The Emergence of Carbapenem-Resistant Gram-Negative Bacteria in Mizoram, Northeast India

Round 1

Reviewer 1 Report

The topic of this manuscript is of interest as the carbapenem resistance is one of the biggest clinical challenges nowadays. The manuscript is well written and designed, the ideas are easy to follow. However, I would suggest to rewrite the conclusions in the Abstract, making them more specific as they appear in the Conclusion section.

Author Response

The topic of this manuscript is of interest as the carbapenem resistance is one of the biggest clinical challenges nowadays. The manuscript is well written and designed, the ideas are easy to follow. However, I would suggest to rewrite the conclusions in the Abstract, making them more specific as they appear in the Conclusion section.

R: Thank you for your suggestion. The conclusion section of the abstract has been modified.

Reviewer 2 Report

Section 2.1

This section could be enriched, including methods of strain isolation, as well as details on the PCR setup of 16S (reaction chemistry and amplification cycles.

 

Lines 108-111

Has resistance gene sequencing been done?

This is not clear from the text, but to talk about variants of genes such as OXA-48 or CTX-M-1, and sequencing is necessary.

Author Response

Section 2.1: This section could be enriched, including methods of strain isolation, as well as details on the PCR setup of 16S (reaction chemistry and amplification cycles.

R: Thank you for your suggestion. (1) For this study, the clinical isolates/bacteria were collected from the hospital laboratories and the clinical samples were not collected and processed. So, we don’t want to include it. (2) The PCR for 16S rRNA was universal, therefore, the authors believe that it is not going to enrich the content of the article.

Lines 108-111: Has resistance gene sequencing been done? This is not clear from the text, but to talk about variants of genes such as OXA-48 or CTX-M-1, and sequencing is necessary.

R: Yes, the resistance genes were sequenced and resistance gene identification is based on BLAST results (Line no. 174, 175) and accession numbers were provided in the ‘data availability statement’.

Reviewer 3 Report

The manuscript entitled „The Emergence of Carbapenem-resistant Gram-negative Bacteria in the Mizoram Region, Northeast India” details investigations of antibiotic resistant major Gram-negative pathogens. Obtained results are novel in this study.

In my opinion some modifications are required in the text.

 

Comments

1) In the Abstract and in the main text you mention, that 12 strains were non-lactose fermenters in this study. Please, name these species, because in the Material and methods part you indicate identification based on Vitek, and 16s rRNA sequence. Or in case these strains are not identified on the species level please, name the genus level. But this phrase „non-fermenter” is not proper.

 

2) In the Abstract you mention that 48% of isolates were colistin resistant. Do you mean acquired colistin resistance? It is important because Serratia spp., and Proteus spp have intrinsic colistin resistance. This should be clarified in the abstract and in all over the manuscript.

 

3) In the Materials and methods this sentence is written: „MIC was performed for all the isolates using meropenem, cefotaxime, colistin and tigecycline” What was the reason to test these antibiotics?

I suggest to authors to perform ciprofloxacin, amikacin, gentamicin MIC too.

 

 

Author Response

The manuscript entitled „The Emergence of Carbapenem-resistant Gram-negative Bacteria in the Mizoram Region, Northeast India” details investigations of antibiotic-resistant major Gram-negative pathogens. Obtained results are novel in this study. In my opinion, some modifications are required in the text.

Comments

1) In the Abstract and in the main text you mention, that 12 strains were non-lactose fermenters in this study. Please, name these species, because in the Material and methods part you indicate identification based on Vitek, and 16s rRNA sequence. Or in case these strains are not identified on the species level please, name the genus level. But this phrase „non-fermenter” is not proper. 

R: Thanks for pointing out this mistake. Yes, the NLF isolates are Acinetobacter spp. Changes have been incorporated into the manuscript.

2) In the Abstract you mention that 48% of isolates were colistin-resistant. Do you mean acquired colistin resistance? It is important because Serratia spp., and Proteus spp have intrinsic colistin resistance. This should be clarified in the abstract and in all over the manuscript. 

R: That’s a valuable query. But the present study design is limited to resistance identification at the antibiogram/MIC and PCR levels, a more detailed molecular characterization/evolution study is required to mention the exact resistance mechanism underneath.

But in our (authors) opinion, the possibility of intrinsic resistance is less common in pathogenic strains in the study region, therefore the resistance should be acquired.

3) In the Materials and methods this sentence is written: „MIC was performed for all the isolates using meropenem, cefotaxime, colistin and tigecycline” What was the reason to test these antibiotics? I suggest to the authors perform ciprofloxacin, amikacin, and gentamicin MIC too.

R: Thanks for the suggestion but we don’t want to broaden the aim of this study which is ‘the emergence of resistance to last-resort antibiotics in the north-eastern parts of India’. Therefore, we wanted to stick to our study objectives and report the emergence of meropenem, cefotaxime, colistin and tigecycline resistance. The authors believe, our decision will not disappoint the reviewer in this case.