Effect of saliva viscosity on the co‐aggregation between oral streptococci and Actinomyces naeslundii

Abstract

Effect of saliva viscosity on the co-aggregation between oral streptococci and Actinomyces naeslundii 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. Objectives: To examine the direct effect of saliva viscosity on the co-aggregation of oral streptococci with actinomyces. Materials and methods: Fifteen oral streptococcal and a single actinomyces strain were used. Coaggregation 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). Conclusion: 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.

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Devising negative pressure within intercuff space reduces microaspiration

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