**Acknowledgements**

*Bacterial Biofilms*

**4.3 Potential risks of the use of probiotics**

disturbed immune system or patients with AIDS [64].

Before introduction of any probiotic product to market, it has to comply with very strict conditions. The product should be a result of thorough research of the relevant strain and each dose should contain sufficient bacteria even after storage of the preparation [63]. Probiotics are considered safe as they contain nonpathogenic microorganisms, and this is one of the reasons for high willingness of patients to use them. Risk to health may occur during a long-term use of probiotic preparation at diseases or states that enable their potential passage to the body at the development of secondary infection. Such states include bloody diarrhoea, immunosuppressive treatment or irradiation. Additional potential risks include transfer of vancomycin resistance by strains of *Enterococcus faecium*, administration of high doses of probiotics to autoimmune patients, infants and newborns with immunity and intestinal permeability disorders and administration to patients with immature or markedly

Probiotics can be routinely used as a food supplement, and their positive health claims were well described [65]. Despite that, some undesirable effects of the use of probiotics can also occur [66]. Usually, this involves only mild reactions that affect small percentage of users. When using probiotic products, it is necessary to consult a doctor about potential indications and undesirable effects [67]. Clinical indications of the use of probiotics are very extensive. One of their unwanted effects are digestion problems that may involve tympany and increased thirst [68]. Biogenic amines are low molecular weight organic compounds produced by degradation of amino acids, which may affect negatively the human organism [69]. The biogenic amines produced from the accepted food by fermentation activity of probiotic bacteria have excitation effect on the nervous system and decrease blood flow through organs, which can result in headaches [70]. Biogenic amines are histamine, tyramine, tryptamine, putrescin, spermidine and phenyl ethylamine [71]. In some groups of people, the use of probiotic products results in increased risk of infections, such as in immunosuppressed individuals or patients after surgeries hospitalised for long time. One should not forget to mention allergic reactions associated with the use of probiotic components. Probiotic products contain various additives such as lactose, eggs, soya or other generally known allergens. The consumers should avoid components that may induce in them hypersensitivity or allergic reactions [72]. Basically, such cases are rare and the probiotic treatment can be referred to as the treatment on a natural basis. At the same time, it is recommended to increase gradually the doses of probiotics until reaching the full dose in order to prevent potential side effects that occur particularly in weakened individuals.

There is an increasing concern about the fact that oral diseases put a systemic load on the organism. This stresses the importance of oral health for the overall health of an individual and the population. Predictions have been made in the past that the scientific and technological advances in the field of molecular biology, immunology and genetics, together with ageing of the population, will require future complex health service measures within which the care of the oral health will become important from the point of view of management of overall health and economy, and thus will necessitate novel oral health approaches. Bioactive compounds, as substances capable of affecting the microbiocenosis environment, are considered an alternative when searching for replacement for antibiotics. Results of the studies focused on microbiocenosis of the dental biofilm and interactions

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**5. Conclusion**

This publication was supported by the project of the Ministry of Education Science Research and Sport of the Slovak Republic VEGA 1/0081/17 and by the Slovak Research and Development Agency under the contract no. APVV-15-0377.
