Assessment of microbial contamination in laser materials processing laboratories used for prototyping of biomedical devices

  1. Yinka M. Somorin
  2. Gerard M. O'Connor

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Abstract

Microbial contamination of medical devices during pilot production can be a significant barrier as the laboratory environment is a source of contamination. There is limited information on microbial contaminants in laser laboratories and environments involved in the pilot production of medical devices. This study aimed to determine the bioburden and microbial contaminants present in three laser laboratories – an ISO class 7 clean room, a pilot line facility and a standard laser laboratory. Microbiological air sampling was by passive air sampling using settle plates and the identity of isolates was confirmed by DNA sequencing. Particulate matter was analysed using a portable optical particle counter. Twenty bacterial and 16 fungal genera were isolated, with the genera Staphylococcus and Micrococcus being predominant. Most isolates are associated with skin, mouth, or upper respiratory tract. There was no significant correlation between microbial count and PM 2.5 concentration in the three laboratories. There were low levels but diverse microbial population in the laser-processing environments. Pathogenic bacteria such as Acinetobacter baumannii and Candida parapsilosis were isolated in those environments. These results provide data that will be useful for developing a contamination control plan for controlling microbial contamination and facilitating advanced manufacturing of laser-based pilot production of medical devices.

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  1. Version published to 10.1099/acmi.0.000494.v3 on Access Microbiology
  3. Version published to 10.1099/acmi.0.000494.v2 on Access Microbiology
  4. Access Microbiology

    The work presented is clear and the arguments well formed. This study would be a valuable contribution to the existing literature. The reviewers have highlighted minor concerns with the work presented. Please ensure that you address their comments.

  5. Access Microbiology

    Comments to Author

    The manuscript (ACMI-D-22-00146) entitled "Assessment of microbial contamination in laser materials processing laboratories used for prototyping of biomedical concepts" by Somorin & O'Connor investigated the presence of pathogens in three medical device production units. They have isolated various bacteria and fungi in different production units demanding attention for future planning to prevent contamination. This study provides important data to the scientific community involved in the production of medical devices as well as the user. The author's way of presentation (Text and graphic) is very understandable to the reader. I have no further comments.

    Please rate the manuscript for methodological rigour

    Very good

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

    Very good

    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)?

    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

  6. Access Microbiology

    Comments to Author

    This manuscript details an interesting study investigating the level of microbial contamination in three laser processing laboratories, in addition to providing genotypic identification for the organisms recovered. The manuscript also samples the air quality during use and at rest for the locations. In general, the article is well written and informative, and of an appropriate length. The number of figures and tables is suitable for the data presented. The title of the article makes reference to 'biomedical concepts' - this is somewhat vague and could be amended to 'biomedical devices' or similar. The Introduction specifies that the laser materials processing laboratories are involved in the production of medical devices, materials fabrication and machining, and improving electrical properties of materials for biomedical sensing. The research need is clearly established, however elaboration on the reasons why terminal sterilisation methods have limited application would be welcomed. The aims are well set out, but make reference to a 'typical' laser laboratory, which is not immediately obvious to non-specialists. The Methods section is generally very good. The descriptions of the different laboratories and workstations are helpful and welcomed. The manuscript states the occupancy levels for the various locations, but including an estimate of the length of time per 'visit' would help to contextualise this. The investigative approach has no major flaws or errors, but some omissions are noted. For example, number of settle plates used, number of replicates, and details regarding the 'pre-defined' positions of the (detailed in major comments below). After recovering microorganisms from the environment, standard genomic techniques were used to identify them - it would be welcomed if the primers detailed for this were appropriately cited. Air quality measurements described well. Statistical tests seem appropriate. The Results section is clear and informative, and clearly relates to the methods section. The main findings are presented concisely and effectively. The microbial identification data are nicely presented in the figures and the use of the overlapping coloured circles is welcomed. However the use of Kruskal-Wallis and Spearman's rank tests imply non-normal distribution of the data. If so, median values should be stated throughout instead of mean values. If the data were normally distributed, appropriate parametric equivalent tests should be performed instead to improve power. All figure legends should include the number of replicates and an indication as to what the error bars represent. The Discussion is well presented in general and places the work in a more medical microbiology context, focussing on the sources of contamination for various organisms, as well as citing literature related to potential consequences of contamination for specific organisms. Reference to other microbially controlled locations such as food production facilities and operating theatres provide context and are welcome. In highlighting Candida parapsilosis, its recent status as an emerging antifungal resistant organism should be mentioned (Daneshnia et al. 2023 The Lancet, DOI:https://doi.org/10.1016/S2666-5247(23)00067-8). The manuscript gives suggestions for a contamination control plan, which is welcomed - this should also be stated in the abstract as a key outcome. Major comments: Multiple lines: Use of KW and Spearman's tests imply non-parametric datasets. If this is the case, mean values should be replaced with median values throughout. If datasets were normally distributed, appropriate parametric tests should be used instead. Multiple lines: All figure legends must contain number of replicates and an indication of what the error bars represent. Line 122-123: No details on numbers of plates used in each location. No details about location of settle plates or rationale behind these locations. Please provide these details. Minor comments: Line 2: Consider amending 'biomedical concepts' to something more specific such as 'biomedical devices'. Abstract: Please include key outcomes such as identification of major human pathogens (Acinetobacter baumanii, Candida paraspilosis, etc.) and include a short summary of the developed contamination control plan. Line 65: Please make explicit that this was previous work by the group. Line 79-82: Please provide an explanation as to why terminal sterilisation by gamma irradiation or ethylene oxide aren't appropriate, and add a relevant citation. Line 91: Please provide a brief description of a typical laser laboratory. Line 115: An indication into typical visit times to each location would be welcomed. Line 121: TSA and MEA plates are used, but if it were suspected that Streptococcus spp were present then a blood-enriched agar type could've been used. It is unclear if greater numbers of this genera would've then been isolated/recovered, and this should be mentioned in the discussion. Line 133-134 and 136: If the primers detailed were designed by the authors, please detail this in the methods section. Alternatively, please provide a citation for all primers used. Line 235: Full stop missing after 'laboratories'. Please include this. Line 284 and 285: Please state the p-value for the Spearman's correlations in addition to the r-value if possible. Line 346: Please highlight Candida parapsilosis as an emerging antifungal resistant organism.

    Please rate the manuscript for methodological rigour

    Good

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

    Very good

    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)?

    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

  7. Access Microbiology

    Comments to Author

    1. Methodological rigour, reproducibility and availability of underlying data The objectives were clearly stated. The objectives were measurable and all were met. The methods used for colony counts is reproducible. Identification of microorganisms was confirmed by molecular method. Statistical methods were adequate for the data. 2. Presentation of results The findings were significant as it provided data that will be used in future to control contamination in such laboratories. Findings offer advancement in knowledge for it specify particular microorganisms which can still be found in such controlled environments. Results were properly interpreted and were based on sound data. 3. How the style and organization of the paper communicates and represents key findings Introduction uses literature to connect problem statement and purpose of the study. The study gives clear and measurable objectives on which the design and method is based. The method of data collection was precise and reproducible and gave sound data. The data analysis method was adequate for the type of data collected. Inference from the data clearly specified key findings. 4. Literature analysis or discussion Literature review was adequate. The review in introduction was well directed to both problem statement and purpose of the study. However in discussion there were no mention of similar studies in similar environment probably this was the first study of its kind in laser laboratories. 5. Any other relevant comments I think it could have been important to mention, in discussion, that this is the first study of its kind in laser laboratories after a thorough such of literature for similar studies without success.

    Please rate the manuscript for methodological rigour

    Very good

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

    Very good

    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)?

    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

  8. Version published to 10.1099/acmi.0.000494.v1 on Access Microbiology