty (line 87-88).

• Line 85: Suggest “importance” instead of “significance.” The latter term should be reserved for statistical significance and does not convey the correct message.

R: The change was made as suggested.

• Lines 114-116: Eligibility criteria should include non-natural, non-healthcare environments, as described in the abstract.

R: The eligibility criteria was added as suggested (line 125 and 126).

• Line 155: Missing the full name of the National Center for Biotechnology Information.

R: Information was added as suggested.

• Line 162: Scientific names should be italicized

R: Changes were made accordingly.

• Table 2: Suggest renaming the title of this table. Finding C. auris in certain locations within healthcare settings simply indicates the fungus is present in that location, not necessarily a reservoir. The title notes they are “potential” reservoirs, but I see no need to make such an extrapolation. Recommend calling them “sites of detection” or something like that. C. auris can be identified in a multitude of locations within healthcare settings, largely dependent on where shedding from colonized patients occurs.

R: Changes were made as suggested.

• Line 216: Suggest removing the contraction “there’s” in this scientific manuscript

R: Changes were made as suggested

• Line 224: Please specify which samples that “these samples” refer to. Sand/beach or salt marsh?

R: The term “these samples” was changed to “salt marsh” (line 241).

• Line 250: Suggest commenting on detection bias. It is highly likely that the locations where C. auris has been detected are highly dependent on where certain investigators have chosen to sample. The samples from the natural environment underscore that we are sampling only the tiniest tip of the environmental C. auris iceberg.

R: Risk of bias assessment were only performed in hospital environmental studies, due to the heterogenicity of the studies regarding natural environments. Regarding the natural environments, comments on sampling limitations were included in discussion section (line 442-445).

• Discussion: I think the link between this systematic review and helping with prevention and management may be overstated. This review is a worthwhile endeavor, but I would suggest being more circumspect about its direct impacts.

R: Improvements were made in the discussion section.

• Line 263: “Lack of agreement” seems a strange term for the diversity of sampling methods, as does the word “disparities.” Suggest alternate phrasing.

R: Changes were made as suggested (line 281-283).

• Lines 278-280: Please confirm that the FDA-approved libraries are no longer as effective at identifying C. auris as RUO libraries. I suspect this may have changed since the referenced papers were published. Also, FDA and RUO should be defined.

R: Thank you for pointing this out. Since the publication of the referenced paper, FDA and RUO libraries have been updated, and both are recommended for the detection of C.auris (Fasciana T, Cortegiani A, Ippolito M, et al. Candida auris: An Overview of How to Screen, Detect, Test and Control This Emerging Pathogen. Antibiotics (Basel). 2020;9(11):778. Published 2020 Nov 5. doi:10.3390/antibiotics9110778). We have chosen to delete this sentence from the manuscript. 

• Line 280: C. auris is more often misidentified with C. duobushaemulonii than C. haemulonii in this study. Identification of Candida auris by Use of the Updated Vitek 2 Yeast Identification System, Version 8.01: a Multilaboratory Evaluation Study - PubMed (nih.gov). Also, C. haemulonii should be italicized.

R: Older versions of this software didn't have C. auris and C. duobushaemulonii in their database, and often misidentified them as C. haemuloni. As this is no longer the case with version 8.01, the following changes have been made: “The Vitek 2 technology, with software version 8.01, may misidentify C. auris as C. duobushaemulonii”. In addition, we did not find information on the accuracy of C.auris identification with the most recent version (version 9.02).

• Line 290: Why use the term “distinct” to describe these countries? Aren’t countries distinct from each other by their very nature? It may be more helpful to note that they were on two different continents.

R: Changes were made as suggested.

• Line 299: Suggest noting that, “In humans, most Candida infections are caused by colonizing strains.” As written, it sounds as if most C. auris infections.

R: The sentence has been rewritten as suggested (line 322-326).

• Line 301: The “moreover” here seems out of place, and the flow of sentences and logic should be improved.

R: Changes were made as suggested.

• Line 304: It is a stretch to use reference 79 to imply that C. auris on apples may pose a risk of exposure and infection. The possibility exists, but it may be remote. Suggest rephrasing with more tempered language.

R: We have changed the entire paragraph. (lines 328-333)

• Lines 320-323: This paper is rife with speculation but becomes oddly cautious when saying that correlations between colonized patients are not clearly linked to C. auris in the healthcare environment. I suggest re-reviewing the papers on healthcare colonization, many of which have shown that environmental contamination is closely correlated with presence of a colonized patient. Note for example the title of this paper: Positive Correlation Between Candida auris Skin-Colonization Burden and Environmental Contamination at a Ventilator-Capable Skilled Nursing Facility in Chicago | Clinical Infectious Diseases | Oxford Academic (oup.com).

R: The authors refer only to the studies included in this systematic review. Even though they found that the environmental and patient samples were similar, no correlation was established between the origin of the infection was determined.

• Line 326: Sporicidal disinfectants are not always needed for C. auris. The US EPA now has a specific C. auris claim distinct from, and less stringent than, sporicidal. EPA’s Registered Antimicrobial Products Effective Against Candida auris [List P] | US EPA

R: We have changed the sentence and added a new reference.

• Line 335: Referring to echinocandins as first line (correctly) conflicts with statements from the introduction about combination therapy.

R: This issue has already been amended and clarified (line 389-394).

• Lines 354-368: This section, while containing useful information and hypotheses/speculation, is not well tied to the findings of the paper. I think the speculation that climate change may lead to more fungal infections is very interesting and persuasive, but the actual data behind it are scant, at best.

R: We have changed this paragraph to the conclusion according to another review. This set of paragraphs has been relocated to the conclusion to minimize its prominence.

• Lines 370-376: These are accurate statements but not areas for future research, so do not align well with the section title. Also, this section fails to note the importance of hand hygiene for healthcare staff as a key element in spread of C. auris throughout the healthcare environment, which the authors describe above.

R: The section title has been replaced by “Strategic surveillance approach”. The importance of hand hygiene has been added to this section.

• Lines 377-381: This overly simplistic statement about optimal method is not well supported by the results of the paper, which do not specifically evaluate performance of different sampling and testing methods. The salt Sabouraud enrichment broth is a useful technique, but it has its limitations (e.g., time consuming) and may not be required for all C. auris environmental sampling. This section could benefit from a more nuanced but still brief description of the strengths and weaknesses of the various methods and a call for research on more head-to-head comparisons for optimal results in various settings.

R: As the Reviewer stated, the performance of the sampling methods was not the aim of this systematic review. The authors only add their point of view regarding the best approach to perform environmental sample identification and antifungal analysis.

• Section 4.9 (Limitations): Perhaps the biggest limitation is sampling bias. That is, very few researchers have performed environmental sampling for C. auris, and so detections outside of healthcare environments are limited to those areas where they thought to test, often in relatively close proximity to their laboratories. We are seeing only the tiniest sliver of where C. auris exists in the world. This is a far, far greater limitation than the minor differences in sampling methods.

R: We agree that this is a limitation. We have clarify this issue in section 4.9.

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors,

The diagnosis and treatment of invasive candidosis caused by multi-resistant C. auris is still a big challenge. Your article is very interesting, current and suitable for Journal of Fungi. Regarding the C. auris, there are few laboratories that would be able to identify this species and more important there is little knowledge about reservoirs which could be positional source for spreading of infection caused by this pathogen.

My recommendation is for this manuscript to be published after minor revision

My suggestions:

In the end of paper it will better to unite the parts Global Warming and Future research in one part or global warming add to conclusion as an alarming phenomenon that will complicate this problem even more.

All infective agents - fungi and bacteria have to be written italic.

Also, when you mention fungi in this case it will be better to use term yeast.

Comments on the Quality of English Language

Moderate editing of English language required

Author Response

Responses to Reviewer 3 Comments to the Authors:

 

Dear authors,

The diagnosis and treatment of invasive candidosis caused by multi-resistant C. auris is still a big challenge. Your article is very interesting, current and suitable for Journal of Fungi. Regarding the C. auris, there are few laboratories that would be able to identify this species and more important there is little knowledge about reservoirs which could be positional source for spreading of infection caused by this pathogen.

My recommendation is for this manuscript to be published after minor revision

My suggestions:

In the end of paper it will better to unite the parts Global Warming and Future research in one part or global warming add to conclusion as an alarming phenomenon that will complicate this problem even more.

R: The authors would like to thank the Reviewer for the comments. We have changed this paragraph to a conclusion based on this comment.

All infective agents - fungi and bacteria have to be written italic.

R: Changes were made accordingly.

Also, when you mention fungi in this case it will be better to use term yeast.

R: Changes were made as suggested.

Reviewer 4 Report

Comments and Suggestions for Authors

The manuscript ``Potential Environmental Reservoirs of Candida auris: A Systematic Review``, written by Silva et al approaches an important public health issue. I would recommend the following changes:

Abstract- please rephrase it and shorten it, for a more logical flow

Introduction - there are six clades. Please correct the info

Table 2 - is too long, please move it in the supplementary files and only leave a summary of it, a figure or a few ideas.

Although it is a manuscript on environmental reservoirs, the discussion on the possible natural reservoirs and climate changes is reduced. Please at least add a figure on how climate change, wetlands and animals might have lead to the spread of C. auris.

Author Response

Responses to Reviewer 4 Comments to the Authors:

The manuscript ``Potential Environmental Reservoirs of Candida auris: A Systematic Review``, written by Silva et al approaches an important public health issue. I would recommend the following changes:

Abstract- please rephrase it and shorten it, for a more logical flow

R: The authors would like to thank the Reviewer for the comments. The abstract has been rephrased as suggested.

Introduction - there are six clades. Please correct the info

R: Thank you for pointing this out. This sentence has been rewritten and a reference has been added (line 62-64 and reference 24 ).

Table 2 - is too long, please move it in the supplementary files and only leave a summary of it, a figure or a few ideas.

R: While we appreciate the reviewer's feedback, we respectfully disagree. Table 2 not only represents a significant part of our research but also provides a comprehensive summary of the locations where contamination was identified in a hospital environment. We believe this information is extremely useful for readers who need to know where to take samples to ensure proper decontamination.

Although it is a manuscript on environmental reservoirs, the discussion on the possible natural reservoirs and climate changes is reduced. Please at least add a figure on how climate change, wetlands and animals might have lead to the spread of C. auris.

R: New information regarding environmental reservoirs has been added to the discussion section. The graphical abstract has been improved according to the Reviewer's suggestion.