On 2013 Oct 29, Kenneth Witwer commented:

This paper describes an extremely well controlled study of the respiratory tract microbiome by high throughput sequencing. In addition to the interesting biological findings, the article (along with Charlson ES, 2012) has important technical implications. Nucleic acid contamination is widespread and will confound results if not controlled for carefully, as these authors have so elegantly done. Here, diverse sequences were obtained even from "microbiologically sterile" solutions and medical instruments. Users of sensitive sequencing techniques to investigate foreign sequences should take note.

On 2013 Oct 29, Kenneth Witwer commented:

This paper describes an extremely well controlled study of the respiratory tract microbiome by high throughput sequencing. In addition to the interesting biological findings, the article (along with Charlson ES, 2012) has important technical implications. Nucleic acid contamination is widespread and will confound results if not controlled for carefully, as these authors have so elegantly done. Here, diverse sequences were obtained even from "microbiologically sterile" solutions and medical instruments. Users of sensitive sequencing techniques to investigate foreign sequences should take note.