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Oral Microbiome Changes Implicated in Gum Inflammation in E-Cigarette Users

NEW YORK – New research suggests regular vaping can alter the composition of the oral microbial community, corresponding with a rise in representation by potential bacterial pathogens that can contribute to enhanced gum inflammation.

Researchers from New York University and the University of Pennsylvania did high-throughput 16S ribosomal RNA gene sequencing on saliva samples from more than 100 regular e-cigarette users, routine cigarette smokers, or non-smoking/vaping control individuals, using the sequences to compare and contrast the microbes found in the mouths of these participants.

In parallel, they looked at immune features in the individuals' saliva using proinflammatory immune panel assays and did in vitro analyses of pro-inflammatory cytokines in cell lines exposed to e-cigarette smoke, Porphyromonas gingivalis and Fusobacterium nucleatum

Together, the team reported, the results revealed oral microbiome shifts in smokers and vapers, along with increased inflammatory responses that may bump up individuals' risk of gum disease or infections relative to their non-smoking, non-vaping counterparts. The findings appeared in the Cell Press journal iScience on Wednesday.

"Our study suggests that vaping electronic cigarettes causes shifts in the oral environment and highly influences the colonization of complex microbial biofilms, which raises the risk for oral inflammation and infection," co-senior author Deepak Saxena, a basic science and craniofacial biology researcher at the NYU College of Dentistry, said in a statement.

Although e-cigarettes have been marketed as a relatively safe alternative to cigarette smoking, the team explained, recent studies suggest that e-cigarette use, or vaping, exposes users not only to nicotine, but also to potentially risky compounds related to tobacco, flavor additives, and other chemicals present in e-cigarette liquid and delivery methods.

In an effort to explore the effects that these compounds might have on mouth health, the researchers set out to assess oral microbiome patterns and corresponding immune features in 40 cigarette smokers, 40 e-cigarette users, and 39 never-smoker/vapers with available periodontal disease, salivary marker, exhaled carbon monoxide, cigarette/e-cigarette use frequency, and other data.

"The oral microbiome is of interest to us because research shows that changes in its microbial community as a result of environmental and host factors contribute to a range of health issues," Saxena explained, "including cavities, gum disease, halitosis, and medical conditions such as diabetes, cardiovascular disease, and cancers."

For example, the team documented gum disease or infection in almost 73 percent of the cigarette smokers and 42.5 percent of e-cigarette users compared to just over 28 percent of the non-smokers and non-vapers.

Based on nearly 8.3 million 16S sequence reads generated from participants' saliva samples, the researchers identified microbes spanning 911 operational taxonomic units (OTUs) and 11 bacterial phyla. The oral microbiomes appeared to have distinct features in the cigarette smokers, vapers, and non-smokers, they noted, with both smoking groups showing shifts in Neisseria species, Fusobacterium species, and bugs from the Actinobacteria phylum compared to non-smokers.

From these and other findings, the authors suggested that "microbial dysbiosis" may be a common feature found in the mouths of both combustible cigarette smokers and e-cigarette users.

Still other microbes were more or less common in the cigarette smokers' mouths compared to saliva samples from e-cigarette users, the team reported, while the e-cigarette-related oral microbiome contained microbial sub-clusters that appeared to be influenced by the amount of nicotine users took in.

Along with salivary cytokine clues, the oral microbiomes highlighted the potential importance of periodontal disease-related species such as P. gingivalis and F. nucleatum in the mouths of e-cigarette users, prompting a series of follow-up immune and inflammatory response experiments in cell lines exposed to the potential bacterial pathogens and/or e-cigarette aerosols.

"The presented data suggest that vaping e-cigarettes [cause] oral environmental shifts and highly influences the colonization of complex heterogeneous microbial biofilms," the authors wrote. "More elaborate studies would help in identifying the detrimental effects of e-cigarette aerosols and its toxic components, albeit taking into consideration other confounding factors such as vaping behavior and the dual use of e-cigarettes and conventional cigarettes."