Isolation and Bacteriocin-Related Typing of Streptococcus dentisani

Abstract

Streptococcus oralis subspecies dentisani 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 S. dentisani 7746 (AB-Dentisanium®) was tested under a variety of environmental conditions for its inhibitory effect on six S. mutans , two S. sobrinus , 15 other oral or intestinal streptococci, 15 S. dentisani strains, and six representatives of other species including periodontopathogens. All except one of the S. mutans 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. S. sanguinis OMI 332, S. salivarius OMI 315, S. parasanguinis OMI 335, S. vestibularis OMI 238, and the intestinal S. dysgalactiae OMI 339 were not inhibited, while the other 10 streptococcal strains (especially S. oralis OMI 334 and intestinal S. gallolyticus OMI 326) showed a certain degree of inhibition. From the panel of other bacterial species only Aggregatibacter actinomycetemcomitans was slightly inhibited. With the exception of OMI 285 and OMI 291 that possessed a 7746 bacteriocin-like gene cluster, all S. dentisani strains and especially type strain 7747 T were strongly inhibited by 7746. In conclusion, probiotic strain 7746 might antagonize the initiation and progression of dental caries by reducing S. mutans if not too abundant. S. dentisani 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 S. mutans by AB-Dentisanium® are required that should also monitor the impact on the oral microbiome composition including resident S. dentisani strains.

A concerted probiotic activity to inhibit periodontitis-associated bacteria

“…Among them are Firmicutes , including streptococci and lactobacilli, the most promising candidates. Recently, we have published about the in vitro anti-cariogenic potential of Streptococcus oralis subspecies dentisani 7746 in comparison to other probiotic strains or combinations of strains [ 15 ]. Here, we explored the in vitro anti-periodontitis potential of this species in comparison to Streptococcus salivarius subsp.…”

“…It is known that S . dentisani 7746 produces about ten different bacteriocins [ 15 ]. Combined with the plasmid-encoded salivaricin-variants A2, B, 9, and MPS produced by K12 and M18 [ 33 ], as well as bacteriocin immunity factors, a concerted activity directed against the pathogens is needed avoiding a friendly fire of against the co-producer.…”

“…dentisani 7746 and only a weak inhibition of A . actinomycetemcomitans applying agar diffusion tests [ 15 ]. These discrepancies were explained with differences in the inhibitory potential of different (adapted, mutated) subcultures or clones of S .…”

Topic Application of the Probiotic Streptococcus dentisani Improves Clinical and Microbiological Parameters Associated With Oral Health

“…Thus, we propose that future work aims to identify the specific bacteriocins which are responsible for the inhibition of this major human pathogen. On the other hand, a potentially negative effect of the S. dentisani strain 7746 bacteriocins effect is their inhibitory action against other S. dentisani strains (Conrads et al, 2018 , 2019 ). Thus, although our data show an increase in S. dentisani levels after the administration of the probiotic, this could be so at the expense of a reduction in the indigenous population of this species.…”

“…Streptococcus dentisani was first isolated in 2011 from caries-free individuals where a metagenomic analysis of dental plaque samples had shown an over-representation of genes coding for antimicrobial peptides (Belda-Ferre et al, 2012 ). In fact, at least 11 bacteriocins have been described in this organism based on bioinformatic analysis (Conrads et al, 2019 ) and has been shown to inhibit different oral pathogens ranging from Fusobacterium nucleatum to Porphyromonas gingivalis or Streptococcus mutans (López-López et al, 2017 ; Esteban-Fernández et al, 2019 ; Llena et al, 2019 ). Genomic and physiological analysis determined that this bacterium represented a new species (Benítez-Páez et al, 2014 ) although its potential assignment as a subspecies of S. oralis is under debate (Jensen et al, 2016 ; Velsko et al, 2019 ).…”