• Phakawan Musikapong B.Sc.
• Pasutha Thunyakitpisal D.D.S., Ph.D.
• Sunanta Pongsamart Ph.D.

Objective To investigate the antimicrobial activity of polysaccharide gel (PG) extracted from fruithulls
of durian against Streptococcus mutans and Actinobacillus actinomycetemcomitans, in vitro.

Materials and methods An inhibitory activity was determined by using broth dilution technique and
time kill analysis. S. mutans and A. actinomycetemcomitans were grown in Tryptic Soy Broth and
Brain Heart Infusion, respectively. Both organisms were treated with different concentrations of PG
(1, 5, 10, 20 and 35 mg/ml) in broth medium at 37˚C, 5% CO2 for 24 hours. Their survival were
evaluated in comparison to the control using drop plate method.

Results The minimum inhibitory concentrations (MICs) of S. mutans and A. actinomycetemcomitans
were 20 and 15 mg/ml, respectively, while the minimum bactericidal concentration (MBC) of
S. mutans and A. actinomycetemcomitans was 35 mg/ml. Bacterial counts of both S. mutans and
A. actinomycetemcomitans survival were declined to zero at 4 hours incubation in medium with
35 mg/ml PG.

Conclusion PG, at 35 mg/ml, revealed the bactericidal activities against both S. mutans and A.
actinomycetemcomitans. PG, at 20 and 15 mg/ml, exhibited an inhibitory activities against S. mutans
and A. actinomycetemcomitans, respectively.

(CU Dent J. 2005;28:137-44)