Effects of Chlorhexidine mouthwash on the oral microbiome

Abstract

Following a single blind, cross-over and non-randomized design we investigated the effect of 7-day use of chlorhexidine (CHX) mouthwash on the salivary microbiome as well as several saliva and plasma biomarkers in 36 healthy individuals. They rinsed their mouth (for 1 min) twice a day for seven days with a placebo mouthwash and then repeated this protocol with CHX mouthwash for a further seven days. Saliva and blood samples were taken at the end of each treatment to analyse the abundance and diversity of oral bacteria, and pH, lactate, glucose, nitrate and nitrite concentrations. CHX significantly increased the abundance of Firmicutes and Proteobacteria, and reduced the content of Bacteroidetes, TM7, SR1 and Fusobacteria. This shift was associated with a significant decrease in saliva pH and buffering capacity, accompanied by an increase in saliva lactate and glucose levels. Lower saliva and plasma nitrite concentrations were found after using CHX, followed by a trend of increased systolic blood pressure. Overall, this study demonstrates that mouthwash containing CHX is associated with a major shift in the salivary microbiome, leading to more acidic conditions and lower nitrite availability in healthy individuals.Chlorhexidine (CHX) has been commonly used in dental practice as antiseptic agent since 1970, due to its long-lasting antibacterial activity with a broad-spectrum of action 1 . Since then, many clinical trials have shown effective results of CHX for the clinical management of dental plaque and gingival inflammation and bleeding 2-4 . This is supported by other studies using in vitro methods and reporting positive results of CHX in reducing the proliferation of bacterial species associated with periodontal disease, such as Enterobacteria, Porphyromonas gingivalis, Fusobacterium nucleatum, as well as different species of Actinomyces and Streptococcus, including Streptococcus mutans, which is considered the main etiological agent of dental caries 4,5 . Other studies have also reported that the use of CHX was effective in the treatment of halitosis, especially in reducing the levels of halitosis-related bacteria colonising the dorsal surface of the tongue 6 .The anti-microbial activity of CHX however, has been extensively studied using in vitro culture methods, which limit the identification and cultivation of all microorganisms in the environment 4 . To the best of our knowledge, only one recent study has investigated the effect of CHX mouthwash on mixed bacterial communities (microbiome) of the tongue using new genome sequencing techniques such as 16 S rRNA 7 . The study found differences in over 10 different species colonizing the tongue, and a lower microbial diversity after using CHX for a week, but did not analyse other parameters related to oral health such as pH, lactate production or buffering capacity 7 . Additionally, we and others have recently shown that the use of CHX in healthy subjects can attenuate the nitrate-reducing activity of oral bacteria by at least 80% 8-11 . This in turn leads to lo...

Oral nitrate reduction is not impaired after training in chlorinated swimming pool water in elite swimmers

“…Several previous studies have reported a detrimental effect of antibacterial chlorohexidine mouthwash on ONR capacity (Kapil et al 2013(Kapil et al , 2018Bondonno et al 2015;McDonagh et al 2015;Sundqvist et al 2016;Woessner et al 2016;Ashworth et al 2019;Bescos et al 2020). However, despite the established antimicrobial properties of chlorine, and contrary to our hypothesis, there was no difference between the abilities of swimmers and non-swimmers to form NO 2 − in the oral cavity when administered a NR mouth rinse.…”

Treatment of stage I–III periodontitis—The EFP S3 level clinical practice guideline

“…• Potential negative impacts on beneficial aspects of the oral microbiome highlighted in recent evidence (e.g. impact on nitric oxide pathway) (Bescos et al, 2020).…”

“…The decision to select a specific toothpaste or a mouth rinse should be also based on a combination of factors: Patient preferences including cost, taste, etc. Unwanted effects including staining, burning sensation during use, etc. Potential negative impacts on beneficial aspects of the oral microbiome highlighted in recent evidence (e.g. impact on nitric oxide pathway) (Bescos et al, 2020). Potential negative impacts on blood pressure: one short‐term (7‐days) study suggested a non‐statistically significant “trend” for chlorhexidine mouth rinse to cause a small elevation in systolic blood pressure from 103 mmHg to 106 mHg (Bescos et al, 2020).…”

Antiseptic mouthwash, the nitrate–nitrite–nitric oxide pathway, and hospital mortality: a hypothesis generating review

“…Salvage from mouthwash use showed enhancement of the oral bacteria capable of reducing nitrate. Finally, Bescos et al demonstrated that chlorhexidine mouthwashes for 7 days led to a major shift in salivary microbiome resulting in more acidic conditions, lower nitrite availability and higher systolic blood pressure in healthy study subjects [74].…”