Inactivation of Bacteriophage ɸ6 and SARS-CoV-2 in Antimicrobial Surface Tests

Round 1

Reviewer 1 Report

The manuscript contains quite a useful information about thorough comparative inactivation pair testing of bacteriophage Phi6  and SARS-CoV2 coronavirus on copper-coating PET. This comparative test demonstrated practicalle idenical results which showed that non-dangerous Phi6 bacteriophage may be used instead of usage of very dangerous coronavirus in experimental testing of different surfaces for inactivating properties. Phi6 bacteriophage has a lipid envelope with inserted proteins and its RNA is packed inside this envelope which is very similar to coronavirus virion structure. The only significant difference is the dsRNA inside Phi6 virion instead of ssRNA inside the SARS-CoV2 virion.  The authors presented detailed introduction in which they mentioned previous usage of Phi6 by other authors as a model for another human viruses in inactivation tests which made much easier the  evaluation of the inactivating properties in their experiments. In my opinion, the current manuscript is very good and useful and deserves the publication. 

Author Response

Dear Reviewer 1,

thank you for the revision and the positiv feedback.

Reviewer 2 Report

The authors report the results of inactivation of SARS-CoV-2 virus on PET surfaces coated with different concentration of copper. Along they used Phi6 phage, and the level of inactivation shows a strong correlation for both viruses – this is an important point as the handling of this model organism requires less exhaustive safety measures, and thus potentially a broader range of possible inhibitory substances could be tested and several parameters explored and orientationally set. Time dependency of the inactivation on coated surface is also shown. One parameter the authors should comment on is the initial virus load: how does the efficiency of inactivation correlate with the initial load?

In principle, this contribution is valuable in supporting pandemic preparedness. Technically, certain Figures should be prepared better (please see the comments below). Further, Figure 5 is not cited in the text and it seems that Figure 4 sometimes is referred to as Figure 3 (please see comments below). Unfortunately, the supplementary materials were not available, and I cannot assess the results cited within.

The language of the article (especially certain passages in Materials and Methods) is too colloquial and this should be corrected. Please find below the list of remarks which I hope will find helpful.  

Line 23: on any (or in any) of the tested samples

Line 23 (and throughout the text): plural of specimen is specimens

Figure 2. The labels of the figures are not well legible (even upon magnification)

Line 127: 10,000g: please use comma as a decimal separator only

Line 144: gently mixing

Line 164: was obtained

Line 180: prior to infection

Line 183: MEM with

Line 186: immunohistochemical staining

Line 191: MEM with 2% FCS

Line 194: MEM without FCS

Line 200 (and throughout the text): CO2, 2 in subscript

Lines 215-222: please organize the list of primers and probes (using semicolons, table or similar)

Line 227: PCT, please explain the abbreviation

Line 251: 10-min-incubation

Line 251: in each sample

Line 256: specimens

Line 282: copper

Line 287: do you mean Figure 4?

Line 296: Please can the authors explain what exactly is presented in Figure 4 and Figure 5. I assume Figure 4 is RT-PCR from “virus only”, and Figure 5 RT-PCR from the supernatants of infected cells. Figure 5 is not cited in the text.

Figure 4: measures of significance should be included.

Line 384: For a final strong statement, a better expression would be: “allow access to extensive testing of several antiviral agents and disinfection conditions”, or similar

Lines 386-395: Supplementary materials were not accessible along with the article to review

Line 432: the format of reference 5 is unusual

Line 463: the format of reference 17 is unusual

Author Response

Dear Reviewer 2,

thank you for the detailed revision.

Please find below in the word document the response to you comments.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The authors have improved the data presentation and the description of methods. With this, I can recommend the manuscript for publication.