EFFECTS OF SUBINHIBITORY CONCENTRATIONS OF CHEMICAL-AGENTS ON HYDROPHOBICITY AND IN-VITRO ADHERENCE OF STREPTOCOCCUS-MUTANS AND STREPTOCOCCUS-SANGUIS

The aim of this investigation was to determine whether sublethal conce ntrations of chlorhexidine (Cx), hexetidine (Hx), cetylpyridinium chlo ride (Cc), sodium dodecyl sulfate (SDS), sanguinarine (Sg), sodium flu oride (NaF), and ammonium fluoride (NH4F) could affect hydrophobicity and adhesion of Streptococcus sanguis and Streptococcus mutans to sali va-coated hydroxyapatite (S-HA). Determination of the minimum inhibito ry concentrations (MICs) showed that both species were susceptible to all agents tested. Growth in the presence of sub-MIC concentrations of Cx, SDS, Cc, NaF, or NH4F did not change significantly the hydrophobi city of S. sanguis cells when compared to the control which lacked any agent. However, growth in the presence of Hx or Sg resulted in a sign ificant reduction in their hydrophobicity. Sub-MIC levels of SDS or Sg in the growth medium resulted in S. mutans cells with increased affin ity for hexadecane compared with the control. The adherence of S. sang uis was changed significantly only by Hx or Sg, resulting in less cell s adhering to S-HA. However, S. mutans cells previously incubated with NaF, NH4F, or Sg showed a higher adherence to S-HA than the control. The mechanisms of interference with adherence are at present not compl etely understood. Thus, antimicrobial agents at sub-MIC concentrations can interfere selectively with hydrophobicity and/or adhesion of oral streptococci.