Abstract
Recent advances in the field of microbial and medical ecology emphasize the critical role played by oral bacteria in the delicate dynamic equilibrium of human health and disease, creating the need to define the bacterial communities associated with healthy and non-healthy conditions and to capture shifts in community structure germane to diagnosis. Employing PCR-RFLP of the 16S rDNA gene from metagenomes and plate-wash (cultured) bacteria of oral wash from 10 volunteers, this study evaluated the stability of oral bacteria in healthy subjects and documented community shifts in smokers. Sequence analysis of selected 16S gene amplicons cloned with the Gene Hunter PCR-Trap vector and pCR 4-TOPO cloning kits was conducted to determine the bacteria identity and diversity indices of the two groups. Ribopatterns generated by the restriction enzymes HaeIII and Sau3AI were significantly (p AluI using the GelCompare II software cluster analysis. A stable core of bacteria DNA fingerprint was detected in all healthy subjects, and remained unchanged over the study period of 3 months. Signature bands (1500 bp with HaeIII) in smokers and in non-smokers (800 bp and 700 bp with Sau3A1) were evidently suggesting the presence of potential biomarkers of healthy and non-healthy states. There was no significant difference in the DNA fingerprints of cultured and metagenomic extracts. The genera Xanthomonas, Streptococcus and phylum Candidatus occurred in large numbers in both groups, however, a major shift in composition with the dominance of gram-negative bacteria in smokers compared to healthy subjects was quite remarkable. Taxonomic diversity in smokers was quite high, including members of the genera Rothia, Synechococcus, Neisseria, Thiomargarita and Pyrobaculum. These data highlight the presence of a stable core microbiome amidst a wide diversity, identify a distinct smokers’ cluster and open the way for the search for potential biomarkers for specific diseases.
Highlights
The human oral microbiome is the most studied human microflora, due to the fact that it is sampled and is strongly associated with important oral infectious diseases such as tooth decay, gum disease and other diseases such as cardiac disease and cancers [1]-[9]
Among the 700 bacterial species found in the oral cavity, most are commensal bacteria and are required to keep equilibrium in the mouth ecosystem some of them play a key role in the development of oral diseases such as dental caries, periodontal disease [7] [10]-[12] and evenoral/pharyngeal cancers like oral squamous cell carcinomas [8] [9]
A large body of evidence show that 42% of periodontitis in the United States is attributable to tobacco smoking [14], and numerous studies have reported a critical role for smoking in increasing the risk for developing extensive and severe forms of this disease [14]-[18]
Summary
The human oral microbiome is the most studied human microflora, due to the fact that it is sampled and is strongly associated with important oral infectious diseases such as tooth decay (dental caries), gum disease (periodontitis) and other diseases such as cardiac disease and cancers (pancreatic gastrointestinal and oral) [1]-[9]. Among the 700 bacterial species found in the oral cavity, most are commensal bacteria and are required to keep equilibrium in the mouth ecosystem some of them play a key role in the development of oral diseases such as dental caries, periodontal disease [7] [10]-[12] and evenoral/pharyngeal cancers like oral squamous cell carcinomas [8] [9]. A large body of evidence show that 42% of periodontitis in the United States is attributable to tobacco smoking [14], and numerous studies have reported a critical role for smoking in increasing the risk for developing extensive and severe forms of this disease [14]-[18]. Normal oral flora activate the tobacco smoke nitrosamine, nitrosodiethylamine (NDEA), to its carcinogenic (IARC, Group 2A), adduct-forming hydroxylated product [19]-[21]. This in turn increases the risk of oral cancer. Studies have shown that smoking alters the microbial signatures of the oral cavity, with a decrease in the commensal population and a concomitant increase in pathogens [25] [26]
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