The human oral cavity is a fascinating ecosystem. Thousands of bacterial species colonize our tongue, teeth, gums, and mucous membranes—the so-called oral flora. These microorganisms are not incompatible with health; quite the opposite: Many of them are essential helpers in maintaining a healthy balance. But what happens when this balance is disturbed?
Antibiotics are an indispensable part of modern medicine. They save lives – without a doubt. But their effect isn't selective. In addition to pathogenic germs, they also affect the bacteria that are supposed to protect us. The oral flora is particularly sensitive to this drug intervention. And the consequences can be more far-reaching than many people think.
The oral flora: guardian of health
The oral flora—or oral microbiome—consists of more than 700 known bacterial species. Most of these are so-called commensals: microorganisms that live in a harmonious relationship with the host. They form a natural protective shield against pathogenic invaders, support the immune system, and regulate inflammatory processes in the oral cavity.
A balanced oral flora fulfills key functions:
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Protection against pathogenic germs: Good bacteria compete with harmful microbes for space and nutrients. They prevent pathogenic species such as Candida albicans or Porphyromonas gingivalis from multiplying uncontrollably.
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pH regulation: The bacteria influence the pH value in the mouth and thus help prevent tooth decay.
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Stimulation of the immune system: They train local immune cells and ensure that the body can distinguish between friend and foe.
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Decomposition of food residues: Commensal microbes help break down food and contribute to pre-digestion.
This finely balanced system can be thrown off balance by many factors – one of the most powerful of which is the use of antibiotics.
How antibiotics change the oral flora
Antibiotics work by inhibiting the growth of bacteria or by killing them. Depending on the type of antibiotic, their mechanisms of action vary: Some block cell wall formation, others interfere with protein synthesis or DNA replication. The problem: These drugs can hardly distinguish whether a bacterium is "good" or "bad."
Broad-spectrum antibiotics, such as amoxicillin or clindamycin, in particular, target a wide range of microorganisms. Even when prescribed for pneumonia or cystitis, for example, they exert their effects systemically and thus also affect the oral cavity.
The consequences for the oral flora:
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Reduction in biodiversity (dysbiosis): Many beneficial bacterial strains die off. This reduces microbiological diversity—an important indicator of microbiome stability.
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Loss of protective functions: Without protective germs, pathogenic bacteria can settle and multiply more easily.
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Altered pH: Some protective species regulate acidity in the mouth. Loss of these compounds increases the risk of tooth decay.
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Fungal proliferation: When bacteria become unbalanced, yeasts such as Candida can multiply explosively – which can lead to oral thrush.
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Increased risk of periodontitis: Studies show that the risk of gum disease increases significantly after antibiotic treatment.
Dysbiosis in the mouth – the underestimated risk
Many people don't notice an imbalance in the oral flora immediately. Often, the symptoms are vague, such as unpleasant bad breath, increased plaque on the tongue, bleeding gums, or frequent cavities, which only appear weeks or months after antibiotic treatment. However, the change at the microscopic level is dramatic: Studies show that even a short course of antibiotics can have a long-term impact on the composition of the oral flora.
Some problematic developments:
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Proliferation of opportunistic germs: Streptococcus mutans , a major cause of caries, takes advantage of the opportunity and gains ground.
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Reduction of anti-inflammatory germs: Species such as Streptococcus salivarius or Veillonella parvula , which regulate inflammation, are decimated.
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Biofilm instability: The bacterial biofilm on the tooth surface becomes unstable – this increases susceptibility to plaque and tartar.
How can the oral flora recover after antibiotic treatment?
The body has amazing self-healing powers – including microbial ones. However, depending on lifestyle, diet, and individual immune status, the regeneration of the oral flora can take weeks or even months. In some cases, the microbiome remains permanently altered, which significantly increases the risk of chronic oral diseases.
Important factors for regeneration:
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Low-sugar diet: Sugar promotes the proliferation of harmful bacteria.
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Adequate saliva production: Saliva contains antibacterial enzymes and helps rebuild the flora.
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Avoid antibacterial mouthwashes: These often kill beneficial germs.
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Probiotics for the oral cavity: This is where Streptococcus salivarius M18 comes into play.
Streptococcus salivarius M18 : The natural helper for the oral flora
In recent years, interest in probiotic microorganisms has grown significantly – especially for the gut. However, there are also promising candidates for the mouth. One of the best-researched is Streptococcus salivarius M18 .
What is Streptococcus salivarius M18 ?
Streptococcus salivarius is a natural inhabitant of the oral cavity, particularly on the tongue. Strains K12 and M18 are considered key pathogens because they actively contribute to the balance of oral flora. Strain M18 has several remarkable properties that make it an ideal probiotic for oral health.
Advantages of S. salivarius M18 :
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Production of bacteriocins: These antimicrobial substances inhibit the growth of pathogenic germs, such as Streptococcus mutans or P. gingivalis .
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Neutralization of acids: M18 produces enzymes such as urease, which neutralize acids in the mouth – this protects against tooth decay.
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Promotes microbial balance: By colonizing the tongue, M18 can support other beneficial bacteria.
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Anti-inflammatory effect: Studies show that M18 can modulate the local immune response and thus reduce inflammation in the gums.
Probiotic oral care – more than just a trend
The targeted administration of Streptococcus salivarius M18 after antibiotic therapy can help restore the microbiological balance in the mouth more quickly. Products in the form of lozenges or sprays are particularly effective, as they allow for a longer residence time in the oral cavity and promote colonization.
Clinical studies show:
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Stable colonization with M18 can be observed after just 7–14 days.
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The risk of tooth decay is significantly reduced.
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Inflammatory markers in saliva decrease.
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The diversity of oral flora is increasing again.
Conclusion: The oral flora is an underestimated protective mechanism – antibiotics threaten it
Antibiotics are undoubtedly a blessing of modern medicine. But their impact on the oral microbiome should not be underestimated. The oral flora plays a central role in our health – far beyond the mouth. A disturbed microbial balance increases the risk of tooth decay, gingivitis, oral thrush, and other diseases.
The targeted rebuilding of the oral flora after antibiotic therapy is therefore essential. Streptococcus salivarius M18, as a probiotic leader, can play a key role in this process. Due to its diverse positive effects on the oral microbiome, it represents a useful complement to conventional oral hygiene—especially in times of microbial imbalance.
Recommendations for a healthy oral flora after antibiotics:
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Eat a varied and low-sugar diet.
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Avoid alcoholic or antibacterial mouthwashes.
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Make sure you take care of your teeth thoroughly but gently.
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Use targeted probiotics such as S. salivarius M18 for rebuilding.
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Drink plenty of water and chew sugar-free gum to stimulate saliva flow.
Stay balanced – even in your mouth.
Because health begins with the first bite.
