title: Effect of saliva viscosity on the co-aggregation between oral streptococci and Actinomyces naeslundii.
abstract: BACKGROUND
  The co-aggregation of oral bacteria leads to their clearance from the oral cavity. Poor oral hygiene and high saliva viscosity are common amongst the elderly; thus, they frequently suffer from pneumonia caused by the aspiration of oral microorganisms.
  
  
  OBJECTIVE
  To examine the direct effect of saliva viscosity on the co-aggregation of oral streptococci with actinomyces.
  
  
  METHODS
  Fifteen oral streptococcal and a single actinomyces strain were used. Co-aggregation was assessed by a visual assay in phosphate buffer and a spectrophotometric assay in the same buffer containing 0-60% glycerol or whole saliva.
  
  
  RESULTS
  Nine oral streptococci co-aggregated with Actinomyces naeslundii ATCC12104 in the visual assay and were subsequently used for the spectrophotometric analysis. All tested strains displayed a decrease in co-aggregation with increasing amounts of glycerol in the buffer. The co-aggregation of Streptococcus oralis with A. naeslundii recovered to baseline level following the removal of glycerol. The per cent co-aggregation of S. oralis with A. naeslundii was significantly correlated with the viscosity in unstimulated and stimulated whole saliva samples (correlation coefficients: -0.52 and -0.48, respectively).
  
  
  CONCLUSIONS
  This study suggests that saliva viscosity affects the co-aggregation of oral streptococci with actinomyces and that bacterial co-aggregation decreases with increasing saliva viscosity.
authors.affiliation: Department of Preventive Dentistry, Kagoshima University Graduate School of Medical and Dental Sciences, Sakuragaoka, Kagoshima, Japan.
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Kitada
authors.forename: Takahiko
authors.initials: T
authors.lastname: Oho
mesh_terms: D000190:Actinomyces / Q000187:drug effects / Q000502:physiology*; D000328:Adult; D002021:Buffers; D005990:Glycerol / Q000008:administration & dosage / Q000494:pharmacology; D006801:Humans; D056265:Microbial Interactions / Q000187:drug effects / Q000502:physiology; D008875:Middle Aged; D010710:Phosphates / Q000737:chemistry; D012463:Saliva / Q000382:microbiology / Q000502:physiology*; D013053:Spectrophotometry; D013291:Streptococcus / Q000187:drug effects / Q000502:physiology*; D034366:Streptococcus anginosus / Q000187:drug effects / Q000502:physiology; D034365:Streptococcus constellatus / Q000187:drug effects / Q000502:physiology; D054773:Streptococcus gordonii / Q000187:drug effects / Q000502:physiology; D034367:Streptococcus intermedius / Q000187:drug effects / Q000502:physiology; D034361:Streptococcus mitis / Q000187:drug effects / Q000502:physiology; D013295:Streptococcus mutans / Q000187:drug effects / Q000502:physiology; D019533:Streptococcus oralis / Q000187:drug effects / Q000502:physiology; D013296:Streptococcus pneumoniae / Q000187:drug effects / Q000502:physiology; D013298:Streptococcus sanguis / Q000187:drug effects / Q000502:physiology; D014783:Viscosity; D055815:Young Adult
chemical_list: D002021:Buffers; D010710:Phosphates; D005990:Glycerol