Hydrophobicity test in mutans streptococci.

Kinetic hydrophobic measurements were performed by confronting 40 mutans streptococci from thirty 10- to 20-year-old patients with 200 ml hexadecane (Sigma). Fourteen patients had high dental caries risk (Group A), dmft + DMFT > 5 with 3 or more active caries, and 16 had low dental caries risk (Group B), dmft + DMFT < 3 without active caries. Twenty bacteria from Group A and 20 bacteria from Group B were typed using De La Higuera's procedure and confirmed by API strip (bio-Merieux). From the 14 patients in Group A we obtained 12 S. mutans (8 hydrophobic/4 non-hydrophobic), 5 S. sobrinus (4 hydrophobic/1 non-hydrophobic) and 3 S. rattus (hydrophobic). From the 16 patients in Group B we obtained 11 Streptococcus mutans (10 non-hydrophobic/1 hydrophobic), 7 Streptococcus sobrinus (6 non-hydrophobic/ 1 hydrophobic) and 2 Streptococcus rattus (hydrophobic). Patients with high dental caries risk have a higher prevalence of hydrophobic bacteria than patients with low dental caries risk (p = 0.0003). All typed S. rattus were hydrophobic.