Antimicrobial activity of probiotics against endodontic pathogens:- A preliminary study

The purpose of this study was to evaluate the antibacterial effectiveness of probiotics lactobacilli group and Bifidobacterium against Enterococcus faecalis and Candida albicans in both planktonic stage and biofilm stage.

Phase 1 of the study was conducted by agar well diffusion method. About 0.5 ml of test pathogen culture was inoculated on 20 ml of molten agar and allowed to solidify. 4-5 circular wells of diameter 8-10 mm were punched in each poured plates and 150 μl of diluted test samples were added to the wells. Phase 2 was deferred antagonism test, wherein purified culture of pathogen strain was streaked at right angle to the original producer growth and incubated at 37°C for 24 h. Zone of inhibition was measured for both the phases. Phase 3 biofilm stage evaluation was conducted by mixing 9 ml of 30% poloxamer 407 and De Man, Rogosa and Sharpe (MRS) broth in a test tube with 500 μl of either pathogen, together with 500 μl of test probiotic strains and incubated (37°C, 48 h), followed by serially diluting the mixture by 1 ml into 9 ml sterile saline till 10⁸ dilutions for evaluation of colony-forming unit/ml counts. Controls were endodontic pathogens in 30% poloxamer with MRS broth and no probiotics.

Results were evaluated and statistically analysed using one-way analysis of variance and unpaired t-test. In the planktonic stage, probiotics showed inhibitory activity against endodontic pathogens with valid statistical significance (P < 0.05), while there was no activity by deferred antagonism method. In biofilm stage, all three probiotics showed growth reduction for E. faecalis, while lactobacilli group showed reduction in C. albicans colonies.

This preliminary study suggested that probiotics are effective for preventing the growth of endodontic pathogens in vitro. Poloxamer could be utilised as an ideal delivery vehicle for probiotics.