AUTHOR=Conrads Georg , Westenberger Jacqueline , Lürkens Martha , Abdelbary Mohamed M. H. 

TITLE=Isolation and Bacteriocin-Related Typing of Streptococcus dentisani

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=9

YEAR=2019

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2019.00110

DOI=10.3389/fcimb.2019.00110

ISSN=2235-2988

ABSTRACT=<p><italic>Streptococcus oralis</italic> subspecies <italic>dentisani</italic> is explored as an anti-cariogenic probiotic. Here, subjecting freshly stimulated saliva samples of 35 healthy volunteers, six epidemiologically unrelated and two related strains were isolated (prevalence around 20%) applying a newly developed three-step procedure. Furthermore, the probiotic strain <italic>S. dentisani</italic> 7746 (AB-Dentisanium®) was tested under a variety of environmental conditions for its inhibitory effect on six <italic>S. mutans</italic>, two <italic>S. sobrinus</italic>, 15 other oral or intestinal streptococci, 15 <italic>S. dentisani</italic> strains, and six representatives of other species including periodontopathogens. All except one of the <italic>S. mutans</italic> strains were inhibited by 7746 colonies or culture supernatant concentrate but only if either the test cell number was low or the producer or its bacteriocin concentration, respectively, was high. <italic>S. sanguinis</italic> OMI 332, <italic>S. salivarius</italic> OMI 315, <italic>S. parasanguinis</italic> OMI 335, <italic>S. vestibularis</italic> OMI 238, and the intestinal <italic>S. dysgalactiae</italic> OMI 339 were not inhibited, while the other 10 streptococcal strains (especially <italic>S. oralis</italic> OMI 334 and intestinal <italic>S. gallolyticus</italic> OMI 326) showed a certain degree of inhibition. From the panel of other bacterial species only <italic>Aggregatibacter actinomycetemcomitans</italic> was slightly inhibited. With the exception of OMI 285 and OMI 291 that possessed a 7746 bacteriocin-like gene cluster, all <italic>S. dentisani</italic> strains and especially type strain 7747<sup>T</sup> were strongly inhibited by 7746. In conclusion, probiotic strain 7746 might antagonize the initiation and progression of dental caries by reducing <italic>S. mutans</italic> if not too abundant. <italic>S. dentisani</italic> strains inhibit each other, but strains with similar bacteriocin-related gene clusters, including immunity genes, are able to co-exist due to cross-resistance. In addition, development of resistance and adaptation to 7746-bacteriocins was observed during our study and needs attention. Hence, mechanisms underlying such processes need to be further investigated using omics-approaches. On the manufacturing level, probiotic strains should be continuously tested for function. Further clinical studies investigating inhibition of <italic>S. mutans</italic> by AB-Dentisanium® are required that should also monitor the impact on the oral microbiome composition including resident <italic>S. dentisani</italic> strains.</p>