Retention of streptococci to defined solid surfaces in the presence of saliva secretions

The initial surface retention of Streptococcus sanguis (G9B and ATCC 10556) and Streptococcus salivarius (ATCC 9758 and ATCC 13419) was examined using a well defined flow cell system. The microorganisms, known to be recovered from hard vs. soft tissue surfaces, respectively, were suspended in either Ringer solution, human parotid saliva (HPS), human submandibular and sublingual saliva (HSMSL), or mixed saliva. Microbial retention was evaluated on germanium prisms of low (20-25 mNm-1) and medium (30-35 mNm-1) critical surface tensions following distilled water rinse at 1 ml/min for 15 min. When suspended in only Ringer solution, the tested microorganisms showed patterns of generally high retention, that reflected the influence of both bacterial and substratum surface properties. However, in the saliva suspensions an overall reduction of retention was found with preferential retention to surfaces of medium critical surface tension for all bacteria. When comparing HPS and HSMSL as the suspending medium, a statistically significant observation was that smaller numbers of retained bacteria were recorded in the presence of HSMSL. The most frequently observed relationship between the tested salivas and numbers of retained cells was HSMSL less than MIXED less than HPS.