# blanks sequencing for sterile swabs

**URL:** https://forum.qiime2.org/t/blanks-sequencing-for-sterile-swabs/14451
**Category:** General Discussion
**Tags:** miseq, exclude-seqs
**Created:** [April 13, 2020, 7:37am UTC](https://forum.qiime2.org/t/blanks-sequencing-for-sterile-swabs/14451 "2020-04-13T07:37:56Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![Cravo\_Adri](https://forum.qiime2.org/user_avatar/forum.qiime2.org/cravo_adri/32/3386_2.png) [@Cravo\_Adri](https://forum.qiime2.org/u/Cravo_Adri)
#### Post date: [April 13, 2020, 7:37am UTC](https://forum.qiime2.org/t/blanks-sequencing-for-sterile-swabs/14451/1 "2020-04-13T07:37:57Z")

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Good morning, everyone,  
I have a general questions that goes back to the sequencing step, before QIIME2 pipeline.  
I work with amphibian samples, that are taken with sterile swabs. My question is: should I also sequence some blanks (new swabs, not used) to check for possible contamination or it is not necessary, since the material is sterile?  
I appreciate your feedback!

Thanks

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### Author: ![yanxianl](https://forum.qiime2.org/user_avatar/forum.qiime2.org/yanxianl/32/2039_2.png) [@yanxianl](https://forum.qiime2.org/u/yanxianl)
#### Post date: [April 13, 2020, 3:16pm UTC](https://forum.qiime2.org/t/blanks-sequencing-for-sterile-swabs/14451/2 "2020-04-13T15:16:18Z")

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Hi @Cravo_Adri,

It's a good practice to always include and sequence your negative controls. Generally speaking, it's sufficient to include negative controls starting from the sample DNA extraction. However, if you're dealing with low-biomass samples, i.e., the microbial DNA is expected to be very low in your samples, it's also recommended to include negative controls during the sampling. You can take out a few sterile swabs, pretend to take samples and preserve these swabs as you do for real biological samples.

For more information, you can read this paper by [Kim et al., 2017: Optimizing methods and dodging pitfalls in microbiome research](https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-017-0267-5)

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### Author: ![Cravo\_Adri](https://forum.qiime2.org/user_avatar/forum.qiime2.org/cravo_adri/32/3386_2.png) [@Cravo\_Adri](https://forum.qiime2.org/u/Cravo_Adri)
#### Post date: [April 29, 2020, 7:24am UTC](https://forum.qiime2.org/t/blanks-sequencing-for-sterile-swabs/14451/3 "2020-04-29T07:24:16Z")

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hi, @yanxianl, sorry for the delay, I just forgot to answer. But yes, I've done what you suggested and added some blanks, but starting from the dna extraction, since I could not go back to the sampling location.  
Thanks a lot!