Reader Comments

Post a new comment on this article

Problems with some aspects of the press release from the authors and some of the claims in the paper

Posted by jeisen on 04 Nov 2013 at 14:52 GMT

I have written a blog post about this paper here: In the post I discuss what I believe to be misleading or inaccurate comments from the authors in their Press Release associated with this paper as well as in the paper itself.

For example in the Press Release it is written: "The most important point of this paper is discovering that ethnicity-specific oral microbial communities may predispose individuals to future disease”.. I cannot find anything anywhere that indicates anything about predisposition to disease

Also in the PR it is written: “Nature appears to win over nurture in shaping these communities,” Kumar noted, because African Americans and whites had distinct microbial signatures despite sharing environmental exposures to nutrition and lifestyle over several generations.

This claim is also in the paper: "Our data demonstrates that ethnicity exerts a selection pressure on the oral microbiome, and that this selection pressure is genetic rather than environmental, since the two ethnicities that shared a common food, nutritional and lifestyle heritage (Caucasians and African Americans) demonstrated significant microbial divergence."

I see no scientific justification for such a set of claims. OK - different ethnic groups have different microbes. Yet the logic that leads the authors to conclude that these differences must be genetic is severely flawed. First, there is no evidence presented that the people in the study from the Caucasian and African American ethnic groups had similar environmental exposures. Second, even if these two groups has some similarity in exposure, to then conclude that any differences between them must be due to genetic differences between the people is inappropriate. And this is quite a risky claim as it could lead people to make health decisions based on ethnicity even without any evidence that it plays a role.

No competing interests declared.

RE: Problems with some aspects of the press release from the authors and some of the claims in the paper

purnimakumar replied to jeisen on 06 Nov 2013 at 12:50 GMT

The goal of this study was not to examine predisposition to oral diseases based on ethnicity. Several authors have carried out those studies over many decades; the most recent of which came from Eke et al, using the NHANES data. These studies have established that certain ethnicities demonstrate a higher predilection for oral diseases, namely, caries, periodontitis and cancer, after controlling for potential confounders, for example, socio-economic status and smoking. Since dysbiotic oral communities are the primary etiology of these diseases, our study sought to examine if the composition of biofilms in health could exhibit a similar ethnicity-specific clustering; and found that it did. If biofilm compositions are different between ethnicities, and so is the incidence and severity of biofilm-induced diseases, then it is logical that these two facts correlate.
The results of this study are very similar to the findings of the Human Microbiome Project, which demonstrated the strongest association between ethnic affiliation and bacterial composition (and metabolic pathways) in certain niches in the human body.
Subjects were selected based on extensive questionnaire surveys and clinical examinations to ensure homogeneity. These questionnaires evaluated educational level, socio-economic status, diet and nutritional history, systemic health status, oral hygiene habits and dental visits, among other things. The subjects also received a clinical examination to ensure that they fit the criteria of oral health. Therefore, the differences in microbiota that were observed between ethnicities were not attributable to amount of plaque, presence of inflammation, systemic disease, medications, diet, brushing habits, tobacco exposure or visits to the dentist, in short, none of the environmental factors that have been shown to affect oral microbial colonization. This suggests that the ethnicity specific clustering goes beyond an environmental effect. Also, ethnicity-specific clustering was most obvious in the subgingival microbiome, a community that is relatively sheltered from friction, food habits and saliva, and is largely shaped by host-associated factors.

No competing interests declared.

RE: RE: Problems with some aspects of the press release from the authors and some of the claims in the paper

jeisen replied to purnimakumar on 21 Nov 2013 at 23:15 GMT

The response does not sway my opinion at all. I see nothing in this paper that presents any evidence that microbiome patterns have a genetic component. Here there is a correlation to ethnicity. That is it (and I am still uncertain as to how ethnicity was measured). The fact that you cannot find an environmental explanation is almost irrelevant. There are 1000s of potential environmental explanations. A few were tested and possibly ruled out. How does that prove genetics is important?

No competing interests declared.