The association between body mass index and the oral Firmicutes and Bacteroidetes profiles of healthy individuals

Introduction: Microbiome status is considered an important factor that contributes to obesity. Investigations have shown that the oral microbiome comprises a vast array of bacterial species that can influence human health.

Objective: To determine the association between the presence of the bacterial phyla Firmicutes and Bacteroidetes and the body mass index (BMI) status of normal, overweight and obese subjects in Duhok, Iraq. Additionally, to investigate the composition of oral Firmicutes and Bacteroidetes profiles for individuals with different BMI statuses.

Methods: A total of 155 saliva samples were collected from participants in Duhok, Iraq. Bacterial genomic DNA was then extracted from the collected saliva. The presence of Firmicutes and Bacteroidetes phyla was detected via polymerase chain reaction.

Results: Firmicutes and Bacteroidetes were detected in 63.2 and 37.4% of the population, respectively. Differences in the carriage rates of oral Firmicutes in overweight (78%) and obese individuals (83%) were statistically significant when compared to normal weight individuals (36%) (P<0.0001). The percentage rates of Bacteroidetes in obese individuals (26.4%) was statistically significant when compared to normal weight individuals (50.8%) (P=0.0078). The Firmicutes/ Bacteroidetes ratios (obese=3.1, overweight= 2.5 and normal weight=0.7) were higher with increasing BMI.

Conclusion: This study provides evidence of the Firmicutes/Bacteroidetes ratio growing with increasing BMI. High rates of Firmicutes could serve a role in the development of obesity. Further studies are required to clarify the exact relationship between oral bacteria and obesity, which could lead to a promising therapeutic method for improving the physical health of humans.