The Impact of Mouthwash

on Human Health

In many parts of our body, friendly bacteria assist us in regulating important physiological functions. The balance of our microbiome can help ward off disease and inversely, the imbalance can lead to many

complications. Our oral microbiome is no different. Mouthwash is routinely recommended by oral health experts to control plaque and gingivitis. However, a recent study suggests that this common part of our morning routine could be causing more harm than good.

A healthy oral microbiome is linked to a healthy cardiovascular

system. Bacteria in our mouths assist in converting dietary nitrate into

nitric oxide, an essential cardiovascular signaling molecule. While the body converts arginine to nitric oxide through the process of endogenous nitric oxide synthase, oral microbes utilize bacterial nitrate reductases to reduce dietary nitrate to nitrite. Swallowing nitrite helps stimulate nitric oxide signaling.

Longitudinal studies and clinical trials have shown that chronic mouthwash use is associated

with increased blood pressure and increased risk for prediabetes/diabetes and hypertension.(4)

Several commensal oral bacteria are able to reduce nitrate, primarily the

genera Neisseria, Haemophilus, Granulicatella, Veillonella, Prevotella, Corynebacterium, Actinomyces, and Rothia. Nitrate reductase activity is highest in the posterior of the dorsum of the tongue, especially under anaerobic conditions, but is also present in dental plaque and in saliva and under aerobic conditions. There is significant inter- and intrapersonal variability in the abundance of nitrate-reducing species; the most variable nitrate-reducing species on the human tongue are Rothia dentocariosa and Haemophilus parainfluenzae, while Prevotella melaninogenica and Veillonella dispar are the most constant and most abundant nitrate-reducing species.(4)

Most available mouthwashes contain bactericidal ingredients such

as chlorhexidine. Long-term use can disrupt the microflora of the mouth, driving out nitric oxide-producing bacteria. Without the supplementation provided by these beneficial microbes, cardiovascular health could decline and increase the risk of hypertension. A study found that one week of twice-daily use of chlorhexidine was accompanied by a significant rise in systolic blood pressure. Halting the use of chlorhexidine led to the recovery of nitric oxide-producing oral bacteria and blood pressure returning to pre-study levels.

While further studies are required to confirm causality, current data suggests that long-term use of mouthwash can lead to an increased risk of hypertension.

In 2017, it was found that 62% of Americans used a mouthwash or

dental rinse. Some common mouthwashes have evidence-based benefits and a seal of acceptance from the American Dental Association. Prescribed mouthwashes can be useful for conditions such as halitosis and dental caries. Studies evaluating these products for safety criteria though are mostly short-term. Long-term

prospective clinical trials should be considered to measure the systemic impact of mouthwashes in different populations. In the meantime, preserving the delicate balance of a healthy microbiome should be our top priority.

By Alexandra Lopez

References: 1, 2, 3, 4

The Effects of Stevia Consumption on Gut Health

As 2023 draws to a close, many people begin to think about new goals and intentions for the New Year ahead. The most common New Year’s resolution is to improve health, which often involves better food alternatives and eating healthier. One of the most popular plant-based sweetener alternatives used in the food and beverage industry is Stevia. Stevia is a no-calorie sugar substitute made from highly refined extracts of Stevia rebaudiana leaves, called steviol glycosides. (1) Stevia does not provide any calories or impact blood glucose levels because steviol glycosides are not absorbed in the upper gastrointestinal tract. Steviol glycosides are degraded by cleavage of the glycoside linkage in the colon, forming steviol and glucose. The formed glucose molecules are used as an energy source and the remaining steviol is absorbed via the portal vein, metabolized by the liver, and excreted in urine. (2)

Stevia is the growing sweetener of choice for many consumers looking for natural and healthy products and is Generally Recognized as Safe (GRAS) by the Food and Drug Administration (FDA). However, emerging scientific data has implicated the sweetener in causing a gut microbial imbalance. (3)

The microbiota plays a crucial role in our health and the various types of bacteria, fungi, and other microorganisms must remain in symbiosis with the host. A new study published by researchers from Ben-Gurion University of the Negev (BGU) in Israel showed that exposure to steviol glycosides over time, at an undetermined quantity, may negatively affect the gut microbial balance, by interfering in the AHL-mediated quorum sensing (QS) and thereby inducing associated health complications. (3) QS is an inter-cell communication between bacterial populations through chemical signaling molecules called autoinducers, that increase in concentration as a function of cell density.(4)

In another study that tested stevia consumption on rats, they concluded “In the current study, we found RebA (Rebaudoside A from Stevia) altered certain microbial taxa compared to the control group, but prebiotics seemed to have a greater impact on gut microbiota composition, even when consumed alongside RebA. RebA consumption reduced members of Bifidobacteriaceae, a widely-recognized and well-established “health-promoting” microbiota known for its role in short-chain fatty acid production, greater presence in breast-fed infants, protection from childhood obesity, and in treatment of various diseases through supplementation (6).

With the effects identified in this study and the growing consumption of stevia worldwide, there is an urge for more research to help further clarify the effects of these sweeteners and to shape guidelines for stevia intake. Those that use stevia should proceed with caution and moderation. Conclusive evidence on the way our microbiome affects weight management, diabetes, and other health issues is needed. 

By Yesenia Morales

Technical Services Microbiologist



References: 1, 2, 3, 4, 5, 6

New Therapies for Difficult-to-Treat Pathogens:

Sulbactam-Durlobactam

and Rezafungin

Healthcare professionals face a constant challenge with ever-evolving bacterial and fungal infections. Multidrug-resistant pathogens threaten the efficacy of existing treatments and highlight the need for new antimicrobial therapies. These microorganisms are typically resistant to the majority of antimicrobial agents, including carbapenems, making them difficult to treat. The Centers for Disease Control and Prevention (CDC) has identified carbapenem-resistant Acinetobacter baumannii (CRAB) as an urgent public health threat.

Sulbactam-Durlobactam (Xacduro) was FDA approved in May to treat hospital-acquired bacterial pneumonia (HABP) and ventilator-associated bacterial pneumonia (VABP) caused by Acinetobacter baumannii-calcoaceticus complex. HardyDisk™ AST Sulbactam-Durlobactam was subsequently FDA cleared 44 days later. The intravenous drug developed by Entasis Therapeutics Inc., provides a promising solution to treatment of CRAB.

Rezafungin (Rezzayo) is a new antifungal agent that gained FDA approval in March. HardyDisk™ AST Rezafungin was subsequently FDA cleared 71 days later. Cidara Therapeutics developed this echinocandin antifungal agent to combat invasive fungal infections. This marks the first new treatment option approved for individuals with candidemia and invasive candidiasis in over 10 years.

Drug-resistant fungal infections are becoming more common, especially in patients with weakened immune systems. Serious fungal infections are often life-threatening with a mortality rate of up to 60%. Candida is part of the normal human microflora and invasive infections can occur if the organism is introduced into the bloodstream via catheter insertions, injections, endocarditis, or peritonitis. Candidemia and invasive candidiasis are often treated with antifungal agents such as fluconazole, caspofungin, and amphotericin B. However, the emergence of antimicrobial resistance in Candida species has complicated treatment strategies.

The introduction of Sulbactam-Durlobactam and Rezafungin expands the armamentarium of healthcare professionals. These new therapies provide hope for improved patient outcomes when drug-resistant microorganisms are encountered.

HardyDisk™ AST Sulbactam-durlobactam and HardyDisk™ AST Rezafungin will allow clinicians to make informed treatment decisions, ultimately improving patient care, and contributing to the global fight against antimicrobial resistance. Click here to see Hardy's complete selection of products for Antimicrobial Susceptibility Testing.

By Anna Klavins and Lauren Hamilton

Sulbactam-Durlobactam (Xanduro)

   Catalog# Z9461 - Single Pack

   Catalog# Z9465 - 5 Pack

Rezafungin (Rezzayo)

   Catalog# Z9471 - Single Pack

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