Construction and Characterization of an Effector Strain of Streptococcus mutans for Replacement Therapy of Dental Caries

Abstract

An effector strain has been constructed for use in the replacement therapy of dental caries. Recombinant DNA methods were used to make the Streptococcus mutans supercolonizing strain, JH1140, lactate dehydrogenase deficient by deleting virtually all of the ldh open reading frame (ORF). To compensate for the resulting metabolic imbalance, a supplemental alcohol dehydrogenase activity was introduced by substituting the adhB ORF from Zymomonas mobilis in place of the deleted ldh ORF. The resulting clone, BCS3-L1, was found to produce no detectable lactic acid during growth on a variety of carbon sources, and it produced significantly less total acid due to its increased production of ethanol and acetoin. BCS3-L1 was significantly less cariogenic than JH1140 in both gnotobiotic-and conventional-rodent models. It colonized the teeth of conventional rats as well as JH1140 in both aggressive-displacement and preemptive-colonization models. No gross or microscopic abnormalities of major organs were associated with oral colonization of rats with BCS3-L1 for 6 months. Acid-producing revertants of BCS3-L1 were not observed in samples taken from infected animals (reversion frequency, <10 ؊3 ) or by screening cultures grown in vitro, where no revertants were observed among 10 5 colonies examined on pH indicator medium. The reduced pathogenic potential of BCS3-L1, its strong colonization potential, and its genetic stability suggest that this strain is well suited to serve as an effector strain in the replacement therapy of dental caries in humans.

The Biofilm Concept: Consequences for Future Prophylaxis of Oral Diseases?

“…This strain produces mutacin, which enables it to replace wild-type strains efficiently. It lacks the enzyme lactate dehydrogenase and therefore does not form lactate (Hillman et al, 2000). Other recombinant strains which are ureolytic have also been constructed (Clancy et al, 2000).…”

Streptococcus mutans Out-competes Streptococcus gordonii in vivo

“…Thus, there is interest in "bacterial interference therapy" to pre-empt establishment or replace mutans streptococci from tooth surfaces by non-cariogenic tooth-colonizing bacteria. This concept is not new (Aly et al, 1982;Sprunt and Leidy, 1982;Tanzer et al, 1985a,b;Hillman et al, 2000). The non-mutans species-formerly classified as Streptococcus sanguis, which now includes the species Streptococcus sanguinis, Streptococcus oralis, and Streptococcus gordoniiare found in high numbers on supragingival tooth surfaces.…”

Microbiology of Oral Biofilm-Dependent Diseases: Have We Made Significant Progress to Understand and Treat These Diseases?

“…Because this strain produces high amounts of mutacin 1140, a lantibiotic with antimicrobial activity against other strains of S. mutans, it is able to dislocate the wild-type strain and colonize its habitat. Some advantages of this ecological method are the lifelong protection, lack of risks, and no need for patient compliance [66]. Other investigations have explored the potential role for probiotic lactobacilli and bifidobacteria to modulate the oral microbial ecology [67].…”