Probiotic activity of Lactobacillus delbrueckii subsp. bulgaricus in the oral cavity

Abstract

Yogurt consumption has been related to longevity of some populations living on the Balkans. Yogurt starter L. delbrueckii subsp. bulgaricus and Str. thermophilus have been recognized as probiotics with verified beneficial health effects. The oral cavity emerges as a arget for probiotic applications. Probiotics have demonstrated promising results in controlling dental diseases and oral yeast infections. However, L. bulgaricus despite its broad availability in dairy products has not been evaluated for probiotic activity in the mouth.

These series of studies investigated in vitro properties of L. bulgaricus to outline its potential as an oral probiotic. Prerequisite probiotic properties in the mouth are resistance to oral defense mechanisms, adherence to saliva-coated surfaces, and inhibition of oral pathogens. L. bulgaricus strains showed a strain-dependent inhibition of oral streptococci and Aggregatibacter actinomycetemcomitans, whereas none of the dairy starter strains could affect growth of Porphyromonas gingivalis and Fusobacterium nucleatum. Adhesion is a factor contributing to colonization of the species at the target site. Radiolabeled L. bulgaricus strains and L. rhamnosus GG were tested for their ability to adhere to saliva-coated surfaces. The effects of lysozyme on adhesion and adhesion of Streptococcus sanguinis after lactobacilli pretreatment were also assessed. Adhesion of L. bulgaricus remained lower in comparison to L. rhamnosus GG. One L. bulgaricus strain showed binding frequency comparable to S. sanguinis. Lysozyme pretreatment significantly increased Lactobacillus adhesion.

Low gelatinolytic activity was observed for all strains and no conversion of proMMP-9 to its active form was induced by L. bulgaricus. Safety assessment ruled out deleterious effects of L. bulgaricus on extracellular matrix structures. Cytokine response of oral epithelial cells was assessed by measuring IL-8 and TNF-α in cell culture supernatants. The effect of P. gingivalis on cytokine secretion after lactobacilli pretreatment was also assessed. A strain- and time-dependent induction of IL-8 was observed with live bacteria inducing the highest levels of cytokine secretion. Levels of TNF-α were low and only one of ten L. bulgaricus strains stimulated TNF-α secretion similar to positive control. The addition of P. gingivalis produced immediate reduction of cytokine levels within the first hours of incubation irrespective of lactobacilli strains co-cultured with epithelial cells.

According to these studies strains among the L. delbrueckii subsp. bulgaricus species may have beneficial probiotic properties in the mouth. Their potential in prevention and management of common oral infectious diseases needs to be further studied.

Jogurttibakteereista apua suu- ja hammassairauksiin?

Jo 1900-luvun alussa esitettiin teoria jonka mukaan jogurtti edesauttaa terveyttä. Sittemmin jogurtin valmistuksessa käytettäviä bakteereita, erityisesti laktobasilleja on tutkittu paljon varsinkin suolistosai-rauksien suhteen. Probioottisista eli terveysvaikutteisista bakteereista saattaa olla apua myös suusai-rauksien kurissapitämisessä. Tässä väitöskirjatutkimuksessa tutkittiin bulgarialaisten meijerikantojen, Lactobacillus bulgaricus-bakteerien turvallisuutta ja kudosvaikutuksia. Laktobasillien tarttumisominai-suuksia tutkittiin laboratoriossa käyttäen hydroksiapatiittia simuloimaan hammaskudosta. Tulokset osoittivat, että tietyt meijeribakteerikannat tarttuivat selvästi toisia paremmin ja soveltuvat siten jatko-tarkasteluun. Syljen puolustusentsyymi lysotsyymi edesauttoi bakteerien tarttumista. Havainnoilla on käytännön merkitystä, sillä probioottinen teho edellyttää bakteerien kykyä tarttua kohdekudokseen. Kudosturvallisuus on tärkeää kaikessa bakteeriterapiassa. Tutkimussarjan toisessa osassa keskityttiin Lactobacillus bulgaricus-kantojen vaikutuksiin tulehdusreaktioiden ja kudosmodulaation kannalta. Tu-lokset osoittivat, että verrattaessa meijeribakteerikantojen vaikutusta tunnettujen patogeenibakteerien vaikutukseen, eivät tutkitut laktobasillit aktivoineet kudosmatriisin metalloproteinaaseja. Havainto ko-rostaa laktobasillien harmittomuutta joten ne vaikuttavat turvallisilta.