A spontaneous lactate dehydrogenase deficient mutant of Streptococcus rattus for use as a probiotic in the prevention of dental caries

  • Nov 11 2019

Authors: J.D. Hillman, E. McDonell, T. Cramm, C.H. Hillman, R.T. Zahradnik — Oragenics Inc., Alachua, FL; University of Illinois, Champaign, IL

Journal: Journal of Applied Microbiology | Published: 2009 | Vol. 107: 1551–1558

DOI: 10.1111/j.1365-2672.2009.04333.x

Abstract

Aims: To study the ability of daily applications of Streptococcus rattus strain JH145 to affect the numbers of an implanted Streptococcus mutans strain in a rat model.

Methods and Results: A spontaneous L(+)-lactate dehydrogenase (LDH)-deficient mutant of Streptococcus rattus, JH146, was isolated by screening on selective medium and compared with the previously isolated spontaneous LDH-deficient strain JH145. Both strains were shown to have single base pair deletion mutations in the structural gene (ldh) for LDH, with similar reversion frequencies.

Animals treated once daily with 2×10⁸ CFU of JH145 showed a statistically significant, dose-dependent decrease in the proportion of implanted S. mutans to total cultivable bacteria in oral swab samples. No adverse effects were observed in any treated animals, and histopathological, haematological, and blood chemistry analyses were unremarkable.

Conclusions: Daily application of JH145, a naturally occurring LDH-deficient variant of S. rattus, can compete with S. mutans for its habitat on the tooth surface, supporting its use as a probiotic for dental caries prevention.

Study Design

72 Sprague Dawley rats were infected with S. mutans strain NG8 and treated once daily, Monday through Friday, for 26 weeks with doses of JH145 ranging from 10² to 10⁸ CFU across six groups. Oral swab samples were taken weekly to monitor NG8, JH145, and total cultivable bacteria levels.

Key Results

  • A significant and persistent decline in S. mutans proportion was observed within 3–6 weeks following onset of treatment at higher dose levels (10⁵–10⁸ CFU)
  • Lower doses (10³–10⁴ CFU) achieved significant effects at 9–12 weeks
  • The effect did not diminish over the 26-week course of treatment, indicating S. mutans did not develop resistance
  • Post-treatment analysis showed a carry-forward effect in the 4-week period immediately following cessation of treatment
  • After 26 weeks at the highest dose level, full necropsy and laboratory analyses revealed no significant differences from control animals

Significance

Streptococcus rattus JH145 — a key component of the ProBiora3® probiotic blend — demonstrated a dose-dependent ability to competitively reduce levels of cariogenic S. mutans on the tooth surface over a 26-week period, with an excellent safety profile. This study provides direct evidence of both the efficacy and safety of JH145 as a probiotic for dental caries prevention.

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