The adhering capacity of single- and mixed-species bacteria

Objectives: The objective of the study was to investigate and compare the adhering capacity of single- and mixed-species bacteria to an experimental pellicle.

Methods: A known population of oral bacteria (Strep. mitis, Strep. sanguinis and Actinomyces sp.) either as single- or mixed-species was allowed to adhere to the experimental pellicle of biofilm developed in an artificial mouth (NAM) model. The bacterial population (single- or mixed-species) adhering to the experimental pellicle was determined and expressed as colony forming unit (CFU/ml).

Results: It was found that for the single-species biofilm, Strep. mitis demonstrated maximum adherence (1153.33 ± 132.46 x 10⁴ CFU/ml), followed by Strep. sanguinis (183.00 ± 10.33 x 10⁴ CFU/ml) and by Actinomyces sp. (42.33 ± 3.20 x 10⁴ CFU/ml). The adherence of the bacteria was found to be reduced when a mixture of two-species instead of single-species was inoculated. Maximum adherence was observed with a two mixed-species of Strep. mitis - Strep. sanguinis (186.17 ± 5.27 x 10⁴ CFU/ml), of Strep. mitis – Actinomyces sp. (148.00 ± 7.43 x 10⁴ CFU/ml) and of Strep. sanguinis – Actinomyces sp. (95.00 ± 2.45 x 10⁴ CFU/ml). However, it was found that when the three species are together (Strep. mitis - Strep. sanguinis – Actinomyces sp.) in the development of the biofilm, the bacterial adherence was higher (208.33 ± 25.85 x 10⁴ CFU/ml) compared to when they are present in a mixture of any two species. The difference in the adherence capacity of these bacteria to the experimental pellicle was found to be statistically significant (p<0.05).

Conclusion: The results obtained in this study indicate that the adhering capacity of the bacteria to the experimental pellicle is species dependent and is very much influenced by the types of bacteria present in the inoculum.

This study was funded by IRPA Grant No 09-02-03-0197 EA 197.